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-\input texinfo
-@c %**start of header
-@setfilename omni-utils.info
-@settitle @sc{gnu} Omni-utils
-
-@c %**end of header
-
-@include version.texi
-@include constants.texi
-
-@c Define new indices.
-@defcodeindex op
-@defcodeindex fl
-
-@c Put everything in one index (arbitrarily chosen to be the concept index).
-@syncodeindex fl cp
-@syncodeindex fn cp
-@syncodeindex ky cp
-@syncodeindex op cp
-@syncodeindex pg cp
-@syncodeindex vr cp
-
-@ifinfo
-@format
-START-INFO-DIR-ENTRY
-* @sc{gnu} Utilities: (omni-utils).              @sc{gnu} Utilities.
-* Common options:                                Common options.
-* File permissions:                              Access modes.
-* Date input formats:                            Specifying date strings.
-* Opening the software toolbox:                  The software tools philosophy.
-* GNU Free Documentation License:                The license for this documentation.
-
-* basename: (omni-utils)basename invocation.     Strip directory and suffix.
-* cat: (omni-utils)cat invocation.               Concatenate and write files.
-* chgrp: (omni-utils)chgrp invocation.           Change file groups.
-* chmod: (omni-utils)chmod invocation.           Change file permissions.
-* chown: (omni-utils)chown invocation.           Change file owners/groups.
-* chroot: (omni-utils)chroot invocation.         Specify the root directory.
-* cksum: (omni-utils)cksum invocation.           Print @sc{posix} CRC checksum.
-* comm: (omni-utils)comm invocation.             Compare sorted files by line.
-* cp: (omni-utils)cp invocation.                 Copy files.
-* csplit: (omni-utils)csplit invocation.         Split by context.
-* cut: (omni-utils)cut invocation.               Print selected parts of lines.
-* date: (omni-utils)date invocation.             Print/set system date and time.
-* dd: (omni-utils)dd invocation.                 Copy and convert a file.
-* df: (omni-utils)df invocation.                 Report filesystem disk usage.
-* dir: (omni-utils)dir invocation.               List directories briefly.
-* dircolors: (omni-utils)dircolors invocation.   Color setup for ls.
-* dirname: (omni-utils)dirname invocation.       Strip non-directory suffix.
-* du: (omni-utils)du invocation.                 Report on disk usage.
-* echo: (omni-utils)echo invocation.             Print a line of text.
-* env: (omni-utils)env invocation.               Modify the environment.
-* expand: (omni-utils)expand invocation.         Convert tabs to spaces.
-* expr: (omni-utils)expr invocation.             Evaluate expressions.
-* factor: (omni-utils)factor invocation.         Print prime factors
-* false: (omni-utils)false invocation.           Do nothing, unsuccessfully.
-* fmt: (omni-utils)fmt invocation.               Reformat paragraph text.
-* fold: (omni-utils)fold invocation.             Wrap long input lines.
-* groups: (omni-utils)groups invocation.         Print group names a user is in.
-* head: (omni-utils)head invocation.             Output the first part of files.
-* hostid: (omni-utils)hostid invocation.         Print numeric host identifier.
-* hostname: (omni-utils)hostname invocation.     Print or set system name.
-* id: (omni-utils)id invocation.                 Print real/effective uid/gid.
-* install: (omni-utils)install invocation.       Copy and change attributes.
-* join: (omni-utils)join invocation.             Join lines on a common field.
-* ln: (omni-utils)ln invocation.                 Make links between files.
-* logname: (omni-utils)logname invocation.       Print current login name.
-* ls: (omni-utils)ls invocation.                 List directory contents.
-* md5sum: (omni-utils)md5sum invocation.         Print or check message-digests.
-* mkdir: (omni-utils)mkdir invocation.           Create directories.
-* mkfifo: (omni-utils)mkfifo invocation.         Create FIFOs (named pipes).
-* mknod: (omni-utils)mknod invocation.           Create special files.
-* mv: (omni-utils)mv invocation.                 Rename files.
-* nice: (omni-utils)nice invocation.             Modify scheduling priority.
-* nl: (omni-utils)nl invocation.                 Number lines and write files.
-* nohup: (omni-utils)nohup invocation.           Immunize to hangups.
-* od: (omni-utils)od invocation.                 Dump files in octal, etc.
-* paste: (omni-utils)paste invocation.           Merge lines of files.
-* pathchk: (omni-utils)pathchk invocation.       Check file name portability.
-* pr: (omni-utils)pr invocation.                 Paginate or columnate files.
-* printenv: (omni-utils)printenv invocation.     Print environment variables.
-* printf: (omni-utils)printf invocation.         Format and print data.
-* ptx: (omni-utils)ptx invocation.               Produce permuted indexes.
-* pwd: (omni-utils)pwd invocation.               Print working directory.
-* rm: (omni-utils)rm invocation.                 Remove files.
-* rmdir: (omni-utils)rmdir invocation.           Remove empty directories.
-* seq: (omni-utils)seq invocation.               Print numeric sequences
-* shred: (omni-utils)shred invocation.           Remove files more securely.
-* sleep: (omni-utils)sleep invocation.           Delay for a specified time.
-* sort: (omni-utils)sort invocation.             Sort text files.
-* split: (omni-utils)split invocation.           Split into fixed-size pieces.
-* stty: (omni-utils)stty invocation.             Print/change terminal settings.
-* su: (omni-utils)su invocation.                 Modify user and group id.
-* sum: (omni-utils)sum invocation.               Print traditional checksum.
-* sync: (omni-utils)sync invocation.             Synchronize memory and disk.
-* tac: (omni-utils)tac invocation.               Reverse files.
-* tail: (omni-utils)tail invocation.             Output the last part of files.
-* tee: (omni-utils)tee invocation.               Redirect to multiple files.
-* test: (omni-utils)test invocation.             File/string tests.
-* touch: (omni-utils)touch invocation.           Change file timestamps.
-* tr: (omni-utils)tr invocation.                 Translate characters.
-* true: (omni-utils)true invocation.             Do nothing, successfully.
-* tsort: (omni-utils)tsort invocation.           Topological sort.
-* tty: (omni-utils)tty invocation.               Print terminal name.
-* uname: (omni-utils)uname invocation.           Print system information.
-* unexpand: (omni-utils)unexpand invocation.     Convert spaces to tabs.
-* uniq: (omni-utils)uniq invocation.             Uniquify files.
-* users: (omni-utils)users invocation.           Print current user names.
-* vdir: (omni-utils)vdir invocation.             List directories verbosely.
-* wc: (omni-utils)wc invocation.                 Byte, word, and line counts.
-* who: (omni-utils)who invocation.               Print who is logged in.
-* whoami: (omni-utils)whoami invocation.         Print effective user id.
-* yes: (omni-utils)yes invocation.               Print a string indefinitely.
-END-INFO-DIR-ENTRY
-@end format
-@end ifinfo
-
-@ifinfo
-This file documents the GNU command line utilities.
-
-Copyright (C) 1994, 95, 96, 2001 Free Software Foundation, Inc.
-
-Permission is granted to copy, distribute and/or modify this document
-under the terms of the GNU Free Documentation License, Version 1.1 or
-any later version published by the Free Software Foundation; with no
-Invariant Sections, with no Front-Cover Texts, and with no Back-Cover
-Texts.  A copy of the license is included in the section entitled ``GNU
-Free Documentation License''.
-
-@end ifinfo
-
-@titlepage
-@title @sc{gnu} @code{Omni-utils}
-@subtitle A set of command line utilities
-@subtitle for version @value{VERSION}, @value{UPDATED}
-@author David MacKenzie et al.
-
-@page
-@vskip 0pt plus 1filll
-Copyright @copyright{} 1994, 95, 96, 2000 Free Software Foundation, Inc.
-
-Permission is granted to copy, distribute and/or modify this document
-under the terms of the GNU Free Documentation License, Version 1.1 or
-any later version published by the Free Software Foundation; with no
-Invariant Sections, with no Front-Cover Texts, and with no Back-Cover
-Texts.  A copy of the license is included in the section entitled ``GNU
-Free Documentation License''.
-@end titlepage
-
-
-@c If your makeinfo doesn't grok this @ifnottex directive, then either
-@c get a newer version of makeinfo or do s/ifnottex/ifinfo/ here and on
-@c the matching @end directive below.
-@ifnottex
-@node Top
-@top GNU Omni-utils
-
-@cindex text utilities
-@cindex shell utilities
-@cindex file utilities
-This manual documents version @value{VERSION} of the @sc{gnu} command
-line utilities.
-
-@menu
-* Introduction::                       Caveats, overview, and authors.
-* Common options::                     Common options.
-* Output of entire files::             cat tac nl od
-* Formatting file contents::           fmt pr fold
-* Output of parts of files::           head tail split csplit
-* Summarizing files::                  wc sum cksum md5sum
-* Operating on sorted files::          sort uniq comm ptx tsort
-* Operating on fields within a line::  cut paste join
-* Operating on characters::            tr expand unexpand
-* Directory listing::                  ls dir vdir d v dircolors
-* Basic operations::                   cp dd install mv rm shred
-* Special file types::                 ln mkdir rmdir mkfifo mknod
-* Changing file attributes::           chgrp chmod chown touch
-* Disk usage::                         df du sync
-* Printing text::                      echo printf yes
-* Conditions::                         false true test expr
-* Redirection::                        tee
-* File name manipulation::             dirname basename pathchk
-* Working context::                    pwd stty printenv tty
-* User information::                   id logname whoami groups users who
-* System context::                     date uname hostname
-* Modified command invocation::        chroot env nice nohup su
-* Delaying::                           sleep
-* Numeric operations::                 factor seq
-* File permissions::                   Access modes.
-* Date input formats::                 Specifying date strings.
-* Opening the software toolbox::       The software tools philosophy.
-* GNU Free Documentation License::     The license for this documentation.
-* Index::                              General index.
-
-@detailmenu
- --- The Detailed Node Listing ---
-
-Common Options
-
-* Backup options::              Backup options
-* Block size::                  Block size
-* Target directory::            Target directory
-* Trailing slashes::            Trailing slashes
-
-Output of entire files
-
-* cat invocation::              Concatenate and write files.
-* tac invocation::              Concatenate and write files in reverse.
-* nl invocation::               Number lines and write files.
-* od invocation::               Write files in octal or other formats.
-
-Formatting file contents
-
-* fmt invocation::              Reformat paragraph text.
-* pr invocation::               Paginate or columnate files for printing.
-* fold invocation::             Wrap input lines to fit in specified width.
-
-Output of parts of files
-
-* head invocation::             Output the first part of files.
-* tail invocation::             Output the last part of files.
-* split invocation::            Split a file into fixed-size pieces.
-* csplit invocation::           Split a file into context-determined pieces.
-
-Summarizing files
-
-* wc invocation::               Print byte, word, and line counts.
-* sum invocation::              Print checksum and block counts.
-* cksum invocation::            Print CRC checksum and byte counts.
-* md5sum invocation::           Print or check message-digests.
-
-Operating on sorted files
-
-* sort invocation::             Sort text files.
-* uniq invocation::             Uniquify files.
-* comm invocation::             Compare two sorted files line by line.
-* ptx invocation::              Produce a permuted index of file contents.
-* tsort invocation::            Topological sort.
-
-@code{ptx}: Produce permuted indexes
-
-* General options in ptx::      Options which affect general program behavior.
-* Charset selection in ptx::    Underlying character set considerations.
-* Input processing in ptx::     Input fields, contexts, and keyword selection.
-* Output formatting in ptx::    Types of output format, and sizing the fields.
-* Compatibility in ptx::        The GNU extensions to @code{ptx}
-
-Operating on fields within a line
-
-* cut invocation::              Print selected parts of lines.
-* paste invocation::            Merge lines of files.
-* join invocation::             Join lines on a common field.
-
-Operating on characters
-
-* tr invocation::               Translate, squeeze, and/or delete characters.
-* expand invocation::           Convert tabs to spaces.
-* unexpand invocation::         Convert spaces to tabs.
-
-@code{tr}: Translate, squeeze, and/or delete characters
-
-* Character sets::              Specifying sets of characters.
-* Translating::                 Changing one characters to another.
-* Squeezing::                   Squeezing repeats and deleting.
-* Warnings in tr::              Warning messages.
-
-Directory listing
-
-* ls invocation::               List directory contents
-* dir invocation::              Briefly list directory contents
-* vdir invocation::             Verbosely list directory contents
-* dircolors invocation::        Color setup for @code{ls}
-
-@code{ls}:  List directory contents
-
-* Which files are listed::      Which files are listed
-* What information is listed::  What information is listed
-* Sorting the output::          Sorting the output
-* More details about version sort::  More details about version sort
-* General output formatting::   General output formatting
-* Formatting the file names::   Formatting the file names
-
-Basic operations
-
-* cp invocation::               Copy files and directories
-* dd invocation::               Convert and copy a file
-* install invocation::               Copy files and set attributes
-* mv invocation::               Move (rename) files
-* rm invocation::               Remove files or directories
-* shred invocation::               Remove files more securely
-
-Special file types
-
-* ln invocation::               Make links between files
-* mkdir invocation::               Make directories
-* mkfifo invocation::               Make FIFOs (named pipes)
-* mknod invocation::               Make block or character special files
-* rmdir invocation::               Remove empty directories
-
-Changing file attributes
-
-* chown invocation::               Change file owner and group
-* chgrp invocation::               Change group ownership
-* chmod invocation::               Change access permissions
-* touch invocation::               Change file timestamps
-
-Disk usage
-
-* df invocation::               Report filesystem disk space usage
-* du invocation::               Estimate file space usage
-* sync invocation::               Synchronize data on disk with memory
-
-Printing text
-
-* echo invocation::               Print a line of text
-* printf invocation::             Format and print data
-* yes invocation::                Print a string until interrupted
-
-Conditions
-
-* false invocation::              Do nothing, unsuccessfully
-* true invocation::               Do nothing, successfully
-* test invocation::               Check file types and compare values
-* expr invocation::               Evaluate expressions
-
-@code{test}: Check file types and compare values
-
-* File type tests::               File type tests
-* Access permission tests::       Access permission tests
-* File characteristic tests::     File characteristic tests
-* String tests::                  String tests
-* Numeric tests::                 Numeric tests
-
-@code{expr}: Evaluate expression
-
-* String expressions::         <colon> match substr index length quote
-* Numeric expressions::        + - * / %
-* Relations for expr::         | & < <= = == != >= >
-* Examples of expr::           Examples of using @code{expr}
-
-Redirection
-
-* tee invocation::               Redirect output to multiple files
-
-File name manipulation
-
-* basename invocation::          Strip directory and suffix from a file name
-* dirname invocation::           Strip non-directory suffix from a file name
-* pathchk invocation::           Check file name portability
-
-Working context
-
-* pwd invocation::               Print working directory
-* stty invocation::              Print or change terminal characteristics
-* printenv invocation::          Print all or some environment variables
-* tty invocation::               Print file name of terminal on standard input
-
-@code{stty}: Print or change terminal characteristics
-
-* Control::                     Control settings
-* Input::                       Input settings
-* Output::                      Output settings
-* Local::                       Local settings
-* Combination::                 Combination settings
-* Characters::                  Special characters
-* Special::                     Special settings
-
-User information
-
-* id invocation::                Print real and effective uid and gid
-* logname invocation::           Print current login name
-* whoami invocation::            Print effective user id
-* groups invocation::            Print group names a user is in
-* users invocation::             Print login names of users currently logged in
-* who invocation::               Print who is currently logged in
-
-System context
-
-* date invocation::              Print or set system date and time
-* uname invocation::             Print system information
-* hostname invocation::          Print or set system name
-* hostid invocation::            Print numeric host identifier.
-
-@code{date}: Print or set system date and time
-
-* Time directives::              Time directives
-* Date directives::              Date directives
-* Literal directives::           Literal directives
-* Padding::                      Padding
-* Setting the time::             Setting the time
-* Options for date::             Options for @code{date}
-* Examples of date::             Examples of @code{date}
-
-Modified command invocation
-
-* chroot invocation::            Run a command with a different root directory
-* env invocation::               Run a command in a modified environment
-* nice invocation::              Run a command with modified scheduling priority
-* nohup invocation::             Run a command immune to hangups
-* su invocation::                Run a command with substitute user and group id
-
-Delaying
-
-* sleep invocation::             Delay for a specified time
-
-Numeric operations
-
-* factor invocation::            Print prime factors
-* seq invocation::               Print numeric sequences
-
-File permissions
-
-* Mode Structure::               Structure of File Permissions
-* Symbolic Modes::               Mnemonic permissions representation
-* Numeric Modes::                Permissions as octal numbers
-
-Date input formats
-
-* General date syntax:           General date syntax
-* Calendar date items:           Calendar date items
-* Time of day items:             Time of day items
-* Time zone items:               Time zone items
-* Day of week items:             Day of week items
-* Relative items in date strings:  Relative items in date strings
-* Pure numbers in date strings:  Pure numbers in date strings
-* Authors of getdate:            Authors of getdate
-
-Opening the software toolbox
-
-* Toolbox introduction::         Toolbox introduction
-* I/O redirection::              I/O redirection
-* The who command::              The @code{who} command
-* The cut command::              The @code{cut} command
-* The sort command::             The @code{sort} command
-* The uniq command::             The @code{uniq} command
-* Putting the tools together::   Putting the tools together
-
-GNU Free Documentation License
-
-* How to use this License for your documents::
-
-@end detailmenu
-@end menu
-
-@end ifnottex
-
-
-@node Introduction
-@chapter Introduction
-
-This manual is incomplete: No attempt is made to explain basic concepts
-in a way suitable for novices.  Thus, if you are interested, please get
-involved in improving this manual.  The entire @sc{gnu} community will
-benefit.
-
-@cindex @sc{posix.2}
-The @sc{gnu} utilities documented here are mostly compatible with the
-@sc{posix.2} standard.
-@cindex bugs, reporting
-Please report bugs to @email{bug-omni-utils@@gnu.org}.  Remember
-to include the version number, machine architecture, input files, and
-any other information needed to reproduce the bug: your input, what you
-expected, what you got, and why it is wrong.  Diffs are welcome, but
-please include a description of the problem as well, since this is
-sometimes difficult to infer. @xref{Bugs, , , gcc, Using and Porting GNU CC}.
-
-@cindex Berry, K.
-@cindex Paterson, R.
-@cindex Stallman, R.
-@cindex Pinard, F.
-@cindex MacKenzie, D.
-@cindex Meyering, J.
-@cindex Youmans, B.
-This manual was originally derived from the Unix man pages in the
-distributions, which were written by David MacKenzie and updated by Jim
-Meyering.  What you are reading now is the authoritative documentation
-for these utilities; the man pages are no longer being maintained.  The
-original @code{fmt} man page was written by Ross Paterson.  Fran@,{c}ois
-Pinard did the initial conversion to Texinfo format.  Karl Berry did the
-indexing, some reorganization, and editing of the results.  Brian
-Youmans of the Free Software Foundation office staff combined the
-manuals for textutils, fileutils, and sh-utils to produce the present
-omnibus manual.  Richard Stallman contributed his usual invaluable
-insights to the overall process.
-
-@node Common options
-@chapter Common options
-
-@cindex common options
-
-Certain options are available in all of these programs.  Rather than
-writing identical descriptions for each of the programs, they are
-described here.  (In fact, every @sc{gnu} program accepts (or should accept)
-these options.)
-
-@vindex POSIXLY_CORRECT
-Normally options and operands can appear in any order, and programs act
-as if all the options appear before any operands.  For example,
-@samp{sort -r passwd -t :} acts like @samp{sort -r -t : passwd}, since
-@samp{:} is an option-argument of @option{-t}.  However, if the
-@env{POSIXLY_CORRECT} environment variable is set, options must appear
-before operands, unless otherwise specified for a particular command.
-
-Some of these programs recognize the @samp{--help} and @samp{--version}
-options only when one of them is the sole command line argument.
-
-@table @samp
-
-@item --help
-@opindex --help
-@cindex help, online
-Print a usage message listing all available options, then exit successfully.
-
-@item --version
-@opindex --version
-@cindex version number, finding
-Print the version number, then exit successfully.
-
-@item --
-@opindex --
-@cindex option delimiter
-Delimit the option list.  Later arguments, if any, are treated as
-operands even if they begin with @samp{-}.  For example, @samp{sort --
--r} reads from the file named @file{-r}.
-
-@end table
-
-@cindex standard input
-@cindex standard output
-A single @samp{-} is not really an option, though it looks like one.  It
-stands for standard input, or for standard output if that is clear from
-the context, and it can be used either as an operand or as an
-option-argument.  For example, @samp{sort -o - -} outputs to standard
-output and reads from standard input, and is equivalent to plain
-@samp{sort}.  Unless otherwise specified, @samp{-} can appear in any
-context that requires a file name.
-
-@menu
-* Backup options::              -b -S -V, in some programs.
-* Block size::                  BLOCK_SIZE and --block-size, in some programs.
-* Target directory::            --target-directory, in some programs.
-* Trailing slashes::            --strip-trailing-slashes, in some programs.
-@end menu
-
-
-@node Backup options
-@section Backup options
-
-@cindex backup options
-
-Some @sc{gnu} programs (at least @code{cp}, @code{install}, @code{ln}, and
-@code{mv}) optionally make backups of files before writing new versions.
-These options control the details of these backups.  The options are also
-briefly mentioned in the descriptions of the particular programs.
-
-@table @samp
-
-@item -b
-@itemx @w{@kbd{--backup}[=@var{method}]}
-@opindex -b
-@opindex --backup
-@vindex VERSION_CONTROL
-@cindex backups, making
-Make a backup of each file that would otherwise be overwritten or removed.
-Without this option, the original versions are destroyed.
-Use @var{method} to determine the type of backups to make.
-When this option is used but @var{method} is not specified,
-then the value of the @env{VERSION_CONTROL}
-environment variable is used.  And if @env{VERSION_CONTROL} is not set,
-the default backup type is @samp{existing}.
-
-Note that the short form of this option, @samp{-b} does not accept any
-argument.  Using @samp{-b} is equivalent to using @samp{--backup=existing}.
-
-@vindex version-control @r{Emacs variable}
-This option corresponds to the Emacs variable @samp{version-control};
-the values for @var{method} are the same as those used in Emacs.
-This option also accepts more descriptive names.
-The valid @var{method}s are (unique abbreviations are accepted):
-
-@table @samp
-@item none
-@itemx off
-@opindex none @r{backup method}
-Never make backups.
-
-@item numbered
-@itemx t
-@opindex numbered @r{backup method}
-Always make numbered backups.
-
-@item existing
-@itemx nil
-@opindex existing @r{backup method}
-Make numbered backups of files that already have them, simple backups
-of the others.
-
-@item simple
-@itemx never
-@opindex simple @r{backup method}
-Always make simple backups.  Please note @samp{never} is not to be
-confused with @samp{none}.
-
-@end table
-
-@item -S @var{suffix}
-@itemx --suffix=@var{suffix}
-@opindex -S
-@opindex --suffix
-@cindex backup suffix
-@vindex SIMPLE_BACKUP_SUFFIX
-Append @var{suffix} to each backup file made with @samp{-b}.  If this
-option is not specified, the value of the @env{SIMPLE_BACKUP_SUFFIX}
-environment variable is used.  And if @env{SIMPLE_BACKUP_SUFFIX} is not
-set, the default is @samp{~}, just as in Emacs.
-
-@itemx --version-control=@var{method}
-@opindex --version-control
-@c FIXME: remove this block one or two releases after the actual
-@c removal from the code.
-This option is obsolete and will be removed in a future release.
-It has been replaced with @w{@kbd{--backup}}.
-
-@end table
-
-@node Block size
-@section Block size
-
-@cindex block size
-
-Some @sc{gnu} programs (at least @code{df}, @code{du}, and @code{ls}) display
-file sizes in ``blocks''.  You can adjust the block size to make file
-sizes easier to read.  The block size used for display is independent of
-any filesystem block size.
-
-Normally, disk usage sizes are rounded up, disk free space sizes are
-rounded down, and other sizes are rounded to the nearest value with ties
-rounding to an even value.
-
-@opindex --block-size=@var{size}
-@vindex BLOCK_SIZE
-@vindex DF_BLOCK_SIZE
-@vindex DU_BLOCK_SIZE
-@vindex LS_BLOCK_SIZE
-@vindex POSIXLY_CORRECT@r{, and block size}
-
-The default block size is chosen by examining the following environment
-variables in turn; the first one that is set determines the block size.
-
-@table @code
-
-@item DF_BLOCK_SIZE
-This specifies the default block size for the @code{df} command.
-Similarly, @env{DU_BLOCK_SIZE} specifies the default for @code{du} and
-@env{LS_BLOCK_SIZE} for @code{ls}.
-
-@item BLOCK_SIZE
-This specifies the default block size for all three commands, if the
-above command-specific environment variables are not set.
-
-@item POSIXLY_CORRECT
-If neither the @env{@var{command}_BLOCK_SIZE} nor the @env{BLOCK_SIZE}
-variables are set, but this variable is set, the block size defaults to 512.
-
-@end table
-
-If none of the above environment variables are set, the block size
-currently defaults to 1024 bytes, but this number may change in the
-future.
-
-@cindex human-readable output
-@cindex SI output
-
-A block size specification can be a positive integer specifying the number
-of bytes per block, or it can be @code{human-readable} or @code{si} to
-select a human-readable format.
-
-
-With human-readable formats, output sizes are followed by a size letter
-such as @samp{M} for megabytes.  @code{BLOCK_SIZE=human-readable} uses
-powers of 1024; @samp{M} stands for 1,048,576 bytes.
-@code{BLOCK_SIZE=si} is similar, but uses powers of 1000; @samp{M} stands
-for 1,000,000 bytes.  (SI, the International System of Units, defines
-these power-of-1000 prefixes.)
-
-An integer block size can be followed by a size letter to specify a
-multiple of that size.  When this notation is used, the size letters
-normally stand for powers of 1024, and can be followed by an optional
-@samp{B} for ``byte''; but if followed by @samp{D} (for ``decimal
-byte''), they stand for powers of 1000.  For example,
-@code{BLOCK_SIZE=4MB} is equivalent to @code{BLOCK_SIZE=4194304}, and
-@code{BLOCK_SIZE=4MD} is equivalent to @code{BLOCK_SIZE=4000000}.
-
-The following size letters are defined.  Large sizes like @code{1Y}
-may be rejected by your computer due to limitations of its arithmetic.
-
-@table @samp
-@item k
-kilo: @math{2^10 = 1024} for @code{human-readable},
-or @math{10^3 = 1000} for @code{si}.
-@item M
-Mega: @math{2^20 = 1,048,576}
-or @math{10^6 = 1,000,000}.
-@item G
-Giga: @math{2^30 = 1,073,741,824}
-or @math{10^9 = 1,000,000,000}.
-@item T
-Tera: @math{2^40 = 1,099,511,627,776}
-or @math{10^12 = 1,000,000,000,000}.
-@item P
-Peta: @math{2^50 = 1,125,899,906,842,624}
-or @math{10^15 = 1,000,000,000,000,000}.
-@item E
-Exa: @math{2^60 = 1,152,921,504,606,846,976}@*
-or @math{10^18 = 1,000,000,000,000,000,000}.
-@item Z
-Zetta: @math{2^70 = 1,180,591,620,717,411,303,424}@*
-or @math{10^21 = 1,000,000,000,000,000,000,000}.
-@item Y
-Yotta: @math{2^80 = 1,208,925,819,614,629,174,706,176}@*
-or @math{10^24 = 1,000,000,000,000,000,000,000,000}.
-@end table
-
-@opindex -k
-@opindex --kilobytes
-@opindex -h
-@opindex --human-readable
-@opindex --si
-
-Block size defaults can be overridden by an explicit
-@samp{--block-size=@var{size}} option.  The @samp{-k} or
-@samp{--kilobytes} option is equivalent to @samp{--block-size=1k}, which
-is the default unless the @env{POSIXLY_CORRECT} environment variable is
-set.  The @samp{-h} or @samp{--human-readable} option is equivalent to
-@samp{--block-size=human-readable}.  The @samp{--si} option is
-equivalent to @samp{--block-size=si}.
-
-@node Target directory
-@section Target directory
-
-@cindex target directory
-
-Some @sc{gnu} programs (at least @code{cp}, @code{install}, @code{ln}, and
-@code{mv}) allow you to specify the target directory via this option:
-
-@table @samp
-
-@itemx @w{@kbd{--target-directory}=@var{directory}}
-@opindex --target-directory
-@cindex target directory
-@cindex destination directory
-Specify the destination @var{directory}.
-
-The interface for most programs is that after processing options and a
-finite (possibly zero) number of fixed-position arguments, the remaining
-argument list is either expected to be empty, or is a list of items
-(usually files) that will all be handled identically.  The @code{xargs}
-program is designed to work well with this convention.
-
-The commands in the @code{mv}-family are unusual in that they take
-a variable number of arguments with a special case at the @emph{end}
-(namely, the target directory).  This makes it nontrivial to perform some
-operations, e.g., ``move all files from here to ../d/'', because
-@code{mv * ../d/} might exhaust the argument space, and @code{ls | xargs ...}
-doesn't have a clean way to specify an extra final argument for each
-invocation of the subject command.  (It can be done by going through a
-shell command, but that requires more human labor and brain power than
-it should.)
-
-The @w{@kbd{--target-directory}} option allows the @code{cp},
-@code{install}, @code{ln}, and @code{mv} programs to be used conveniently
-with @code{xargs}.  For example, you can move the files from the
-current directory to a sibling directory, @code{d} like this:
-(However, this doesn't move files whose names begin with @samp{.}.)
-
-@smallexample
-ls |xargs mv --target-directory=../d
-@end smallexample
-
-If you use the @sc{gnu} @code{find} program, you can move @emph{all}
-files with this command:
-@example
-find . -mindepth 1 -maxdepth 1 \
-  | xargs mv --target-directory=../d
-@end example
-
-But that will fail if there are no files in the current directory
-or if any file has a name containing a newline character.
-The following example removes those limitations and requires both
-@sc{gnu} @code{find} and @sc{gnu} @code{xargs}:
-@example
-find . -mindepth 1 -maxdepth 1 -print0 \
-  | xargs --null --no-run-if-empty \
-      mv --target-directory=../d
-@end example
-
-@end table
-
-@node Trailing slashes
-@section Trailing slashes
-
-@cindex trailing slashes
-
-Some @sc{gnu} programs (at least @code{cp} and @code{mv}) allow you to
-remove any trailing slashes from each @var{source} argument before
-operating on it.  The @w{@kbd{--strip-trailing-slashes}} option enables
-this behavior.
-
-This is useful when a @var{source} argument may have a trailing slash and
-specify a symbolic link to a directory.  This scenario is in fact rather
-common because some shells can automatically append a trailing slash when
-performing file name completion on such symbolic links.  Without this
-option, @code{mv}, for example, (via the system's rename function) must
-interpret a trailing slash as a request to dereference the symbolic link
-and so must rename the indirectly referenced @emph{directory} and not
-the symbolic link.  Although it may seem surprising that such behavior
-be the default, it is required by @sc{posix.2} and is consistent with
-other parts of that standard.
-
-@node Output of entire files
-@chapter Output of entire files
-
-@cindex output of entire files
-@cindex entire files, output of
-
-These commands read and write entire files, possibly transforming them
-in some way.
-
-@menu
-* cat invocation::              Concatenate and write files.
-* tac invocation::              Concatenate and write files in reverse.
-* nl invocation::               Number lines and write files.
-* od invocation::               Write files in octal or other formats.
-@end menu
-
-@node cat invocation
-@section @code{cat}: Concatenate and write files
-
-@pindex cat
-@cindex concatenate and write files
-@cindex copying files
-
-@code{cat} copies each @var{file} (@samp{-} means standard input), or
-standard input if none are given, to standard output.  Synopsis:
-
-@example
-cat [@var{option}] [@var{file}]@dots{}
-@end example
-
-The program accepts the following options.  Also see @ref{Common options}.
-
-@table @samp
-
-@item -A
-@itemx --show-all
-@opindex -A
-@opindex --show-all
-Equivalent to @samp{-vET}.
-
-@item -B
-@itemx --binary
-@opindex -B
-@opindex --binary
-@cindex binary and text I/O in cat
-On MS-DOS and MS-Windows only, read and write the files in binary mode.
-By default, @code{cat} on MS-DOS/MS-Windows uses binary mode only when
-standard output is redirected to a file or a pipe; this option overrides
-that.  Binary file I/O is used so that the files retain their format
-(Unix text as opposed to DOS text and binary), because @code{cat} is
-frequently used as a file-copying program.  Some options (see below)
-cause @code{cat} to read and write files in text mode because in those
-cases the original file contents aren't important (e.g., when lines are
-numbered by @code{cat}, or when line endings should be marked).  This is
-so these options work as DOS/Windows users would expect; for example,
-DOS-style text files have their lines end with the CR-LF pair of
-characters, which won't be processed as an empty line by @samp{-b} unless
-the file is read in text mode.
-
-@item -b
-@itemx --number-nonblank
-@opindex -b
-@opindex --number-nonblank
-Number all nonblank output lines, starting with 1.  On MS-DOS and
-MS-Windows, this option causes @code{cat} to read and write files in
-text mode.
-
-@item -e
-@opindex -e
-Equivalent to @samp{-vE}.
-
-@item -E
-@itemx --show-ends
-@opindex -E
-@opindex --show-ends
-Display a @samp{$} after the end of each line.  On MS-DOS and
-MS-Windows, this option causes @code{cat} to read and write files in
-text mode.
-
-@item -n
-@itemx --number
-@opindex -n
-@opindex --number
-Number all output lines, starting with 1.  On MS-DOS and MS-Windows,
-this option causes @code{cat} to read and write files in text mode.
-
-@item -s
-@itemx --squeeze-blank
-@opindex -s
-@opindex --squeeze-blank
-@cindex squeezing blank lines
-Replace multiple adjacent blank lines with a single blank line.  On
-MS-DOS and MS-Windows, this option causes @code{cat} to read and write
-files in text mode.
-
-@item -t
-@opindex -t
-Equivalent to @samp{-vT}.
-
-@item -T
-@itemx --show-tabs
-@opindex -T
-@opindex --show-tabs
-Display TAB characters as @samp{^I}.
-
-@item -u
-@opindex -u
-Ignored; for Unix compatibility.
-
-@item -v
-@itemx --show-nonprinting
-@opindex -v
-@opindex --show-nonprinting
-Display control characters except for LFD and TAB using
-@samp{^} notation and precede characters that have the high bit set with
-@samp{M-}.  On MS-DOS and MS-Windows, this option causes @code{cat} to
-read files and standard input in DOS binary mode, so the CR
-characters at the end of each line are also visible.
-
-@end table
-
-
-@node tac invocation
-@section @code{tac}: Concatenate and write files in reverse
-
-@pindex tac
-@cindex reversing files
-
-@code{tac} copies each @var{file} (@samp{-} means standard input), or
-standard input if none are given, to standard output, reversing the
-records (lines by default) in each separately.  Synopsis:
-
-@example
-tac [@var{option}]@dots{} [@var{file}]@dots{}
-@end example
-
-@dfn{Records} are separated by instances of a string (newline by
-default).  By default, this separator string is attached to the end of
-the record that it follows in the file.
-
-The program accepts the following options.  Also see @ref{Common options}.
-
-@table @samp
-
-@item -b
-@itemx --before
-@opindex -b
-@opindex --before
-The separator is attached to the beginning of the record that it
-precedes in the file.
-
-@item -r
-@itemx --regex
-@opindex -r
-@opindex --regex
-Treat the separator string as a regular expression.  Users of @code{tac}
-on MS-DOS/MS-Windows should note that, since @code{tac} reads files in
-binary mode, each line of a text file might end with a CR/LF pair
-instead of the Unix-style LF.
-
-@item -s @var{separator}
-@itemx --separator=@var{separator}
-@opindex -s
-@opindex --separator
-Use @var{separator} as the record separator, instead of newline.
-
-@end table
-
-
-@node nl invocation
-@section @code{nl}: Number lines and write files
-
-@pindex nl
-@cindex numbering lines
-@cindex line numbering
-
-@code{nl} writes each @var{file} (@samp{-} means standard input), or
-standard input if none are given, to standard output, with line numbers
-added to some or all of the lines.  Synopsis:
-
-@example
-nl [@var{option}]@dots{} [@var{file}]@dots{}
-@end example
-
-@cindex logical pages, numbering on
-@code{nl} decomposes its input into (logical) pages; by default, the
-line number is reset to 1 at the top of each logical page.  @code{nl}
-treats all of the input files as a single document; it does not reset
-line numbers or logical pages between files.
-
-@cindex headers, numbering
-@cindex body, numbering
-@cindex footers, numbering
-A logical page consists of three sections: header, body, and footer.
-Any of the sections can be empty.  Each can be numbered in a different
-style from the others.
-
-The beginnings of the sections of logical pages are indicated in the
-input file by a line containing exactly one of these delimiter strings:
-
-@table @samp
-@item \:\:\:
-start of header;
-@item \:\:
-start of body;
-@item \:
-start of footer.
-@end table
-
-The two characters from which these strings are made can be changed from
-@samp{\} and @samp{:} via options (see below), but the pattern and
-length of each string cannot be changed.
-
-A section delimiter is replaced by an empty line on output.  Any text
-that comes before the first section delimiter string in the input file
-is considered to be part of a body section, so @code{nl} treats a
-file that contains no section delimiters as a single body section.
-
-The program accepts the following options.  Also see @ref{Common options}.
-
-@table @samp
-
-@item -b @var{style}
-@itemx --body-numbering=@var{style}
-@opindex -b
-@opindex --body-numbering
-Select the numbering style for lines in the body section of each
-logical page.  When a line is not numbered, the current line number
-is not incremented, but the line number separator character is still
-prepended to the line.  The styles are:
-
-@table @samp
-@item a
-number all lines,
-@item t
-number only nonempty lines (default for body),
-@item n
-do not number lines (default for header and footer),
-@item p@var{regexp}
-number only lines that contain a match for @var{regexp}.
-@end table
-
-@item -d @var{cd}
-@itemx --section-delimiter=@var{cd}
-@opindex -d
-@opindex --section-delimiter
-@cindex section delimiters of pages
-Set the section delimiter characters to @var{cd}; default is
-@samp{\:}. If only @var{c} is given, the second remains @samp{:}.
-(Remember to protect @samp{\} or other metacharacters from shell
-expansion with quotes or extra backslashes.)
-
-@item -f @var{style}
-@itemx --footer-numbering=@var{style}
-@opindex -f
-@opindex --footer-numbering
-Analogous to @samp{--body-numbering}.
-
-@item -h @var{style}
-@itemx --header-numbering=@var{style}
-@opindex -h
-@opindex --header-numbering
-Analogous to @samp{--body-numbering}.
-
-@item -i @var{number}
-@itemx --page-increment=@var{number}
-@opindex -i
-@opindex --page-increment
-Increment line numbers by @var{number} (default 1).
-
-@item -l @var{number}
-@itemx --join-blank-lines=@var{number}
-@opindex -l
-@opindex --join-blank-lines
-@cindex empty lines, numbering
-@cindex blank lines, numbering
-Consider @var{number} (default 1) consecutive empty lines to be one
-logical line for numbering, and only number the last one.  Where fewer
-than @var{number} consecutive empty lines occur, do not number them.
-An empty line is one that contains no characters, not even spaces
-or tabs.
-
-@item -n @var{format}
-@itemx --number-format=@var{format}
-@opindex -n
-@opindex --number-format
-Select the line numbering format (default is @code{rn}):
-
-@table @samp
-@item ln
-@opindex ln @r{format for @code{nl}}
-left justified, no leading zeros;
-@item rn
-@opindex rn @r{format for @code{nl}}
-right justified, no leading zeros;
-@item rz
-@opindex rz @r{format for @code{nl}}
-right justified, leading zeros.
-@end table
-
-@item -p
-@itemx --no-renumber
-@opindex -p
-@opindex --no-renumber
-Do not reset the line number at the start of a logical page.
-
-@item -s @var{string}
-@itemx --number-separator=@var{string}
-@opindex -s
-@opindex --number-separator
-Separate the line number from the text line in the output with
-@var{string} (default is the TAB character).
-
-@item -v @var{number}
-@itemx --starting-line-number=@var{number}
-@opindex -v
-@opindex --starting-line-number
-Set the initial line number on each logical page to @var{number} (default 1).
-
-@item -w @var{number}
-@itemx --number-width=@var{number}
-@opindex -w
-@opindex --number-width
-Use @var{number} characters for line numbers (default 6).
-
-@end table
-
-
-@node od invocation
-@section @code{od}: Write files in octal or other formats
-
-@pindex od
-@cindex octal dump of files
-@cindex hex dump of files
-@cindex ASCII dump of files
-@cindex file contents, dumping unambiguously
-
-@code{od} writes an unambiguous representation of each @var{file}
-(@samp{-} means standard input), or standard input if none are given.
-Synopsis:
-
-@example
-od [@var{option}]@dots{} [@var{file}]@dots{}
-od -C [@var{file}] [[+]@var{offset} [[+]@var{label}]]
-@end example
-
-Each line of output consists of the offset in the input, followed by
-groups of data from the file. By default, @code{od} prints the offset in
-octal, and each group of file data is two bytes of input printed as a
-single octal number.
-
-The program accepts the following options.  Also see @ref{Common options}.
-
-@table @samp
-
-@item -A @var{radix}
-@itemx --address-radix=@var{radix}
-@opindex -A
-@opindex --address-radix
-@cindex radix for file offsets
-@cindex file offset radix
-Select the base in which file offsets are printed.  @var{radix} can
-be one of the following:
-
-@table @samp
-@item d
-decimal;
-@item o
-octal;
-@item x
-hexadecimal;
-@item n
-none (do not print offsets).
-@end table
-
-The default is octal.
-
-@item -j @var{bytes}
-@itemx --skip-bytes=@var{bytes}
-@opindex -j
-@opindex --skip-bytes
-Skip @var{bytes} input bytes before formatting and writing.  If
-@var{bytes} begins with @samp{0x} or @samp{0X}, it is interpreted in
-hexadecimal; otherwise, if it begins with @samp{0}, in octal; otherwise,
-in decimal.  Appending @samp{b} multiplies @var{bytes} by 512, @samp{k}
-by 1024, and @samp{m} by 1048576.
-
-@item -N @var{bytes}
-@itemx --read-bytes=@var{bytes}
-@opindex -N
-@opindex --read-bytes
-Output at most @var{bytes} bytes of the input.  Prefixes and suffixes on
-@code{bytes} are interpreted as for the @samp{-j} option.
-
-@item -s [@var{n}]
-@itemx --strings[=@var{n}]
-@opindex -s
-@opindex --strings
-@cindex string constants, outputting
-Instead of the normal output, output only @dfn{string constants}: at
-least @var{n} (3 by default) consecutive @sc{ascii} graphic characters,
-followed by a null (zero) byte.
-
-@item -t @var{type}
-@itemx --format=@var{type}
-@opindex -t
-@opindex --format
-Select the format in which to output the file data.  @var{type} is a
-string of one or more of the below type indicator characters.  If you
-include more than one type indicator character in a single @var{type}
-string, or use this option more than once, @code{od} writes one copy
-of each output line using each of the data types that you specified,
-in the order that you specified.
-
-Adding a trailing ``z'' to any type specification appends a display
-of the @sc{ascii} character representation of the printable characters
-to the output line generated by the type specification.
-
-@table @samp
-@item a
-named character
-@item c
-@sc{ascii} character or backslash escape,
-@item d
-signed decimal
-@item f
-floating point
-@item o
-octal
-@item u
-unsigned decimal
-@item x
-hexadecimal
-@end table
-
-The type @code{a} outputs things like @samp{sp} for space, @samp{nl} for
-newline, and @samp{nul} for a null (zero) byte.  Type @code{c} outputs
-@samp{ }, @samp{\n}, and @code{\0}, respectively.
-
-@cindex type size
-Except for types @samp{a} and @samp{c}, you can specify the number
-of bytes to use in interpreting each number in the given data type
-by following the type indicator character with a decimal integer.
-Alternately, you can specify the size of one of the C compiler's
-built-in data types by following the type indicator character with
-one of the following characters.  For integers (@samp{d}, @samp{o},
-@samp{u}, @samp{x}):
-
-@table @samp
-@item C
-char
-@item S
-short
-@item I
-int
-@item L
-long
-@end table
-
-For floating point (@code{f}):
-
-@table @asis
-@item F
-float
-@item D
-double
-@item L
-long double
-@end table
-
-@item -v
-@itemx --output-duplicates
-@opindex -v
-@opindex --output-duplicates
-Output consecutive lines that are identical.  By default, when two or
-more consecutive output lines would be identical, @code{od} outputs only
-the first line, and puts just an asterisk on the following line to
-indicate the elision.
-
-@item -w[@var{n}]
-@itemx --width[=@var{n}]
-@opindex -w
-@opindex --width
-Dump @code{n} input bytes per output line.  This must be a multiple of
-the least common multiple of the sizes associated with the specified
-output types.  If @var{n} is omitted, the default is 32.  If this option
-is not given at all, the default is 16.
-
-@end table
-
-The next several options map the old, pre-@sc{posix} format specification
-options to the corresponding @sc{posix} format specs.
-@sc{gnu} @code{od} accepts
-any combination of old- and new-style options.  Format specification
-options accumulate.
-
-@table @samp
-
-@item -a
-@opindex -a
-Output as named characters.  Equivalent to @samp{-ta}.
-
-@item -b
-@opindex -b
-Output as octal bytes.  Equivalent to @samp{-toC}.
-
-@item -c
-@opindex -c
-Output as @sc{ascii} characters or backslash escapes.  Equivalent to
-@samp{-tc}.
-
-@item -d
-@opindex -d
-Output as unsigned decimal shorts.  Equivalent to @samp{-tu2}.
-
-@item -f
-@opindex -f
-Output as floats.  Equivalent to @samp{-tfF}.
-
-@item -h
-@opindex -h
-Output as hexadecimal shorts.  Equivalent to @samp{-tx2}.
-
-@item -i
-@opindex -i
-Output as decimal shorts.  Equivalent to @samp{-td2}.
-
-@item -l
-@opindex -l
-Output as decimal longs.  Equivalent to @samp{-td4}.
-
-@item -o
-@opindex -o
-Output as octal shorts.  Equivalent to @samp{-to2}.
-
-@item -x
-@opindex -x
-Output as hexadecimal shorts.  Equivalent to @samp{-tx2}.
-
-@item -C
-@itemx --traditional
-@opindex --traditional
-Recognize the pre-@sc{posix} non-option arguments that traditional @code{od}
-accepted.  The following syntax:
-
-@smallexample
-od --traditional [@var{file}] [[+]@var{offset}[.][b] [[+]@var{label}[.][b]]]
-@end smallexample
-
-@noindent
-can be used to specify at most one file and optional arguments
-specifying an offset and a pseudo-start address, @var{label}.  By
-default, @var{offset} is interpreted as an octal number specifying how
-many input bytes to skip before formatting and writing.  The optional
-trailing decimal point forces the interpretation of @var{offset} as a
-decimal number.  If no decimal is specified and the offset begins with
-@samp{0x} or @samp{0X} it is interpreted as a hexadecimal number.  If
-there is a trailing @samp{b}, the number of bytes skipped will be
-@var{offset} multiplied by 512.  The @var{label} argument is interpreted
-just like @var{offset}, but it specifies an initial pseudo-address.  The
-pseudo-addresses are displayed in parentheses following any normal
-address.
-
-@end table
-
-
-@node Formatting file contents
-@chapter Formatting file contents
-
-@cindex formatting file contents
-
-These commands reformat the contents of files.
-
-@menu
-* fmt invocation::              Reformat paragraph text.
-* pr invocation::               Paginate or columnate files for printing.
-* fold invocation::             Wrap input lines to fit in specified width.
-@end menu
-
-
-@node fmt invocation
-@section @code{fmt}: Reformat paragraph text
-
-@pindex fmt
-@cindex reformatting paragraph text
-@cindex paragraphs, reformatting
-@cindex text, reformatting
-
-@code{fmt} fills and joins lines to produce output lines of (at most)
-a given number of characters (75 by default).  Synopsis:
-
-@example
-fmt [@var{option}]@dots{} [@var{file}]@dots{}
-@end example
-
-@code{fmt} reads from the specified @var{file} arguments (or standard
-input if none are given), and writes to standard output.
-
-By default, blank lines, spaces between words, and indentation are
-preserved in the output; successive input lines with different
-indentation are not joined; tabs are expanded on input and introduced on
-output.
-
-@cindex line-breaking
-@cindex sentences and line-breaking
-@cindex Knuth, Donald E.
-@cindex Plass, Michael F.
-@code{fmt} prefers breaking lines at the end of a sentence, and tries to
-avoid line breaks after the first word of a sentence or before the last
-word of a sentence.  A @dfn{sentence break} is defined as either the end
-of a paragraph or a word ending in any of @samp{.?!}, followed by two
-spaces or end of line, ignoring any intervening parentheses or quotes.
-Like @TeX{}, @code{fmt} reads entire ``paragraphs'' before choosing line
-breaks; the algorithm is a variant of that in ``Breaking Paragraphs Into
-Lines'' (Donald E. Knuth and Michael F. Plass, @cite{Software---Practice
-and Experience}, 11 (1981), 1119--1184).
-
-The program accepts the following options.  Also see @ref{Common options}.
-
-@table @samp
-
-@item -c
-@itemx --crown-margin
-@opindex -c
-@opindex --crown-margin
-@cindex crown margin
-@dfn{Crown margin} mode: preserve the indentation of the first two
-lines within a paragraph, and align the left margin of each subsequent
-line with that of the second line.
-
-@item -t
-@itemx --tagged-paragraph
-@opindex -t
-@opindex --tagged-paragraph
-@cindex tagged paragraphs
-@dfn{Tagged paragraph} mode: like crown margin mode, except that if
-indentation of the first line of a paragraph is the same as the
-indentation of the second, the first line is treated as a one-line
-paragraph.
-
-@item -s
-@itemx --split-only
-@opindex -s
-@opindex --split-only
-Split lines only.  Do not join short lines to form longer ones.  This
-prevents sample lines of code, and other such ``formatted'' text from
-being unduly combined.
-
-@item -u
-@itemx --uniform-spacing
-@opindex -u
-@opindex --uniform-spacing
-Uniform spacing.  Reduce spacing between words to one space, and spacing
-between sentences to two spaces.
-
-@item -@var{width}
-@itemx -w @var{width}
-@itemx --width=@var{width}
-@opindex -@var{width}
-@opindex -w
-@opindex --width
-Fill output lines up to @var{width} characters (default 75).  @code{fmt}
-initially tries to make lines about 7% shorter than this, to give it
-room to balance line lengths.
-
-@item -p @var{prefix}
-@itemx --prefix=@var{prefix}
-Only lines beginning with @var{prefix} (possibly preceded by whitespace)
-are subject to formatting. The prefix and any preceding whitespace are
-stripped for the formatting and then re-attached to each formatted output
-line.  One use is to format certain kinds of program comments, while
-leaving the code unchanged.
-
-@end table
-
-
-@node pr invocation
-@section @code{pr}: Paginate or columnate files for printing
-
-@pindex pr
-@cindex printing, preparing files for
-@cindex multicolumn output, generating
-@cindex merging files in parallel
-
-@code{pr} writes each @var{file} (@samp{-} means standard input), or
-standard input if none are given, to standard output, paginating and
-optionally outputting in multicolumn format; optionally merges all
-@var{file}s, printing all in parallel, one per column.  Synopsis:
-
-@example
-pr [@var{option}]@dots{} [@var{file}]@dots{}
-@end example
-
-@vindex LC_MESSAGES
-By default, a 5-line header is printed at each page: two blank lines;
-a line with the date, the filename, and the page count; and two more
-blank lines.  A footer of five blank lines is also printed.  With the @samp{-F}
-option, a 3-line header is printed: the leading two blank lines are
-omitted; no footer is used.  The default @var{page_length} in both cases is 66
-lines.  The default number of text lines changes from 56 (without @samp{-F})
-to 63 (with @samp{-F}).  The text line of the header takes the form
-@samp{@var{date} @var{string} @var{page}}, with spaces inserted around
-@var{string} so that the line takes up the full @var{page_width}.  Here,
-@var{date} is the date (see the @option{-D} or @option{--date-format}
-option for details), @var{string} is the centered header string, and
-@var{page} identifies the page number.  The @env{LC_MESSAGES} locale
-category affects the spelling of @var{page}; in the default C locale, it
-is @samp{Page @var{number}} where @var{number} is the decimal page
-number.
-
-Form feeds in the input cause page breaks in the output.  Multiple form
-feeds produce empty pages.
-
-Columns are of equal width, separated by an optional string (default
-is @samp{space}).  For multicolumn output, lines will always be truncated to
-@var{page_width} (default 72), unless you use the @samp{-J} option.  For single
-column output no line truncation occurs by default.  Use @samp{-W} option to
-truncate lines in that case.
-
-The following changes were made in version 1.22i and apply to later
-versions of @command{pr}:
-@c FIXME: this whole section here sounds very awkward to me. I
-@c made a few small changes, but really it all needs to be redone. - Brian
-@c OK, I fixed another sentence or two, but some of it I just don't understand.
-@ - Brian
-@itemize @bullet
-
-@item
-Some small @var{letter options} (@samp{-s}, @samp{-w}) have been
-redefined for better @sc{posix} compliance.  The output of some further
-cases has been adapted to other Unix systems.  These changes are not
-compatible with earlier versions of the program.
-
-@item
-Some @var{new capital letter} options (@samp{-J}, @samp{-S}, @samp{-W})
-have been introduced to turn off unexpected interferences of small letter
-options.  The @samp{-N} option and the second argument @var{last_page}
-of @samp{+FIRST_PAGE} offer more flexibility.  The detailed handling of
-form feeds set in the input files requires the @samp{-T} option.
-
-@item
-Capital letter options override small letter ones.
-
-@item
-Some of the option-arguments (compare @samp{-s}, @samp{-S}, @samp{-e},
-@samp{-i}, @samp{-n}) cannot be specified as separate arguments from the
-preceding option letter (already stated in the @sc{posix} specification).
-@end itemize
-
-The program accepts the following options.  Also see @ref{Common options}.
-
-@table @samp
-
-@item +@var{first_page}[:@var{last_page}]
-@itemx --pages=@var{first_page}[:@var{last_page}]
-@opindex +@var{first_page}[:@var{last_page}]
-@opindex --pages
-Begin printing with page @var{first_page} and stop with @var{last_page}.
-Missing @samp{:@var{last_page}} implies end of file.  While estimating
-the number of skipped pages each form feed in the input file results
-in a new page.  Page counting with and without @samp{+@var{first_page}}
-is identical.  By default, counting starts with the first page of input
-file (not first page printed).  Line numbering may be altered by @samp{-N}
-option.
-
-@item -@var{column}
-@itemx --columns=@var{column}
-@opindex -@var{column}
-@opindex --columns
-@cindex down columns
-With each single @var{file}, produce @var{column} columns of output
-(default is 1) and print columns down, unless @samp{-a} is used.  The
-column width is automatically decreased as @var{column} increases; unless
-you use the @samp{-W/-w} option to increase @var{page_width} as well.
-This option might well cause some lines to be truncated.  The number of
-lines in the columns on each page are balanced.  The options @samp{-e}
-and @samp{-i} are on for multiple text-column output.  Together with
-@samp{-J} option column alignment and line truncation is turned off.
-Lines of full length are joined in a free field format and @samp{-S}
-option may set field separators.  @samp{-@var{column}} may not be used
-with @samp{-m} option.
-
-@item -a
-@itemx --across
-@opindex -a
-@opindex --across
-@cindex across columns
-With each single @var{file}, print columns across rather than down.  The
-@samp{-@var{column}} option must be given with @var{column} greater than one.
-If a line is too long to fit in a column, it is truncated.
-
-@item -c
-@itemx --show-control-chars
-@opindex -c
-@opindex --show-control-chars
-Print control characters using hat notation (e.g., @samp{^G}); print
-other nonprinting characters in octal backslash notation.  By default,
-nonprinting characters are not changed.
-
-@item -d
-@itemx --double-space
-@opindex -d
-@opindex --double-space
-@cindex double spacing
-Double space the output.
-
-@item -D @var{format}
-@itemx --date-format=@var{format}
-@cindex time formats
-@cindex formatting times
-Format header dates using @var{format}, using the same conventions as
-for the the command @samp{date +@var{format}}; @xref{date invocation, ,
-,sh-utils,GNU shell utilities}.  Except for directives, which start with
-@samp{%}, characters in @var{format} are printed unchanged.  You can use
-this option to specify an arbitrary string in place of the header date,
-e.g., @samp{--date-format="Monday morning"}.
-
-@vindex POSIXLY_CORRECT
-@vindex LC_TIME
-If the @env{POSIXLY_CORRECT} environment variable is not set, the date
-format defaults to @samp{%Y-%m-%d %H:%M} (for example, @samp{2001-12-04
-23:59}); otherwise, the format depends on the @env{LC_TIME} locale
-category, with the default being @samp{%b %e %H:%M %Y} (for example,
-@samp{Dec@ @ 4 23:59 2001}.
-
-@item -e[@var{in-tabchar}[@var{in-tabwidth}]]
-@itemx --expand-tabs[=@var{in-tabchar}[@var{in-tabwidth}]]
-@opindex -e
-@opindex --expand-tabs
-@cindex input tabs
-Expand @var{tab}s to spaces on input.  Optional argument @var{in-tabchar} is
-the input tab character (default is the TAB character).  Second optional
-argument @var{in-tabwidth} is the input tab character's width (default
-is 8).
-
-@item -f
-@itemx -F
-@itemx --form-feed
-@opindex -F
-@opindex -f
-@opindex --form-feed
-Use a form feed instead of newlines to separate output pages.  The default
-page length of 66 lines is not altered.  But the number of lines of text
-per page changes from default 56 to 63 lines.
-
-@item -h @var{HEADER}
-@itemx --header=@var{HEADER}
-@opindex -h
-@opindex --header
-Replace the filename in the header with the centered string @var{header}.
-When using the shell, @var{header} should be quoted and should be
-separated from @option{-h} by a space.
-
-@item -i[@var{out-tabchar}[@var{out-tabwidth}]]
-@itemx --output-tabs[=@var{out-tabchar}[@var{out-tabwidth}]]
-@opindex -i
-@opindex --output-tabs
-@cindex output tabs
-Replace spaces with @var{tab}s on output.  Optional argument @var{out-tabchar}
-is the output tab character (default is the TAB character).  Second optional
-argument @var{out-tabwidth} is the output tab character's width (default
-is 8).
-
-@item -J
-@itemx --join-lines
-@opindex -J
-@opindex --join-lines
-Merge lines of full length.  Used together with the column options
-@samp{-@var{column}}, @samp{-a -@var{column}} or @samp{-m}.  Turns off
-@samp{-W/-w} line truncation;
-no column alignment used; may be used with @samp{-S[@var{string}]}.
-@samp{-J} has been introduced (together with @samp{-W} and @samp{-S})
-to disentangle the old (@sc{posix}-compliant) options @samp{-w} and
-@samp{-s} along with the three column options.
-
-
-@item -l @var{page_length}
-@itemx --length=@var{page_length}
-@opindex -l
-@opindex --length
-Set the page length to @var{page_length} (default 66) lines, including
-the lines of the header [and the footer].  If @var{page_length} is less
-than or equal to 10 (or <= 3 with @samp{-F}), the header and footer are
-omitted, and all form feeds set in input files are eliminated, as if
-the @samp{-T} option had been given.
-
-@item -m
-@itemx --merge
-@opindex -m
-@opindex --merge
-Merge and print all @var{file}s in parallel, one in each column.  If a
-line is too long to fit in a column, it is truncated, unless the @samp{-J}
-option is used.  @samp{-S[@var{string}]} may be used.  Empty pages in
-some @var{file}s (form feeds set) produce empty columns, still marked
-by @var{string}.  The result is a continuous line numbering and column
-marking throughout the whole merged file.  Completely empty merged pages
-show no separators or line numbers.  The default header becomes
-@samp{@var{date} @var{page}} with spaces inserted in the middle; this
-may be used with the @option{-h} or @option{--header} option to fill up
-the middle blank part.
-
-@item -n[@var{number-separator}[@var{digits}]]
-@itemx --number-lines[=@var{number-separator}[@var{digits}]]
-@opindex -n
-@opindex --number-lines
-Provide @var{digits} digit line numbering (default for @var{digits} is
-5).  With multicolumn output the number occupies the first @var{digits}
-column positions of each text column or only each line of @samp{-m}
-output.  With single column output the number precedes each line just as
-@samp{-m} does.  Default counting of the line numbers starts with the
-first line of the input file (not the first line printed, compare the
-@samp{--page} option and @samp{-N} option).
-Optional argument @var{number-separator} is the character appended to
-the line number to separate it from the text followed.  The default
-separator is the TAB character.  In a strict sense a TAB is always
-printed with single column output only.  The @var{TAB}-width varies
-with the @var{TAB}-position, e.g. with the left @var{margin} specified
-by @samp{-o} option.  With multicolumn output priority is given to
-@samp{equal width of output columns} (a @sc{posix} specification).
-The @var{TAB}-width is fixed to the value of the first column and does
-not change with different values of left @var{margin}.  That means a
-fixed number of spaces is always printed in the place of the
-@var{number-separator tab}.  The tabification depends upon the output
-position.
-
-@item -N @var{line_number}
-@itemx --first-line-number=@var{line_number}
-@opindex -N
-@opindex --first-line-number
-Start line counting with the number @var{line_number} at first line of
-first page printed (in most cases not the first line of the input file).
-
-@item -o @var{margin}
-@itemx --indent=@var{margin}
-@opindex -o
-@opindex --indent
-@cindex indenting lines
-@cindex left margin
-Indent each line with a margin @var{margin} spaces wide (default is zero).
-The total page width is the size of the margin plus the @var{page_width}
-set with the @samp{-W/-w} option.  A limited overflow may occur with
-numbered single column output (compare @samp{-n} option).
-
-@item -r
-@itemx --no-file-warnings
-@opindex -r
-@opindex --no-file-warnings
-Do not print a warning message when an argument @var{file} cannot be
-opened.  (The exit status will still be nonzero, however.)
-
-@item -s[@var{char}]
-@itemx --separator[=@var{char}]
-@opindex -s
-@opindex --separator
-Separate columns by a single character @var{char}.  The default for
-@var{char} is the TAB character without @samp{-w} and @samp{no
-character} with @samp{-w}.  Without @samp{-s} the default separator
-@samp{space} is set.  @samp{-s[char]} turns off line truncation of all
-three column options (@samp{-COLUMN}|@samp{-a -COLUMN}|@samp{-m}) unless
-@samp{-w} is set.  This is a @sc{posix}-compliant formulation.
-
-
-@item -S[@var{string}]
-@itemx --sep-string[=@var{string}]
-@opindex -S
-@opindex --sep-string
-Use @var{string} to separate output columns.  The @samp{-S} option doesn't
-affect the @samp{-W/-w} option, unlike the @samp{-s} option which does.  It
-does not affect line truncation or column alignment.
-Without @samp{-S}, and with @samp{-J}, @code{pr} uses the default output
-separator, TAB.
-Without @samp{-S} or @samp{-J}, @code{pr} uses a @samp{space}
-(same as @samp{-S" "}).
-Using @samp{-S} with no @var{string} is equivalent to @samp{-S""}.
-Note that for some of @code{pr}'s options the single-letter option
-character must be followed immediately by any corresponding argument;
-there may not be any intervening white space.
-@samp{-S/-s} is one of them.  Don't use @samp{-S "STRING"}.
-@sc{posix} requires this.
-
-@item -t
-@itemx --omit-header
-@opindex -t
-@opindex --omit-header
-Do not print the usual header [and footer] on each page, and do not fill
-out the bottom of pages (with blank lines or a form feed).  No page
-structure is produced, but form feeds set in the input files are retained.
-The predefined pagination is not changed.  @samp{-t} or @samp{-T} may be
-useful together with other options; e.g.: @samp{-t -e4}, expand TAB characters
-in the input file to 4 spaces but don't make any other changes.  Use of
-@samp{-t} overrides @samp{-h}.
-
-@item -T
-@itemx --omit-pagination
-@opindex -T
-@opindex --omit-pagination
-Do not print header [and footer].  In addition eliminate all form feeds
-set in the input files.
-
-@item -v
-@itemx --show-nonprinting
-@opindex -v
-@opindex --show-nonprinting
-Print nonprinting characters in octal backslash notation.
-
-@item -w @var{page_width}
-@itemx --width=@var{page_width}
-@opindex -w
-@opindex --width
-Set page width to @var{page_width} characters for multiple text-column
-output only (default for @var{page_width} is 72).  @samp{-s[CHAR]} turns
-off the default page width and any line truncation and column alignment.
-Lines of full length are merged, regardless of the column options
-set.  No @var{page_width} setting is possible with single column output.
-A @sc{posix}-compliant formulation.
-
-@item -W @var{page_width}
-@itemx --page_width=@var{page_width}
-@opindex -W
-@opindex --page_width
-Set the page width to @var{page_width} characters.  That's valid with and
-without a column option.  Text lines are truncated, unless @samp{-J}
-is used.  Together with one of the three column options
-(@samp{-@var{column}}, @samp{-a -@var{column}} or @samp{-m}) column
-alignment is always used.  The separator options @samp{-S} or @samp{-s}
-don't affect the @samp{-W} option.  Default is 72 characters.  Without
-@samp{-W @var{page_width}} and without any of the column options NO line
-truncation is used (defined to keep downward compatibility and to meet
-most frequent tasks).  That's equivalent to @samp{-W 72 -J}.  The header
-line is never truncated.
-
-@end table
-
-
-@node fold invocation
-@section @code{fold}: Wrap input lines to fit in specified width
-
-@pindex fold
-@cindex wrapping long input lines
-@cindex folding long input lines
-
-@code{fold} writes each @var{file} (@samp{-} means standard input), or
-standard input if none are given, to standard output, breaking long
-lines.  Synopsis:
-
-@example
-fold [@var{option}]@dots{} [@var{file}]@dots{}
-@end example
-
-By default, @code{fold} breaks lines wider than 80 columns.  The output
-is split into as many lines as necessary.
-
-@cindex screen columns
-@code{fold} counts screen columns by default; thus, a tab may count more
-than one column, backspace decreases the column count, and carriage
-return sets the column to zero.
-
-The program accepts the following options.  Also see @ref{Common options}.
-
-@table @samp
-
-@item -b
-@itemx --bytes
-@opindex -b
-@opindex --bytes
-Count bytes rather than columns, so that tabs, backspaces, and carriage
-returns are each counted as taking up one column, just like other
-characters.
-
-@item -s
-@itemx --spaces
-@opindex -s
-@opindex --spaces
-Break at word boundaries: the line is broken after the last blank before
-the maximum line length.  If the line contains no such blanks, the line
-is broken at the maximum line length as usual.
-
-@item -w @var{width}
-@itemx --width=@var{width}
-@opindex -w
-@opindex --width
-Use a maximum line length of @var{width} columns instead of 80.
-
-@end table
-
-
-@node Output of parts of files
-@chapter Output of parts of files
-
-@cindex output of parts of files
-@cindex parts of files, output of
-
-These commands output pieces of the input.
-
-@menu
-* head invocation::             Output the first part of files.
-* tail invocation::             Output the last part of files.
-* split invocation::            Split a file into fixed-size pieces.
-* csplit invocation::           Split a file into context-determined pieces.
-@end menu
-
-@node head invocation
-@section @code{head}: Output the first part of files
-
-@pindex head
-@cindex initial part of files, outputting
-@cindex first part of files, outputting
-
-@code{head} prints the first part (10 lines by default) of each
-@var{file}; it reads from standard input if no files are given or
-when given a @var{file} of @samp{-}.  Synopses:
-
-@example
-head [@var{option}]@dots{} [@var{file}]@dots{}
-head -@var{number} [@var{option}]@dots{} [@var{file}]@dots{}
-@end example
-
-If more than one @var{file} is specified, @code{head} prints a
-one-line header consisting of
-@example
-==> @var{file name} <==
-@end example
-@noindent
-before the output for each @var{file}.
-
-@code{head} accepts two option formats: the new one, in which numbers
-are arguments to the options (@samp{-q -n 1}), and the old one, in which
-the number precedes any option letters (@samp{-1q}).
-
-The program accepts the following options.  Also see @ref{Common options}.
-
-@table @samp
-
-@item -@var{count}@var{options}
-@opindex -@var{count}
-This option is only recognized if it is specified first.  @var{count} is
-a decimal number optionally followed by a size letter (@samp{b},
-@samp{k}, @samp{m}) as in @code{-c}, or @samp{l} to mean count by lines,
-or other option letters (@samp{cqv}).
-
-@item -c @var{bytes}
-@itemx --bytes=@var{bytes}
-@opindex -c
-@opindex --bytes
-Print the first @var{bytes} bytes, instead of initial lines.  Appending
-@samp{b} multiplies @var{bytes} by 512, @samp{k} by 1024, and @samp{m}
-by 1048576.
-
-@itemx -n @var{n}
-@itemx --lines=@var{n}
-@opindex -n
-@opindex --lines
-Output the first @var{n} lines.
-
-@item -q
-@itemx --quiet
-@itemx --silent
-@opindex -q
-@opindex --quiet
-@opindex --silent
-Never print file name headers.
-
-@item -v
-@itemx --verbose
-@opindex -v
-@opindex --verbose
-Always print file name headers.
-
-@end table
-
-
-@node tail invocation
-@section @code{tail}: Output the last part of files
-
-@pindex tail
-@cindex last part of files, outputting
-
-@code{tail} prints the last part (10 lines by default) of each
-@var{file}; it reads from standard input if no files are given or
-when given a @var{file} of @samp{-}.  Synopses:
-
-@example
-tail [@var{option}]@dots{} [@var{file}]@dots{}
-tail -@var{number} [@var{option}]@dots{} [@var{file}]@dots{}
-tail +@var{number} [@var{option}]@dots{} [@var{file}]@dots{} # obsolescent
-@end example
-
-If more than one @var{file} is specified, @code{tail} prints a
-one-line header consisting of
-@example
-==> @var{file name} <==
-@end example
-@noindent
-before the output for each @var{file}.
-
-@cindex BSD @code{tail}
-@sc{gnu} @code{tail} can output any amount of data (some other versions of
-@code{tail} cannot).  It also has no @samp{-r} option (print in
-reverse), since reversing a file is really a different job from printing
-the end of a file; BSD @code{tail} (which is the one with @code{-r}) can
-only reverse files that are at most as large as its buffer, which is
-typically 32k.  A more reliable and versatile way to reverse files is
-the @sc{gnu} @code{tac} command.
-
-@code{tail} accepts two option formats: the new one, in which numbers
-are arguments to the options (@samp{-n 1}), and the obsolescent one, in
-which the number precedes any option letters (@samp{-1} or @samp{+1}).
-Warning: support for the @samp{+1} form will be withdrawn, as future
-versions of @sc{posix} will not allow it.
-
-If any option-argument is a number @var{n} starting with a @samp{+},
-@code{tail} begins printing with the @var{n}th item from the start of
-each file, instead of from the end.
-
-The program accepts the following options.  Also see @ref{Common options}.
-
-@table @samp
-
-@item -@var{count}
-@itemx +@var{count}
-@opindex -@var{count}
-@opindex +@var{count}
-This option is only recognized if it is specified first.  @var{count} is
-a decimal number optionally followed by a size letter (@samp{b},
-@samp{k}, @samp{m}) as in @code{-c}, or @samp{l} to mean count by lines,
-or other option letters (@samp{cfqv}).
-
-Warning: the @samp{+@var{count}} usage is obsolescent.  Future versions
-of @sc{posix} will require that support for it be withdrawn.  Use
-@samp{-n +@var{count}} instead.
-
-@item -c @var{bytes}
-@itemx --bytes=@var{bytes}
-@opindex -c
-@opindex --bytes
-Output the last @var{bytes} bytes, instead of final lines.  Appending
-@samp{b} multiplies @var{bytes} by 512, @samp{k} by 1024, and @samp{m}
-by 1048576.
-
-@item -f
-@itemx --follow[=@var{how}]
-@opindex -f
-@opindex --follow
-@cindex growing files
-@vindex name @r{follow option}
-@vindex descriptor @r{follow option}
-Loop forever trying to read more characters at the end of the file,
-presumably because the file is growing.  This option is ignored when
-reading from a pipe.
-If more than one file is given, @code{tail} prints a header whenever it
-gets output from a different file, to indicate which file that output is
-from.
-
-There are two ways to specify how you'd like to track files with this option,
-but that difference is noticeable only when a followed file is removed or
-renamed.
-If you'd like to continue to track the end of a growing file even after
-it has been unlinked, use @samp{--follow=descriptor}.  This is the default
-behavior, but it is not useful if you're tracking a log file that may be
-rotated (removed or renamed, then reopened).  In that case, use
-@samp{--follow=name} to track the named file by reopening it periodically
-to see if it has been removed and recreated by some other program.
-
-No matter which method you use, if the tracked file is determined to have
-shrunk, @code{tail} prints a message saying the file has been truncated
-and resumes tracking the end of the file from the newly-determined endpoint.
-
-When a file is removed, @code{tail}'s behavior depends on whether it is
-following the name or the descriptor.  When following by name, tail can
-detect that a file has been removed and gives a message to that effect,
-and if @samp{--retry} has been specified it will continue checking
-periodically to see if the file reappears.
-When following a descriptor, tail does not detect that the file has
-been unlinked or renamed and issues no message;  even though the file
-may no longer be accessible via its original name, it may still be
-growing.
-
-The option values @samp{descriptor} and @samp{name} may be specified only
-with the long form of the option, not with @samp{-f}.
-
-@itemx --retry
-@opindex --retry
-This option is meaningful only when following by name.
-Without this option, when tail encounters a file that doesn't
-exist or is otherwise inaccessible, it reports that fact and
-never checks it again.
-
-@itemx --sleep-interval=@var{n}
-@opindex --sleep-interval
-Change the number of seconds to wait between iterations (the default is 1).
-During one iteration, every specified file is checked to see if it has
-changed size.
-
-@itemx --pid=@var{pid}
-@opindex --pid
-When following by name or by descriptor, you may specify the process ID,
-@var{pid}, of the sole writer of all @var{file} arguments.  Then, shortly
-after that process terminates, tail will also terminate.  This will
-work properly only if the writer and the tailing process are running on
-the same machine.  For example, to save the output of a build in a file
-and to watch the file grow, if you invoke @code{make} and @code{tail}
-like this then the tail process will stop when your build completes.
-Without this option, you would have had to kill the @code{tail -f}
-process yourself.
-@example
-$ make >& makerr & tail --pid=$! -f makerr
-@end example
-If you specify a @var{pid} that is not in use or that does not correspond
-to the process that is writing to the tailed files, then @code{tail}
-may terminate long before any @var{file}s stop growing or it may not
-terminate until long after the real writer has terminated.
-Note that @samp{--pid} cannot be supported on some systems; @code{tail}
-will print a warning if this is the case.
-
-@itemx --max-unchanged-stats=@var{n}
-@opindex --max-unchanged-stats
-When tailing a file by name, if there have been @var{n} (default
-n=@value{DEFAULT_MAX_N_UNCHANGED_STATS_BETWEEN_OPENS}) consecutive
-iterations for which the size has remained the same, then
-@code{open}/@code{fstat} the file to determine if that file name is
-still associated with the same device/inode-number pair as before.
-When following a log file that is rotated, this is approximately the
-number of seconds between when tail prints the last pre-rotation lines
-and when it prints the lines that have accumulated in the new log file.
-This option is meaningful only when following by name.
-
-@itemx -n @var{n}
-@itemx --lines=@var{n}
-@opindex -n
-@opindex --lines
-Output the last @var{n} lines.
-
-@item -q
-@itemx -quiet
-@itemx --silent
-@opindex -q
-@opindex --quiet
-@opindex --silent
-Never print file name headers.
-
-@item -v
-@itemx --verbose
-@opindex -v
-@opindex --verbose
-Always print file name headers.
-
-@end table
-
-
-@node split invocation
-@section @code{split}: Split a file into fixed-size pieces
-
-@pindex split
-@cindex splitting a file into pieces
-@cindex pieces, splitting a file into
-
-@code{split} creates output files containing consecutive sections of
-@var{input} (standard input if none is given or @var{input} is
-@samp{-}).  Synopsis:
-
-@example
-split [@var{option}] [@var{input} [@var{prefix}]]
-@end example
-
-By default, @code{split} puts 1000 lines of @var{input} (or whatever is
-left over for the last section), into each output file.
-
-@cindex output file name prefix
-The output files' names consist of @var{prefix} (@samp{x} by default)
-followed by a group of letters @samp{aa}, @samp{ab}, and so on, such
-that concatenating the output files in sorted order by file name produces
-the original input file.  (If more than 676 output files are required,
-@code{split} uses @samp{zaa}, @samp{zab}, etc.)
-
-The program accepts the following options.  Also see @ref{Common options}.
-
-@table @samp
-
-@item -@var{lines}
-@itemx -l @var{lines}
-@itemx --lines=@var{lines}
-@opindex -l
-@opindex --lines
-Put @var{lines} lines of @var{input} into each output file.
-
-@item -b @var{bytes}
-@itemx --bytes=@var{bytes}
-@opindex -b
-@opindex --bytes
-Put the first @var{bytes} bytes of @var{input} into each output file.
-Appending @samp{b} multiplies @var{bytes} by 512, @samp{k} by 1024, and
-@samp{m} by 1048576.
-
-@item -C @var{bytes}
-@itemx --line-bytes=@var{bytes}
-@opindex -C
-@opindex --line-bytes
-Put into each output file as many complete lines of @var{input} as
-possible without exceeding @var{bytes} bytes.  For lines longer than
-@var{bytes} bytes, put @var{bytes} bytes into each output file until
-less than @var{bytes} bytes of the line are left, then continue
-normally.  @var{bytes} has the same format as for the @samp{--bytes}
-option.
-
-@itemx --verbose
-@opindex --verbose
-Write a diagnostic to standard error just before each output file is opened.
-
-@end table
-
-
-@node csplit invocation
-@section @code{csplit}: Split a file into context-determined pieces
-
-@pindex csplit
-@cindex context splitting
-@cindex splitting a file into pieces by context
-
-@code{csplit} creates zero or more output files containing sections of
-@var{input} (standard input if @var{input} is @samp{-}).  Synopsis:
-
-@example
-csplit [@var{option}]@dots{} @var{input} @var{pattern}@dots{}
-@end example
-
-The contents of the output files are determined by the @var{pattern}
-arguments, as detailed below.  An error occurs if a @var{pattern}
-argument refers to a nonexistent line of the input file (e.g., if no
-remaining line matches a given regular expression).  After every
-@var{pattern} has been matched, any remaining input is copied into one
-last output file.
-
-By default, @code{csplit} prints the number of bytes written to each
-output file after it has been created.
-
-The types of pattern arguments are:
-
-@table @samp
-
-@item @var{n}
-Create an output file containing the input up to but not including line
-@var{n} (a positive integer).  If followed by a repeat count, also
-create an output file containing the next @var{line} lines of the input
-file once for each repeat.
-
-@item /@var{regexp}/[@var{offset}]
-Create an output file containing the current line up to (but not
-including) the next line of the input file that contains a match for
-@var{regexp}.  The optional @var{offset} is a @samp{+} or @samp{-}
-followed by a positive integer.  If it is given, the input up to the
-matching line plus or minus @var{offset} is put into the output file,
-and the line after that begins the next section of input.
-
-@item %@var{regexp}%[@var{offset}]
-Like the previous type, except that it does not create an output
-file, so that section of the input file is effectively ignored.
-
-@item @{@var{repeat-count}@}
-Repeat the previous pattern @var{repeat-count} additional
-times. @var{repeat-count} can either be a positive integer or an
-asterisk, meaning repeat as many times as necessary until the input is
-exhausted.
-
-@end table
-
-The output files' names consist of a prefix (@samp{xx} by default)
-followed by a suffix.  By default, the suffix is an ascending sequence
-of two-digit decimal numbers from @samp{00} to @samp{99}.  In any case,
-concatenating the output files in sorted order by filename produces the
-original input file.
-
-By default, if @code{csplit} encounters an error or receives a hangup,
-interrupt, quit, or terminate signal, it removes any output files
-that it has created so far before it exits.
-
-The program accepts the following options.  Also see @ref{Common options}.
-
-@table @samp
-
-@item -f @var{prefix}
-@itemx --prefix=@var{prefix}
-@opindex -f
-@opindex --prefix
-@cindex output file name prefix
-Use @var{prefix} as the output file name prefix.
-
-@item -b @var{suffix}
-@itemx --suffix=@var{suffix}
-@opindex -b
-@opindex --suffix
-@cindex output file name suffix
-Use @var{suffix} as the output file name suffix.  When this option is
-specified, the suffix string must include exactly one
-@code{printf(3)}-style conversion specification, possibly including
-format specification flags, a field width, a precision specifications,
-or all of these kinds of modifiers.  The format letter must convert a
-binary integer argument to readable form; thus, only @samp{d}, @samp{i},
-@samp{u}, @samp{o}, @samp{x}, and @samp{X} conversions are allowed.  The
-entire @var{suffix} is given (with the current output file number) to
-@code{sprintf(3)} to form the file name suffixes for each of the
-individual output files in turn.  If this option is used, the
-@samp{--digits} option is ignored.
-
-@item -n @var{digits}
-@itemx --digits=@var{digits}
-@opindex -n
-@opindex --digits
-Use output file names containing numbers that are @var{digits} digits
-long instead of the default 2.
-
-@item -k
-@itemx --keep-files
-@opindex -k
-@opindex --keep-files
-Do not remove output files when errors are encountered.
-
-@item -z
-@itemx --elide-empty-files
-@opindex -z
-@opindex --elide-empty-files
-Suppress the generation of zero-length output files.  (In cases where
-the section delimiters of the input file are supposed to mark the first
-lines of each of the sections, the first output file will generally be a
-zero-length file unless you use this option.)  The output file sequence
-numbers always run consecutively starting from 0, even when this option
-is specified.
-
-@item -s
-@itemx -q
-@itemx --silent
-@itemx --quiet
-@opindex -s
-@opindex -q
-@opindex --silent
-@opindex --quiet
-Do not print counts of output file sizes.
-
-@end table
-
-
-@node Summarizing files
-@chapter Summarizing files
-
-@cindex summarizing files
-
-These commands generate just a few numbers representing entire
-contents of files.
-
-@menu
-* wc invocation::               Print byte, word, and line counts.
-* sum invocation::              Print checksum and block counts.
-* cksum invocation::            Print CRC checksum and byte counts.
-* md5sum invocation::           Print or check message-digests.
-@end menu
-
-
-@node wc invocation
-@section @code{wc}: Print byte, word, and line counts
-
-@pindex wc
-@cindex byte count
-@cindex character count
-@cindex word count
-@cindex line count
-
-@code{wc} counts the number of bytes, characters, whitespace-separated
-words, and newlines in each given @var{file}, or standard input if none
-are given or for a @var{file} of @samp{-}.  Synopsis:
-
-@example
-wc [@var{option}]@dots{} [@var{file}]@dots{}
-@end example
-
-@cindex total counts
-@vindex POSIXLY_CORRECT
-@code{wc} prints one line of counts for each file, and if the file was
-given as an argument, it prints the file name following the counts.  If
-more than one @var{file} is given, @code{wc} prints a final line
-containing the cumulative counts, with the file name @file{total}.  The
-counts are printed in this order: newlines, words, characters, bytes.
-By default, each count is output right-justified in a 7-byte field with
-one space between fields so that the numbers and file names line up nicely
-in columns.  However, @sc{posix} requires that there be exactly one space
-separating columns.  You can make @code{wc} use the @sc{posix}-mandated
-output format by setting the @env{POSIXLY_CORRECT} environment variable.
-
-By default, @code{wc} prints three counts: the newline, words, and byte
-counts.  Options can specify that only certain counts be printed.
-Options do not undo others previously given, so
-
-@example
-wc --bytes --words
-@end example
-
-@noindent
-prints both the byte counts and the word counts.
-
-With the @code{--max-line-length} option, @code{wc} prints the length
-of the longest line per file, and if there is more than one file it
-prints the maximum (not the sum) of those lengths.
-
-The program accepts the following options.  Also see @ref{Common options}.
-
-@table @samp
-
-@item -c
-@itemx --bytes
-@opindex -c
-@opindex --bytes
-Print only the byte counts.
-
-@item -m
-@itemx --chars
-@opindex -m
-@opindex --chars
-Print only the character counts.
-
-@item -w
-@itemx --words
-@opindex -w
-@opindex --words
-Print only the word counts.
-
-@item -l
-@itemx --lines
-@opindex -l
-@opindex --lines
-Print only the newline counts.
-
-@item -L
-@itemx --max-line-length
-@opindex -L
-@opindex --max-line-length
-Print only the maximum line lengths.
-
-@end table
-
-
-@node sum invocation
-@section @code{sum}: Print checksum and block counts
-
-@pindex sum
-@cindex 16-bit checksum
-@cindex checksum, 16-bit
-
-@code{sum} computes a 16-bit checksum for each given @var{file}, or
-standard input if none are given or for a @var{file} of @samp{-}.  Synopsis:
-
-@example
-sum [@var{option}]@dots{} [@var{file}]@dots{}
-@end example
-
-@code{sum} prints the checksum for each @var{file} followed by the
-number of blocks in the file (rounded up).  If more than one @var{file}
-is given, file names are also printed (by default).  (With the
-@samp{--sysv} option, corresponding file names are printed when there is
-at least one file argument.)
-
-By default, @sc{gnu} @code{sum} computes checksums using an algorithm
-compatible with BSD @code{sum} and prints file sizes in units of
-1024-byte blocks.
-
-The program accepts the following options.  Also see @ref{Common options}.
-
-@table @samp
-
-@item -r
-@opindex -r
-@cindex BSD @code{sum}
-Use the default (BSD compatible) algorithm.  This option is included for
-compatibility with the System V @code{sum}.  Unless @samp{-s} was also
-given, it has no effect.
-
-@item -s
-@itemx --sysv
-@opindex -s
-@opindex --sysv
-@cindex System V @code{sum}
-Compute checksums using an algorithm compatible with System V
-@code{sum}'s default, and print file sizes in units of 512-byte blocks.
-
-@end table
-
-@code{sum} is provided for compatibility; the @code{cksum} program (see
-next section) is preferable in new applications.
-
-
-@node cksum invocation
-@section @code{cksum}: Print CRC checksum and byte counts
-
-@pindex cksum
-@cindex cyclic redundancy check
-@cindex CRC checksum
-
-@code{cksum} computes a cyclic redundancy check (CRC) checksum for each
-given @var{file}, or standard input if none are given or for a
-@var{file} of @samp{-}.  Synopsis:
-
-@example
-cksum [@var{option}]@dots{} [@var{file}]@dots{}
-@end example
-
-@code{cksum} prints the CRC checksum for each file along with the number
-of bytes in the file, and the filename unless no arguments were given.
-
-@code{cksum} is typically used to ensure that files
-transferred by unreliable means (e.g., netnews) have not been corrupted,
-by comparing the @code{cksum} output for the received files with the
-@code{cksum} output for the original files (typically given in the
-distribution).
-
-The CRC algorithm is specified by the @sc{posix.2} standard.  It is not
-compatible with the BSD or System V @code{sum} algorithms (see the
-previous section); it is more robust.
-
-The only options are @samp{--help} and @samp{--version}.  @xref{Common
-options}.
-
-
-@node md5sum invocation
-@section @code{md5sum}: Print or check message-digests
-
-@pindex md5sum
-@cindex 128-bit checksum
-@cindex checksum, 128-bit
-@cindex fingerprint, 128-bit
-@cindex message-digest, 128-bit
-
-@code{md5sum} computes a 128-bit checksum (or @dfn{fingerprint} or
-@dfn{message-digest}) for each specified @var{file}.
-If a @var{file} is specified as @samp{-} or if no files are given
-@code{md5sum} computes the checksum for the standard input.
-@code{md5sum} can also determine whether a file and checksum are
-consistent. Synopses:
-
-@example
-md5sum [@var{option}]@dots{} [@var{file}]@dots{}
-md5sum [@var{option}]@dots{} --check [@var{file}]
-@end example
-
-For each @var{file}, @samp{md5sum} outputs the MD5 checksum, a flag
-indicating a binary or text input file, and the filename.
-If @var{file} is omitted or specified as @samp{-}, standard input is read.
-
-The program accepts the following options.  Also see @ref{Common options}.
-
-@table @samp
-
-@item -b
-@itemx --binary
-@opindex -b
-@opindex --binary
-@cindex binary input files
-Treat all input files as binary.  This option has no effect on Unix
-systems, since they don't distinguish between binary and text files.
-This option is useful on systems that have different internal and
-external character representations.  On MS-DOS and MS-Windows, this is
-the default.
-
-@item -c
-@itemx --check
-Read filenames and checksum information from the single @var{file}
-(or from stdin if no @var{file} was specified) and report whether
-each named file and the corresponding checksum data are consistent.
-The input to this mode of @code{md5sum} is usually the output of
-a prior, checksum-generating run of @samp{md5sum}.
-Each valid line of input consists of an MD5 checksum, a binary/text
-flag, and then a filename.
-Binary files are marked with @samp{*}, text with @samp{ }.
-For each such line, @code{md5sum} reads the named file and computes its
-MD5 checksum.  Then, if the computed message digest does not match the
-one on the line with the filename, the file is noted as having
-failed the test.  Otherwise, the file passes the test.
-By default, for each valid line, one line is written to standard
-output indicating whether the named file passed the test.
-After all checks have been performed, if there were any failures,
-a warning is issued to standard error.
-Use the @samp{--status} option to inhibit that output.
-If any listed file cannot be opened or read, if any valid line has
-an MD5 checksum inconsistent with the associated file, or if no valid
-line is found, @code{md5sum} exits with nonzero status.  Otherwise,
-it exits successfully.
-
-@itemx --status
-@opindex --status
-@cindex verifying MD5 checksums
-This option is useful only when verifying checksums.
-When verifying checksums, don't generate the default one-line-per-file
-diagnostic and don't output the warning summarizing any failures.
-Failures to open or read a file still evoke individual diagnostics to
-standard error.
-If all listed files are readable and are consistent with the associated
-MD5 checksums, exit successfully.  Otherwise exit with a status code
-indicating there was a failure.
-
-@item -t
-@itemx --text
-@opindex -t
-@opindex --text
-@cindex text input files
-Treat all input files as text files.  This is the reverse of
-@samp{--binary}.
-
-@item -w
-@itemx --warn
-@opindex -w
-@opindex --warn
-@cindex verifying MD5 checksums
-When verifying checksums, warn about improperly formatted MD5 checksum lines.
-This option is useful only if all but a few lines in the checked input
-are valid.
-
-@end table
-
-
-@node Operating on sorted files
-@chapter Operating on sorted files
-
-@cindex operating on sorted files
-@cindex sorted files, operations on
-
-These commands work with (or produce) sorted files.
-
-@menu
-* sort invocation::             Sort text files.
-* uniq invocation::             Uniquify files.
-* comm invocation::             Compare two sorted files line by line.
-* ptx invocation::              Produce a permuted index of file contents.
-* tsort invocation::            Topological sort.
-@end menu
-
-
-@node sort invocation
-@section @code{sort}: Sort text files
-
-@pindex sort
-@cindex sorting files
-
-@code{sort} sorts, merges, or compares all the lines from the given
-files, or standard input if none are given or for a @var{file} of
-@samp{-}.  By default, @code{sort} writes the results to standard
-output.  Synopsis:
-
-@example
-sort [@var{option}]@dots{} [@var{file}]@dots{}
-@end example
-
-@code{sort} has three modes of operation: sort (the default), merge,
-and check for sortedness.  The following options change the operation
-mode:
-
-@table @samp
-
-@item -c
-@itemx --check
-@opindex -c
-@opindex --check
-@cindex checking for sortedness
-Check whether the given files are already sorted: if they are not all
-sorted, print an error message and exit with a status of 1.
-Otherwise, exit successfully.
-
-@item -m
-@itemx --merge
-@opindex -m
-@opindex --merge
-@cindex merging sorted files
-Merge the given files by sorting them as a group.  Each input file must
-always be individually sorted.  It always works to sort instead of
-merge; merging is provided because it is faster, in the case where it
-works.
-
-@end table
-
-@vindex LC_COLLATE
-A pair of lines is compared as follows: if any key fields have been
-specified, @code{sort} compares each pair of fields, in the order
-specified on the command line, according to the associated ordering
-options, until a difference is found or no fields are left.
-Unless otherwise specified, all comparisons use the character
-collating sequence specified by the @env{LC_COLLATE} locale.
-
-If any of the global options @samp{bdfgiMnr} are given but no key fields
-are specified, @code{sort} compares the entire lines according to the
-global options.
-
-Finally, as a last resort when all keys compare equal (or if no ordering
-options were specified at all), @code{sort} compares the entire lines.
-The last resort comparison honors the @option{--reverse} (@option{-r})
-global option.  The @option{--stable} (@option{-s}) option disables this
-last-resort comparison so that lines in which all fields compare equal
-are left in their original relative order.  If no fields or global
-options are specified, @option{--stable} (@option{-s}) has no effect.
-
-@sc{gnu} @code{sort} (as specified for all @sc{gnu} utilities) has no limits on
-input line length or restrictions on bytes allowed within lines.  In
-addition, if the final byte of an input file is not a newline, @sc{gnu}
-@code{sort} silently supplies one.  A line's trailing newline is not
-part of the line for comparison purposes.@footnote{@sc{posix}.2-1992
-requires that the trailing newline be part of the comparison, and some
-@code{sort} implementations obey this requirement, but it is widely
-considered to be a bug in the standard and the next version of
-@sc{posix}.2 will likely remove this requirement.}
-
-Upon any error, @code{sort} exits with a status of @samp{2}.
-
-@vindex TMPDIR
-If the environment variable @env{TMPDIR} is set, @code{sort} uses its
-value as the directory for temporary files instead of @file{/tmp}.  The
-@option{--temporary-directory} (@option{-T}) option in turn overrides
-the environment variable.
-
-
-The following options affect the ordering of output lines.  They may be
-specified globally or as part of a specific key field.  If no key
-fields are specified, global options apply to comparison of entire
-lines; otherwise the global options are inherited by key fields that do
-not specify any special options of their own.  In pre-@sc{posix}
-versions of @command{sort}, global options affect only later key fields,
-so portable shell scripts should specify global options first.
-
-@table @samp
-
-@item -b
-@itemx --ignore-leading-blanks
-@opindex -b
-@opindex --ignore-leading-blanks
-@cindex blanks, ignoring leading
-@vindex LC_CTYPE
-Ignore leading blanks when finding sort keys in each line.
-The @env{LC_CTYPE} locale determines character types.
-
-@item -d
-@itemx --dictionary-order
-@opindex -d
-@opindex --dictionary-order
-@cindex dictionary order
-@cindex phone directory order
-@cindex telephone directory order
-@vindex LC_CTYPE
-Sort in @dfn{phone directory} order: ignore all characters except
-letters, digits and blanks when sorting.
-The @env{LC_CTYPE} locale determines character types.
-
-@item -f
-@itemx --ignore-case
-@opindex -f
-@opindex --ignore-case
-@cindex ignoring case
-@cindex case folding
-@vindex LC_CTYPE
-Fold lowercase characters into the equivalent uppercase characters when
-comparing so that, for example, @samp{b} and @samp{B} sort as equal.
-The @env{LC_CTYPE} locale determines character types.
-
-@item -g
-@itemx --general-numeric-sort
-@opindex -g
-@opindex --general-numeric-sort
-@cindex general numeric sort
-@vindex LC_NUMERIC
-Sort numerically, using the standard C function @code{strtod} to convert
-a prefix of each line to a double-precision floating point number.
-This allows floating point numbers to be specified in scientific notation,
-like @code{1.0e-34} and @code{10e100}.
-The @env{LC_NUMERIC} locale determines the decimal-point character.
-Do not report overflow, underflow, or conversion errors.
-Use the following collating sequence:
-
-@itemize @bullet
-@item
-Lines that do not start with numbers (all considered to be equal).
-@item
-NaNs (``Not a Number'' values, in IEEE floating point arithmetic)
-in a consistent but machine-dependent order.
-@item
-Minus infinity.
-@item
-Finite numbers in ascending numeric order (with @math{-0} and @math{+0} equal).
-@item
-Plus infinity.
-@end itemize
-
-Use this option only if there is no alternative; it is much slower than
-@option{--numeric-sort} (@option{-n}) and it can lose information when
-converting to floating point.
-
-@item -i
-@itemx --ignore-nonprinting
-@opindex -i
-@opindex --ignore-nonprinting
-@cindex nonprinting characters, ignoring
-@cindex unprintable characters, ignoring
-@vindex LC_CTYPE
-Ignore nonprinting characters.
-The @env{LC_CTYPE} locale determines character types.
-
-@item -M
-@itemx --month-sort
-@opindex -M
-@opindex --month-sort
-@cindex months, sorting by
-@vindex LC_TIME
-An initial string, consisting of any amount of whitespace, followed
-by a month name abbreviation, is folded to UPPER case and
-compared in the order @samp{JAN} < @samp{FEB} < @dots{} < @samp{DEC}.
-Invalid names compare low to valid names.  The @env{LC_TIME} locale
-determines the month spellings.
-
-@item -n
-@itemx --numeric-sort
-@opindex -n
-@opindex --numeric-sort
-@cindex numeric sort
-@vindex LC_NUMERIC
-Sort numerically: the number begins each line; specifically, it consists
-of optional whitespace, an optional @samp{-} sign, and zero or more
-digits possibly separated by thousands separators, optionally followed
-by a decimal-point character and zero or more digits.  The @env{LC_NUMERIC}
-locale specifies the decimal-point character and thousands separator.
-
-Numeric sort uses what might be considered an unconventional method to
-compare strings representing floating point numbers.  Rather than first
-converting each string to the C @code{double} type and then comparing
-those values, @command{sort} aligns the decimal-point characters in the
-two strings and compares the strings a character at a time.  One benefit
-of using this approach is its speed.  In practice this is much more
-efficient than performing the two corresponding string-to-double (or
-even string-to-integer) conversions and then comparing doubles.  In
-addition, there is no corresponding loss of precision.  Converting each
-string to @code{double} before comparison would limit precision to about
-16 digits on most systems.
-
-Neither a leading @samp{+} nor exponential notation is recognized.
-To compare such strings numerically, use the
-@option{--general-numeric-sort} (@option{-g}) option.
-
-@item -r
-@itemx --reverse
-@opindex -r
-@opindex --reverse
-@cindex reverse sorting
-Reverse the result of comparison, so that lines with greater key values
-appear earlier in the output instead of later.
-
-@end table
-
-Other options are:
-
-@table @samp
-
-@item -o @var{output-file}
-@itemx --output=@var{output-file}
-@opindex -o
-@opindex --output
-@cindex overwriting of input, allowed
-Write output to @var{output-file} instead of standard output.
-If necessary, @command{sort} reads input before opening
-@var{output-file}, so you can safely sort a file in place by using
-commands like @code{sort -o F F} and @code{cat F | sort -o F}.
-
-@vindex POSIXLY_CORRECT
-If @option{-c} is not also specified, @option{-o} may appear after an
-input file even if @env{POSIXLY_CORRECT} is set, e.g., @samp{sort F -o
-F}.  Warning: this usage is obsolescent.  Future versions of @sc{posix}
-will require that support for it be withdrawn.  Portable scripts should
-specify @samp{-o @var{output-file}} before any input files.
-
-@item -S @var{size}
-@itemx --buffer-size=@var{size}
-@opindex -S
-@opindex --buffer-size
-@cindex size for main memory sorting
-Use a main-memory sort buffer of the given @var{size}.  By default,
-@var{size} is in units of 1,024 bytes.  Appending @samp{%} causes
-@var{size} to be interpreted as a percentage of physical memory.
-Appending @samp{k} multiplies @var{size} by 1,024 (the default),
-@samp{M} by 1,048,576, @samp{G} by 1,073,741,824, and so on for
-@samp{T}, @samp{P}, @samp{E}, @samp{Z}, and @samp{Y}.  Appending
-@samp{b} causes @var{size} to be interpreted as a byte count, with no
-multiplication.
-
-This option can improve the performance of @command{sort} by causing it
-to start with a larger or smaller sort buffer than the default.
-However, this option affects only the initial buffer size.  The buffer
-grows beyond @var{size} if @command{sort} encounters input lines larger
-than @var{size}.
-
-@item -t @var{separator}
-@itemx --field-separator=@var{separator}
-@opindex -t
-@opindex --field-separator
-@cindex field separator character
-Use character @var{separator} as the field separator when finding the
-sort keys in each line.  By default, fields are separated by the empty
-string between a non-whitespace character and a whitespace character.
-That is, given the input line @w{@samp{ foo bar}}, @code{sort} breaks it
-into fields @w{@samp{ foo}} and @w{@samp{ bar}}.  The field separator is
-not considered to be part of either the field preceding or the field
-following.  But note that sort fields that extend to the end of the line,
-as @samp{-k 2}, or sort fields consisting of a range, as @samp{-k 2,3},
-retain the field separators present between the endpoints of the range.
-
-@item -T @var{tempdir}
-@itemx --temporary-directory=@var{tempdir}
-@opindex -T
-@opindex --temporary-directory
-@cindex temporary directory
-@vindex TMPDIR
-Use directory @var{tempdir} to store temporary files, overriding the
-@env{TMPDIR} environment variable.  If this option is given more than
-once, temporary files are stored in all the directories given.  If you
-have a large sort or merge that is I/O-bound, you can often improve
-performance by using this option to specify directories on different
-disks and controllers.
-
-@item -u
-@itemx --unique
-@opindex -u
-@opindex --unique
-@cindex uniquifying output
-
-Normally, output only the first of a sequence of lines that compare
-equal.  For the @option{--check} (@option{-c}) option,
-check that no pair of consecutive lines compares equal.
-
-@item -k @var{pos1}[,@var{pos2}]
-@itemx --key=@var{pos1}[,@var{pos2}]
-@opindex -k
-@opindex --key
-@cindex sort field
-Specify a sort field that consists of the part of the line between
-@var{pos1} and @var{pos2} (or the end of the line, if @var{pos2} is
-omitted), @emph{inclusive}.  Fields and character positions are numbered
-starting with 1.  So to sort on the second field, you'd use
-@samp{--key=2,2} (@samp{-k 2,2}).  See below for more examples.
-
-@item -z
-@itemx --zero-terminated
-@opindex -z
-@opindex --zero-terminated
-@cindex sort zero-terminated lines
-Treat the input as a set of lines, each terminated by a zero byte (@sc{ascii}
-@sc{nul} (Null) character) instead of an @sc{ascii} @sc{lf} (Line Feed).
-This option can be useful in conjunction with @samp{perl -0} or
-@samp{find -print0} and @samp{xargs -0} which do the same in order to
-reliably handle arbitrary pathnames (even those which contain Line Feed
-characters.)
-
-@item +@var{pos1} [-@var{pos2}]
-The obsolescent, traditional option for specifying a sort field.  The field
-consists of the line between @var{pos1} and up to but @emph{not including}
-@var{pos2} (or the end of the line if @var{pos2} is omitted).  Fields
-and character positions are numbered starting with 0.  See below.
-
-Warning: the @samp{+@var{pos1}} usage is obsolescent.  Future versions of
-@sc{posix} will require that support for it be withdrawn.  Use
-@option{--key} (@option{-k}) instead.
-
-@end table
-
-Historical (BSD and System V) implementations of @code{sort} have
-differed in their interpretation of some options, particularly
-@samp{-b}, @samp{-f}, and @samp{-n}.  @sc{gnu} sort follows the @sc{posix}
-behavior, which is usually (but not always!) like the System V behavior.
-According to @sc{posix}, @samp{-n} no longer implies @samp{-b}.  For
-consistency, @samp{-M} has been changed in the same way.  This may
-affect the meaning of character positions in field specifications in
-obscure cases.  The only fix is to add an explicit @samp{-b}.
-
-A position in a sort field specified with the @samp{-k} or @samp{+}
-option has the form @samp{@var{f}.@var{c}}, where @var{f} is the number
-of the field to use and @var{c} is the number of the first character
-from the beginning of the field (for @samp{+@var{pos}}) or from the end
-of the previous field (for @samp{-@var{pos}}).  If the @samp{.@var{c}}
-is omitted, it is taken to be the first character in the field.  If the
-@samp{-b} option was specified, the @samp{.@var{c}} part of a field
-specification is counted from the first nonblank character of the field
-(for @samp{+@var{pos}}) or from the first nonblank character following
-the previous field (for @samp{-@var{pos}}).
-
-A sort key option may also have any of the option letters @samp{Mbdfinr}
-appended to it, in which case the global ordering options are not used
-for that particular field.  The @samp{-b} option may be independently
-attached to either or both of the @samp{+@var{pos}} and
-@samp{-@var{pos}} parts of a field specification, and if it is inherited
-from the global options it will be attached to both.
-Keys may span multiple fields.
-
-Here are some examples to illustrate various combinations of options.
-In them, the @sc{posix} @samp{-k} option is used to specify sort keys rather
-than the obsolescent @samp{+@var{pos1}-@var{pos2}} syntax.
-
-@itemize @bullet
-
-@item
-Sort in descending (reverse) numeric order.
-
-@example
-sort -nr
-@end example
-
-@item
-Sort alphabetically, omitting the first and second fields.
-This uses a single key composed of the characters beginning
-at the start of field three and extending to the end of each line.
-
-@example
-sort -k 3
-@end example
-
-@item
-Sort numerically on the second field and resolve ties by sorting
-alphabetically on the third and fourth characters of field five.
-Use @samp{:} as the field delimiter.
-
-@example
-sort -t : -k 2,2n -k 5.3,5.4
-@end example
-
-Note that if you had written @samp{-k 2} instead of @samp{-k 2,2}
-@command{sort} would have used all characters beginning in the second field
-and extending to the end of the line as the primary @emph{numeric}
-key.  For the large majority of applications, treating keys spanning
-more than one field as numeric will not do what you expect.
-
-Also note that the @samp{n} modifier was applied to the field-end
-specifier for the first key.  It would have been equivalent to
-specify @samp{-k 2n,2} or @samp{-k 2n,2n}.  All modifiers except
-@samp{b} apply to the associated @emph{field}, regardless of whether
-the modifier character is attached to the field-start and/or the
-field-end part of the key specifier.
-
-@item
-Sort the password file on the fifth field and ignore any
-leading white space.  Sort lines with equal values in field five
-on the numeric user ID in field three.
-
-@example
-sort -t : -k 5b,5 -k 3,3n /etc/passwd
-@end example
-
-An alternative is to use the global numeric modifier @samp{-n}.
-
-@example
-sort -t : -n -k 5b,5 -k 3,3 /etc/passwd
-@end example
-
-@item
-Generate a tags file in case-insensitive sorted order.
-
-@smallexample
-find src -type f -print0 | sort -t / -z -f | xargs -0 etags --append
-@end smallexample
-
-The use of @samp{-print0}, @samp{-z}, and @samp{-0} in this case means
-that pathnames that contain Line Feed characters will not get broken up
-by the sort operation.
-
-Finally, to ignore both leading and trailing white space, you
-could have applied the @samp{b} modifier to the field-end specifier
-for the first key,
-
-@example
-sort -t : -n -k 5b,5b -k 3,3 /etc/passwd
-@end example
-
-or by using the global @samp{-b} modifier instead of @samp{-n}
-and an explicit @samp{n} with the second key specifier.
-
-@example
-sort -t : -b -k 5,5 -k 3,3n /etc/passwd
-@end example
-
-@c This example is a bit contrived and needs more explanation.
-@c @item
-@c Sort records separated by an arbitrary string by using a pipe to convert
-@c each record delimiter string to @samp{\0}, then using sort's -z option,
-@c and converting each @samp{\0} back to the original record delimiter.
-@c
-@c @example
-@c printf 'c\n\nb\n\na\n'|perl -0pe 's/\n\n/\n\0/g'|sort -z|perl -0pe 's/\0/\n/g'
-@c @end example
-
-@end itemize
-
-
-@node uniq invocation
-@section @code{uniq}: Uniquify files
-
-@pindex uniq
-@cindex uniquify files
-
-@code{uniq} writes the unique lines in the given @file{input}, or
-standard input if nothing is given or for an @var{input} name of
-@samp{-}.  Synopsis:
-
-@example
-uniq [@var{option}]@dots{} [@var{input} [@var{output}]]
-@end example
-
-By default, @code{uniq} prints the unique lines in a sorted file, i.e.,
-discards all but one of identical successive lines.  Optionally, it can
-instead show only lines that appear exactly once, or lines that appear
-more than once.
-
-The input must be sorted.  If your input is not sorted, perhaps you want
-to use @code{sort -u}.
-
-If no @var{output} file is specified, @code{uniq} writes to standard
-output.
-
-The program accepts the following options.  Also see @ref{Common options}.
-
-@table @samp
-
-@item -@var{n}
-@itemx -f @var{n}
-@itemx --skip-fields=@var{n}
-@opindex -@var{n}
-@opindex -f
-@opindex --skip-fields
-Skip @var{n} fields on each line before checking for uniqueness.  Fields
-are sequences of non-space non-tab characters that are separated from
-each other by at least one space or tab.
-
-@item +@var{n}
-@itemx -s @var{n}
-@itemx --skip-chars=@var{n}
-@opindex +@var{n}
-@opindex -s
-@opindex --skip-chars
-Skip @var{n} characters before checking for uniqueness.  If you use both
-the field and character skipping options, fields are skipped over first.
-
-Warning: the @samp{+@var{n}} usage is obsolescent.  Future versions of
-@sc{posix} will require that support for it be withdrawn.  Use @samp{-s
-@var{n}} instead.
-
-@item -c
-@itemx --count
-@opindex -c
-@opindex --count
-Print the number of times each line occurred along with the line.
-
-@item -i
-@itemx --ignore-case
-@opindex -i
-@opindex --ignore-case
-Ignore differences in case when comparing lines.
-
-@item -d
-@itemx --repeated
-@opindex -d
-@opindex --repeated
-@cindex duplicate lines, outputting
-Print only duplicate lines.
-
-@item -D
-@itemx --all-repeated[=@var{delimit-method}]
-@opindex -D
-@opindex --all-repeated
-@cindex all duplicate lines, outputting
-Print all duplicate lines and only duplicate lines.
-This option is useful mainly in conjunction with other options e.g.,
-to ignore case or to compare only selected fields.
-The optional @var{delimit-method} tells how to delimit
-groups of duplicate lines, and must be one of the following:
-
-@table @samp
-
-@item none
-Do not delimit groups of duplicate lines.
-This is equivalent to @option{--all-repeated} (@option{-D}).
-
-@item prepend
-Output a newline before each group of duplicate lines.
-
-@item separate
-Separate groups of duplicate lines with a single newline.
-This is the same as using @samp{prepend}, except that
-there is no newline before the first group, and hence
-may be better suited for output direct to users.
-@end table
-
-Note that when groups are delimited and the input stream contains
-two or more consecutive blank lines, then the output is ambiguous.
-To avoid that, filter the input through @samp{tr -s '\n'} to replace
-each sequence of consecutive newlines with a single newline.
-
-This is a @sc{gnu} extension.
-@c FIXME: give an example showing *how* it's useful
-
-@item -u
-@itemx --unique
-@opindex -u
-@opindex --unique
-@cindex unique lines, outputting
-Print only unique lines.
-
-@item -w @var{n}
-@itemx --check-chars=@var{n}
-@opindex -w
-@opindex --check-chars
-Compare @var{n} characters on each line (after skipping any specified
-fields and characters).  By default the entire rest of the lines are
-compared.
-
-@end table
-
-
-@node comm invocation
-@section @code{comm}: Compare two sorted files line by line
-
-@pindex comm
-@cindex line-by-line comparison
-@cindex comparing sorted files
-
-@code{comm} writes to standard output lines that are common, and lines
-that are unique, to two input files; a file name of @samp{-} means
-standard input.  Synopsis:
-
-@example
-comm [@var{option}]@dots{} @var{file1} @var{file2}
-@end example
-
-@vindex LC_COLLATE
-Before @code{comm} can be used, the input files must be sorted using the
-collating sequence specified by the @env{LC_COLLATE} locale.
-If an input file ends in a non-newline
-character, a newline is silently appended.  The @code{sort} command with
-no options always outputs a file that is suitable input to @code{comm}.
-
-@cindex differing lines
-@cindex common lines
-With no options, @code{comm} produces three column output.  Column one
-contains lines unique to @var{file1}, column two contains lines unique
-to @var{file2}, and column three contains lines common to both files.
-Columns are separated by a single TAB character.
-@c FIXME: when there's an option to supply an alternative separator
-@c string, append `by default' to the above sentence.
-
-@opindex -1
-@opindex -2
-@opindex -3
-The options @samp{-1}, @samp{-2}, and @samp{-3} suppress printing of
-the corresponding columns.  Also see @ref{Common options}.
-
-Unlike some other comparison utilities, @code{comm} has an exit
-status that does not depend on the result of the comparison.
-Upon normal completion @code{comm} produces an exit code of zero.
-If there is an error it exits with nonzero status.
-
-
-@node tsort invocation
-@section @code{tsort}: Topological sort
-
-@pindex tsort
-@cindex topological sort
-
-@code{tsort} performs a topological sort on the given @var{file}, or
-standard input if no input file is given or for a @var{file} of
-@samp{-}.  Synopsis:
-
-@example
-tsort [@var{option}] [@var{file}]
-@end example
-
-@code{tsort} reads its input as pairs of strings, separated by blanks,
-indicating a partial ordering.  The output is a total ordering that
-corresponds to the given partial ordering.
-
-For example
-
-@example
-tsort <<EOF
-a b c
-d
-e f
-b c d e
-EOF
-@end example
-
-@noindent
-will produce the output
-
-@example
-a
-b
-c
-d
-e
-f
-@end example
-
-@code{tsort} will detect cycles in the input and writes the first cycle
-encountered to standard error.
-
-Note that for a given partial ordering, generally there is no unique
-total ordering.
-
-The only options are @samp{--help} and @samp{--version}.  @xref{Common
-options}.
-
-
-@node ptx invocation
-@section @code{ptx}: Produce permuted indexes
-
-@pindex ptx
-
-@code{ptx} reads a text file and essentially produces a permuted index, with
-each keyword in its context.  The calling sketch is either one of:
-
-@example
-ptx [@var{option} @dots{}] [@var{file} @dots{}]
-ptx -G [@var{option} @dots{}] [@var{input} [@var{output}]]
-@end example
-
-The @samp{-G} (or its equivalent: @samp{--traditional}) option disables
-all @sc{gnu} extensions and reverts to traditional mode, thus introducing some
-limitations and changing several of the program's default option values.
-When @samp{-G} is not specified, @sc{gnu} extensions are always enabled.
-@sc{gnu} extensions to @code{ptx} are documented wherever appropriate in this
-document.  For the full list, see @xref{Compatibility in ptx}.
-
-Individual options are explained in the following sections.
-
-When @sc{gnu} extensions are enabled, there may be zero, one or several
-@var{file}s after the options.  If there is no @var{file}, the program
-reads the standard input.  If there is one or several @var{file}s, they
-give the name of input files which are all read in turn, as if all the
-input files were concatenated.  However, there is a full contextual
-break between each file and, when automatic referencing is requested,
-file names and line numbers refer to individual text input files.  In
-all cases, the program outputs the permuted index to the standard
-output.
-
-When @sc{gnu} extensions are @emph{not} enabled, that is, when the program
-operates in traditional mode, there may be zero, one or two parameters
-besides the options.  If there are no parameters, the program reads the
-standard input and outputs the permuted index to the standard output.
-If there is only one parameter, it names the text @var{input} to be read
-instead of the standard input.  If two parameters are given, they give
-respectively the name of the @var{input} file to read and the name of
-the @var{output} file to produce.  @emph{Be very careful} to note that,
-in this case, the contents of file given by the second parameter is
-destroyed.  This behavior is dictated by System V @code{ptx}
-compatibility; @sc{gnu} Standards normally discourage output parameters not
-introduced by an option.
-
-Note that for @emph{any} file named as the value of an option or as an
-input text file, a single dash @kbd{-} may be used, in which case
-standard input is assumed.  However, it would not make sense to use this
-convention more than once per program invocation.
-
-@menu
-* General options in ptx::      Options which affect general program behavior.
-* Charset selection in ptx::    Underlying character set considerations.
-* Input processing in ptx::     Input fields, contexts, and keyword selection.
-* Output formatting in ptx::    Types of output format, and sizing the fields.
-* Compatibility in ptx::
-@end menu
-
-
-@node General options in ptx
-@subsection General options
-
-@table @samp
-
-@item -C
-@itemx --copyright
-Print a short note about the copyright and copying conditions, then
-exit without further processing.
-
-@item -G
-@itemx --traditional
-As already explained, this option disables all @sc{gnu} extensions to
-@code{ptx} and switches to traditional mode.
-
-@item --help
-Print a short help on standard output, then exit without further
-processing.
-
-@item --version
-Print the program version on standard output, then exit without further
-processing.
-
-@end table
-
-
-@node Charset selection in ptx
-@subsection Charset selection
-
-@c FIXME:  People don't necessarily know what an IBM-PC was these days.
-As it is set up now, the program assumes that the input file is coded
-using 8-bit ISO 8859-1 code, also known as Latin-1 character set,
-@emph{unless} it is compiled for MS-DOS, in which case it uses the
-character set of the IBM-PC.  (@sc{gnu} @code{ptx} is not known to work on
-smaller MS-DOS machines anymore.)  Compared to 7-bit @sc{ascii}, the set
-of characters which are letters is different; this alters the behavior
-of regular expression matching.  Thus, the default regular expression
-for a keyword allows foreign or diacriticized letters.  Keyword sorting,
-however, is still crude; it obeys the underlying character set ordering
-quite blindly.
-
-@table @samp
-
-@item -f
-@itemx --ignore-case
-Fold lower case letters to upper case for sorting.
-
-@end table
-
-
-@node Input processing in ptx
-@subsection Word selection and input processing
-
-@table @samp
-
-@item -b @var{file}
-@item --break-file=@var{file}
-
-This option provides an alternative (to @samp{-W}) method of describing
-which characters make up words.  It introduces the name of a
-file which contains a list of characters which can@emph{not} be part of
-one word; this file is called the @dfn{Break file}.  Any character which
-is not part of the Break file is a word constituent.  If both options
-@samp{-b} and @samp{-W} are specified, then @samp{-W} has precedence and
-@samp{-b} is ignored.
-
-When @sc{gnu} extensions are enabled, the only way to avoid newline as a
-break character is to write all the break characters in the file with no
-newline at all, not even at the end of the file.  When @sc{gnu} extensions
-are disabled, spaces, tabs and newlines are always considered as break
-characters even if not included in the Break file.
-
-@item -i @var{file}
-@itemx --ignore-file=@var{file}
-
-The file associated with this option contains a list of words which will
-never be taken as keywords in concordance output.  It is called the
-@dfn{Ignore file}.  The file contains exactly one word in each line; the
-end of line separation of words is not subject to the value of the
-@samp{-S} option.
-
-There is a default Ignore file used by @code{ptx} when this option is
-not specified, usually found in @file{/usr/local/lib/eign} if this has
-not been changed at installation time.  If you want to deactivate the
-default Ignore file, specify @code{/dev/null} instead.
-
-@item -o @var{file}
-@itemx --only-file=@var{file}
-
-The file associated with this option contains a list of words which will
-be retained in concordance output; any word not mentioned in this file
-is ignored.  The file is called the @dfn{Only file}.  The file contains
-exactly one word in each line; the end of line separation of words is
-not subject to the value of the @samp{-S} option.
-
-There is no default for the Only file.  When both an Only file and an
-Ignore file are specified, a word is considered a keyword only
-if it is listed in the Only file and not in the Ignore file.
-
-@item -r
-@itemx --references
-
-On each input line, the leading sequence of non-white space characters will be
-taken to be a reference that has the purpose of identifying this input
-line in the resulting permuted index.  For more information about reference
-production, see @xref{Output formatting in ptx}.
-Using this option changes the default value for option @samp{-S}.
-
-Using this option, the program does not try very hard to remove
-references from contexts in output, but it succeeds in doing so
-@emph{when} the context ends exactly at the newline.  If option
-@samp{-r} is used with @samp{-S} default value, or when @sc{gnu} extensions
-are disabled, this condition is always met and references are completely
-excluded from the output contexts.
-
-@item -S @var{regexp}
-@itemx --sentence-regexp=@var{regexp}
-
-This option selects which regular expression will describe the end of a
-line or the end of a sentence.  In fact, this regular expression is not
-the only distinction between end of lines or end of sentences, and input
-line boundaries have no special significance outside this option.  By
-default, when @sc{gnu} extensions are enabled and if @samp{-r} option is not
-used, end of sentences are used.  In this case, this @var{regex} is
-imported from @sc{gnu} Emacs:
-
-@example
-[.?!][]\"')@}]*\\($\\|\t\\|  \\)[ \t\n]*
-@end example
-
-Whenever @sc{gnu} extensions are disabled or if @samp{-r} option is used, end
-of lines are used; in this case, the default @var{regexp} is just:
-
-@example
-\n
-@end example
-
-Using an empty @var{regexp} is equivalent to completely disabling end of
-line or end of sentence recognition.  In this case, the whole file is
-considered to be a single big line or sentence.  The user might want to
-disallow all truncation flag generation as well, through option @samp{-F
-""}.  @xref{Regexps, , Syntax of Regular Expressions, emacs, The GNU Emacs
-Manual}.
-
-When the keywords happen to be near the beginning of the input line or
-sentence, this often creates an unused area at the beginning of the
-output context line; when the keywords happen to be near the end of the
-input line or sentence, this often creates an unused area at the end of
-the output context line.  The program tries to fill those unused areas
-by wrapping around context in them; the tail of the input line or
-sentence is used to fill the unused area on the left of the output line;
-the head of the input line or sentence is used to fill the unused area
-on the right of the output line.
-
-As a matter of convenience to the user, many usual backslashed escape
-sequences from the C language are recognized and converted to the
-corresponding characters by @code{ptx} itself.
-
-@item -W @var{regexp}
-@itemx --word-regexp=@var{regexp}
-
-This option selects which regular expression will describe each keyword.
-By default, if @sc{gnu} extensions are enabled, a word is a sequence of
-letters; the @var{regexp} used is @samp{\w+}.  When @sc{gnu} extensions are
-disabled, a word is by default anything which ends with a space, a tab
-or a newline; the @var{regexp} used is @samp{[^ \t\n]+}.
-
-An empty @var{regexp} is equivalent to not using this option.
-@xref{Regexps, , Syntax of Regular Expressions, emacs, The GNU Emacs
-Manual}.
-
-As a matter of convenience to the user, many usual backslashed escape
-sequences, as found in the C language, are recognized and converted to
-the corresponding characters by @code{ptx} itself.
-
-@end table
-
-
-@node Output formatting in ptx
-@subsection Output formatting
-
-Output format is mainly controlled by the @samp{-O} and @samp{-T} options
-described in the table below.  When neither @samp{-O} nor @samp{-T} are
-selected, and if @sc{gnu} extensions are enabled, the program chooses an
-output format suitable for a dumb terminal.  Each keyword occurrence is
-output to the center of one line, surrounded by its left and right
-contexts.  Each field is properly justified, so the concordance output
-can be readily observed.  As a special feature, if automatic
-references are selected by option @samp{-A} and are output before the
-left context, that is, if option @samp{-R} is @emph{not} selected, then
-a colon is added after the reference; this nicely interfaces with @sc{gnu}
-Emacs @code{next-error} processing.  In this default output format, each
-white space character, like newline and tab, is merely changed to
-exactly one space, with no special attempt to compress consecutive
-spaces.  This might change in the future.  Except for those white space
-characters, every other character of the underlying set of 256
-characters is transmitted verbatim.
-
-Output format is further controlled by the following options.
-
-@table @samp
-
-@item -g @var{number}
-@itemx --gap-size=@var{number}
-
-Select the size of the minimum white space gap between the fields on the
-output line.
-
-@item -w @var{number}
-@itemx --width=@var{number}
-
-Select the maximum output width of each final line.  If references are
-used, they are included or excluded from the maximum output width
-depending on the value of option @samp{-R}.  If this option is not
-selected, that is, when references are output before the left context,
-the maximum output width takes into account the maximum length of all
-references.  If this option is selected, that is, when references are
-output after the right context, the maximum output width does not take
-into account the space taken by references, nor the gap that precedes
-them.
-
-@item -A
-@itemx --auto-reference
-
-Select automatic references.  Each input line will have an automatic
-reference made up of the file name and the line ordinal, with a single
-colon between them.  However, the file name will be empty when standard
-input is being read.  If both @samp{-A} and @samp{-r} are selected, then
-the input reference is still read and skipped, but the automatic
-reference is used at output time, overriding the input reference.
-
-@item -R
-@itemx --right-side-refs
-
-In the default output format, when option @samp{-R} is not used, any
-references produced by the effect of options @samp{-r} or @samp{-A} are
-placed to the far right of output lines, after the right context.  With
-default output format, when the @samp{-R} option is specified, references
-are rather placed at the beginning of each output line, before the left
-context.  For any other output format, option @samp{-R} is
-ignored, with one exception:  with @samp{-R} the width of references
-is @emph{not} taken into account in total output width given by @samp{-w}.
-
-This option is automatically selected whenever @sc{gnu} extensions are
-disabled.
-
-@item -F @var{string}
-@itemx --flac-truncation=@var{string}
-
-This option will request that any truncation in the output be reported
-using the string @var{string}.  Most output fields theoretically extend
-towards the beginning or the end of the current line, or current
-sentence, as selected with option @samp{-S}.  But there is a maximum
-allowed output line width, changeable through option @samp{-w}, which is
-further divided into space for various output fields.  When a field has
-to be truncated because it cannot extend beyond the beginning or the end of
-the current line to fit in, then a truncation occurs.  By default,
-the string used is a single slash, as in @samp{-F /}.
-
-@var{string} may have more than one character, as in @samp{-F ...}.
-Also, in the particular case when @var{string} is empty (@samp{-F ""}),
-truncation flagging is disabled, and no truncation marks are appended in
-this case.
-
-As a matter of convenience to the user, many usual backslashed escape
-sequences, as found in the C language, are recognized and converted to
-the corresponding characters by @code{ptx} itself.
-
-@item -M @var{string}
-@itemx --macro-name=@var{string}
-
-Select another @var{string} to be used instead of @samp{xx}, while
-generating output suitable for @code{nroff}, @code{troff} or @TeX{}.
-
-@item -O
-@itemx --format=roff
-
-Choose an output format suitable for @code{nroff} or @code{troff}
-processing.  Each output line will look like:
-
-@smallexample
-.xx "@var{tail}" "@var{before}" "@var{keyword_and_after}" "@var{head}" "@var{ref}"
-@end smallexample
-
-so it will be possible to write a @samp{.xx} roff macro to take care of
-the output typesetting.  This is the default output format when @sc{gnu}
-extensions are disabled.  Option @samp{-M} can be used to change
-@samp{xx} to another macro name.
-
-In this output format, each non-graphical character, like newline and
-tab, is merely changed to exactly one space, with no special attempt to
-compress consecutive spaces.  Each quote character: @kbd{"} is doubled
-so it will be correctly processed by @code{nroff} or @code{troff}.
-
-@item -T
-@itemx --format=tex
-
-Choose an output format suitable for @TeX{} processing.  Each output
-line will look like:
-
-@smallexample
-\xx @{@var{tail}@}@{@var{before}@}@{@var{keyword}@}@{@var{after}@}@{@var{head}@}@{@var{ref}@}
-@end smallexample
-
-@noindent
-so it will be possible to write a @code{\xx} definition to take care of
-the output typesetting.  Note that when references are not being
-produced, that is, neither option @samp{-A} nor option @samp{-r} is
-selected, the last parameter of each @code{\xx} call is inhibited.
-Option @samp{-M} can be used to change @samp{xx} to another macro
-name.
-
-In this output format, some special characters, like @kbd{$}, @kbd{%},
-@kbd{&}, @kbd{#} and @kbd{_} are automatically protected with a
-backslash.  Curly brackets @kbd{@{}, @kbd{@}} are protected with a
-backslash and a pair of dollar signs (to force mathematical mode).  The
-backslash itself produces the sequence @code{\backslash@{@}}.
-Circumflex and tilde diacritics produce the sequence @code{^\@{ @}} and
-@code{~\@{ @}} respectively.  Other diacriticized characters of the
-underlying character set produce an appropriate @TeX{} sequence as far
-as possible.  The other non-graphical characters, like newline and tab,
-and all other characters which are not part of @sc{ascii}, are merely
-changed to exactly one space, with no special attempt to compress
-consecutive spaces.  Let me know how to improve this special character
-processing for @TeX{}.
-
-@end table
-
-
-@node Compatibility in ptx
-@subsection The @sc{gnu} extensions to @code{ptx}
-
-This version of @code{ptx} contains a few features which do not exist in
-System V @code{ptx}.  These extra features are suppressed by using the
-@samp{-G} command line option, unless overridden by other command line
-options.  Some @sc{gnu} extensions cannot be recovered by overriding, so the
-simple rule is to avoid @samp{-G} if you care about @sc{gnu} extensions.
-Here are the differences between this program and System V @code{ptx}.
-
-@itemize @bullet
-
-@item
-This program can read many input files at once, it always writes the
-resulting concordance on standard output.  On the other hand, System V
-@code{ptx} reads only one file and sends the result to standard output
-or, if a second @var{file} parameter is given on the command, to that
-@var{file}.
-
-Having output parameters not introduced by options is a dangerous
-practice which @sc{gnu} avoids as far as possible.  So, for using @code{ptx}
-portably between @sc{gnu} and System V, you should always use it with a
-single input file, and always expect the result on standard output.  You
-might also want to automatically configure in a @samp{-G} option to
-@code{ptx} calls in products using @code{ptx}, if the configurator finds
-that the installed @code{ptx} accepts @samp{-G}.
-
-@item
-The only options available in System V @code{ptx} are options @samp{-b},
-@samp{-f}, @samp{-g}, @samp{-i}, @samp{-o}, @samp{-r}, @samp{-t} and
-@samp{-w}.  All other options are @sc{gnu} extensions and are not repeated in
-this enumeration.  Moreover, some options have a slightly different
-meaning when @sc{gnu} extensions are enabled, as explained below.
-
-@item
-By default, concordance output is not formatted for @code{troff} or
-@code{nroff}.  It is rather formatted for a dumb terminal.  @code{troff}
-or @code{nroff} output may still be selected through option @samp{-O}.
-
-@item
-Unless @samp{-R} option is used, the maximum reference width is
-subtracted from the total output line width.  With @sc{gnu} extensions
-disabled, width of references is not taken into account in the output
-line width computations.
-
-@item
-All 256 characters, even @kbd{NUL}s, are always read and processed from
-input file with no adverse effect, even if @sc{gnu} extensions are disabled.
-However, System V @code{ptx} does not accept 8-bit characters, a few
-control characters are rejected, and the tilde @kbd{~} is also rejected.
-
-@item
-Input line length is only limited by available memory, even if @sc{gnu}
-extensions are disabled.  However, System V @code{ptx} processes only
-the first 200 characters in each line.
-
-@item
-The break (non-word) characters default to be every character except all
-letters of the underlying character set, diacriticized or not.  When @sc{gnu}
-extensions are disabled, the break characters default to space, tab and
-newline only.
-
-@item
-The program makes better use of output line width.  If @sc{gnu} extensions
-are disabled, the program rather tries to imitate System V @code{ptx},
-but still, there are some slight disposition glitches this program does
-not completely reproduce.
-
-@item
-The user can specify both an Ignore file and an Only file.  This is not
-allowed with System V @code{ptx}.
-
-@end itemize
-
-
-@node Operating on fields within a line
-@chapter Operating on fields within a line
-
-@menu
-* cut invocation::              Print selected parts of lines.
-* paste invocation::            Merge lines of files.
-* join invocation::             Join lines on a common field.
-@end menu
-
-
-@node cut invocation
-@section @code{cut}: Print selected parts of lines
-
-@pindex cut
-@code{cut} writes to standard output selected parts of each line of each
-input file, or standard input if no files are given or for a file name of
-@samp{-}.  Synopsis:
-
-@example
-cut [@var{option}]@dots{} [@var{file}]@dots{}
-@end example
-
-In the table which follows, the @var{byte-list}, @var{character-list},
-and @var{field-list} are one or more numbers or ranges (two numbers
-separated by a dash) separated by commas.  Bytes, characters, and
-fields are numbered starting at 1.  Incomplete ranges may be
-given: @samp{-@var{m}} means @samp{1-@var{m}}; @samp{@var{n}-} means
-@samp{@var{n}} through end of line or last field.
-
-The program accepts the following options.  Also see @ref{Common
-options}.
-
-@table @samp
-
-@item -b @var{byte-list}
-@itemx --bytes=@var{byte-list}
-@opindex -b
-@opindex --bytes
-Print only the bytes in positions listed in @var{byte-list}.  Tabs and
-backspaces are treated like any other character; they take up 1 byte.
-
-@item -c @var{character-list}
-@itemx --characters=@var{character-list}
-@opindex -c
-@opindex --characters
-Print only characters in positions listed in @var{character-list}.
-The same as @samp{-b} for now, but internationalization will change
-that.  Tabs and backspaces are treated like any other character; they
-take up 1 character.
-
-@item -f @var{field-list}
-@itemx --fields=@var{field-list}
-@opindex -f
-@opindex --fields
-Print only the fields listed in @var{field-list}.  Fields are
-separated by a TAB character by default.
-Also print any line that contains no delimiter character, unless
-the @samp{--only-delimited} (@samp{-s}) option is specified
-
-@item -d @var{input_delim_byte}
-@itemx --delimiter=@var{input_delim_byte}
-@opindex -d
-@opindex --delimiter
-For @samp{-f}, fields are separated in the input by the first character
-in @var{input_delim_byte} (default is TAB).
-
-@item -n
-@opindex -n
-Do not split multi-byte characters (no-op for now).
-
-@item -s
-@itemx --only-delimited
-@opindex -s
-@opindex --only-delimited
-For @samp{-f}, do not print lines that do not contain the field separator
-character.
-
-@itemx --output-delimiter=@var{output_delim_string}
-@opindex --output-delimiter
-For @samp{-f}, output fields are separated by @var{output_delim_string}.
-The default is to use the input delimiter.
-
-
-@end table
-
-
-@node paste invocation
-@section @code{paste}: Merge lines of files
-
-@pindex paste
-@cindex merging files
-
-@code{paste} writes to standard output lines consisting of sequentially
-corresponding lines of each given file, separated by a TAB character.
-Standard input is used for a file name of @samp{-} or if no input files
-are given.
-
-Synopsis:
-
-@example
-paste [@var{option}]@dots{} [@var{file}]@dots{}
-@end example
-
-The program accepts the following options.  Also see @ref{Common options}.
-
-@table @samp
-
-@item -s
-@itemx --serial
-@opindex -s
-@opindex --serial
-Paste the lines of one file at a time rather than one line from each
-file.
-
-@item -d @var{delim-list}
-@itemx --delimiters=@var{delim-list}
-@opindex -d
-@opindex --delimiters
-Consecutively use the characters in @var{delim-list} instead of
-TAB to separate merged lines.  When @var{delim-list} is
-exhausted, start again at its beginning.
-
-@end table
-
-
-@node join invocation
-@section @code{join}: Join lines on a common field
-
-@pindex join
-@cindex common field, joining on
-
-@code{join} writes to standard output a line for each pair of input
-lines that have identical join fields.  Synopsis:
-
-@example
-join [@var{option}]@dots{} @var{file1} @var{file2}
-@end example
-
-@vindex LC_COLLATE
-Either @var{file1} or @var{file2} (but not both) can be @samp{-},
-meaning standard input.  @var{file1} and @var{file2} should be already
-sorted in increasing textual order on the join fields, using the
-collating sequence specified by the @env{LC_COLLATE} locale.  Unless
-the @samp{-t} option is given, the input should be sorted ignoring blanks at
-the start of the join field, as in @code{sort -b}.  If the
-@samp{--ignore-case} option is given, lines should be sorted without
-regard to the case of characters in the join field, as in @code{sort -f}.
-
-The defaults are: the join field is the first field in each line;
-fields in the input are separated by one or more blanks, with leading
-blanks on the line ignored; fields in the output are separated by a
-space; each output line consists of the join field, the remaining
-fields from @var{file1}, then the remaining fields from @var{file2}.
-
-The program accepts the following options.  Also see @ref{Common options}.
-
-@table @samp
-
-@item -a @var{file-number}
-@opindex -a
-Print a line for each unpairable line in file @var{file-number} (either
-@samp{1} or @samp{2}), in addition to the normal output.
-
-@item -e @var{string}
-@opindex -e
-Replace those output fields that are missing in the input with
-@var{string}.
-
-@item -i
-@itemx --ignore-case
-@opindex -i
-@opindex --ignore-case
-Ignore differences in case when comparing keys.
-With this option, the lines of the input files must be ordered in the same way.
-Use @samp{sort -f} to produce this ordering.
-
-@item -1 @var{field}
-@itemx -j1 @var{field}
-@opindex -1
-@opindex -j1
-Join on field @var{field} (a positive integer) of file 1.
-
-@item -2 @var{field}
-@itemx -j2 @var{field}
-@opindex -2
-@opindex -j2
-Join on field @var{field} (a positive integer) of file 2.
-
-@item -j @var{field}
-Equivalent to @samp{-1 @var{field} -2 @var{field}}.
-
-@item -o @var{field-list}@dots{}
-Construct each output line according to the format in @var{field-list}.
-Each element in @var{field-list} is either the single character @samp{0} or
-has the form @var{m.n} where the file number, @var{m}, is @samp{1} or
-@samp{2} and @var{n} is a positive field number.
-
-A field specification of @samp{0} denotes the join field.
-In most cases, the functionality of the @samp{0} field spec
-may be reproduced using the explicit @var{m.n} that corresponds
-to the join field.  However, when printing unpairable lines
-(using either of the @samp{-a} or @samp{-v} options), there is no way
-to specify the join field using @var{m.n} in @var{field-list}
-if there are unpairable lines in both files.
-To give @code{join} that functionality, @sc{posix} invented the @samp{0}
-field specification notation.
-
-The elements in @var{field-list}
-are separated by commas or blanks.  Multiple @var{field-list}
-arguments can be given after a single @samp{-o} option; the values
-of all lists given with @samp{-o} are concatenated together.
-All output lines -- including those printed because of any -a or -v
-option -- are subject to the specified @var{field-list}.
-
-@item -t @var{char}
-Use character @var{char} as the input and output field separator.
-
-@item -v @var{file-number}
-Print a line for each unpairable line in file @var{file-number}
-(either @samp{1} or @samp{2}), instead of the normal output.
-
-@end table
-
-In addition, when @sc{gnu} @code{join} is invoked with exactly one argument,
-options @samp{--help} and @samp{--version} are recognized.  @xref{Common
-options}.
-
-
-@node Operating on characters
-@chapter Operating on characters
-
-@cindex operating on characters
-
-This commands operate on individual characters.
-
-@menu
-* tr invocation::               Translate, squeeze, and/or delete characters.
-* expand invocation::           Convert tabs to spaces.
-* unexpand invocation::         Convert spaces to tabs.
-@end menu
-
-
-@node tr invocation
-@section @code{tr}: Translate, squeeze, and/or delete characters
-
-@pindex tr
-
-Synopsis:
-
-@example
-tr [@var{option}]@dots{} @var{set1} [@var{set2}]
-@end example
-
-@code{tr} copies standard input to standard output, performing
-one of the following operations:
-
-@itemize @bullet
-@item
-translate, and optionally squeeze repeated characters in the result,
-@item
-squeeze repeated characters,
-@item
-delete characters,
-@item
-delete characters, then squeeze repeated characters from the result.
-@end itemize
-
-The @var{set1} and (if given) @var{set2} arguments define ordered
-sets of characters, referred to below as @var{set1} and @var{set2}.  These
-sets are the characters of the input that @code{tr} operates on.
-The @samp{--complement} (@samp{-c}) option replaces @var{set1} with its
-complement (all of the characters that are not in @var{set1}).
-
-@menu
-* Character sets::              Specifying sets of characters.
-* Translating::                 Changing one characters to another.
-* Squeezing::                   Squeezing repeats and deleting.
-* Warnings in tr::              Warning messages.
-@end menu
-
-
-@node Character sets
-@subsection Specifying sets of characters
-
-@cindex specifying sets of characters
-
-The format of the @var{set1} and @var{set2} arguments resembles
-the format of regular expressions; however, they are not regular
-expressions, only lists of characters.  Most characters simply
-represent themselves in these strings, but the strings can contain
-the shorthands listed below, for convenience.  Some of them can be
-used only in @var{set1} or @var{set2}, as noted below.
-
-@table @asis
-
-@item Backslash escapes
-@cindex backslash escapes
-
-A backslash followed by a character not listed below causes an error
-message.
-
-@table @samp
-@item \a
-Control-G.
-@item \b
-Control-H.
-@item \f
-Control-L.
-@item \n
-Control-J.
-@item \r
-Control-M.
-@item \t
-Control-I.
-@item \v
-Control-K.
-@item \@var{ooo}
-The character with the value given by @var{ooo}, which is 1 to 3
-octal digits,
-@item \\
-A backslash.
-@end table
-
-@item Ranges
-@cindex ranges
-
-The notation @samp{@var{m}-@var{n}} expands to all of the characters
-from @var{m} through @var{n}, in ascending order.  @var{m} should
-collate before @var{n}; if it doesn't, an error results.  As an example,
-@samp{0-9} is the same as @samp{0123456789}.
-
-@sc{gnu} @code{tr} does not support the System V syntax that uses square
-brackets to enclose ranges.  Translations specified in that format
-sometimes work as expected, since the brackets are often transliterated
-to themselves.  However, they should be avoided because they sometimes
-behave unexpectedly.  For example, @samp{tr -d '[0-9]'} deletes brackets
-as well as digits.
-
-Many historically common and even accepted uses of ranges are not
-portable.  For example, on @sc{ebcdic} hosts using the @samp{A-Z}
-range will not do what most would expect because @samp{A} through @samp{Z}
-are not contiguous as they are in @sc{ascii}.
-If you can rely on a @sc{posix} compliant version of @code{tr}, then
-the best way to work around this is to use character classes (see below).
-Otherwise, it is most portable (and most ugly) to enumerate the members
-of the ranges.
-
-@item Repeated characters
-@cindex repeated characters
-
-The notation @samp{[@var{c}*@var{n}]} in @var{set2} expands to @var{n}
-copies of character @var{c}.  Thus, @samp{[y*6]} is the same as
-@samp{yyyyyy}.  The notation @samp{[@var{c}*]} in @var{string2} expands
-to as many copies of @var{c} as are needed to make @var{set2} as long as
-@var{set1}.  If @var{n} begins with @samp{0}, it is interpreted in
-octal, otherwise in decimal.
-
-@item Character classes
-@cindex character classes
-
-The notation @samp{[:@var{class}:]} expands to all of the characters in
-the (predefined) class @var{class}.  The characters expand in no
-particular order, except for the @code{upper} and @code{lower} classes,
-which expand in ascending order.  When the @samp{--delete} (@samp{-d})
-and @samp{--squeeze-repeats} (@samp{-s}) options are both given, any
-character class can be used in @var{set2}.  Otherwise, only the
-character classes @code{lower} and @code{upper} are accepted in
-@var{set2}, and then only if the corresponding character class
-(@code{upper} and @code{lower}, respectively) is specified in the same
-relative position in @var{set1}.  Doing this specifies case conversion.
-The class names are given below; an error results when an invalid class
-name is given.
-
-@table @code
-@item alnum
-@opindex alnum
-Letters and digits.
-@item alpha
-@opindex alpha
-Letters.
-@item blank
-@opindex blank
-Horizontal whitespace.
-@item cntrl
-@opindex cntrl
-Control characters.
-@item digit
-@opindex digit
-Digits.
-@item graph
-@opindex graph
-Printable characters, not including space.
-@item lower
-@opindex lower
-Lowercase letters.
-@item print
-@opindex print
-Printable characters, including space.
-@item punct
-@opindex punct
-Punctuation characters.
-@item space
-@opindex space
-Horizontal or vertical whitespace.
-@item upper
-@opindex upper
-Uppercase letters.
-@item xdigit
-@opindex xdigit
-Hexadecimal digits.
-@end table
-
-@item Equivalence classes
-@cindex equivalence classes
-
-The syntax @samp{[=@var{c}=]} expands to all of the characters that are
-equivalent to @var{c}, in no particular order.  Equivalence classes are
-a relatively recent invention intended to support non-English alphabets.
-But there seems to be no standard way to define them or determine their
-contents.  Therefore, they are not fully implemented in @sc{gnu} @code{tr};
-each character's equivalence class consists only of that character,
-which is of no particular use.
-
-@end table
-
-
-@node Translating
-@subsection Translating
-
-@cindex translating characters
-
-@code{tr} performs translation when @var{set1} and @var{set2} are
-both given and the @samp{--delete} (@samp{-d}) option is not given.
-@code{tr} translates each character of its input that is in @var{set1}
-to the corresponding character in @var{set2}.  Characters not in
-@var{set1} are passed through unchanged.  When a character appears more
-than once in @var{set1} and the corresponding characters in @var{set2}
-are not all the same, only the final one is used.  For example, these
-two commands are equivalent:
-
-@example
-tr aaa xyz
-tr a z
-@end example
-
-A common use of @code{tr} is to convert lowercase characters to
-uppercase.  This can be done in many ways.  Here are three of them:
-
-@example
-tr abcdefghijklmnopqrstuvwxyz ABCDEFGHIJKLMNOPQRSTUVWXYZ
-tr a-z A-Z
-tr '[:lower:]' '[:upper:]'
-@end example
-
-@noindent
-But note that using ranges like @code{a-z} above is not portable.
-
-When @code{tr} is performing translation, @var{set1} and @var{set2}
-typically have the same length.  If @var{set1} is shorter than
-@var{set2}, the extra characters at the end of @var{set2} are ignored.
-
-On the other hand, making @var{set1} longer than @var{set2} is not
-portable; @sc{posix.2} says that the result is undefined.  In this situation,
-BSD @code{tr} pads @var{set2} to the length of @var{set1} by repeating
-the last character of @var{set2} as many times as necessary.  System V
-@code{tr} truncates @var{set1} to the length of @var{set2}.
-
-By default, @sc{gnu} @code{tr} handles this case like BSD @code{tr}.  When
-the @samp{--truncate-set1} (@samp{-t}) option is given, @sc{gnu} @code{tr}
-handles this case like the System V @code{tr} instead.  This option is
-ignored for operations other than translation.
-
-Acting like System V @code{tr} in this case breaks the relatively common
-BSD idiom:
-
-@example
-tr -cs A-Za-z0-9 '\012'
-@end example
-
-@noindent
-because it converts only zero bytes (the first element in the
-complement of @var{set1}), rather than all non-alphanumerics, to
-newlines.
-
-@noindent
-By the way, the above idiom is not portable because it uses ranges.
-Assuming a @sc{posix} compliant @code{tr}, here is a better way to write it:
-
-@example
-tr -cs '[:alnum:]' '[\n*]'
-@end example
-
-
-@node Squeezing
-@subsection Squeezing repeats and deleting
-
-@cindex squeezing repeat characters
-@cindex deleting characters
-
-When given just the @samp{--delete} (@samp{-d}) option, @code{tr}
-removes any input characters that are in @var{set1}.
-
-When given just the @samp{--squeeze-repeats} (@samp{-s}) option,
-@code{tr} replaces each input sequence of a repeated character that
-is in @var{set1} with a single occurrence of that character.
-
-When given both @samp{--delete} and @samp{--squeeze-repeats}, @code{tr}
-first performs any deletions using @var{set1}, then squeezes repeats
-from any remaining characters using @var{set2}.
-
-The @samp{--squeeze-repeats} option may also be used when translating,
-in which case @code{tr} first performs translation, then squeezes
-repeats from any remaining characters using @var{set2}.
-
-Here are some examples to illustrate various combinations of options:
-
-@itemize @bullet
-
-@item
-Remove all zero bytes:
-
-@example
-tr -d '\000'
-@end example
-
-@item
-Put all words on lines by themselves.  This converts all
-non-alphanumeric characters to newlines, then squeezes each string
-of repeated newlines into a single newline:
-
-@example
-tr -cs '[:alnum:]' '[\n*]'
-@end example
-
-@item
-Convert each sequence of repeated newlines to a single newline:
-
-@example
-tr -s '\n'
-@end example
-
-@item
-Find doubled occurrences of words in a document.
-For example, people often write ``the the'' with the duplicated words
-separated by a newline.  The bourne shell script below works first
-by converting each sequence of punctuation and blank characters to a
-single newline.  That puts each ``word'' on a line by itself.
-Next it maps all uppercase characters to lower case, and finally it
-runs @code{uniq} with the @samp{-d} option to print out only the words
-that were adjacent duplicates.
-
-@example
-#!/bin/sh
-cat "$@@" \
-  | tr -s '[:punct:][:blank:]' '\n' \
-  | tr '[:upper:]' '[:lower:]' \
-  | uniq -d
-@end example
-
-@item
-Deleting a small set of characters is usually straightforward.  For example,
-to remove all @samp{a}s, @samp{x}s, and @samp{M}s you would do this:
-
-@example
-tr -d axM
-@end example
-
-However, when @samp{-} is one of those characters, it can be tricky because
-@samp{-} has special meanings.  Performing the same task as above but also
-removing all @samp{-} characters, we might try @code{tr -d -axM}, but
-that would fail because @code{tr} would try to interpret @samp{-a} as
-a command-line option.  Alternatively, we could try putting the hyphen
-inside the string, @code{tr -d a-xM}, but that wouldn't work either because
-it would make @code{tr} interpret @code{a-x} as the range of characters
-@samp{a}@dots{}@samp{x} rather than the three.
-One way to solve the problem is to put the hyphen at the end of the list
-of characters:
-
-@example
-tr -d axM-
-@end example
-
-More generally, use the character class notation @code{[=c=]}
-with @samp{-} (or any other character) in place of the @samp{c}:
-
-@example
-tr -d '[=-=]axM'
-@end example
-
-Note how single quotes are used in the above example to protect the
-square brackets from interpretation by a shell.
-
-@end itemize
-
-
-@node Warnings in tr
-@subsection Warning messages
-
-@vindex POSIXLY_CORRECT
-Setting the environment variable @env{POSIXLY_CORRECT} turns off the
-following warning and error messages, for strict compliance with
-@sc{posix.2}.  Otherwise, the following diagnostics are issued:
-
-@enumerate
-
-@item
-When the @samp{--delete} option is given but @samp{--squeeze-repeats}
-is not, and @var{set2} is given, @sc{gnu} @code{tr} by default prints
-a usage message and exits, because @var{set2} would not be used.
-The @sc{posix} specification says that @var{set2} must be ignored in
-this case. Silently ignoring arguments is a bad idea.
-
-@item
-When an ambiguous octal escape is given.  For example, @samp{\400}
-is actually @samp{\40} followed by the digit @samp{0}, because the
-value 400 octal does not fit into a single byte.
-
-@end enumerate
-
-@sc{gnu} @code{tr} does not provide complete BSD or System V compatibility.
-For example, it is impossible to disable interpretation of the @sc{posix}
-constructs @samp{[:alpha:]}, @samp{[=c=]}, and @samp{[c*10]}.  Also, @sc{gnu}
-@code{tr} does not delete zero bytes automatically, unlike traditional
-Unix versions, which provide no way to preserve zero bytes.
-
-
-@node expand invocation
-@section @code{expand}: Convert tabs to spaces
-
-@pindex expand
-@cindex tabs to spaces, converting
-@cindex converting tabs to spaces
-
-@code{expand} writes the contents of each given @var{file}, or standard
-input if none are given or for a @var{file} of @samp{-}, to standard
-output, with tab characters converted to the appropriate number of
-spaces.  Synopsis:
-
-@example
-expand [@var{option}]@dots{} [@var{file}]@dots{}
-@end example
-
-By default, @code{expand} converts all tabs to spaces.  It preserves
-backspace characters in the output; they decrement the column count for
-tab calculations.  The default action is equivalent to @samp{-8} (set
-tabs every 8 columns).
-
-The program accepts the following options.  Also see @ref{Common options}.
-
-@table @samp
-
-@item -@var{tab1}[,@var{tab2}]@dots{}
-@itemx -t @var{tab1}[,@var{tab2}]@dots{}
-@itemx --tabs=@var{tab1}[,@var{tab2}]@dots{}
-@opindex -@var{tab}
-@opindex -t
-@opindex --tabs
-@cindex tabstops, setting
-If only one tab stop is given, set the tabs @var{tab1} spaces apart
-(default is 8).  Otherwise, set the tabs at columns @var{tab1},
-@var{tab2}, @dots{} (numbered from 0), and replace any tabs beyond the
-last tabstop given with single spaces.  If the tabstops are specified
-with the @samp{-t} or @samp{--tabs} option, they can be separated by
-blanks as well as by commas.
-
-@item -i
-@itemx --initial
-@opindex -i
-@opindex --initial
-@cindex initial tabs, converting
-Only convert initial tabs (those that precede all non-space or non-tab
-characters) on each line to spaces.
-
-@end table
-
-
-@node unexpand invocation
-@section @code{unexpand}: Convert spaces to tabs
-
-@pindex unexpand
-
-@code{unexpand} writes the contents of each given @var{file}, or
-standard input if none are given or for a @var{file} of @samp{-}, to
-standard output, with strings of two or more space or tab characters
-converted to as many tabs as possible followed by as many spaces as are
-needed.  Synopsis:
-
-@example
-unexpand [@var{option}]@dots{} [@var{file}]@dots{}
-@end example
-
-By default, @code{unexpand} converts only initial spaces and tabs (those
-that precede all non space or tab characters) on each line.  It
-preserves backspace characters in the output; they decrement the column
-count for tab calculations.  By default, tabs are set at every 8th
-column.
-
-The program accepts the following options.  Also see @ref{Common options}.
-
-@table @samp
-
-@item -@var{tab1}[,@var{tab2}]@dots{}
-@itemx -t @var{tab1}[,@var{tab2}]@dots{}
-@itemx --tabs=@var{tab1}[,@var{tab2}]@dots{}
-@opindex -@var{tab}
-@opindex -t
-@opindex --tabs
-If only one tab stop is given, set the tabs @var{tab1} spaces apart
-instead of the default 8.  Otherwise, set the tabs at columns
-@var{tab1}, @var{tab2}, @dots{} (numbered from 0), and leave spaces and
-tabs beyond the tabstops given unchanged.  If the tabstops are specified
-with the @samp{-t} or @samp{--tabs} option, they can be separated by
-blanks as well as by commas.  This option implies the @samp{-a} option.
-
-@item -a
-@itemx --all
-@opindex -a
-@opindex --all
-Convert all strings of two or more spaces or tabs, not just initial
-ones, to tabs.
-
-@end table
-
-
-@node Directory listing
-@chapter Directory listing
-
-This chapter describes the @code{ls} command and its variants @code{dir}
-and @code{vdir}, which list information about files.
-
-@menu
-* ls invocation::               List directory contents.
-* dir invocation::              Briefly ls.
-* vdir invocation::             Verbosely ls.
-* dircolors invocation::        Color setup for ls, etc.
-@end menu
-
-
-@node ls invocation
-@section @code{ls}: List directory contents
-
-@pindex ls
-@cindex directory listing
-
-The @code{ls} program lists information about files (of any type,
-including directories).  Options and file arguments can be intermixed
-arbitrarily, as usual.
-
-For non-option command-line arguments that are directories, by default
-@code{ls} lists the contents of directories, not recursively, and
-omitting files with names beginning with @samp{.}.  For other non-option
-arguments, by default @code{ls} lists just the file name.  If no
-non-option argument is specified, @code{ls} operates on the current
-directory, acting as if it had been invoked with a single argument of @samp{.}.
-
-@vindex LC_COLLATE
-By default, the output is sorted alphabetically, according to the locale
-settings in effect. @footnote{If you have arranged to use a non-@sc{posix}
-locale (e.g., by setting @env{LC_ALL} to @samp{en_US}), then @code{ls} may
-produce output that is sorted differently than you're accustomed to.
-In that case, set the @env{LC_COLLATE} environment variable to @samp{C}.}
-If standard output is
-a terminal, the output is in columns (sorted vertically) and control
-characters are output as question marks; otherwise, the output is listed
-one per line and control characters are output as-is.
-
-Because @code{ls} is such a fundamental program, it has accumulated many
-options over the years.  They are described in the subsections below;
-within each section, options are listed alphabetically (ignoring case).
-The division of options into the subsections is not absolute, since some
-options affect more than one aspect of @code{ls}'s operation.
-
-Also see @ref{Common options}.
-
-@menu
-* Which files are listed::
-* What information is listed::
-* Sorting the output::
-* More details about version sort::
-* General output formatting::
-* Formatting file timestamps::
-* Formatting the file names::
-@end menu
-
-
-@node Which files are listed
-@subsection Which files are listed
-
-These options determine which files @code{ls} lists information for.
-By default, any files and the contents of any directories on the command
-line are shown.
-
-@table @samp
-
-@item -a
-@itemx --all
-@opindex -a
-@opindex --all
-List all files in directories, including files that start with @samp{.}.
-
-@item -A
-@itemx --almost-all
-@opindex -A
-@opindex --almost-all
-List all files in directories except for @file{.} and @file{..}.
-
-@item -B
-@itemx --ignore-backups
-@opindex -B
-@opindex --ignore-backups
-@cindex backup files, ignoring
-Do not list files that end with @samp{~}, unless they are given on the
-command line.
-
-@item -d
-@itemx --directory
-@opindex -d
-@opindex --directory
-List just the names of directories, as with other types of files, rather
-than listing their contents.
-
-@item -H
-@itemx --dereference-command-line
-@opindex -H
-@opindex --dereference-command-line
-@cindex symbolic links, dereferencing
-If a command line argument specifies a symbolic link, show information
-for the file the link references rather than for the link itself.
-
-@item -I PATTERN
-@itemx --ignore=PATTERN
-@opindex -I
-@opindex --ignore=@var{pattern}
-Do not list files whose names match the shell pattern (not regular
-expression) @var{pattern} unless they are given on the command line.  As
-in the shell, an initial @samp{.} in a file name does not match a
-wildcard at the start of @var{pattern}.  Sometimes it is useful
-to give this option several times.  For example,
-
-@smallexample
-$ ls --ignore='.??*' --ignore='.[^.]' --ignore='#*'
-@end smallexample
-
-The first option ignores names of length 3 or more that start with @samp{.},
-the second ignores all two-character names that start with @samp{.}
-except @samp{..}, and the third ignores names that start with @samp{#}.
-
-@item -L
-@itemx --dereference
-@opindex -L
-@opindex --dereference
-@cindex symbolic links, dereferencing
-When showing file information for a symbolic link, show information
-for the file the link references rather than the link itself.
-
-@item -R
-@itemx --recursive
-@opindex -R
-@opindex --recursive
-@cindex recursive directory listing
-@cindex directory listing, recursive
-List the contents of all directories recursively.
-
-@end table
-
-
-@node What information is listed
-@subsection What information is listed
-
-These options affect the information that @code{ls} displays.  By
-default, only file names are shown.
-
-@table @samp
-
-@item -D
-@itemx --dired
-@opindex -D
-@opindex --dired
-@cindex dired Emacs mode support
-With the long listing (@samp{-l}) format, print an additional line after
-the main output:
-
-@example
-//DIRED// @var{beg1 end1 beg2 end2 @dots{}}
-@end example
-
-@noindent
-The @var{begN} and @var{endN} are unsigned integers that record the
-byte position of the beginning and end of each file name in the output.
-This makes it easy for Emacs to find the names, even when they contain
-unusual characters such as space or newline, without fancy searching.
-
-If directories are being listed recursively (@code{-R}), output a similar
-line after each subdirectory:
-@example
-//SUBDIRED// @var{format} @var{beg1 end1 @dots{}}
-@end example
-
-Finally, output a line of the form:
-@example
-//DIRED-OPTIONS// --quoting-style=@var{word}
-@end example
-where @var{word} is the quoting style (@pxref{Formatting the file names}).
-
-@item --full-time
-@opindex --full-time
-Produce long format directory listings, and list times in full.  It is
-equivalent to using @option{--format=long} with
-@option{--time-style=full-iso} (@pxref{Formatting file timestamps}).
-
-@item -g
-@opindex -g
-Produce long format directory listings, but don't display owner information.
-
-@item -G
-@itemx --no-group
-@opindex -G
-@opindex --no-group
-Inhibit display of group information in a long format directory listing.
-(This is the default in some non-@sc{gnu} versions of @code{ls}, so we
-provide this option for compatibility.)
-
-@item -h
-@itemx --human-readable
-@opindex -h
-@opindex --human-readable
-@cindex human-readable output
-Append a size letter such as @samp{M} for megabytes to each size.
-Powers of 1024 are used, not 1000; @samp{M} stands for 1,048,576 bytes.
-Use the @samp{--si} option if you prefer powers of 1000.
-
-@item -i
-@itemx --inode
-@opindex -i
-@opindex --inode
-@cindex inode number, printing
-Print the inode number (also called the file serial number and index
-number) of each file to the left of the file name.  (This number
-uniquely identifies each file within a particular filesystem.)
-
-@item -l
-@itemx --format=long
-@itemx --format=verbose
-@opindex -l
-@opindex --format
-@opindex long ls @r{format}
-@opindex verbose ls @r{format}
-In addition to the name of each file, print the file type, permissions,
-number of hard links, owner name, group name, size in bytes, and
-timestamp (@pxref{Formatting file timestamps}), normally
-the modification time.
-
-For each directory that is listed, preface the files with a line
-@samp{total @var{blocks}}, where @var{blocks} is the total disk allocation
-for all files in that directory.  The block size currently defaults to 1024
-bytes, but this can be overridden (@pxref{Block size}).
-The @var{blocks} computed counts each hard link separately;
-this is arguably a deficiency.
-
-@cindex permissions, output by @code{ls}
-The permissions listed are similar to symbolic mode specifications
-(@pxref{Symbolic Modes}).  But @code{ls} combines multiple bits into the
-third character of each set of permissions as follows:
-@table @samp
-@item s
-If the setuid or setgid bit and the corresponding executable bit
-are both set.
-
-@item S
-If the setuid or setgid bit is set but the corresponding executable bit
-is not set.
-
-@item t
-If the sticky bit and the other-executable bit are both set.
-
-@item T
-If the sticky bit is set but the other-executable bit is not set.
-
-@item x
-If the executable bit is set and none of the above apply.
-
-@item -
-Otherwise.
-@end table
-
-Following the permission bits is a single character that specifies
-whether an alternate access method applies to the file.  When that
-character is a space, there is no alternate access method.  When it
-is a printing character (e.g., @samp{+}), then there is such a method.
-
-@item -n
-@itemx --numeric-uid-gid
-@opindex -n
-@opindex --numeric-uid-gid
-@cindex numeric uid and gid
-Produce long format directory listings, but
-display numeric UIDs and GIDs instead of the owner and group names.
-
-@item -o
-@opindex -o
-Produce long format directory listings, but don't display group information.
-It is equivalent to using @samp{--format=long} with @samp{--no-group} .
-
-@item -s
-@itemx --size
-@opindex -s
-@opindex --size
-@cindex disk allocation
-@cindex size of files, reporting
-Print the disk allocation of each file to the left of the file name.
-This is the amount of disk space used by the file, which is usually a
-bit more than the file's size, but it can be less if the file has holes.
-
-Normally the disk allocation is printed in units of
-1024 bytes, but this can be overridden (@pxref{Block size}).
-
-@cindex NFS mounts from BSD to HP-UX
-For files that are NFS-mounted from an HP-UX system to a BSD system,
-this option reports sizes that are half the correct values.  On HP-UX
-systems, it reports sizes that are twice the correct values for files
-that are NFS-mounted from BSD systems.  This is due to a flaw in HP-UX;
-it also affects the HP-UX @code{ls} program.
-
-@itemx --si
-@opindex --si
-@cindex SI output
-Append a size letter such as @samp{M} for megabytes to each size.  (SI
-is the International System of Units, which defines these letters as
-prefixes.)  Powers of 1000 are used, not 1024; @samp{M} stands for
-1,000,000 bytes.  Use the @samp{-h} or @samp{--human-readable} option if
-you prefer powers of 1024.
-
-@end table
-
-
-@node Sorting the output
-@subsection Sorting the output
-
-@cindex sorting @code{ls} output
-These options change the order in which @code{ls} sorts the information
-it outputs.  By default, sorting is done by character code (e.g., ASCII
-order).
-
-@table @samp
-
-@item -c
-@itemx --time=ctime
-@itemx --time=status
-@itemx --time=use
-@opindex -c
-@opindex --time
-@opindex ctime@r{, printing or sorting by}
-@opindex status time@r{, printing or sorting by}
-@opindex use time@r{, printing or sorting files by}
-If the long listing format (e.g., @samp{-l}, @samp{-o}) is being used,
-print the status change time (the @samp{ctime} in the inode) instead of
-the modification time.
-When explicitly sorting by time (@samp{--sort=time} or @samp{-t})
-or when not using a long listing format,
-sort according to the status change time.
-
-@item -f
-@opindex -f
-@cindex unsorted directory listing
-@cindex directory order, listing by
-Primarily, like @samp{-U}---do not sort; list the files in whatever
-order they are stored in the directory.  But also enable @samp{-a} (list
-all files) and disable @samp{-l}, @samp{--color}, and @samp{-s} (if they
-were specified before the @samp{-f}).
-
-@item -r
-@itemx --reverse
-@opindex -r
-@opindex --reverse
-@cindex reverse sorting
-Reverse whatever the sorting method is---e.g., list files in reverse
-alphabetical order, youngest first, smallest first, or whatever.
-
-@item -S
-@itemx --sort=size
-@opindex -S
-@opindex --sort
-@opindex size of files@r{, sorting files by}
-Sort by file size, largest first.
-
-@item -t
-@itemx --sort=time
-@opindex -t
-@opindex --sort
-@opindex modification time@r{, sorting files by}
-Sort by modification time (the @samp{mtime} in the inode), newest first.
-
-@item -u
-@itemx --time=atime
-@itemx --time=access
-@opindex -u
-@opindex --time
-@opindex use time@r{, printing or sorting files by}
-@opindex atime@r{, printing or sorting files by}
-@opindex access time@r{, printing or sorting files by}
-If the long listing format (e.g., @samp{--format=long}) is being used,
-print the last access time (the @samp{atime} in the inode).
-When explicitly sorting by time (@samp{--sort=time} or @samp{-t})
-or when not using a long listing format, sort according to the access time.
-
-@item -U
-@itemx --sort=none
-@opindex -U
-@opindex --sort
-@opindex none@r{, sorting option for @code{ls}}
-Do not sort; list the files in whatever order they are
-stored in the directory.  (Do not do any of the other unrelated things
-that @samp{-f} does.)  This is especially useful when listing very large
-directories, since not doing any sorting can be noticeably faster.
-
-@item -v
-@itemx --sort=version
-@opindex -v
-@opindex --sort
-@opindex version@r{, sorting option for @code{ls}}
-Sort by version name and number, lowest first.  It behaves like a default
-sort, except that each sequence of decimal digits is treated numerically
-as an index/version number.  (@xref{More details about version sort}.)
-
-@item -X
-@itemx --sort=extension
-@opindex -X
-@opindex --sort
-@opindex extension@r{, sorting files by}
-Sort directory contents alphabetically by file extension (characters
-after the last @samp{.}); files with no extension are sorted first.
-
-@end table
-
-
-@node More details about version sort
-@subsection More details about version sort
-
-The version sort takes into account the fact that file names frequently include
-indices or version numbers.  Standard sorting functions usually do not produce
-the ordering that people expect because comparisons are made on a
-character-by-character basis.  The version
-sort addresses this problem, and is especially useful when browsing
-directories that contain many files with indices/version numbers in their
-names:
-
-@example
-      > ls -1            > ls -1v
-      foo.zml-1.gz       foo.zml-1.gz
-      foo.zml-100.gz     foo.zml-2.gz
-      foo.zml-12.gz      foo.zml-6.gz
-      foo.zml-13.gz      foo.zml-12.gz
-      foo.zml-2.gz       foo.zml-13.gz
-      foo.zml-25.gz      foo.zml-25.gz
-      foo.zml-6.gz       foo.zml-100.gz
-@end example
-
-Note also that numeric parts with leading zeroes are considered as
-fractional one:
-
-@example
-      > ls -1            > ls -1v
-      abc-1.007.tgz      abc-1.007.tgz
-      abc-1.012b.tgz     abc-1.01a.tgz
-      abc-1.01a.tgz      abc-1.012b.tgz
-@end example
-
-@node General output formatting
-@subsection General output formatting
-
-These options affect the appearance of the overall output.
-
-@table @samp
-
-@item -1
-@itemx --format=single-column
-@opindex -1
-@opindex --format
-@opindex single-column @r{output of files}
-List one file per line.  This is the default for @code{ls} when standard
-output is not a terminal.
-
-@item -C
-@itemx --format=vertical
-@opindex -C
-@opindex --format
-@opindex vertical @r{sorted files in columns}
-List files in columns, sorted vertically.  This is the default for
-@code{ls} if standard output is a terminal.  It is always the default
-for the @code{dir} and @code{d} programs.
-@sc{gnu} @code{ls} uses variable width columns to display as many files as
-possible in the fewest lines.
-
-@item --color [=@var{when}]
-@opindex --color
-@cindex color, distinguishing file types with
-Specify whether to use color for distinguishing file types.  @var{when}
-may be omitted, or one of:
-@itemize @bullet
-@item none
-@vindex none @r{color option}
-- Do not use color at all.  This is the default.
-@item auto
-@vindex auto @r{color option}
-@cindex terminal, using color iff
-- Only use color if standard output is a terminal.
-@item always
-@vindex always @r{color option}
-- Always use color.
-@end itemize
-Specifying @samp{--color} and no @var{when} is equivalent to
-@samp{--color=always}.
-Piping a colorized listing through a pager like @code{more} or
-@code{less} usually produces unreadable results.  However, using
-@code{more -f} does seem to work.
-
-@item -F
-@itemx --classify
-@itemx --indicator-style=classify
-@opindex -F
-@opindex --classify
-@opindex --indicator-style
-@cindex file type and executables, marking
-@cindex executables and file type, marking
-Append a character to each file name indicating the file type.  Also,
-for regular files that are executable, append @samp{*}.  The file type
-indicators are @samp{/} for directories, @samp{@@} for symbolic links,
-@samp{|} for FIFOs, @samp{=} for sockets, and nothing for regular files.
-
-@item --indicator-style=@var{word}
-@opindex --indicator-style
-Append a character indicator with style @var{word} to entry names,
-as follows:
-@table @samp
-@item none
-Do not append any character indicator; this is the default.
-@item file-type
-Append @samp{/} for directories, @samp{@@} for symbolic links, @samp{|}
-for FIFOs, @samp{=} for sockets, and nothing for regular files.  This is
-the same as the @samp{-p} or @samp{--file-type} option.
-@item classify
-Append @samp{*} for executable regular files, otherwise behave as for
-@samp{file-type}.  This is the same as the @samp{-F} or
-@samp{--classify} option.
-@end table
-
-@item -k
-@itemx --kilobytes
-@opindex -k
-@opindex --kilobytes
-Print file sizes in 1024-byte blocks, overriding the default block
-size (@pxref{Block size}).
-
-@item -m
-@itemx --format=commas
-@opindex -m
-@opindex --format
-@opindex commas@r{, outputting between files}
-List files horizontally, with as many as will fit on each line,
-separated by @samp{, } (a comma and a space).
-
-@item -p
-@itemx --file-type
-@itemx --indicator-style=file-type
-@opindex --file-type
-@opindex --indicator-style
-@cindex file type, marking
-Append a character to each file name indicating the file type. This is
-like @samp{-F}, except that executables are not marked.
-
-@item -x @var{format}
-@itemx --format=across
-@itemx --format=horizontal
-@opindex -x
-@opindex --format
-@opindex across@r{, listing files}
-@opindex horizontal@r{, listing files}
-List the files in columns, sorted horizontally.
-
-@item -T @var{cols}
-@itemx --tabsize=@var{cols}
-@opindex -T
-@opindex --tabsize
-Assume that each tabstop is @var{cols} columns wide.  The default is 8.
-@code{ls} uses tabs where possible in the output, for efficiency.  If
-@var{cols} is zero, do not use tabs at all.
-
-@item -w
-@itemx --width=@var{cols}
-@opindex -w
-@opindex --width
-@vindex COLUMNS
-Assume the screen is @var{cols} columns wide.  The default is taken
-from the terminal settings if possible; otherwise the environment
-variable @env{COLUMNS} is used if it is set; otherwise the default
-is 80.
-
-@end table
-
-
-@node Formatting file timestamps
-@subsection Formatting file timestamps
-
-By default, file timestamps are output in abbreviated form.  For files
-with a time more than six months old or in the future, the timestamp
-contains the year instead of the time of day.  If the timestamp contains
-today's date with the year rather than a time of day, the file's time is
-in the future, which means you probably have clock skew problems which
-may break programs like @command{make} that rely on file times.
-
-The following option changes how file timestamps are printed.
-
-@table @samp
-@item --time-style=@var{word}
-@opindex --time-style
-@cindex time style
-Use style @var{word} to output file timestamps.  The @var{word} should
-be one of the following:
-
-@table @samp
-@item full-iso
-List timestamps in full, rather than using the standard abbreviation
-heuristics.  The format is @sc{iso} 8601 date, time, and time zone
-format with nanosecond precision, e.g., @samp{2001-05-14
-23:45:56.477817180 -0700}.  It's not possible to change the format, but
-you can extract out the date string with @code{cut} and then pass the
-result to @code{date -d}.  @xref{date invocation, @code{date}
-invocation, , sh-utils, Shell utilities}.
-
-This is useful because the time output includes all the information that
-is available from the operating system.  For example, this can help
-when you have a Makefile that is not regenerating files properly.
-
-@item iso
-Use @sc{iso}-style time stamps like @samp{2001-05-14@ } and @samp{05-14
-23:45}.
-
-@item locale
-@vindex LC_ALL
-@vindex LC_TIME
-@vindex LANG
-Use locale-dependent dates like @samp{touko@ @ 14 2001} and @samp{touko@
-@ 14 23:45}, time stamps that might occur in a Finnish locale.  The
-locale for formatting timestamps is specified by the first of three
-environment variables @env{LC_ALL}, @env{LC_TIME}, @env{LANG} that is
-set.
-
-@item posix-iso
-Use traditional @sc{posix}-locale dates like @samp{May 14@ @ 2001} and
-@samp{May 14 23:45} unless the user specifies a non-@sc{posix} locale,
-in which case use @sc{iso}-style dates.  This is the default.
-@end table
-@end table
-
-@vindex TIME_STYLE
-You can specify the default value of the @option{--time-style} option
-with the environment variable @env{TIME_STYLE}.  @sc{gnu} Emacs 21 and
-later can parse @sc{iso} dates, but older Emacs versions do not, so if
-you are using an older version of Emacs and specify a non-@sc{posix}
-locale, you may need to set @samp{TIME_STYLE="locale"}.
-
-
-@node Formatting the file names
-@subsection Formatting the file names
-
-These options change how file names themselves are printed.
-
-@table @samp
-
-@item -b
-@itemx --escape
-@itemx --quoting-style=escape
-@opindex -b
-@opindex --escape
-@opindex --quoting-style
-@cindex backslash sequences for file names
-Quote nongraphic characters in file names using alphabetic and octal
-backslash sequences like those used in C.
-
-@item -N
-@itemx --literal
-@opindex -N
-@opindex --literal
-Do not quote file names.
-
-@item -q
-@itemx --hide-control-chars
-@opindex -q
-@opindex --hide-control-chars
-Print question marks instead of nongraphic characters in file names.
-This is the default if the output is a terminal and the program is
-@code{ls}.
-
-@item -Q
-@itemx --quote-name
-@itemx --quoting-style=c
-@opindex -Q
-@opindex --quote-name
-@opindex --quoting-style
-Enclose file names in double quotes and quote nongraphic characters as
-in C.
-
-@item --quoting-style=@var{word}
-@opindex --quoting-style
-@cindex quoting style
-Use style @var{word} to quote output names.  The @var{word} should
-be one of the following:
-@table @samp
-@item literal
-Output names as-is.
-@item shell
-Quote names for the shell if they contain shell metacharacters or would
-cause ambiguous output.
-@item shell-always
-Quote names for the shell, even if they would normally not require quoting.
-@item c
-Quote names as for a C language string; this is the same as the
-@samp{-Q} or @samp{--quote-name} option.
-@item escape
-Quote as with @samp{c} except omit the surrounding double-quote
-characters; this is the same as the @samp{-b} or @samp{--escape} option.
-@item clocale
-Quote as with @samp{c} except use quotation marks appropriate for the
-locale.
-@item locale
-@c Use @t instead of @samp to avoid duplicate quoting in some output styles.
-Like @samp{clocale}, but quote @t{`like this'} instead of @t{"like
-this"} in the default C locale.  This looks nicer on many displays.
-@end table
-
-You can specify the default value of the @samp{--quoting-style} option
-with the environment variable @env{QUOTING_STYLE}.  If that environment
-variable is not set, the default value is @samp{literal}, but this
-default may change to @samp{shell} in a future version of this package.
-
-@item --show-control-chars
-@opindex --show-control-chars
-Print nongraphic characters as-is in file names.
-This is the default unless the output is a terminal and the program is
-@code{ls}.
-
-@end table
-
-
-@node dir invocation
-@section @code{dir}: Briefly list directory contents
-
-@pindex dir
-@cindex directory listing, brief
-
-@code{dir} (also installed as @code{d}) is equivalent to @code{ls -C
--b}; that is, by default files are listed in columns, sorted vertically,
-and special characters are represented by backslash escape sequences.
-
-@xref{ls invocation, @code{ls}}.
-
-
-@node vdir invocation
-@section @code{vdir}: Verbosely list directory contents
-
-@pindex vdir
-@cindex directory listing, verbose
-
-@code{vdir} (also installed as @code{v}) is equivalent to @code{ls -l
--b}; that is, by default files are listed in long format and special
-characters are represented by backslash escape sequences.
-
-@node dircolors invocation
-@section @code{dircolors}: Color setup for @code{ls}
-
-@pindex dircolors
-@cindex color setup
-@cindex setup for color
-
-@code{dircolors} outputs a sequence of shell commands to set up the
-terminal for color output from @code{ls} (and @code{dir}, etc.).
-Typical usage:
-
-@example
-eval `dircolors [@var{option}]@dots{} [@var{file}]`
-@end example
-
-If @var{file} is specified, @code{dircolors} reads it to determine which
-colors to use for which file types and extensions.  Otherwise, a
-precompiled database is used.  For details on the format of these files,
-run @samp{dircolors --print-database}.
-
-@vindex LS_COLORS
-@vindex SHELL @r{environment variable, and color}
-The output is a shell command to set the @env{LS_COLORS} environment
-variable.  You can specify the shell syntax to use on the command line,
-or @code{dircolors} will guess it from the value of the @env{SHELL}
-environment variable.
-
-The program accepts the following options.  Also see @ref{Common options}.
-
-@table @samp
-@item -b
-@itemx --sh
-@itemx --bourne-shell
-@opindex -b
-@opindex --sh
-@opindex --bourne-shell
-@cindex Bourne shell syntax for color setup
-@cindex @code{sh} syntax for color setup
-Output Bourne shell commands.  This is the default if the @env{SHELL}
-environment variable is set and does not end with @samp{csh} or
-@samp{tcsh}.
-
-@item -c
-@itemx --csh
-@itemx --c-shell
-@opindex -c
-@opindex --csh
-@opindex --c-shell
-@cindex C shell syntax for color setup
-@cindex @code{csh} syntax for color setup
-Output C shell commands.  This is the default if @code{SHELL} ends with
-@code{csh} or @code{tcsh}.
-
-@item -p
-@itemx --print-database
-@opindex -p
-@opindex --print-database
-@cindex color database, printing
-@cindex database for color setup, printing
-@cindex printing color database
-Print the (compiled-in) default color configuration database.  This
-output is itself a valid configuration file, and is fairly descriptive
-of the possibilities.
-
-@end table
-
-
-@node Basic operations
-@chapter Basic operations
-
-@cindex manipulating files
-
-This chapter describes the commands for basic file manipulation:
-copying, moving (renaming), and deleting (removing).
-
-@menu
-* cp invocation::               Copy files.
-* dd invocation::               Convert and copy a file.
-* install invocation::          Copy files and set attributes.
-* mv invocation::               Move (rename) files.
-* rm invocation::               Remove files or directories.
-* shred invocation::            Remove files more securely.
-@end menu
-
-
-@node cp invocation
-@section @code{cp}: Copy files and directories
-
-@pindex cp
-@cindex copying files and directories
-@cindex files, copying
-@cindex directories, copying
-
-@code{cp} copies files (or, optionally, directories).  The copy is
-completely independent of the original.  You can either copy one file to
-another, or copy arbitrarily many files to a destination directory.
-Synopsis:
-
-@example
-cp [@var{option}]@dots{} @var{source} @var{dest}
-cp [@var{option}]@dots{} @var{source}@dots{} @var{directory}
-@end example
-
-If the last argument names an existing directory, @code{cp} copies each
-@var{source} file into that directory (retaining the same name).
-Otherwise, if only two files are given, it copies the first onto the
-second.  It is an error if the last argument is not a directory and more
-than two non-option arguments are given.
-
-Generally, files are written just as they are read.  For exceptions,
-see the @samp{--sparse} option below.
-
-By default, @command{cp} does not copy directories.  However, the
-@option{-R}, @option{-a}, and @option{-r} options cause @command{cp} to
-copy recursively by descending into source directories and copying files
-to corresponding destination directories.
-
-By default, @command{cp} follows symbolic links only when not copying
-recursively.  This default can be overridden with the
-@option{--no-dereference} (@option{-d}), @option{--dereference}
-(@option{-L}), and @option{-H} options.  If more than one of these
-options is specified, the last one silently overrides the others.
-
-@cindex self-backups
-@cindex backups, making only
-@code{cp} generally refuses to copy a file onto itself, with the
-following exception: if @samp{--force --backup} is specified with
-@var{source} and @var{dest} identical, and referring to a regular file,
-@code{cp} will make a backup file, either regular or numbered, as
-specified in the usual ways (@pxref{Backup options}).  This is useful when
-you simply want to make a backup of an existing file before changing it.
-
-The program accepts the following options.  Also see @ref{Common options}.
-
-@table @samp
-@item -a
-@itemx --archive
-@opindex -a
-@opindex --archive
-Preserve as much as possible of the structure and attributes of the
-original files in the copy (but do not attempt to preserve internal
-directory structure;  i.e., @samp{ls -U} may list the entries in a copied
-directory in a different order).
-Equivalent to @samp{-dpR}.
-
-@item -b
-@itemx @w{@kbd{--backup}[=@var{method}]}
-@opindex -b
-@opindex --backup
-@vindex VERSION_CONTROL
-@cindex backups, making
-@xref{Backup options}.
-Make a backup of each file that would otherwise be overwritten or removed.
-As a special case, @code{cp} makes a backup of @var{source} when the force
-and backup options are given and @var{source} and @var{dest} are the same
-name for an existing, regular file.  One useful application of this
-combination of options is this tiny Bourne shell script:
-
-@example
-#!/bin/sh
-# Usage: backup FILE...
-# Create a @sc{gnu}-style backup of each listed FILE.
-for i in "$@"; do
-  cp --backup --force "$i" "$i"
-done
-@end example
-
-@item -d
-@itemx --no-dereference
-@opindex -d
-@opindex --no-dereference
-@cindex symbolic links, copying
-@cindex hard links, preserving
-Copy symbolic links as symbolic links rather than copying the files that
-they point to, and preserve hard links between source files in the
-copies.
-
-@item -f
-@itemx --force
-@opindex -f
-@opindex --force
-When copying without this option and an existing destination file cannot
-be opened for writing, the copy fails.  However, with @samp{--force}),
-when a destination file cannot be opened, @code{cp} then unlinks it and
-tries to open it again.  Contrast this behavior with that enabled by
-@samp{--link} and @samp{--symbolic-link}, whereby the destination file
-is never opened but rather is unlinked unconditionally.  Also see the
-description of @samp{--remove-destination}.
-
-@item -H
-@opindex -H
-If a command line argument specifies a symbolic link, then copy the
-file it points to rather than the symbolic link itself.  However,
-copy (preserving its nature) any symbolic link that is encountered
-via recursive traversal.
-
-@item -i
-@itemx --interactive
-@opindex -i
-@opindex --interactive
-Prompt whether to overwrite existing regular destination files.
-
-@item -l
-@itemx --link
-@opindex -l
-@opindex --link
-Make hard links instead of copies of non-directories.
-
-@item -L
-@itemx --dereference
-@opindex -L
-@opindex --dereference
-Always follow symbolic links.
-
-@item -p
-@itemx --preserve
-@opindex -p
-@opindex --preserve
-@cindex file information, preserving
-Preserve the original files' owner, group, permissions, and timestamps.
-In the absence of this option, each destination file is created with the
-permissions of the corresponding source file, minus the bits set in the
-umask. @xref{File permissions}.
-
-@item -P
-@itemx --parents
-@opindex -P
-@opindex --parents
-@cindex parent directories and @code{cp}
-Form the name of each destination file by appending to the target
-directory a slash and the specified name of the source file.  The last
-argument given to @code{cp} must be the name of an existing directory.
-For example, the command:
-
-@example
-cp --parents a/b/c existing_dir
-@end example
-
-@noindent
-copies the file @file{a/b/c} to @file{existing_dir/a/b/c}, creating
-any missing intermediate directories.
-
-Warning: the meaning of @option{-P} will change in the future to conform
-to @sc{posix}.  Use @option{--parents} for the old meaning, and
-@option{--no-dereference} for the new.
-
-@item -r
-@cindex directories, copying recursively
-@cindex copying directories recursively
-@cindex recursively copying directories
-@cindex non-directories, copying as special files
-Copy directories recursively, copying any non-directories and special
-files (e.g., symbolic links, FIFOs and device files) as if they were
-regular files.  This means trying to read the data in each source
-file and writing it to the destination.  It is usually a mistake to
-apply @code{cp -r} to special files like FIFOs and the ones typically
-found in the @file{/dev} directory.  In most cases, @code{cp -r}
-will hang indefinitely trying to read from FIFOs and special files
-like @file{/dev/console}, and it will fill up your destination disk
-if you use it to copy @file{/dev/zero}.
-Use the @samp{--recursive} (@samp{-R}) option instead if you want
-to copy special files, preserving their special nature
-rather than reading from them to copy their contents.
-
-@item -R
-@itemx --recursive
-@opindex -R
-@opindex --recursive
-Copy directories recursively, preserving non-directories (contrast with
-@samp{-r} just above).
-
-@item --remove-destination
-@opindex --remove-destination
-Remove each existing destination file before attempting to open it
-(contrast with @option{-f} above).
-
-@item --sparse=@var{when}
-@opindex --sparse=@var{when}
-@cindex sparse files, copying
-@cindex holes, copying files with
-@findex read @r{system call, and holes}
-A @dfn{sparse file} contains @dfn{holes}---a sequence of zero bytes that
-does not occupy any physical disk blocks; the @samp{read} system call
-reads these as zeroes.  This can both save considerable disk space and
-increase speed, since many binary files contain lots of consecutive zero
-bytes.  By default, @code{cp} detects holes in input source files via a crude
-heuristic and makes the corresponding output file sparse as well.
-
-The @var{when} value can be one of the following:
-@table @samp
-@item auto
-The default behavior: the output file is sparse if the input file is sparse.
-
-@item always
-Always make the output file sparse.  This is useful when the input
-file resides on a filesystem that does not support sparse files (the
-most notable example is @samp{efs} filesystems in SGI IRIX 5.3 and
-earlier), but the output file is on another type of filesystem.
-
-@item never
-Never make the output file sparse.
-This is useful in creating a file for use with the @code{mkswap} command,
-since such a file must not have any holes.
-@end table
-
-@itemx @w{@kbd{--strip-trailing-slashes}}
-@opindex --strip-trailing-slashes
-@cindex stripping trailing slashes
-Remove any trailing slashes from each @var{source} argument.
-@xref{Trailing slashes}.
-
-@item -s
-@itemx --symbolic-link
-@opindex -s
-@opindex --symbolic-link
-@cindex symbolic links, copying with
-Make symbolic links instead of copies of non-directories.  All source
-file names must be absolute (starting with @samp{/}) unless the
-destination files are in the current directory.  This option merely
-results in an error message on systems that do not support symbolic links.
-
-@item -S @var{suffix}
-@itemx --suffix=@var{suffix}
-@opindex -S
-@opindex --suffix
-Append @var{suffix} to each backup file made with @samp{-b}.
-@xref{Backup options}.
-
-@itemx @w{@kbd{--target-directory}=@var{directory}}
-@opindex --target-directory
-@cindex target directory
-@cindex destination directory
-Specify the destination @var{directory}.
-@xref{Target directory}.
-
-@item -v
-@itemx --verbose
-@opindex -v
-@opindex --verbose
-Print the name of each file before copying it.
-
-@item -V @var{method}
-@itemx --version-control=@var{method}
-@opindex -V
-@opindex --version-control
-Change the type of backups made with @samp{-b}.  The @var{method}
-argument can be @samp{none} (or @samp{off}), @samp{numbered} (or
-@samp{t}), @samp{existing} (or @samp{nil}), or @samp{never} (or
-@samp{simple}).  @xref{Backup options}.
-
-@item -x
-@itemx --one-file-system
-@opindex -x
-@opindex --one-file-system
-@cindex filesystems, omitting copying to different
-Skip subdirectories that are on different filesystems from the one that
-the copy started on.
-However, mount point directories @emph{are} copied.
-
-@end table
-
-
-@node dd invocation
-@section @code{dd}: Convert and copy a file
-
-@pindex dd
-@cindex converting while copying a file
-
-@code{dd} copies a file (from standard input to standard output, by
-default) with a changeable I/O block size, while optionally performing
-conversions on it.  Synopsis:
-
-@example
-dd [@var{option}]@dots{}
-@end example
-
-The program accepts the following options.  Also see @ref{Common options}.
-
-@cindex multipliers after numbers
-The numeric-valued options below (@var{bytes} and @var{blocks}) can be
-followed by a multiplier: @samp{b}=512, @samp{c}=1,
-@samp{w}=2, @samp{x@var{m}}=@var{m}, or any of the
-standard block size suffixes like @samp{k}=1024 (@pxref{Block size}).
-
-Use different @command{dd} invocations to use different block sizes for
-skipping and I/O.  For example, the following shell commands copy data
-in 512 kB blocks between a disk and a tape, but do not save or restore a
-4 kB label at the start of the disk:
-
-@example
-disk=/dev/rdsk/c0t1d0s2
-tape=/dev/rmt/0
-
-# Copy all but the label from disk to tape.
-(dd bs=4k skip=1 count=0 && dd bs=512k) <$disk >$tape
-
-# Copy from tape back to disk, but leave the disk label alone.
-(dd bs=4k seek=1 count=0 && dd bs=512k) <$tape >$disk
-@end example
-
-@table @samp
-
-@item if=@var{file}
-@opindex if
-Read from @var{file} instead of standard input.
-
-@item of=@var{file}
-@opindex of
-Write to @var{file} instead of standard output.  Unless
-@samp{conv=notrunc} is given, @code{dd} truncates @var{file} to zero
-bytes (or the size specified with @samp{seek=}).
-
-@item ibs=@var{bytes}
-@opindex ibs
-@cindex block size of input
-@cindex input block size
-Read @var{bytes} bytes at a time.
-
-@item obs=@var{bytes}
-@opindex obs
-@cindex block size of output
-@cindex output block size
-Write @var{bytes} bytes at a time.
-
-@item bs=@var{bytes}
-@opindex bs
-@cindex block size
-Both read and write @var{bytes} bytes at a time.  This overrides
-@samp{ibs} and @samp{obs}.
-
-@item cbs=@var{bytes}
-@opindex cbs
-@cindex block size of conversion
-@cindex conversion block size
-Convert @var{bytes} bytes at a time.
-
-@item skip=@var{blocks}
-@opindex skip
-Skip @var{blocks} @samp{ibs}-byte blocks in the input file before copying.
-
-@item seek=@var{blocks}
-@opindex seek
-Skip @var{blocks} @samp{obs}-byte blocks in the output file before copying.
-
-@item count=@var{blocks}
-@opindex count
-Copy @var{blocks} @samp{ibs}-byte blocks from the input file, instead
-of everything until the end of the file.
-
-@item conv=@var{conversion}[,@var{conversion}]@dots{}
-@opindex conv
-Convert the file as specified by the @var{conversion} argument(s).
-(No spaces around any comma(s).)
-
-Conversions:
-
-@table @samp
-
-@item ascii
-@opindex ascii@r{, converting to}
-Convert EBCDIC to ASCII.
-
-@item ebcdic
-@opindex ebcdic@r{, converting to}
-Convert ASCII to EBCDIC.
-
-@item ibm
-@opindex alternate ebcdic@r{, converting to}
-Convert ASCII to alternate EBCDIC.
-
-@item block
-@opindex block @r{(space-padding)}
-For each line in the input, output @samp{cbs} bytes, replacing the
-input newline with a space and padding with spaces as necessary.
-
-@item unblock
-@opindex unblock
-Replace trailing spaces in each @samp{cbs}-sized input block with a
-newline.
-
-@item lcase
-@opindex lcase@r{, converting to}
-Change uppercase letters to lowercase.
-
-@item ucase
-@opindex ucase@r{, converting to}
-Change lowercase letters to uppercase.
-
-@item swab
-@opindex swab @r{(byte-swapping)}
-@cindex byte-swapping
-Swap every pair of input bytes.  @sc{gnu} @code{dd}, unlike others, works
-when an odd number of bytes are read---the last byte is simply copied
-(since there is nothing to swap it with).
-
-@item noerror
-@opindex noerror
-@cindex read errors, ignoring
-Continue after read errors.
-
-@item notrunc
-@opindex notrunc
-@cindex truncating output file, avoiding
-Do not truncate the output file.
-
-@item sync
-@opindex sync @r{(padding with nulls)}
-Pad every input block to size of @samp{ibs} with trailing zero bytes.
-When used with @samp{block} or @samp{unblock}, pad with spaces instead of
-zero bytes.
-@end table
-
-@end table
-
-
-@node install invocation
-@section @code{install}: Copy files and set attributes
-
-@pindex install
-@cindex copying files and setting attributes
-
-@code{install} copies files while setting their permission modes and, if
-possible, their owner and group.  Synopses:
-
-@example
-install [@var{option}]@dots{} @var{source} @var{dest}
-install [@var{option}]@dots{} @var{source}@dots{} @var{directory}
-install -d [@var{option}]@dots{} @var{directory}@dots{}
-@end example
-
-In the first of these, the @var{source} file is copied to the @var{dest}
-target file.  In the second, each of the @var{source} files are copied
-to the destination @var{directory}.  In the last, each @var{directory}
-(and any missing parent directories) is created.
-
-@cindex Makefiles, installing programs in
-@code{install} is similar to @code{cp}, but allows you to control the
-attributes of destination files.  It is typically used in Makefiles to
-copy programs into their destination directories.  It refuses to copy
-files onto themselves.
-
-The program accepts the following options.  Also see @ref{Common options}.
-
-@table @samp
-
-@item -b
-@itemx @w{@kbd{--backup}[=@var{method}]}
-@opindex -b
-@opindex --backup
-@vindex VERSION_CONTROL
-@cindex backups, making
-@xref{Backup options}.
-Make a backup of each file that would otherwise be overwritten or removed.
-
-@item -c
-@opindex -c
-Ignored; for compatibility with old Unix versions of @code{install}.
-
-@item -d
-@itemx --directory
-@opindex -d
-@opindex --directory
-@cindex directories, creating with given attributes
-@cindex parent directories, creating missing
-@cindex leading directories, creating missing
-Create each given directory and any missing parent directories, setting
-the owner, group and mode as given on the command line or to the
-defaults.  It also gives any parent directories it creates those
-attributes.  (This is different from the SunOS 4.x @code{install}, which
-gives directories that it creates the default attributes.)
-
-@item -g @var{group}
-@itemx --group=@var{group}
-@opindex -g
-@opindex --group
-@cindex group ownership of installed files, setting
-Set the group ownership of installed files or directories to
-@var{group}. The default is the process' current group.  @var{group}
-may be either a group name or a numeric group id.
-
-@item -m @var{mode}
-@itemx --mode=@var{mode}
-@opindex -m
-@opindex --mode
-@cindex permissions of installed files, setting
-Set the permissions for the installed file or directory to @var{mode},
-which can be either an octal number, or a symbolic mode as in
-@code{chmod}, with 0 as the point of departure (@pxref{File
-permissions}).  The default mode is @samp{u=rwx,go=rx}---read, write,
-and execute for the owner, and read and execute for group and other.
-
-@item -o @var{owner}
-@itemx --owner=@var{owner}
-@opindex -o
-@opindex --owner
-@cindex ownership of installed files, setting
-@cindex appropriate privileges
-@vindex root @r{as default owner}
-If @code{install} has appropriate privileges (is run as root), set the
-ownership of installed files or directories to @var{owner}. The default
-is @code{root}.  @var{owner} may be either a user name or a numeric user
-ID.
-
-@item -p
-@itemx --preserve-timestamps
-@opindex -p
-@opindex --preserve-timestamps
-@cindex timestamps of installed files, preserving
-Set the time of last access and the time of last modification of each
-installed file to match those of each corresponding original file.
-When a file is installed without this option, its last access and
-last modification times are both set to the time of installation.
-This option is useful if you want to use the last modification times
-of installed files to keep track of when they were last built as opposed
-to when they were last installed.
-
-@item -s
-@itemx --strip
-@opindex -s
-@opindex --strip
-@cindex symbol table information, stripping
-@cindex stripping symbol table information
-Strip the symbol tables from installed binary executables.
-
-@item -S @var{suffix}
-@itemx --suffix=@var{suffix}
-@opindex -S
-@opindex --suffix
-Append @var{suffix} to each backup file made with @samp{-b}.
-@xref{Backup options}.
-
-@itemx @w{@kbd{--target-directory}=@var{directory}}
-@opindex --target-directory
-@cindex target directory
-@cindex destination directory
-Specify the destination @var{directory}.
-@xref{Target directory}.
-
-@item -v
-@itemx --verbose
-@opindex -v
-@opindex --verbose
-Print the name of each file before copying it.
-
-@item -V @var{method}
-@itemx --version-control=@var{method}
-@opindex -V
-@opindex --version-control
-Change the type of backups made with @samp{-b}.  The @var{method}
-argument can be @samp{none} (or @samp{off}), @samp{numbered} (or
-@samp{t}), @samp{existing} (or @samp{nil}), or @samp{never} (or
-@samp{simple}).  @xref{Backup options}.
-
-@end table
-
-
-@node mv invocation
-@section @code{mv}: Move (rename) files
-
-@pindex mv
-
-@code{mv} moves or renames files (or directories).  Synopsis:
-
-@example
-mv [@var{option}]@dots{} @var{source} @var{dest}
-mv [@var{option}]@dots{} @var{source}@dots{} @var{directory}
-@end example
-
-If the last argument names an existing directory, @code{mv} moves each
-other given file into a file with the same name in that directory.
-Otherwise, if only two files are given, it renames the first as
-the second.  It is an error if the last argument is not a directory
-and more than two files are given.
-
-@code{mv} can move any type of file from one filesystem to another.
-Prior to version @code{4.0} of the fileutils,
-@code{mv} could move only regular files between filesystems.
-For example, now @code{mv} can move an entire directory hierarchy
-including special device files from one partition to another.  It first
-uses some of the same code that's used by @code{cp -a} to copy the
-requested directories and files, then (assuming the copy succeeded)
-it removes the originals.  If the copy fails, then the part that was
-copied to the destination partition is removed.  If you were to copy
-three directories from one partition to another and the copy of the first
-directory succeeded, but the second didn't, the first would be left on
-the destination partion and the second and third would be left on the
-original partition.
-
-@cindex prompting, and @code{mv}
-If a destination file exists but is normally unwritable, standard input
-is a terminal, and the @samp{-f} or @samp{--force} option is not given,
-@code{mv} prompts the user for whether to replace the file.  (You might
-own the file, or have write permission on its directory.)  If the
-response does not begin with @samp{y} or @samp{Y}, the file is skipped.
-
-@emph{Warning}: If you try to move a symlink that points to a directory,
-and you specify the symlink with a trailing slash, then @code{mv}
-doesn't move the symlink but instead moves the directory referenced
-by the symlink.  @xref{Trailing slashes}.
-
-The program accepts the following options.  Also see @ref{Common options}.
-
-@table @samp
-
-@item -b
-@itemx @w{@kbd{--backup}[=@var{method}]}
-@opindex -b
-@opindex --backup
-@vindex VERSION_CONTROL
-@cindex backups, making
-@xref{Backup options}.
-Make a backup of each file that would otherwise be overwritten or removed.
-
-@item -f
-@itemx --force
-@opindex -f
-@opindex --force
-@cindex prompts, omitting
-Do not prompt the user before removing an unwritable destination file.
-
-@item -i
-@itemx --interactive
-@opindex -i
-@opindex --interactive
-@cindex prompts, forcing
-Prompt whether to overwrite each existing destination file, regardless
-of its permissions.  If the response does not begin with @samp{y} or
-@samp{Y}, the file is skipped.
-
-@item -u
-@itemx --update
-@opindex -u
-@opindex --update
-@cindex newer files, moving only
-Do not move a nondirectory that has an existing destination with the
-same or newer modification time.
-
-@item -v
-@itemx --verbose
-@opindex -v
-@opindex --verbose
-Print the name of each file before moving it.
-
-@itemx @w{@kbd{--strip-trailing-slashes}}
-@opindex --strip-trailing-slashes
-@cindex stripping trailing slashes
-Remove any trailing slashes from each @var{source} argument.
-@xref{Trailing slashes}.
-
-@item -S @var{suffix}
-@itemx --suffix=@var{suffix}
-@opindex -S
-@opindex --suffix
-Append @var{suffix} to each backup file made with @samp{-b}.
-@xref{Backup options}.
-
-@itemx @w{@kbd{--target-directory}=@var{directory}}
-@opindex --target-directory
-@cindex target directory
-@cindex destination directory
-Specify the destination @var{directory}.
-@xref{Target directory}.
-
-@item -V @var{method}
-@itemx --version-control=@var{method}
-@opindex -V
-@opindex --version-control
-Change the type of backups made with @samp{-b}.  The @var{method}
-argument can be @samp{none} (or @samp{off}), @samp{numbered} (or
-@samp{t}), @samp{existing} (or @samp{nil}), or @samp{never} (or
-@samp{simple}).  @xref{Backup options}.
-
-@end table
-
-
-@node rm invocation
-@section @code{rm}: Remove files or directories
-
-@pindex rm
-@cindex removing files or directories
-
-@code{rm} removes each given @var{file}.  By default, it does not remove
-directories.  Synopsis:
-
-@example
-rm [@var{option}]@dots{} [@var{file}]@dots{}
-@end example
-
-@cindex prompting, and @code{rm}
-If a file is unwritable, standard input is a terminal, and the @samp{-f}
-or @samp{--force} option is not given, or the @samp{-i} or
-@samp{--interactive} option @emph{is} given, @code{rm} prompts the user
-for whether to remove the file.  If the response does not begin with
-@samp{y} or @samp{Y}, the file is skipped.
-
-The program accepts the following options.  Also see @ref{Common options}.
-
-@table @samp
-
-@item -d
-@itemx --directory
-@opindex -d
-@opindex --directory
-@cindex directories, removing with @code{unlink}
-@findex unlink
-@pindex fsck
-Attempt to remove directories with @code{unlink} instead of @code{rmdir}, and
-don't require a directory to be empty before trying to unlink it.  This works
-only if you have appropriate privileges and if your operating system supports
-@code{unlink} for directories.  Because unlinking a directory causes any files
-in the deleted directory to become unreferenced, it is wise to @code{fsck} the
-filesystem after doing this.
-
-@item -f
-@itemx --force
-@opindex -f
-@opindex --force
-Ignore nonexistent files and never prompt the user.
-Ignore any previous @samp{--interactive} (@samp{-i}) option.
-
-@item -i
-@itemx --interactive
-@opindex -i
-@opindex --interactive
-Prompt whether to remove each file.  If the response does not begin
-with @samp{y} or @samp{Y}, the file is skipped.
-Ignore any previous @samp{--force} (@samp{-f}) option.
-
-@item -r
-@itemx -R
-@itemx --recursive
-@opindex -r
-@opindex -R
-@opindex --recursive
-@cindex directories, removing (recursively)
-Remove the contents of directories recursively.
-
-@item -v
-@itemx --verbose
-@opindex -v
-@opindex --verbose
-Print the name of each file before removing it.
-
-@end table
-
-@cindex files beginning with @samp{-}, removing
-@cindex @samp{-}, removing files beginning with
-One common question is how to remove files whose names begin with a
-@samp{-}.  @sc{gnu} @code{rm}, like every program that uses the @code{getopt}
-function to parse its arguments, lets you use the @samp{--} option to
-indicate that all following arguments are non-options.  To remove a file
-called @file{-f} in the current directory, you could type either:
-
-@example
-rm -- -f
-@end example
-
-@noindent
-or:
-
-@example
-rm ./-f
-@end example
-
-@opindex - @r{and Unix @code{rm}}
-The Unix @code{rm} program's use of a single @samp{-} for this purpose
-predates the development of the getopt standard syntax.
-
-
-@node shred invocation
-@section @code{shred}: Remove files more securely
-
-@pindex shred
-@cindex data, erasing
-@cindex erasing data
-
-@code{shred} overwrites devices or files, to help prevent even
-very expensive hardware from recovering the data.
-
-Ordinarily when you remove a file (@pxref{rm invocation}), the data is
-not actually destroyed.  Only the index listing where the file is
-stored is destroyed, and the storage is made available for reuse.
-There are undelete utilities that will attempt to reconstruct the index
-and can bring the file back if the parts were not reused.
-
-On a busy system with a nearly-full drive, space can get reused in a few
-seconds.  But there is no way to know for sure.  If you have sensitive
-data, you may want to be sure that recovery is not possible by actually
-overwriting the file with non-sensitive data.
-
-However, even after doing that, it is possible to take the disk back
-to a laboratory and use a lot of sensitive (and expensive) equipment
-to look for the faint ``echoes'' of the original data underneath the
-overwritten data.  If the data has only been overwritten once, it's not
-even that hard.
-
-The best way to remove something irretrievably is to destroy the media
-it's on with acid, melt it down, or the like.  For cheap removable media
-like floppy disks, this is the preferred method.  However, hard drives
-are expensive and hard to melt, so the @code{shred} utility tries
-to achieve a similar effect non-destructively.
-
-This uses many overwrite passes, with the data patterns chosen to
-maximize the damage they do to the old data.  While this will work on
-floppies, the patterns are designed for best effect on hard drives.
-For more details, see the source code and Peter Gutmann's paper
-@cite{Secure Deletion of Data from Magnetic and Solid-State Memory},
-from the proceedings of the Sixth USENIX Security Symposium (San Jose,
-California, 22--25 July, 1996).  The paper is also available online
-@url{http://www.cs.auckland.ac.nz/~pgut001/pubs/secure_del.html}.
-
-@strong{Please note} that @code{shred} relies on a very important assumption:
-that the filesystem overwrites data in place.  This is the traditional
-way to do things, but many modern filesystem designs do not satisfy this
-assumption.  Exceptions include:
-
-@itemize @bullet
-
-@item
-Log-structured or journaled filesystems, such as those supplied with
-AIX and Solaris.
-
-@item
-Filesystems that write redundant data and carry on even if some writes
-fail, such as RAID-based filesystems.
-
-@item
-Filesystems that make snapshots, such as Network Appliance's NFS server.
-
-@item
-Filesystems that cache in temporary locations, such as NFS version 3
-clients.
-
-@item
-Compressed filesystems.
-@end itemize
-
-If you are not sure how your filesystem operates, then you should assume
-that it does not overwrite data in place, which means that shred cannot
-reliably operate on regular files in your filesystem.
-
-Generally speaking, it is more reliable to shred a device than a file,
-since this bypasses the problem of filesystem design mentioned above.
-However, even shredding devices is not always completely reliable.  For
-example, most disks map out bad sectors invisibly to the application; if
-the bad sectors contain sensitive data, @code{shred} won't be able to
-destroy it.
-
-@code{shred} makes no attempt to detect or report this problem, just as
-it makes no attempt to do anything about backups.  However, since it is
-more reliable to shred devices than files, @code{shred} by default does
-not truncate or remove the output file.  This default is more suitable
-for devices, which typically cannot be truncated and should not be
-removed.
-
-Finally, consider the risk of backups and mirrors.
-File system backups and remote mirrors may contain copies of the
-file that cannot be removed, and that will allow a shredded file
-to be recovered later.  So if you keep any data you may later want
-to destroy using @code{shred}, be sure that it is not backed up or mirrored.
-
-@example
-shred [@var{option}]@dots{} @var{file}[@dots{}]
-@end example
-
-The program accepts the following options.  Also see @ref{Common options}.
-
-@table @samp
-
-@item -f
-@itemx --force
-@opindex -f
-@opindex --force
-@cindex force deletion
-Override file permissions if necessary to allow overwriting.
-
-@item -@var{NUMBER}
-@itemx -n @var{NUMBER}
-@itemx --iterations=@var{NUMBER}
-@opindex -n @var{NUMBER}
-@opindex --iterations=@var{NUMBER}
-@cindex iterations, selecting the number of
-By default, @code{shred} uses 25 passes of overwrite.  This is enough
-for all of the useful overwrite patterns to be used at least once.
-You can reduce this to save time, or increase it if you have a lot of
-time to waste.
-
-@item -s @var{BYTES}
-@itemx --size=@var{BYTES}
-@opindex -s @var{BYTES}
-@opindex --size=@var{BYTES}
-@cindex size of file to shred
-Shred the first @var{BYTES} bytes of the file. The default is to shred
-the whole file.  @var{BYTES} can be followed by a size specification like
-@samp{k}, @samp{M}, or @samp{G} to specify a multiple. @xref{Block size}.
-
-@item -u
-@itemx --remove
-@opindex -u
-@opindex --remove
-@cindex removing files after shredding
-After shredding a file, truncate it (if possible) and then remove it.
-If a file has multiple links, only the named links will be removed.
-
-@item -v
-@itemx --verbose
-@opindex -v
-@opindex --verbose
-Display status updates as sterilization proceeds.
-
-@item -x
-@itemx --exact
-@opindex -x
-@opindex --exact
-Normally, shred rounds the file size up to the next multiple of
-the filesystem block size to fully erase the last block of the file.
-This option suppresses that behavior.
-Thus, by default if you shred a 10-byte file on a system with 512-byte
-blocks, the resulting file will be 512 bytes long.  With this option,
-shred does not increase the size of the file.
-
-@item -z
-@itemx --zero
-@opindex -z
-@opindex --zero
-Normally, the last pass that @code{shred} writes is made up of
-random data.  If this would be conspicuous on your hard drive (for
-example, because it looks like encrypted data), or you just think
-it's tidier, the @samp{--zero} option adds an additional overwrite pass with
-all zero bits.  This is in addition to the number of passes specified
-by the @samp{--iterations} option.
-
-@item -
-@opindex -
-Shred standard output.
-
-This argument is considered an option.  If the common @samp{--} option has
-been used to indicate the end of options on the command line, then @samp{-}
-will be interpreted as an ordinary file name.
-
-The intended use of this is to shred a removed temporary file.
-For example
-
-@example
-i=`tempfile -m 0600`
-exec 3<>"$i"
-rm -- "$i"
-echo "Hello, world" >&3
-shred - >&3
-exec 3>-
-@end example
-
-Note that the shell command @samp{shred - >file} does not shred the
-contents of @var{file}, since it truncates @var{file} before invoking
-@code{shred}.  Use the command @samp{shred file} or (if using a
-Bourne-compatible shell) the command @samp{shred - 1<>file} instead.
-
-@end table
-
-You might use the following command to erase all trace of the
-file system you'd created on the floppy disk in your first drive.
-That command takes about 20 minutes to erase a 1.44MB floppy.
-
-@example
-shred --verbose /dev/fd0
-@end example
-
-Similarly, to erase all data on a selected partition of
-your hard disk, you could give a command like this:
-
-@example
-shred --verbose /dev/sda5
-@end example
-
-@node Special file types
-@chapter Special file types
-
-@cindex special file types
-@cindex file types, special
-
-This chapter describes commands which create special types of files (and
-@code{rmdir}, which removes directories, one special file type).
-
-@cindex special file types
-@cindex file types
-Although Unix-like operating systems have markedly fewer special file
-types than others, not @emph{everything} can be treated only as the
-undifferentiated byte stream of @dfn{normal files}.  For example, when a
-file is created or removed, the system must record this information,
-which it does in a @dfn{directory}---a special type of file.  Although
-you can read directories as normal files, if you're curious, in order
-for the system to do its job it must impose a structure, a certain
-order, on the bytes of the file.  Thus it is a ``special'' type of file.
-
-Besides directories, other special file types include named pipes
-(FIFOs), symbolic links, sockets, and so-called @dfn{special files}.
-
-@menu
-* ln invocation::               Make links between files.
-* mkdir invocation::            Make directories.
-* mkfifo invocation::           Make FIFOs (named pipes).
-* mknod invocation::            Make block or character special files.
-* rmdir invocation::            Remove empty directories.
-@end menu
-
-
-@node ln invocation
-@section @code{ln}: Make links between files
-
-@pindex ln
-@cindex links, creating
-@cindex hard links, creating
-@cindex symbolic (soft) links, creating
-@cindex creating links (hard or soft)
-
-@cindex filesystems and hard links
-@code{ln} makes links between files.  By default, it makes hard links;
-with the @samp{-s} option, it makes symbolic (or @dfn{soft}) links.
-Synopses:
-
-@example
-ln [@var{option}]@dots{} @var{target} [@var{linkname}]
-ln [@var{option}]@dots{} @var{target}@dots{} @var{directory}
-@end example
-
-@itemize @bullet
-
-@item If the last argument names an existing directory, @code{ln} creates a
-link to each @var{target} file in that directory, using the
-@var{target}s' names.  (But see the description of the
-@samp{--no-dereference} option below.)
-
-@item If two filenames are given, @code{ln} creates a link from the
-second to the first.
-
-@item If one @var{target} is given, @code{ln} creates a link to that
-file in the current directory.
-
-@item It is an error if the last argument is not a directory and more
-than two files are given.  Without @samp{-f} or @samp{-i} (see below),
-@code{ln} will not remove an existing file.  Use the @samp{--backup}
-option to make @code{ln} rename existing files.
-
-@end itemize
-
-@cindex hard link, defined
-@cindex inode, and hard links
-A @dfn{hard link} is another name for an existing file; the link and the
-original are indistinguishable.  Technically speaking, they share the
-same inode, and the inode contains all the information about a
-file---indeed, it is not incorrect to say that the inode @emph{is} the
-file.  On all existing implementations, you cannot make a hard link to
-a directory, and hard links cannot cross filesystem boundaries.  (These
-restrictions are not mandated by @sc{posix}, however.)
-
-@cindex dereferencing symbolic links
-@cindex symbolic link, defined
-@dfn{Symbolic links} (@dfn{symlinks} for short), on the other hand, are
-a special file type (which not all kernels support: System V release 3
-(and older) systems lack symlinks) in which the link file actually
-refers to a different file, by name.  When most operations (opening,
-reading, writing, and so on) are passed the symbolic link file, the
-kernel automatically @dfn{dereferences} the link and operates on the
-target of the link.  But some operations (e.g., removing) work on the
-link file itself, rather than on its target.  @xref{Symbolic Links,,,
-library, The GNU C Library Reference Manual}.
-
-The program accepts the following options.  Also see @ref{Common options}.
-
-@table @samp
-
-@item -b
-@itemx @w{@kbd{--backup}[=@var{method}]}
-@opindex -b
-@opindex --backup
-@vindex VERSION_CONTROL
-@cindex backups, making
-@xref{Backup options}.
-Make a backup of each file that would otherwise be overwritten or removed.
-
-@item -d
-@itemx -F
-@itemx --directory
-@opindex -d
-@opindex -F
-@opindex --directory
-@cindex hard links to directories
-Allow the super-user to make hard links to directories.
-
-@item -f
-@itemx --force
-@opindex -f
-@opindex --force
-Remove existing destination files.
-
-@item -i
-@itemx --interactive
-@opindex -i
-@opindex --interactive
-@cindex prompting, and @code{ln}
-Prompt whether to remove existing destination files.
-
-@item -n
-@itemx --no-dereference
-@opindex -n
-@opindex --no-dereference
-When given an explicit destination that is a symlink to a directory,
-treat that destination as if it were a normal file.
-
-When the destination is an actual directory (not a symlink to one),
-there is no ambiguity.  The link is created in that directory.
-But when the specified destination is a symlink to a directory,
-there are two ways to treat the user's request.  @code{ln} can
-treat the destination just as it would a normal directory and create
-the link in it.  On the other hand, the destination can be viewed as a
-non-directory---as the symlink itself.  In that case, @code{ln}
-must delete or backup that symlink before creating the new link.
-The default is to treat a destination that is a symlink to a directory
-just like a directory.
-
-@item -s
-@itemx --symbolic
-@opindex -s
-@opindex --symbolic
-Make symbolic links instead of hard links.  This option merely produces
-an error message on systems that do not support symbolic links.
-
-@item -S @var{suffix}
-@itemx --suffix=@var{suffix}
-@opindex -S
-@opindex --suffix
-Append @var{suffix} to each backup file made with @samp{-b}.
-@xref{Backup options}.
-
-@itemx @w{@kbd{--target-directory}=@var{directory}}
-@opindex --target-directory
-@cindex target directory
-@cindex destination directory
-Specify the destination @var{directory}.
-@xref{Target directory}.
-
-@item -v
-@itemx --verbose
-@opindex -v
-@opindex --verbose
-Print the name of each file before linking it.
-
-@item -V @var{method}
-@itemx --version-control=@var{method}
-@opindex -V
-@opindex --version-control
-Change the type of backups made with @samp{-b}.  The @var{method}
-argument can be @samp{none} (or @samp{off}), @samp{numbered} (or
-@samp{t}), @samp{existing} (or @samp{nil}), or @samp{never} (or
-@samp{simple}).  @xref{Backup options}.
-
-@end table
-
-Examples:
-
-@smallexample
-ln -s /some/name  # creates link ./name pointing to /some/name
-ln -s /some/name myname  # creates link ./myname pointing to /some/name
-ln -s a b ..      # creates links ../a and ../b pointing to ./a and ./b
-@end smallexample
-
-
-@node mkdir invocation
-@section @code{mkdir}: Make directories
-
-@pindex mkdir
-@cindex directories, creating
-@cindex creating directories
-
-@code{mkdir} creates directories with the specified names.  Synopsis:
-
-@example
-mkdir [@var{option}]@dots{} @var{name}@dots{}
-@end example
-
-If a @var{name} is an existing file but not a directory, @code{mkdir} prints a
-warning message on stderr and will exit with a status of 1 after
-processing any remaining @var{name}s.  The same is done when a @var{name} is an
-existing directory and the -p option is not given.  If a @var{name} is an
-existing directory and the -p option is given, @code{mkdir} will ignore it.
-That is, @code{mkdir} will not print a warning, raise an error, or change
-the mode of the directory (even if the -m option is given), and will
-move on to processing any remaining @var{name}s.
-
-The program accepts the following options.  Also see @ref{Common options}.
-
-@table @samp
-
-@item -m @var{mode}
-@itemx --mode=@var{mode}
-@opindex -m
-@opindex --mode
-@cindex modes of created directories, setting
-Set the mode of created directories to @var{mode}, which is symbolic as
-in @code{chmod} and uses @samp{a=rwx} (read, write and execute allowed for
-everyone) minus the bits set in the umask for the point of the
-departure.  @xref{File permissions}.
-
-@item -p
-@itemx --parents
-@opindex -p
-@opindex --parents
-@cindex parent directories, creating
-Make any missing parent directories for each argument.  The mode for parent
-directories is set to the umask modified by @samp{u+wx}.
-Ignore arguments corresponding to existing directories.
-
-@item -v
-@item --verbose
-@opindex -v
-@opindex --verbose
-Print a message for each created directory.  This is most useful with
-@samp{--parents}.
-@end table
-
-
-@node mkfifo invocation
-@section @code{mkfifo}: Make FIFOs (named pipes)
-
-@pindex mkfifo
-@cindex FIFOs, creating
-@cindex named pipes, creating
-@cindex creating FIFOs (named pipes)
-
-@code{mkfifo} creates FIFOs (also called @dfn{named pipes}) with the
-specified names.  Synopsis:
-
-@example
-mkfifo [@var{option}] @var{name}@dots{}
-@end example
-
-A @dfn{FIFO} is a special file type that permits independent processes
-to communicate.  One process opens the FIFO file for writing, and
-another for reading, after which data can flow as with the usual
-anonymous pipe in shells or elsewhere.
-
-The program accepts the following option.  Also see @ref{Common options}.
-
-@table @samp
-
-@item -m @var{mode}
-@itemx --mode=@var{mode}
-@opindex -m
-@opindex --mode
-@cindex modes of created FIFOs, setting
-Set the mode of created FIFOs to @var{mode}, which is symbolic as in
-@code{chmod} and uses @samp{a=rw} (read and write allowed for everyone) minus
-the bits set in the umask for the point of departure.  @xref{File permissions}.
-
-@end table
-
-
-@node mknod invocation
-@section @code{mknod}: Make block or character special files
-
-@pindex mknod
-@cindex block special files, creating
-@cindex character special files, creating
-
-@code{mknod} creates a FIFO, character special file, or block special
-file with the specified name.  Synopsis:
-
-@example
-mknod [@var{option}]@dots{} @var{name} @var{type} [@var{major} @var{minor}]
-@end example
-
-@cindex special files
-@cindex block special files
-@cindex character special files
-Unlike the phrase ``special file type'' above, the term @dfn{special
-file} has a technical meaning on Unix: something that can generate or
-receive data.  Usually this corresponds to a physical piece of hardware,
-e.g., a printer or a disk.  (These files are typically created at
-system-configuration time.)  The @code{mknod} command is what creates
-files of this type.  Such devices can be read either a character at a
-time or a ``block'' (many characters) at a time, hence we say there are
-@dfn{block special} files and @dfn{character special} files.
-
-The arguments after @var{name} specify the type of file to make:
-
-@table @samp
-
-@item p
-@opindex p @r{for FIFO file}
-for a FIFO
-
-@item b
-@opindex b @r{for block special file}
-for a block special file
-
-@item c
-@c Don't document the `u' option -- it's just a synonym for `c'.
-@c Do *any* versions of mknod still use it?
-@c @itemx u
-@opindex c @r{for character special file}
-@c @opindex u @r{for character special file}
-for a character special file
-
-@end table
-
-When making a block or character special file, the major and minor
-device numbers must be given after the file type.
-
-The program accepts the following option.  Also see @ref{Common options}.
-
-@table @samp
-
-@item -m @var{mode}
-@itemx --mode=@var{mode}
-@opindex -m
-@opindex --mode
-Set the mode of created files to @var{mode}, which is symbolic as in
-@code{chmod} and uses @samp{a=rw} minus the bits set in the umask as the point
-of departure.  @xref{File permissions}.
-
-@end table
-
-
-@node rmdir invocation
-@section @code{rmdir}: Remove empty directories
-
-@pindex rmdir
-@cindex removing empty directories
-@cindex directories, removing empty
-
-@code{rmdir} removes empty directories.  Synopsis:
-
-@example
-rmdir [@var{option}]@dots{} @var{directory}@dots{}
-@end example
-
-If any @var{directory} argument does not refer to an existing empty
-directory, it is an error.
-
-The program accepts the following option.  Also see @ref{Common options}.
-
-@table @samp
-
-@item --ignore-fail-on-non-empty
-@opindex --ignore-fail-on-non-empty
-@cindex directory deletion, ignoring failures
-Ignore each failure to remove a directory that is solely because
-the directory is non-empty.
-
-@item -p
-@itemx --parents
-@opindex -p
-@opindex --parents
-@cindex parent directories, removing
-Remove @var{directory}, then try to remove each component of @var{directory}.
-So, for example, @samp{rmdir -p a/b/c} is similar to @samp{rmdir a/b/c a/b a}.
-As such, it fails if any of those directories turns out not to be empty.
-Use the @samp{--ignore-fail-on-non-empty} option to make it so such
-a failure does not evoke a diagnostic and does not cause @code{rmdir} to
-exit unsuccessfully.
-
-@item -v
-@item --verbose
-@opindex -v
-@opindex --verbose
-@cindex directory deletion, reporting
-Give a diagnostic for each successful removal.
-@var{directory} is removed.
-
-@end table
-
-@xref{rm invocation}, for how to remove non-empty directories (recursively).
-
-
-@node Changing file attributes
-@chapter Changing file attributes
-
-@cindex changing file attributes
-@cindex file attributes, changing
-@cindex attributes, file
-
-A file is not merely its contents, a name, and a file type
-(@pxref{Special file types}).  A file also has an owner (a userid), a
-group (a group id), permissions (what the owner can do with the file,
-what people in the group can do, and what everyone else can do), various
-timestamps, and other information.  Collectively, we call these a file's
-@dfn{attributes}.
-
-These commands change file attributes.
-
-@menu
-* chown invocation::            Change file owners and groups.
-* chgrp invocation::            Change file groups.
-* chmod invocation::            Change access permissions.
-* touch invocation::            Change file timestamps.
-@end menu
-
-
-@node chown invocation
-@section @code{chown}: Change file owner and group
-
-@pindex chown
-@cindex file ownership, changing
-@cindex group ownership, changing
-@cindex changing file ownership
-@cindex changing group ownership
-
-@code{chown} changes the user and/or group ownership of each given @var{file}
-to @var{new-owner} or to the user and group of an existing reference file.
-Synopsis:
-
-@example
-chown [@var{option}]@dots{} @{@var{new-owner} | --reference=@var{ref_file}@} @var{file}@dots{}
-@end example
-
-If used, @var{new-owner} specifies the new owner and/or group as follows
-(with no embedded white space):
-
-@example
-[@var{owner}] [ [:] [@var{group}] ]
-@end example
-
-Specifically:
-
-@table @var
-@item owner
-If only an @var{owner} (a user name or numeric user id) is given, that
-user is made the owner of each given file, and the files' group is not
-changed.
-
-@itemx owner@samp{:}group
-If the @var{owner} is followed by a colon and a @var{group} (a
-group name or numeric group id), with no spaces between them, the group
-ownership of the files is changed as well (to @var{group}).
-
-@itemx owner@samp{:}
-If a colon but no group name follows @var{owner}, that user is
-made the owner of the files and the group of the files is changed to
-@var{owner}'s login group.
-
-@itemx @samp{:}group
-If the colon and following @var{group} are given, but the owner
-is omitted, only the group of the files is changed; in this case,
-@code{chown} performs the same function as @code{chgrp}.
-
-@end table
-
-You may use @samp{.} in place of the @samp{:} separator.  This is a
-@sc{gnu} extension for compatibility with older scripts.
-New scripts should avoid the use of @samp{.} because @sc{gnu} @code{chown}
-may fail if @var{owner} contains @samp{.} characters.
-
-The program accepts the following options.  Also see @ref{Common options}.
-
-@table @samp
-
-@item -c
-@itemx --changes
-@opindex -c
-@opindex --changes
-@cindex changed owners, verbosely describing
-Verbosely describe the action for each @var{file} whose ownership
-actually changes.
-
-@item -f
-@itemx --silent
-@itemx --quiet
-@opindex -f
-@opindex --silent
-@opindex --quiet
-@cindex error messages, omitting
-Do not print error messages about files whose ownership cannot be
-changed.
-
-@itemx @w{@kbd{--from}=@var{old-owner}}
-@opindex --from
-@cindex symbolic links, changing owner
-Change a @var{file}'s ownership only if it has current attributes specified
-by @var{old-owner}.  @var{old-owner} has the same form as @var{new-owner}
-described above.
-This option is useful primarily from a security standpoint in that
-it narrows considerably the window of potential abuse.
-For example, to reflect a UID numbering change for one user's files
-without an option like this, @code{root} might run
-
-@smallexample
-find / -owner OLDUSER -print0 | xargs -0 chown NEWUSER
-@end smallexample
-
-But that is dangerous because the interval between when the @code{find}
-tests the existing file's owner and when the @code{chown} is actually run
-may be quite large.
-One way to narrow the gap would be to invoke chown for each file
-as it is found:
-
-@example
-find / -owner OLDUSER -exec chown NEWUSER @{@} \;
-@end example
-
-But that is very slow if there are many affected files.
-With this option, it is safer (the gap is narrower still)
-though still not perfect:
-
-@example
-chown -R --from=OLDUSER NEWUSER /
-@end example
-
-@item --dereference
-@opindex --dereference
-@cindex symbolic links, changing owner
-@findex lchown
-Do not act on symbolic links themselves but rather on what they point to.
-
-@item -h
-@itemx --no-dereference
-@opindex -h
-@opindex --no-dereference
-@cindex symbolic links, changing owner
-@findex lchown
-Act on symbolic links themselves instead of what they point to.
-This is the default.
-This mode relies on the @code{lchown} system call.
-On systems that do not provide the @code{lchown} system call,
-@code{chown} fails when a file specified on the command line
-is a symbolic link.
-By default, no diagnostic is issued for symbolic links encountered
-during a recursive traversal, but see @samp{--verbose}.
-
-@item --reference=@var{ref_file}
-@opindex --reference
-Change the user and group of each @var{file} to be the same as those of
-@var{ref_file}.  If @var{ref_file} is a symbolic link, do not use the
-user and group of the symbolic link, but rather those of the file it
-refers to.
-
-@item -v
-@itemx --verbose
-@opindex -v
-@opindex --verbose
-Output a diagnostic for every file processed.
-If a symbolic link is encountered during a recursive traversal
-on a system without the @code{lchown} system call, and @samp{--no-dereference}
-is in effect, then issue a diagnostic saying neither the symbolic link nor
-its referent is being changed.
-
-@item -R
-@itemx --recursive
-@opindex -R
-@opindex --recursive
-@cindex recursively changing file ownership
-Recursively change ownership of directories and their contents.
-
-@end table
-
-
-@node chgrp invocation
-@section @code{chgrp}: Change group ownership
-
-@pindex chgrp
-@cindex group ownership, changing
-@cindex changing group ownership
-
-@code{chgrp} changes the group ownership of each given @var{file}
-to @var{group} (which can be either a group name or a numeric group id)
-or to the group of an existing reference file.  Synopsis:
-
-@example
-chgrp [@var{option}]@dots{} @{@var{group} | --reference=@var{ref_file}@} @var{file}@dots{}
-@end example
-
-The program accepts the following options.  Also see @ref{Common options}.
-
-@table @samp
-
-@item -c
-@itemx --changes
-@opindex -c
-@opindex --changes
-@cindex changed files, verbosely describing
-Verbosely describe the action for each @var{file} whose group actually
-changes.
-
-@item -f
-@itemx --silent
-@itemx --quiet
-@opindex -f
-@opindex --silent
-@opindex --quiet
-@cindex error messages, omitting
-Do not print error messages about files whose group cannot be
-changed.
-
-@item --dereference
-@opindex --dereference
-@cindex symbolic links, changing owner
-@findex lchown
-Do not act on symbolic links themselves but rather on what they point to.
-
-@item -h
-@itemx --no-dereference
-@opindex -h
-@opindex --no-dereference
-@cindex symbolic links, changing group
-@findex lchown
-Act on symbolic links themselves instead of what they point to.
-This is the default.
-This mode relies on the @code{lchown} system call.
-On systems that do not provide the @code{lchown} system call,
-@code{chgrp} fails when a file specified on the command line
-is a symbolic link.
-By default, no diagnostic is issued for symbolic links encountered
-during a recursive traversal, but see @samp{--verbose}.
-
-@item --reference=@var{ref_file}
-@opindex --reference
-Change the group of each @var{file} to be the same as that of
-@var{ref_file}.  If @var{ref_file} is a symbolic link, do not use the
-group of the symbolic link, but rather that of the file it refers to.
-
-@item -v
-@itemx --verbose
-@opindex -v
-@opindex --verbose
-Output a diagnostic for every file processed.
-If a symbolic link is encountered during a recursive traversal
-on a system without the @code{lchown} system call, and @samp{--no-dereference}
-is in effect, then issue a diagnostic saying neither the symbolic link nor
-its referent is being changed.
-
-@item -R
-@itemx --recursive
-@opindex -R
-@opindex --recursive
-@cindex recursively changing group ownership
-Recursively change the group ownership of directories and their contents.
-
-@end table
-
-
-@node chmod invocation
-@section @code{chmod}: Change access permissions
-
-@pindex chmod
-@cindex changing access permissions
-@cindex access permissions, changing
-@cindex permissions, changing access
-
-@code{chmod} changes the access permissions of the named files.  Synopsis:
-
-@example
-chmod [@var{option}]@dots{} @{@var{mode} | --reference=@var{ref_file}@} @var{file}@dots{}
-@end example
-
-@cindex symbolic links, permissions of
-@code{chmod} never changes the permissions of symbolic links, since
-the @code{chmod} system call cannot change their permissions.
-This is not a problem since the permissions of symbolic links are
-never used.  However, for each symbolic link listed on the command
-line, @code{chmod} changes the permissions of the pointed-to file.
-In contrast, @code{chmod} ignores symbolic links encountered during
-recursive directory traversals.
-
-If used, @var{mode} specifies the new permissions.
-For details, see the section on @ref{File permissions}.
-
-The program accepts the following options.  Also see @ref{Common options}.
-
-@table @samp
-
-@item -c
-@itemx --changes
-@opindex -c
-@opindex --changes
-Verbosely describe the action for each @var{file} whose permissions
-actually changes.
-
-@item -f
-@itemx --silent
-@itemx --quiet
-@opindex -f
-@opindex --silent
-@opindex --quiet
-@cindex error messages, omitting
-Do not print error messages about files whose permissions cannot be
-changed.
-
-@item -v
-@itemx --verbose
-@opindex -v
-@opindex --verbose
-Verbosely describe the action or non-action taken for every @var{file}.
-
-@item --reference=@var{ref_file}
-@opindex --reference
-Change the mode of each @var{file} to be the same as that of @var{ref_file}.
-@xref{File permissions}.
-If @var{ref_file} is a symbolic link, do not use the mode
-of the symbolic link, but rather that of the file it refers to.
-
-@item -R
-@itemx --recursive
-@opindex -R
-@opindex --recursive
-@cindex recursively changing access permissions
-Recursively change permissions of directories and their contents.
-
-@end table
-
-
-@node touch invocation
-@section @code{touch}: Change file timestamps
-
-@pindex touch
-@cindex changing file timestamps
-@cindex file timestamps, changing
-@cindex timestamps, changing file
-
-@code{touch} changes the access and/or modification times of the
-specified files.  Synopsis:
-
-@example
-touch [@var{option}]@dots{} @var{file}@dots{}
-@end example
-
-If the first @var{file} would be a valid argument to the @samp{-t}
-option and no timestamp is given with any of the @samp{-d}, @samp{-r},
-or @samp{-t} options and the @samp{--} argument is not given, that
-argument is interpreted as the time for the other files instead of
-as a file name.  Warning: this usage is obsolescent, and future versions
-of @sc{posix} will require that support for it be withdrawn.  Use
-@option{-t} instead.
-
-@cindex empty files, creating
-Any @var{file} that does not exist is created empty.
-
-@cindex permissions, for changing file timestamps
-If changing both the access and modification times to the current
-time, @code{touch} can change the timestamps for files that the user
-running it does not own but has write permission for.  Otherwise, the
-user must own the files.
-
-Although @code{touch} provides options for changing two of the times --
-the times of last access and modification -- of a file, there is actually
-a third one as well: the inode change time.  This is often referred to
-as a file's @code{ctime}.
-The inode change time represents the time when the file's meta-information
-last changed.  One common example of this is when the permissions of a
-file change.  Changing the permissions doesn't access the file, so
-the atime doesn't change, nor does it modify the file, so the mtime
-doesn't change.  Yet, something about the file itself has changed,
-and this must be noted somewhere.  This is the job of the ctime field.
-This is necessary, so that, for example, a backup program can make a
-fresh copy of the file, including the new permissions value.
-Another operation that modifies a file's ctime without affecting
-the others is renaming.  In any case, it is not possible, in normal
-operations, for a user to change the ctime field to a user-specified value.
-
-The program accepts the following options.  Also see @ref{Common options}.
-
-@table @samp
-
-@item -a
-@itemx --time=atime
-@itemx --time=access
-@itemx --time=use
-@opindex -a
-@opindex --time
-@opindex atime@r{, changing}
-@opindex access @r{time, changing}
-@opindex use @r{time, changing}
-Change the access time only.
-
-@item -c
-@itemx --no-create
-@opindex -c
-@opindex --no-create
-Do not create files that do not exist.
-
-@item -d
-@itemx --date=time
-@opindex -d
-@opindex --date
-@opindex time
-Use @var{time} instead of the current time.  It can contain month names,
-time zones, @samp{am} and @samp{pm}, etc.  @xref{Date input formats}.
-
-@item -f
-@opindex -f
-@cindex BSD @code{touch} compatibility
-Ignored; for compatibility with BSD versions of @code{touch}.
-
-@item -m
-@itemx --time=mtime
-@itemx --time=modify
-@opindex -m
-@opindex --time
-@opindex mtime@r{, changing}
-@opindex modify @r{time, changing}
-Change the modification time only.
-
-@item -r @var{file}
-@itemx --reference=@var{file}
-@opindex -r
-@opindex --reference
-Use the times of the reference @var{file} instead of the current time.
-
-@item -t [[CC]YY]MMDDhhmm[.ss]
-Use the argument (optional four-digit or two-digit years, months,
-days, hours, minutes, optional seconds) instead of the current time.
-If the year is specified with only two digits, then @var{CC}
-is 20 for years in the range 0 @dots{} 68, and 19 for years in
-69 @dots{} 99.  If no digits of the year are specified,
-the argument is interpreted as a date in the current year.
-
-@end table
-
-
-@node Disk usage
-@chapter Disk usage
-
-@cindex disk usage
-
-No disk can hold an infinite amount of data.  These commands report on
-how much disk storage is in use or available.  (This has nothing much to
-do with how much @emph{main memory}, i.e., RAM, a program is using when
-it runs; for that, you want @code{ps} or @code{pstat} or @code{swap}
-or some such command.)
-
-@menu
-* df invocation::               Report filesystem disk space usage.
-* du invocation::               Estimate file space usage.
-* sync invocation::             Synchronize memory and disk.
-@end menu
-
-
-@node df invocation
-@section @code{df}: Report filesystem disk space usage
-
-@pindex df
-@cindex filesystem disk usage
-@cindex disk usage by filesystem
-
-@code{df} reports the amount of disk space used and available on
-filesystems.  Synopsis:
-
-@example
-df [@var{option}]@dots{} [@var{file}]@dots{}
-@end example
-
-With no arguments, @code{df} reports the space used and available on all
-currently mounted filesystems (of all types).  Otherwise, @code{df}
-reports on the filesystem containing each argument @var{file}.
-
-Normally the disk space is printed in units of
-1024 bytes, but this can be overridden (@pxref{Block size}).
-
-@cindex disk device file
-@cindex device file, disk
-If an argument @var{file} is a disk device file containing a mounted
-filesystem, @code{df} shows the space available on that filesystem
-rather than on the filesystem containing the device node (i.e., the root
-filesystem).  @sc{gnu} @code{df} does not attempt to determine the disk usage
-on unmounted filesystems, because on most kinds of systems doing so
-requires extremely nonportable intimate knowledge of filesystem
-structures.
-
-The program accepts the following options.  Also see @ref{Common options}.
-
-@table @samp
-
-@item -a
-@itemx --all
-@opindex -a
-@opindex --all
-@cindex automounter filesystems
-@cindex ignore filesystems
-Include in the listing filesystems that have a size of 0 blocks, which
-are omitted by default.  Such filesystems are typically special-purpose
-pseudo-filesystems, such as automounter entries.  Also, filesystems of
-type ``ignore'' or ``auto'', supported by some operating systems, are
-only included if this option is specified.
-
-@item -h
-@itemx --human-readable
-@opindex -h
-@opindex --human-readable
-@cindex human-readable output
-Append a size letter such as @samp{M} for megabytes to each size.
-Powers of 1024 are used, not 1000; @samp{M} stands for 1,048,576 bytes.
-Use the @samp{-H} or @samp{--si} option if you prefer powers of 1000.
-
-@item -H
-@itemx --si
-@opindex -H
-@opindex --si
-@cindex SI output
-Append a size letter such as @samp{M} for megabytes to each size.  (SI
-is the International System of Units, which defines these letters as
-prefixes.)  Powers of 1000 are used, not 1024; @samp{M} stands for
-1,000,000 bytes.  Use the @samp{-h} or @samp{--human-readable} option if
-you prefer powers of 1024.
-
-@item -i
-@itemx --inodes
-@opindex -i
-@opindex --inodes
-@cindex inode usage
-List inode usage information instead of block usage.  An inode (short
-for index node) contains information about a file such as its owner,
-permissions, timestamps, and location on the disk.
-
-@item -k
-@itemx --kilobytes
-@opindex -k
-@opindex --kilobytes
-@cindex kilobytes for filesystem sizes
-Print sizes in 1024-byte blocks, overriding the default block size
-(@pxref{Block size}).
-
-@item -l
-@itemx --local
-@opindex -l
-@opindex --local
-@cindex filesystem types, limiting output to certain
-Limit the listing to local filesystems.  By default, remote filesystems
-are also listed.
-
-@item -m
-@itemx --megabytes
-@opindex -m
-@opindex --megabytes
-@cindex megabytes for filesystem sizes
-Print sizes in megabyte (that is, 1,048,576-byte) blocks.
-
-@item --no-sync
-@opindex --no-sync
-@cindex filesystem space, retrieving old data more quickly
-Do not invoke the @code{sync} system call before getting any usage data.
-This may make @code{df} run significantly faster on systems with many
-disks, but on some systems (notably SunOS) the results may be slightly
-out of date.  This is the default.
-
-@item -P
-@itemx --portability
-@opindex -P
-@opindex --portability
-@cindex one-line output format
-@cindex @sc{posix} output format
-@cindex portable output format
-@cindex output format, portable
-Use the @sc{posix} output format.  This is like the default format except
-for the following:
-
-@enumerate
-@item
-The information about each filesystem is always printed on exactly
-one line; a mount device is never put on a line by itself.  This means
-that if the mount device name is more than 20 characters long (e.g., for
-some network mounts), the columns are misaligned.
-
-@item
-Non-integer values are rounded up, instead of being rounded down or
-rounded to the nearest integer.
-
-@item
-The labels in the header output line are changed to conform to @sc{posix}.
-@end enumerate
-
-@item --sync
-@opindex --sync
-@cindex filesystem space, retrieving current data more slowly
-Invoke the @code{sync} system call before getting any usage data.  On
-some systems (notably SunOS), doing this yields more up to date results,
-but in general this option makes @code{df} much slower, especially when
-there are many or very busy filesystems.
-
-@item -t @var{fstype}
-@itemx --type=@var{fstype}
-@opindex -t
-@opindex --type
-@cindex filesystem types, limiting output to certain
-Limit the listing to filesystems of type @var{fstype}.  Multiple
-filesystem types can be specified by giving multiple @samp{-t} options.
-By default, nothing is omitted.
-
-@item -T
-@itemx --print-type
-@opindex -T
-@opindex --print-type
-@cindex filesystem types, printing
-Print each filesystem's type.  The types printed here are the same ones
-you can include or exclude with @samp{-t} and @samp{-x}.  The particular
-types printed are whatever is supported by the system.  Here are some of
-the common names (this list is certainly not exhaustive):
-
-@table @samp
-
-@item nfs
-@cindex NFS filesystem type
-An NFS filesystem, i.e., one mounted over a network from another
-machine.  This is the one type name which seems to be used uniformly by
-all systems.
-
-@item 4.2@r{, }ufs@r{, }efs@dots{}
-@cindex Linux filesystem types
-@cindex local filesystem types
-@opindex 4.2 @r{filesystem type}
-@opindex ufs @r{filesystem type}
-@opindex efs @r{filesystem type}
-A filesystem on a locally-mounted hard disk.  (The system might even
-support more than one type here; Linux does.)
-
-@item hsfs@r{, }cdfs
-@cindex CD-ROM filesystem type
-@cindex High Sierra filesystem
-@opindex hsfs @r{filesystem type}
-@opindex cdfs @r{filesystem type}
-A filesystem on a CD-ROM drive.  HP-UX uses @samp{cdfs}, most other
-systems use @samp{hsfs} (@samp{hs} for ``High Sierra'').
-
-@item pcfs
-@cindex PC filesystem
-@cindex DOS filesystem
-@cindex MS-DOS filesystem
-@cindex diskette filesystem
-@opindex pcfs
-An MS-DOS filesystem, usually on a diskette.
-
-@end table
-
-@item -x @var{fstype}
-@itemx --exclude-type=@var{fstype}
-@opindex -x
-@opindex --exclude-type
-Limit the listing to filesystems not of type @var{fstype}.
-Multiple filesystem types can be eliminated by giving multiple
-@samp{-x} options.  By default, no filesystem types are omitted.
-
-@item -v
-Ignored; for compatibility with System V versions of @code{df}.
-
-@end table
-
-
-@node du invocation
-@section @code{du}: Estimate file space usage
-
-@pindex du
-@cindex file space usage
-@cindex disk usage for files
-
-@code{du} reports the amount of disk space used by the specified files
-and for each subdirectory (of directory arguments).  Synopsis:
-
-@example
-du [@var{option}]@dots{} [@var{file}]@dots{}
-@end example
-
-With no arguments, @code{du} reports the disk space for the current
-directory.  Normally the disk space is printed in units of
-1024 bytes, but this can be overridden (@pxref{Block size}).
-
-The program accepts the following options.  Also see @ref{Common options}.
-
-@table @samp
-
-@item -a
-@itemx --all
-@opindex -a
-@opindex --all
-Show counts for all files, not just directories.
-
-@item -b
-@itemx --bytes
-@opindex -b
-@opindex --bytes
-Print sizes in bytes, overriding the default block size (@pxref{Block size}).
-
-@item -c
-@itemx --total
-@opindex -c
-@opindex --total
-@cindex grand total of disk space
-Print a grand total of all arguments after all arguments have
-been processed.  This can be used to find out the total disk usage of
-a given set of files or directories.
-
-@item -D
-@itemx --dereference-args
-@opindex -D
-@opindex --dereference-args
-Dereference symbolic links that are command line arguments.
-Does not affect other symbolic links.  This is helpful for finding
-out the disk usage of directories, such as @file{/usr/tmp}, which
-are often symbolic links.
-
-@item -h
-@itemx --human-readable
-@opindex -h
-@opindex --human-readable
-@cindex human-readable output
-Append a size letter such as @samp{M} for megabytes to each size.
-Powers of 1024 are used, not 1000; @samp{M} stands for 1,048,576 bytes.
-Use the @samp{-H} or @samp{--si} option if you prefer powers of 1000.
-
-@item -H
-@itemx --si
-@opindex -H
-@opindex --si
-@cindex SI output
-Append a size letter such as @samp{M} for megabytes to each size.  (SI
-is the International System of Units, which defines these letters as
-prefixes.)  Powers of 1000 are used, not 1024; @samp{M} stands for
-1,000,000 bytes.  Use the @samp{-h} or @samp{--human-readable} option if
-you prefer powers of 1024.
-
-@item -k
-@itemx --kilobytes
-@opindex -k
-@opindex --kilobytes
-Print sizes in 1024-byte blocks, overriding the default block size
-(@pxref{Block size}).
-
-@item -l
-@itemx --count-links
-@opindex -l
-@opindex --count-links
-@cindex hard links, counting in @code{du}
-Count the size of all files, even if they have appeared already (as a
-hard link).
-
-@item -L
-@itemx --dereference
-@opindex -L
-@opindex --dereference
-@cindex symbolic links, dereferencing in @code{du}
-Dereference symbolic links (show the disk space used by the file
-or directory that the link points to instead of the space used by
-the link).
-
-@item --max-depth=@var{DEPTH}
-@opindex --max-depth=@var{DEPTH}
-@cindex limiting output of @code{du}
-Show the total for each directory (and file if --all) that is at
-most MAX_DEPTH levels down from the root of the hierarchy.  The root
-is at level 0, so @code{du --max-depth=0} is equivalent to @code{du -s}.
-
-@item -m
-@itemx --megabytes
-@opindex -m
-@opindex --megabytes
-@cindex megabytes for filesystem sizes
-Print sizes in megabyte (that is, 1,048,576-byte) blocks.
-
-@item -s
-@itemx --summarize
-@opindex -s
-@opindex --summarize
-Display only a total for each argument.
-
-@item -S
-@itemx --separate-dirs
-@opindex -S
-@opindex --separate-dirs
-Report the size of each directory separately, not including the sizes
-of subdirectories.
-
-@item -x
-@itemx --one-file-system
-@opindex -x
-@opindex --one-file-system
-@cindex one filesystem, restricting @code{du} to
-Skip directories that are on different filesystems from the one that
-the argument being processed is on.
-
-@item --exclude=@var{PAT}
-@opindex --exclude=@var{PAT}
-@cindex excluding files from @code{du}
-When recursing, skip subdirectories or files matching @var{PAT}.
-For example, @code{du --exclude='*.o'} excludes files whose names
-end in @samp{.o}.
-
-@item -X @var{FILE}
-@itemx --exclude-from=@var{FILE}
-@opindex -X @var{FILE}
-@opindex --exclude-from=@var{FILE}
-@cindex excluding files from @code{du}
-Like @samp{--exclude}, except take the patterns to exclude from @var{FILE},
-one per line.  If @var{FILE} is @samp{-}, take the patterns from standard
-input.
-
-@end table
-
-@cindex NFS mounts from BSD to HP-UX
-On BSD systems, @code{du} reports sizes that are half the correct
-values for files that are NFS-mounted from HP-UX systems.  On HP-UX
-systems, it reports sizes that are twice the correct values for
-files that are NFS-mounted from BSD systems.  This is due to a flaw
-in HP-UX; it also affects the HP-UX @code{du} program.
-
-
-@node sync invocation
-@section @code{sync}: Synchronize data on disk with memory
-
-@pindex sync
-@cindex synchronize disk and memory
-
-@cindex superblock, writing
-@cindex inodes, written buffered
-@code{sync} writes any data buffered in memory out to disk.  This can
-include (but is not limited to) modified superblocks, modified inodes,
-and delayed reads and writes.  This must be implemented by the kernel;
-The @code{sync} program does nothing but exercise the @code{sync} system
-call.
-
-@cindex crashes and corruption
-The kernel keeps data in memory to avoid doing (relatively slow) disk
-reads and writes.  This improves performance, but if the computer
-crashes, data may be lost or the filesystem corrupted as a
-result. @code{sync} ensures everything in memory is written to disk.
-
-Any arguments are ignored, except for a lone @samp{--help} or
-@samp{--version} (@pxref{Common options}).
-
-@node Printing text
-@chapter Printing text
-
-@cindex printing text, commands for
-@cindex commands for printing text
-
-This section describes commands that display text strings.
-
-@menu
-* echo invocation::             Print a line of text.
-* printf invocation::           Format and print data.
-* yes invocation::              Print a string until interrupted.
-@end menu
-
-
-@node echo invocation
-@section @code{echo}: Print a line of text
-
-@pindex echo
-@cindex displaying text
-@cindex printing text
-@cindex text, displaying
-@cindex arbitrary text, displaying
-
-@code{echo} writes each given @var{string} to standard output, with a
-space between each and a newline after the last one.  Synopsis:
-
-@example
-echo [@var{option}]@dots{} [@var{string}]@dots{}
-@end example
-
-The program accepts the following options.  Also see @ref{Common options}.
-
-@table @samp
-@item -n
-@opindex -n
-Do not output the trailing newline.
-
-@item -e
-@opindex -e
-@cindex backslash escapes
-Enable interpretation of the following backslash-escaped characters in
-each @var{string}:
-
-@table @samp
-@item \a
-alert (bell)
-@item \b
-backspace
-@item \c
-suppress trailing newline
-@item \f
-form feed
-@item \n
-new line
-@item \r
-carriage return
-@item \t
-horizontal tab
-@item \v
-vertical tab
-@item \\
-backslash
-@item \@var{nnn}
-the character whose ASCII code is @var{nnn} (octal); if @var{nnn} is not
-a valid octal number, it is printed literally.
-@end table
-
-@end table
-
-
-@node printf invocation
-@section @code{printf}: Format and print data
-
-@pindex printf
-@code{printf} does formatted printing of text. Synopsis:
-
-@example
-printf @var{format} [@var{argument}]@dots{}
-@end example
-
-@code{printf} prints the @var{format} string, interpreting @samp{%}
-directives and @samp{\} escapes in the same way as the C @code{printf}
-function.  The @var{format} argument is re-used as necessary to convert
-all of the given @var{argument}s.
-
-@code{printf} has one additional directive, @samp{%b}, which prints its
-argument string with @samp{\} escapes interpreted in the same way as in
-the @var{format} string.
-
-@kindex \0ooo
-@kindex \0xhhh
-@code{printf} interprets @samp{\0ooo} in @var{format} as an octal number
-(if @var{ooo} is 0 to 3 octal digits) specifying a character to print,
-and @samp{\xhhh} as a hexadecimal number (if @var{hhh} is 1 to 3 hex
-digits) specifying a character to print.
-
-@kindex \uhhhh
-@kindex \Uhhhhhhhh
-@code{printf} interprets two character syntaxes introduced in ISO C 99:
-@samp{\u} for 16-bit Unicode characters, specified as 4 hex digits
-@var{hhhh}, and @samp{\U} for 32-bit Unicode characters, specified as 8 hex
-digits @var{hhhhhhhh}. @code{printf} outputs the Unicode characters
-according to the LC_CTYPE part of the current locale, i.e. depending
-on the values of the environment variables @code{LC_ALL}, @code{LC_CTYPE},
-@code{LANG}.
-
-The processing of @samp{\u} and @samp{\U} requires a full-featured
-@code{iconv} facility. It is activated on systems with glibc 2.2 (or newer),
-or when @code{libiconv} is installed prior to the sh-utils. Otherwise the
-use of @samp{\u} and @samp{\U} will give an error message.
-
-@kindex \c
-An additional escape, @samp{\c}, causes @code{printf} to produce no
-further output.
-
-The only options are a lone @samp{--help} or
-@samp{--version}.  @xref{Common options}.
-
-The Unicode character syntaxes are useful for writing strings in a locale
-independent way. For example, a string containing the Euro currency symbol
-
-@example
-$ /usr/local/bin/printf '\u20AC 14.95'
-@end example
-
-@noindent
-will be output correctly in all locales supporting the Euro symbol
-(ISO-8859-15, UTF-8, and others). Similarly, a Chinese string
-
-@example
-$ /usr/local/bin/printf '\u4e2d\u6587'
-@end example
-
-@noindent
-will be output correctly in all Chinese locales (GB2312, BIG5, UTF-8, etc).
-
-Note that in these examples, the full pathname of @code{printf} has been
-given, to distinguish it from the GNU @code{bash} builtin function
-@code{printf}.
-
-For larger strings, you don't need to look up the hexadecimal code
-values of each character one by one. ASCII characters mixed with \u
-escape sequences is also known as the JAVA source file encoding. You can
-use GNU recode 3.5c (or newer) to convert strings to this encoding. Here
-is how to convert a piece of text into a shell script which will output
-this text in a locale-independent way:
-
-@smallexample
-$ LC_CTYPE=zh_CN.big5 /usr/local/bin/printf \
-    '\u4e2d\u6587\n' > sample.txt
-$ recode BIG5..JAVA < sample.txt \
-    | sed -e "s|^|/usr/local/bin/printf '|" -e "s|$|\\\\n'|" \
-    > sample.sh
-@end smallexample
-
-
-@node yes invocation
-@section @code{yes}: Print a string until interrupted
-
-@pindex yes
-@cindex repeated output of a string
-
-@code{yes} prints the command line arguments, separated by spaces and
-followed by a newline, forever until it is killed.  If no arguments are
-given, it prints @samp{y} followed by a newline forever until killed.
-
-The only options are a lone @samp{--help} or @samp{--version}.
-@xref{Common options}.
-
-
-@node Conditions
-@chapter Conditions
-
-@cindex conditions
-@cindex commands for exit status
-@cindex exit status commands
-
-This section describes commands that are primarily useful for their exit
-status, rather than their output.  Thus, they are often used as the
-condition of shell @code{if} statements, or as the last command in a
-pipeline.
-
-@menu
-* false invocation::            Do nothing, unsuccessfully.
-* true invocation::             Do nothing, successfully.
-* test invocation::             Check file types and compare values.
-* expr invocation::             Evaluate expressions.
-@end menu
-
-
-@node false invocation
-@section @code{false}: Do nothing, unsuccessfully
-
-@pindex false
-@cindex do nothing, unsuccessfully
-@cindex failure exit status
-@cindex exit status of @code{false}
-
-@code{false} does nothing except return an exit status of 1, meaning
-@dfn{failure}.  It can be used as a place holder in shell scripts
-where an unsuccessful command is needed.
-
-By default, @code{false} honors the @samp{--help} and @samp{--version}
-options.  However, that is contrary to @sc{posix}, so when the environment
-variable @env{POSIXLY_CORRECT} is set, @code{false} ignores @emph{all}
-command line arguments, including @samp{--help} and @samp{--version}.
-
-This version of @code{false} is implemented as a C program, and is thus
-more secure and faster than a shell script implementation, and may safely
-be used as a dummy shell for the purpose of disabling accounts.
-
-
-@node true invocation
-@section @code{true}: Do nothing, successfully
-
-@pindex true
-@cindex do nothing, successfully
-@cindex no-op
-@cindex successful exit
-@cindex exit status of @code{true}
-
-@code{true} does nothing except return an exit status of 0, meaning
-@dfn{success}.  It can be used as a place holder in shell scripts
-where a successful command is needed, although the shell built-in
-command @code{:} (colon) may do the same thing faster.
-In most modern shells, @code{true} is a built-in command, so when
-you use @samp{true} in a script, you're probably using the built-in
-command, not the one documented here.
-
-By default, @code{true} honors the @samp{--help} and @samp{--version}
-options.  However, that is contrary to @sc{posix}, so when the environment
-variable @env{POSIXLY_CORRECT} is set, @code{true} ignores @emph{all}
-command line arguments, including @samp{--help} and @samp{--version}.
-
-This version of @code{true} is implemented as a C program, and is thus
-more secure and faster than a shell script implementation, and may safely
-be used as a dummy shell for the purpose of disabling accounts.
-
-@node test invocation
-@section @code{test}: Check file types and compare values
-
-@pindex test
-@cindex check file types
-@cindex compare values
-@cindex expression evaluation
-
-@code{test} returns a status of 0 (true) or 1 (false) depending on the
-evaluation of the conditional expression @var{expr}.  Each part of the
-expression must be a separate argument.
-
-@code{test} has file status checks, string operators, and numeric
-comparison operators.
-
-@cindex conflicts with shell built-ins
-@cindex built-in shell commands, conflicts with
-Because most shells have a built-in command by the same name, using the
-unadorned command name in a script or interactively may get you
-different functionality than that described here.
-
-Besides the options below, @code{test} accepts a lone @samp{--help} or
-@samp{--version}.  @xref{Common options}.  A single non-option argument
-is also allowed: @code{test} returns true if the argument is not null.
-
-@menu
-* File type tests::             -[bcdfhLpSt]
-* Access permission tests::     -[gkruwxOG]
-* File characteristic tests::   -e -s -nt -ot -ef
-* String tests::                -z -n = !=
-* Numeric tests::               -eq -ne -lt -le -gt -ge
-* Connectives for test::        ! -a -o
-@end menu
-
-
-@node File type tests
-@subsection File type tests
-
-@cindex file type tests
-
-These options test for particular types of files.  (Everything's a file,
-but not all files are the same!)
-
-@table @samp
-
-@item -b @var{file}
-@opindex -b
-@cindex block special check
-True if @var{file} exists and is a block special device.
-
-@item -c @var{file}
-@opindex -c
-@cindex character special check
-True if @var{file} exists and is a character special device.
-
-@item -d @var{file}
-@opindex -d
-@cindex directory check
-True if @var{file} exists and is a directory.
-
-@item -f @var{file}
-@opindex -f
-@cindex regular file check
-True if @var{file} exists and is a regular file.
-
-@item -h @var{file}
-@itemx -L @var{file}
-@opindex -L
-@opindex -h
-@cindex symbolic link check
-True if @var{file} exists and is a symbolic link.
-
-@item -p @var{file}
-@opindex -p
-@cindex named pipe check
-True if @var{file} exists and is a named pipe.
-
-@item -S @var{file}
-@opindex -S
-@cindex socket check
-True if @var{file} exists and is a socket.
-
-@item -t [@var{fd}]
-@opindex -t
-@cindex terminal check
-True if @var{fd} is opened on a terminal.  If @var{fd} is omitted, it
-defaults to 1 (standard output).
-
-@end table
-
-
-@node Access permission tests
-@subsection Access permission tests
-
-@cindex access permission tests
-@cindex permission tests
-
-These options test for particular access permissions.
-
-@table @samp
-
-@item -g @var{file}
-@opindex -g
-@cindex set-group-id check
-True if @var{file} exists and has its set-group-id bit set.
-
-@item -k @var{file}
-@opindex -k
-@cindex sticky bit check
-True if @var{file} has its @dfn{sticky} bit set.
-
-@item -r @var{file}
-@opindex -r
-@cindex readable file check
-True if @var{file} exists and is readable.
-
-@item -u @var{file}
-@opindex -u
-@cindex set-user-id check
-True if @var{file} exists and has its set-user-id bit set.
-
-@item -w @var{file}
-@opindex -w
-@cindex writable file check
-True if @var{file} exists and is writable.
-
-@item -x @var{file}
-@opindex -x
-@cindex executable file check
-True if @var{file} exists and is executable.
-
-@item -O @var{file}
-@opindex -O
-@cindex owned by effective uid check
-True if @var{file} exists and is owned by the current effective user id.
-
-@item -G @var{file}
-@opindex -G
-@cindex owned by effective gid check
-True if @var{file} exists and is owned by the current effective group id.
-
-@end table
-
-@node File characteristic tests
-@subsection File characteristic tests
-
-@cindex file characteristic tests
-
-These options test other file characteristics.
-
-@table @samp
-
-@item -e @var{file}
-@opindex -e
-@cindex existence-of-file check
-True if @var{file} exists.
-
-@item -s @var{file}
-@opindex -s
-@cindex nonempty file check
-True if @var{file} exists and has a size greater than zero.
-
-@item @var{file1} -nt @var{file2}
-@opindex -nt
-@cindex newer-than file check
-True if @var{file1} is newer (according to modification date) than
-@var{file2}.
-
-@item @var{file1} -ot @var{file2}
-@opindex -ot
-@cindex older-than file check
-True if @var{file1} is older (according to modification date) than
-@var{file2}.
-
-@item @var{file1} -ef @var{file2}
-@opindex -ef
-@cindex same file check
-@cindex hard link check
-True if @var{file1} and @var{file2} have the same device and inode
-numbers, i.e., if they are hard links to each other.
-
-@end table
-
-
-@node String tests
-@subsection String tests
-
-@cindex string tests
-
-These options test string characteristics.  Strings are not quoted for
-@code{test}, though you may need to quote them to protect characters
-with special meaning to the shell, e.g., spaces.
-
-@table @samp
-
-@item -z @var{string}
-@opindex -z
-@cindex zero-length string check
-True if the length of @var{string} is zero.
-
-@item -n @var{string}
-@itemx @var{string}
-@opindex -n
-@cindex nonzero-length string check
-True if the length of @var{string} is nonzero.
-
-@item @var{string1} = @var{string2}
-@opindex =
-@cindex equal string check
-True if the strings are equal.
-
-@item @var{string1} != @var{string2}
-@opindex !=
-@cindex not-equal string check
-True if the strings are not equal.
-
-@end table
-
-
-@node Numeric tests
-@subsection Numeric tests
-
-@cindex numeric tests
-@cindex arithmetic tests
-
-Numeric relationals.  The arguments must be entirely numeric (possibly
-negative), or the special expression @w{@code{-l @var{string}}}, which
-evaluates to the length of @var{string}.
-
-@table @samp
-
-@item @var{arg1} -eq @var{arg2}
-@itemx @var{arg1} -ne @var{arg2}
-@itemx @var{arg1} -lt @var{arg2}
-@itemx @var{arg1} -le @var{arg2}
-@itemx @var{arg1} -gt @var{arg2}
-@itemx @var{arg1} -ge @var{arg2}
-@opindex -eq
-@opindex -ne
-@opindex -lt
-@opindex -le
-@opindex -gt
-@opindex -ge
-These arithmetic binary operators return true if @var{arg1} is equal,
-not-equal, less-than, less-than-or-equal, greater-than, or
-greater-than-or-equal than @var{arg2}, respectively.
-
-@end table
-
-For example:
-
-@example
-test -1 -gt -2 && echo yes
-@result{} yes
-test -l abc -gt 1 && echo yes
-@result{} yes
-test 0x100 -eq 1
-@error{} test: integer expression expected before -eq
-@end example
-
-
-@node Connectives for test
-@subsection Connectives for @code{test}
-
-@cindex logical connectives
-@cindex connectives, logical
-
-The usual logical connectives.
-
-@table @samp
-
-@item ! @var{expr}
-@opindex !
-True if @var{expr} is false.
-
-@item @var{expr1} -a @var{expr2}
-@opindex -a
-@cindex logical and operator
-@cindex and operator
-True if both @var{expr1} and @var{expr2} are true.
-
-@item @var{expr1} -o @var{expr2}
-@opindex -o
-@cindex logical or operator
-@cindex or operator
-True if either @var{expr1} or @var{expr2} is true.
-
-@end table
-
-
-@node expr invocation
-@section @code{expr}: Evaluate expressions
-
-@pindex expr
-@cindex expression evaluation
-@cindex evaluation of expressions
-
-@code{expr} evaluates an expression and writes the result on standard
-output.  Each token of the expression must be a separate argument.
-
-Operands are either numbers or strings.  @code{expr} converts
-anything appearing in an operand position to an integer or a string
-depending on the operation being applied to it.
-
-Strings are not quoted for @code{expr} itself, though you may need to
-quote them to protect characters with special meaning to the shell,
-e.g., spaces.
-
-@cindex parentheses for grouping
-Operators may given as infix symbols or prefix keywords.  Parentheses
-may be used for grouping in the usual manner (you must quote parentheses
-to avoid the shell evaluating them, however).
-
-@cindex exit status of @code{expr}
-Exit status:
-
-@display
-0 if the expression is neither null nor 0,
-1 if the expression is null or 0,
-2 for invalid expressions.
-@end display
-
-@menu
-* String expressions::          <colon> match substr index length quote
-* Numeric expressions::         + - * / %
-* Relations for expr::          | & < <= = == != >= >
-* Examples of expr::            Examples.
-@end menu
-
-
-@node String expressions
-@subsection String expressions
-
-@cindex string expressions
-@cindex expressions, string
-
-@code{expr} supports pattern matching and other string operators.  These
-have lower precedence than both the numeric and relational operators (in
-the next sections).
-
-@table @samp
-
-@item @var{string} : @var{regex}
-@cindex pattern matching
-@cindex regular expression matching
-@cindex matching patterns
-Perform pattern matching.  The arguments are converted to strings and the
-second is considered to be a (basic, a la GNU @code{grep}) regular
-expression, with a @code{^} implicitly prepended.  The first argument is
-then matched against this regular expression.
-
-If the match succeeds and @var{regex} uses @samp{\(} and @samp{\)}, the
-@code{:} expression returns the part of @var{string} that matched the
-subexpression; otherwise, it returns the number of characters matched.
-
-If the match fails, the @code{:} operator returns the null string if
-@samp{\(} and @samp{\)} are used in @var{regex}, otherwise 0.
-
-@kindex \( @r{regexp operator}
-Only the first @samp{\( @dots{} \)} pair is relevant to the return
-value; additional pairs are meaningful only for grouping the regular
-expression operators.
-
-@kindex \+ @r{regexp operator}
-@kindex \? @r{regexp operator}
-@kindex \| @r{regexp operator}
-In the regular expression, @code{\+}, @code{\?}, and @code{\|} are
-operators which respectively match one or more, zero or one, or separate
-alternatives.  SunOS and other @code{expr}'s treat these as regular
-characters.  (@sc{posix} allows either behavior.)
-@xref{Top, , Regular Expression Library, regex, Regex}, for details of
-regular expression syntax.  Some examples are in @ref{Examples of expr}.
-
-@item match @var{string} @var{regex}
-@findex match
-An alternative way to do pattern matching.  This is the same as
-@w{@samp{@var{string} : @var{regex}}}.
-
-@item substr @var{string} @var{position} @var{length}
-@findex substr
-Returns the substring of @var{string} beginning at @var{position}
-with length at most @var{length}.  If either @var{position} or
-@var{length} is negative, zero, or non-numeric, returns the null string.
-
-@item index @var{string} @var{charset}
-@findex index
-Returns the first position in @var{string} where the first character in
-@var{charset} was found.  If no character in @var{charset} is found in
-@var{string}, return 0.
-
-@item length @var{string}
-@findex length
-Returns the length of @var{string}.
-
-@item quote @var{token}
-@findex quote
-Interpret @var{token} as a string, even if it is a keyword like @var{match}
-or an operator like @code{/}.
-This makes it possible to test @code{expr length quote "$x"} or
-@code{expr quote "$x" : '.*/\(.\)'} and have it do the right thing even if
-the value of @var{$x} happens to be (for example) @code{/} or @code{index}.
-This operator is a GNU extension.  It is disabled when
-the environment variable @env{POSIXLY_CORRECT} is set.
-
-@end table
-
-To make @code{expr} interpret keywords as strings, you must use the
-@code{quote} operator.
-
-
-@node Numeric expressions
-@subsection Numeric expressions
-
-@cindex numeric expressions
-@cindex expressions, numeric
-
-@code{expr} supports the usual numeric operators, in order of increasing
-precedence.  The string operators (previous section) have lower precedence,
-the connectives (next section) have higher.
-
-@table @samp
-
-@item + -
-@kindex +
-@kindex -
-@cindex addition
-@cindex subtraction
-Addition and subtraction.  Both arguments are converted to numbers;
-an error occurs if this cannot be done.
-
-@item * / %
-@kindex *
-@kindex /
-@kindex %
-@cindex multiplication
-@cindex division
-@cindex remainder
-Multiplication, division, remainder.  Both arguments are converted to
-numbers; an error occurs if this cannot be done.
-
-@end table
-
-
-@node Relations for expr
-@subsection Relations for @code{expr}
-
-@cindex connectives, logical
-@cindex logical connectives
-@cindex relations, numeric or string
-
-@code{expr} supports the usual logical connectives and relations.  These
-are higher precedence than either the string or numeric operators
-(previous sections).  Here is the list, lowest-precedence operator first.
-
-@table @samp
-
-@item |
-@kindex |
-@cindex logical or operator
-@cindex or operator
-Returns its first argument if that is neither null nor 0, otherwise its
-second argument.
-
-@item &
-@kindex &
-@cindex logical and operator
-@cindex and operator
-Return its first argument if neither argument is null or 0, otherwise
-0.
-
-@item < <= = == != >= >
-@kindex <
-@kindex <=
-@kindex =
-@kindex ==
-@kindex >
-@kindex >=
-@cindex comparison operators
-Compare the arguments and return 1 if the relation is true, 0 otherwise.
-@code{==} is a synonym for @code{=}.  @code{expr} first tries to convert
-both arguments to numbers and do a numeric comparison; if either
-conversion fails, it does a lexicographic comparison.
-
-@end table
-
-
-@node Examples of expr
-@subsection Examples of using @code{expr}
-
-@cindex examples of @code{expr}
-Here are a few examples, including quoting for shell metacharacters.
-
-To add 1 to the shell variable @code{foo}, in Bourne-compatible shells:
-@example
-foo=`expr $foo + 1`
-@end example
-
-To print the non-directory part of the file name stored in
-@code{$fname}, which need not contain a @code{/}.
-@example
-expr $fname : '.*/\(^.*\)' '^|' $fname
-@end example
-
-An example showing that @code{\+} is an operator:
-@example
-expr aaa : 'a\+'
-@result{} 3
-@end example
-
-@example
-expr abc : 'a\(.\)c'
-@result{} b
-expr index abcdef cz
-@result{} 3
-expr index index a
-@error{} expr: syntax error
-expr index quote index a
-@result{} 0
-@end example
-
-
-@node Redirection
-@chapter Redirection
-
-@cindex redirection
-@cindex commands for redirection
-
-Unix shells commonly provide several forms of @dfn{redirection}---ways
-to change the input source or output destination of a command.  But one
-useful redirection is performed by a separate command, not by the shell;
-it's described here.
-
-@menu
-* tee invocation::              Redirect output to multiple files.
-@end menu
-
-
-@node tee invocation
-@section @code{tee}: Redirect output to multiple files
-
-@pindex tee
-@cindex pipe fitting
-@cindex destinations, multiple output
-@cindex read from stdin and write to stdout and files
-
-The @code{tee} command copies standard input to standard output and also
-to any files given as arguments.  This is useful when you want not only
-to send some data down a pipe, but also to save a copy.  Synopsis:
-
-@example
-tee [@var{option}]@dots{} [@var{file}]@dots{}
-@end example
-
-If a file being written to does not already exist, it is created.  If a
-file being written to already exists, the data it previously contained
-is overwritten unless the @code{-a} option is used.
-
-The program accepts the following options.  Also see @ref{Common options}.
-
-@table @samp
-@item -a
-@itemx --append
-@opindex -a
-@opindex --append
-Append standard input to the given files rather than overwriting
-them.
-
-@item -i
-@itemx --ignore-interrupts
-@opindex -i
-@opindex --ignore-interrupts
-Ignore interrupt signals.
-
-@end table
-
-
-@node File name manipulation
-@chapter File name manipulation
-
-@cindex file name manipulation
-@cindex manipulation of file names
-@cindex commands for file name manipulation
-
-This section describes commands that manipulate file names.
-
-@menu
-* basename invocation::         Strip directory and suffix from a file name.
-* dirname invocation::          Strip non-directory suffix from a file name.
-* pathchk invocation::          Check file name portability.
-@end menu
-
-
-@node basename invocation
-@section @code{basename}: Strip directory and suffix from a file name
-
-@pindex basename
-@cindex strip directory and suffix from file names
-@cindex directory, stripping from file names
-@cindex suffix, stripping from file names
-@cindex file names, stripping directory and suffix
-@cindex leading directory components, stripping
-
-@code{basename} removes any leading directory components from
-@var{name}.  Synopsis:
-
-@example
-basename @var{name} [@var{suffix}]
-@end example
-
-If @var{suffix} is specified and is identical to the end of @var{name},
-it is removed from @var{name} as well.  @code{basename} prints the
-result on standard output.
-
-The only options are @samp{--help} and @samp{--version}.  @xref{Common
-options}.
-
-
-@node dirname invocation
-@section @code{dirname}: Strip non-directory suffix from a file name
-
-@pindex dirname
-@cindex directory components, printing
-@cindex stripping non-directory suffix
-@cindex non-directory suffix, stripping
-
-@code{dirname} prints all but the final slash-delimited component of
-a string (presumably a filename).  Synopsis:
-
-@example
-dirname @var{name}
-@end example
-
-If @var{name} is a single component, @code{dirname} prints @samp{.}
-(meaning the current directory).
-
-The only options are @samp{--help} and @samp{--version}.  @xref{Common
-options}.
-
-
-@node pathchk invocation
-@section @code{pathchk}: Check file name portability
-
-@pindex pathchk
-@cindex file names, checking validity and portability
-@cindex valid file names, checking for
-@cindex portable file names, checking for
-
-@code{pathchk} checks portability of filenames.  Synopsis:
-
-@example
-pathchk [@var{option}]@dots{} @var{name}@dots{}
-@end example
-
-For each @var{name}, @code{pathchk} prints a message if any of
-these conditions is true:
-@enumerate
-@item
-one of the existing directories in @var{name} does not have search
-(execute) permission,
-@item
-the length of @var{name} is larger than its filesystem's maximum
-file name length,
-@item
-the length of one component of @var{name}, corresponding to an
-existing directory name, is larger than its filesystem's maximum
-length for a file name component.
-@end enumerate
-
-The program accepts the following option.  Also see @ref{Common options}.
-
-@table @samp
-
-@item -p
-@itemx --portability
-@opindex -p
-@opindex --portability
-Instead of performing length checks on the underlying filesystem,
-test the length of each file name and its components against the
-@sc{posix.1} minimum limits for portability.  Also check that the file
-name contains no characters not in the portable file name character set.
-
-@end table
-
-@cindex exit status of @code{pathchk}
-Exit status:
-
-@display
-0 if all specified file names passed all of the tests,
-1 otherwise.
-@end display
-
-
-@node Working context
-@chapter Working context
-
-@cindex working context
-@cindex commands for printing the working context
-
-This section describes commands that display or alter the context in
-which you are working: the current directory, the terminal settings, and
-so forth.  See also the user-related commands in the next section.
-
-@menu
-* pwd invocation::              Print working directory.
-* stty invocation::             Print or change terminal characteristics.
-* printenv invocation::         Print environment variables.
-* tty invocation::              Print file name of terminal on standard input.
-@end menu
-
-
-@node pwd invocation
-@section @code{pwd}: Print working directory
-
-@pindex pwd
-@cindex print name of current directory
-@cindex current working directory, printing
-@cindex working directory, printing
-
-@cindex symbolic links and @code{pwd}
-@code{pwd} prints the fully resolved name of the current directory.
-That is, all components of the printed name will be actual directory
-names---none will be symbolic links.
-
-@cindex conflicts with shell built-ins
-@cindex built-in shell commands, conflicts with
-Because most shells have a built-in command by the same name, using the
-unadorned command name in a script or interactively may get you
-different functionality than that described here.
-
-The only options are a lone @samp{--help} or
-@samp{--version}.  @xref{Common options}.
-
-
-@node stty invocation
-@section @code{stty}: Print or change terminal characteristics
-
-@pindex stty
-@cindex change or print terminal settings
-@cindex terminal settings
-@cindex line settings of terminal
-
-@code{stty} prints or changes terminal characteristics, such as baud rate.
-Synopses:
-
-@example
-stty [@var{option}] [@var{setting}]@dots{}
-stty [@var{option}]
-@end example
-
-If given no line settings, @code{stty} prints the baud rate, line
-discipline number (on systems that support it), and line settings
-that have been changed from the values set by @samp{stty sane}.
-By default, mode reading and setting are performed on the tty line
-connected to standard input, although this can be modified by the
-@samp{--file} option.
-
-@code{stty} accepts many non-option arguments that change aspects of
-the terminal line operation, as described below.
-
-The program accepts the following options.  Also see @ref{Common options}.
-
-@table @samp
-@item -a
-@itemx --all
-@opindex -a
-@opindex --all
-Print all current settings in human-readable form.  This option may not
-be used in combination with any line settings.
-
-@item -F @var{device}
-@itemx --file=@var{device}
-@opindex -F
-@opindex --file
-Set the line opened by the filename specified in @var{device} instead of
-the tty line connected to standard input.  This option is necessary
-because opening a @sc{posix} tty requires use of the @code{O_NONDELAY} flag to
-prevent a @sc{posix} tty from blocking until the carrier detect line is high if
-the @code{clocal} flag is not set.  Hence, it is not always possible
-to allow the shell to open the device in the traditional manner.
-
-@item -g
-@itemx --save
-@opindex -g
-@opindex --save
-@cindex machine-readable @code{stty} output
-Print all current settings in a form that can be used as an argument to
-another @code{stty} command to restore the current settings.  This option
-may not be used in combination with any line settings.
-
-@end table
-
-Many settings can be turned off by preceding them with a @samp{-}.
-Such arguments are marked below with ``May be negated'' in their
-description.  The descriptions themselves refer to the positive
-case, that is, when @emph{not} negated (unless stated otherwise,
-of course).
-
-Some settings are not available on all @sc{posix} systems, since they use
-extensions.  Such arguments are marked below with ``Non-@sc{posix}'' in their
-description.  On non-@sc{posix} systems, those or other settings also may not
-be available, but it's not feasible to document all the variations: just
-try it and see.
-
-@menu
-* Control::                     Control settings
-* Input::                       Input settings
-* Output::                      Output settings
-* Local::                       Local settings
-* Combination::                 Combination settings
-* Characters::                  Special characters
-* Special::                     Special settings
-@end menu
-
-
-@node Control
-@subsection Control settings
-
-@cindex control settings
-Control settings:
-
-@table @samp
-@item parenb
-@opindex parenb
-@cindex two-way parity
-Generate parity bit in output and expect parity bit in input.
-May be negated.
-
-@item parodd
-@opindex parodd
-@cindex odd parity
-@cindex even parity
-Set odd parity (even if negated).  May be negated.
-
-@item cs5
-@itemx cs6
-@itemx cs7
-@itemx cs8
-@opindex cs@var{n}
-@cindex character size
-@cindex eight-bit characters
-Set character size to 5, 6, 7, or 8 bits.
-
-@item hup
-@itemx hupcl
-@opindex hup[cl]
-Send a hangup signal when the last process closes the tty.  May be
-negated.
-
-@item cstopb
-@opindex cstopb
-@cindex stop bits
-Use two stop bits per character (one if negated).  May be negated.
-
-@item cread
-@opindex cread
-Allow input to be received.  May be negated.
-
-@item clocal
-@opindex clocal
-@cindex modem control
-Disable modem control signals.  May be negated.
-
-@item crtscts
-@opindex crtscts
-@cindex hardware flow control
-@cindex flow control, hardware
-@cindex RTS/CTS flow control
-Enable RTS/CTS flow control.  Non-@sc{posix}.  May be negated.
-@end table
-
-
-@node Input
-@subsection Input settings
-
-@cindex input settings
-
-@table @samp
-@item ignbrk
-@opindex ignbrk
-@cindex breaks, ignoring
-Ignore break characters.  May be negated.
-
-@item brkint
-@opindex brkint
-@cindex breaks, cause interrupts
-Make breaks cause an interrupt signal.  May be negated.
-
-@item ignpar
-@opindex ignpar
-@cindex parity, ignoring
-Ignore characters with parity errors.  May be negated.
-
-@item parmrk
-@opindex parmrk
-@cindex parity errors, marking
-Mark parity errors (with a 255-0-character sequence).  May be negated.
-
-@item inpck
-@opindex inpck
-Enable input parity checking.  May be negated.
-
-@item istrip
-@opindex istrip
-@cindex eight-bit input
-Clear high (8th) bit of input characters.  May be negated.
-
-@item inlcr
-@opindex inlcr
-@cindex newline, translating to return
-Translate newline to carriage return.  May be negated.
-
-@item igncr
-@opindex igncr
-@cindex return, ignoring
-Ignore carriage return.  May be negated.
-
-@item icrnl
-@opindex icrnl
-@cindex return, translating to newline
-Translate carriage return to newline.  May be negated.
-
-@item ixon
-@opindex ixon
-@kindex C-s/C-q flow control
-@cindex XON/XOFF flow control
-Enable XON/XOFF flow control (that is, @kbd{CTRL-S}/@kbd{CTRL-Q}).  May
-be negated.
-
-@item ixoff
-@itemx tandem
-@opindex ixoff
-@opindex tandem
-@cindex software flow control
-@cindex flow control, software
-Enable sending of @code{stop} character when the system input buffer
-is almost full, and @code{start} character when it becomes almost
-empty again.  May be negated.
-
-@item iuclc
-@opindex iuclc
-@cindex uppercase, translating to lowercase
-Translate uppercase characters to lowercase.  Non-@sc{posix}.  May be
-negated.
-
-@item ixany
-@opindex ixany
-Allow any character to restart output (only the start character
-if negated).  Non-@sc{posix}.  May be negated.
-
-@item imaxbel
-@opindex imaxbel
-@cindex beeping at input buffer full
-Enable beeping and not flushing input buffer if a character arrives
-when the input buffer is full.  Non-@sc{posix}.  May be negated.
-@end table
-
-
-@node Output
-@subsection Output settings
-
-@cindex output settings
-These arguments specify output-related operations.
-
-@table @samp
-@item opost
-@opindex opost
-Postprocess output.  May be negated.
-
-@item olcuc
-@opindex olcuc
-@cindex lowercase, translating to output
-Translate lowercase characters to uppercase.  Non-@sc{posix}.  May be
-negated.
-
-@item ocrnl
-@opindex ocrnl
-@cindex return, translating to newline
-Translate carriage return to newline.  Non-@sc{posix}.  May be negated.
-
-@item onlcr
-@opindex onlcr
-@cindex newline, translating to crlf
-Translate newline to carriage return-newline.  Non-@sc{posix}.  May be
-negated.
-
-@item onocr
-@opindex onocr
-Do not print carriage returns in the first column.  Non-@sc{posix}.
-May be negated.
-
-@item onlret
-@opindex onlret
-Newline performs a carriage return.  Non-@sc{posix}.  May be negated.
-
-@item ofill
-@opindex ofill
-@cindex pad instead of timing for delaying
-Use fill (padding) characters instead of timing for delays.  Non-@sc{posix}.
-May be negated.
-
-@item ofdel
-@opindex ofdel
-@cindex pad character
-Use delete characters for fill instead of null characters.  Non-@sc{posix}.
-May be negated.
-
-@item nl1
-@itemx nl0
-@opindex nl@var{n}
-Newline delay style.  Non-@sc{posix}.
-
-@item cr3
-@itemx cr2
-@itemx cr1
-@itemx cr0
-@opindex cr@var{n}
-Carriage return delay style.  Non-@sc{posix}.
-
-@item tab3
-@itemx tab2
-@itemx tab1
-@itemx tab0
-@opindex tab@var{n}
-Horizontal tab delay style.  Non-@sc{posix}.
-
-@item bs1
-@itemx bs0
-@opindex bs@var{n}
-Backspace delay style.  Non-@sc{posix}.
-
-@item vt1
-@itemx vt0
-@opindex vt@var{n}
-Vertical tab delay style.  Non-@sc{posix}.
-
-@item ff1
-@itemx ff0
-@opindex ff@var{n}
-Form feed delay style.  Non-@sc{posix}.
-@end table
-
-
-@node Local
-@subsection Local settings
-
-@cindex local settings
-
-@table @samp
-@item isig
-@opindex isig
-Enable @code{interrupt}, @code{quit}, and @code{suspend} special
-characters.  May be negated.
-
-@item icanon
-@opindex icanon
-Enable @code{erase}, @code{kill}, @code{werase}, and @code{rprnt}
-special characters.  May be negated.
-
-@item iexten
-@opindex iexten
-Enable non-@sc{posix} special characters.  May be negated.
-
-@item echo
-@opindex echo
-Echo input characters.  May be negated.
-
-@item echoe
-@itemx crterase
-@opindex echoe
-@opindex crterase
-Echo @code{erase} characters as backspace-space-backspace.  May be
-negated.
-
-@item echok
-@opindex echok
-@cindex newline echoing after @code{kill}
-Echo a newline after a @code{kill} character.  May be negated.
-
-@item echonl
-@opindex echonl
-@cindex newline, echoing
-Echo newline even if not echoing other characters.  May be negated.
-
-@item noflsh
-@opindex noflsh
-@cindex flushing, disabling
-Disable flushing after @code{interrupt} and @code{quit} special
-characters.  May be negated.
-
-@item xcase
-@opindex xcase
-@cindex case translation
-Enable input and output of uppercase characters by preceding their
-lowercase equivalents with @samp{\}, when @code{icanon} is set.
-Non-@sc{posix}.  May be negated.
-
-@item tostop
-@opindex tostop
-@cindex background jobs, stopping at terminal write
-Stop background jobs that try to write to the terminal.  Non-@sc{posix}.
-May be negated.
-
-@item echoprt
-@itemx prterase
-@opindex echoprt
-@opindex prterase
-Echo erased characters backward, between @samp{\} and @samp{/}.
-Non-@sc{posix}.  May be negated.
-
-@item echoctl
-@itemx ctlecho
-@opindex echoctl
-@opindex ctlecho
-@cindex control characters, using @samp{^@var{c}}
-@cindex hat notation for control characters
-Echo control characters in hat notation (@samp{^@var{c}}) instead
-of literally.  Non-@sc{posix}.  May be negated.
-
-@item echoke
-@itemx crtkill
-@opindex echoke
-@opindex crtkill
-Echo the @code{kill} special character by erasing each character on
-the line as indicated by the @code{echoprt} and @code{echoe} settings,
-instead of by the @code{echoctl} and @code{echok} settings.  Non-@sc{posix}.
-May be negated.
-@end table
-
-
-@node Combination
-@subsection Combination settings
-
-@cindex combination settings
-Combination settings:
-
-@table @samp
-@item evenp
-@opindex evenp
-@itemx parity
-@opindex parity
-Same as @code{parenb -parodd cs7}.  May be negated.  If negated, same
-as @code{-parenb cs8}.
-
-@item oddp
-@opindex oddp
-Same as @code{parenb parodd cs7}.  May be negated.  If negated, same
-as @code{-parenb cs8}.
-
-@item nl
-@opindex nl
-Same as @code{-icrnl -onlcr}.  May be negated.  If negated, same as
-@code{icrnl -inlcr -igncr onlcr -ocrnl -onlret}.
-
-@item ek
-@opindex ek
-Reset the @code{erase} and @code{kill} special characters to their default
-values.
-
-@item sane
-@opindex sane
-Same as:
-@c This is too long to write inline.
-@example
-cread -ignbrk brkint -inlcr -igncr icrnl -ixoff
--iuclc -ixany imaxbel opost -olcuc -ocrnl onlcr
--onocr -onlret -ofill -ofdel nl0 cr0 tab0 bs0 vt0
-ff0 isig icanon iexten echo echoe echok -echonl
--noflsh -xcase -tostop -echoprt echoctl echoke
-@end example
-@noindent and also sets all special characters to their default values.
-
-@item cooked
-@opindex cooked
-Same as @code{brkint ignpar istrip icrnl ixon opost isig icanon}, plus
-sets the @code{eof} and @code{eol} characters to their default values
-if they are the same as the @code{min} and @code{time} characters.
-May be negated.  If negated, same as @code{raw}.
-
-@item raw
-@opindex raw
-Same as:
-@example
--ignbrk -brkint -ignpar -parmrk -inpck -istrip
--inlcr -igncr -icrnl -ixon -ixoff -iuclc -ixany
--imaxbel -opost -isig -icanon -xcase min 1 time 0
-@end example
-@noindent May be negated.  If negated, same as @code{cooked}.
-
-@item cbreak
-@opindex cbreak
-Same as @code{-icanon}.  May be negated.  If negated, same as
-@code{icanon}.
-
-@item pass8
-@opindex pass8
-@cindex eight-bit characters
-Same as @code{-parenb -istrip cs8}.  May be negated.  If negated,
-same as @code{parenb istrip cs7}.
-
-@item litout
-@opindex litout
-Same as @code{-parenb -istrip -opost cs8}.  May be negated.
-If negated, same as @code{parenb istrip opost cs7}.
-
-@item decctlq
-@opindex decctlq
-Same as @code{-ixany}.  Non-@sc{posix}.  May be negated.
-
-@item tabs
-@opindex tabs
-Same as @code{tab0}.  Non-@sc{posix}.  May be negated.  If negated, same
-as @code{tab3}.
-
-@item lcase
-@itemx LCASE
-@opindex lcase
-@opindex LCASE
-Same as @code{xcase iuclc olcuc}.  Non-@sc{posix}.  May be negated.
-
-@item crt
-@opindex crt
-Same as @code{echoe echoctl echoke}.
-
-@item dec
-@opindex dec
-Same as @code{echoe echoctl echoke -ixany intr ^C erase ^? kill C-u}.
-@end table
-
-
-@node Characters
-@subsection Special characters
-
-@cindex special characters
-@cindex characters, special
-
-The special characters' default values vary from system to system.
-They are set with the syntax @samp{name value}, where the names are
-listed below and the value can be given either literally, in hat
-notation (@samp{^@var{c}}), or as an integer which may start with
-@samp{0x} to indicate hexadecimal, @samp{0} to indicate octal, or
-any other digit to indicate decimal.
-
-@cindex disabling special characters
-@kindex u@r{, and disabling special characters}
-For GNU stty, giving a value of @code{^-} or @code{undef} disables that
-special character.  (This is incompatible with Ultrix @code{stty},
-which uses  a value of @samp{u} to disable a special character.  GNU
-@code{stty} treats a value @samp{u} like any other, namely to set that
-special character to @key{U}.)
-
-@table @samp
-
-@item intr
-@opindex intr
-Send an interrupt signal.
-
-@item quit
-@opindex quit
-Send a quit signal.
-
-@item erase
-@opindex erase
-Erase the last character typed.
-
-@item kill
-@opindex kill
-Erase the current line.
-
-@item eof
-@opindex eof
-Send an end of file (terminate the input).
-
-@item eol
-@opindex eol
-End the line.
-
-@item eol2
-@opindex eol2
-Alternate character to end the line.  Non-@sc{posix}.
-
-@item swtch
-@opindex swtch
-Switch to a different shell layer.  Non-@sc{posix}.
-
-@item start
-@opindex start
-Restart the output after stopping it.
-
-@item stop
-@opindex stop
-Stop the output.
-
-@item susp
-@opindex susp
-Send a terminal stop signal.
-
-@item dsusp
-@opindex dsusp
-Send a terminal stop signal after flushing the input.  Non-@sc{posix}.
-
-@item rprnt
-@opindex rprnt
-Redraw the current line.  Non-@sc{posix}.
-
-@item werase
-@opindex werase
-Erase the last word typed.  Non-@sc{posix}.
-
-@item lnext
-@opindex lnext
-Enter the next character typed literally, even if it is a special
-character.  Non-@sc{posix}.
-@end table
-
-
-@node Special
-@subsection Special settings
-
-@cindex special settings
-
-@table @samp
-@item min @var{n}
-@opindex min
-Set the minimum number of characters that will satisfy a read until
-the time value has expired, when @code{-icanon} is set.
-
-@item time @var{n}
-@opindex time
-Set the number of tenths of a second before reads time out if the minimum
-number of characters have not been read, when @code{-icanon} is set.
-
-@item ispeed @var{n}
-@opindex ispeed
-Set the input speed to @var{n}.
-
-@item ospeed @var{n}
-@opindex ospeed
-Set the output speed to @var{n}.
-
-@item rows @var{n}
-@opindex rows
-Tell the tty kernel driver that the terminal has @var{n} rows.  Non-@sc{posix}.
-
-@item cols @var{n}
-@itemx columns @var{n}
-@opindex cols
-@opindex columns
-Tell the kernel that the terminal has @var{n} columns.  Non-@sc{posix}.
-
-@item size
-@opindex size
-@vindex LINES
-@vindex COLUMNS
-Print the number of rows and columns that the kernel thinks the
-terminal has.  (Systems that don't support rows and columns in the kernel
-typically use the environment variables @env{LINES} and @env{COLUMNS}
-instead; however, GNU @code{stty} does not know anything about them.)
-Non-@sc{posix}.
-
-@item line @var{n}
-@opindex line
-Use line discipline @var{n}.  Non-@sc{posix}.
-
-@item speed
-@opindex speed
-Print the terminal speed.
-
-@item @var{n}
-@cindex baud rate, setting
-@c FIXME: Is this still true that the baud rate can't be set
-@c higher than 38400?
-Set the input and output speeds to @var{n}.  @var{n} can be one
-of: 0 50 75 110 134 134.5 150 200 300 600 1200 1800 2400 4800 9600
-19200 38400 @code{exta} @code{extb}.  @code{exta} is the same as
-19200; @code{extb} is the same as 38400.  0 hangs up the line if
-@code{-clocal} is set.
-@end table
-
-
-@node printenv invocation
-@section @code{printenv}: Print all or some environment variables
-
-@pindex printenv
-@cindex printing all or some environment variables
-@cindex environment variables, printing
-
-@code{printenv} prints environment variable values.  Synopsis:
-
-@example
-printenv [@var{option}] [@var{variable}]@dots{}
-@end example
-
-If no @var{variable}s are specified, @code{printenv} prints the value of
-every environment variable.  Otherwise, it prints the value of each
-@var{variable} that is set, and nothing for those that are not set.
-
-The only options are a lone @samp{--help} or @samp{--version}.
-@xref{Common options}.
-
-@cindex exit status of @code{printenv}
-Exit status:
-
-@display
-0 if all variables specified were found
-1 if at least one specified variable was not found
-2 if a write error occurred
-@end display
-
-
-@node tty invocation
-@section @code{tty}: Print file name of terminal on standard input
-
-@pindex tty
-@cindex print terminal file name
-@cindex terminal file name, printing
-
-@code{tty} prints the file name of the terminal connected to its standard
-input.  It prints @samp{not a tty} if standard input is not a terminal.
-Synopsis:
-
-@example
-tty [@var{option}]@dots{}
-@end example
-
-The program accepts the following option.  Also see @ref{Common options}.
-
-@table @samp
-
-@item -s
-@itemx --silent
-@itemx --quiet
-@opindex -s
-@opindex --silent
-@opindex --quiet
-Print nothing; only return an exit status.
-
-@end table
-
-@cindex exit status of @code{tty}
-Exit status:
-
-@display
-0 if standard input is a terminal
-1 if standard input is not a terminal
-2 if given incorrect arguments
-3 if a write error occurs
-@end display
-
-
-@node User information
-@chapter User information
-
-@cindex user information, commands for
-@cindex commands for printing user information
-
-This section describes commands that print user-related information:
-logins, groups, and so forth.
-
-@menu
-* id invocation::               Print real and effective uid and gid.
-* logname invocation::          Print current login name.
-* whoami invocation::           Print effective user id.
-* groups invocation::           Print group names a user is in.
-* users invocation::            Print login names of users currently logged in.
-* who invocation::              Print who is currently logged in.
-@end menu
-
-
-@node id invocation
-@section @code{id}: Print real and effective uid and gid
-
-@pindex id
-@cindex real uid and gid, printing
-@cindex effective uid and gid, printing
-@cindex printing real and effective uid and gid
-
-@code{id} prints information about the given user, or the process
-running it if no user is specified.  Synopsis:
-
-@example
-id [@var{option}]@dots{} [@var{username}]
-@end example
-
-By default, it prints the real user id, real group id, effective user id
-if different from the real user id, effective group id if different from
-the real group id, and supplemental group ids.
-
-Each of these numeric values is preceded by an identifying string and
-followed by the corresponding user or group name in parentheses.
-
-The options cause @code{id} to print only part of the above information.
-Also see @ref{Common options}.
-
-@table @samp
-@item -g
-@itemx --group
-@opindex -g
-@opindex --group
-Print only the group id.
-
-@item -G
-@itemx --groups
-@opindex -G
-@opindex --groups
-Print only the supplementary groups.
-
-@item -n
-@itemx --name
-@opindex -n
-@opindex --name
-Print the user or group name instead of the ID number.  Requires
-@code{-u}, @code{-g}, or @code{-G}.
-
-@item -r
-@itemx --real
-@opindex -r
-@opindex --real
-Print the real, instead of effective, user or group id.  Requires
-@code{-u}, @code{-g}, or @code{-G}.
-
-@item -u
-@itemx --user
-@opindex -u
-@opindex --user
-Print only the user id.
-
-@end table
-
-
-@node logname invocation
-@section @code{logname}: Print current login name
-
-@pindex logname
-@cindex printing user's login name
-@cindex login name, printing
-@cindex user name, printing
-
-@flindex /etc/utmp
-@flindex utmp
-
-@code{logname} prints the calling user's name, as found in the file
-@file{/etc/utmp}, and exits with a status of 0.  If there is no
-@file{/etc/utmp} entry for the calling process, @code{logname} prints
-an error message and exits with a status of 1.
-
-The only options are @samp{--help} and @samp{--version}.  @xref{Common
-options}.
-
-
-@node whoami invocation
-@section @code{whoami}: Print effective user id
-
-@pindex whoami
-@cindex effective UID, printing
-@cindex printing the effective UID
-
-@code{whoami} prints the user name associated with the current
-effective user id.  It is equivalent to the command @samp{id -un}.
-
-The only options are @samp{--help} and @samp{--version}.  @xref{Common
-options}.
-
-
-@node groups invocation
-@section @code{groups}: Print group names a user is in
-
-@pindex groups
-@cindex printing groups a user is in
-@cindex supplementary groups, printing
-
-@code{groups} prints the names of the primary and any supplementary
-groups for each given @var{username}, or the current process if no names
-are given.  If names are given, the name of each user is printed before
-the list of that user's groups.  Synopsis:
-
-@example
-groups [@var{username}]@dots{}
-@end example
-
-The group lists are equivalent to the output of the command @samp{id -Gn}.
-
-The only options are @samp{--help} and @samp{--version}.  @xref{Common
-options}.
-
-
-@node users invocation
-@section @code{users}: Print login names of users currently logged in
-
-@pindex users
-@cindex printing current usernames
-@cindex usernames, printing current
-
-@cindex login sessions, printing users with
-@code{users} prints on a single line a blank-separated list of user
-names of users currently logged in to the current host.  Each user name
-corresponds to a login session, so if a user has more than one login
-session, that user's name will appear the same number of times in the
-output. Synopsis:
-
-@example
-users [@var{file}]
-@end example
-
-@flindex /etc/utmp
-@flindex /etc/wtmp
-With no @var{file} argument, @code{users} extracts its information from
-the file @file{/etc/utmp}.  If a file argument is given, @code{users}
-uses that file instead.  A common choice is @file{/etc/wtmp}.
-
-The only options are @samp{--help} and @samp{--version}.  @xref{Common
-options}.
-
-
-@node who invocation
-@section @code{who}: Print who is currently logged in
-
-@pindex who
-@cindex printing current user information
-@cindex information, about current users
-
-@code{who} prints information about users who are currently logged on.
-Synopsis:
-
-@example
-@code{who} [@var{option}] [@var{file}] [am i]
-@end example
-
-@cindex terminal lines, currently used
-@cindex login time
-@cindex remote hostname
-If given no non-option arguments, @code{who} prints the following
-information for each user currently logged on: login name, terminal
-line, login time, and remote hostname or X display.
-
-@flindex /etc/utmp
-@flindex /etc/wtmp
-If given one non-option argument, @code{who} uses that instead of
-@file{/etc/utmp} as the name of the file containing the record of
-users logged on.  @file{/etc/wtmp} is commonly given as an argument
-to @code{who} to look at who has previously logged on.
-
-@opindex am i
-@opindex who am i
-If given two non-option arguments, @code{who} prints only the entry
-for the user running it (determined from its standard input), preceded
-by the hostname.  Traditionally, the two arguments given are @samp{am
-i}, as in @samp{who am i}.
-
-The program accepts the following options.  Also see @ref{Common options}.
-
-@table @samp
-@item -m
-@opindex -m
-Same as @samp{who am i}.
-
-@item -q
-@itemx --count
-@opindex -q
-@opindex --count
-Print only the login names and the number of users logged on.
-Overrides all other options.
-
-@item -s
-@opindex -s
-Ignored; for compatibility with other versions of @code{who}.
-
-@item -i
-@itemx -u
-@itemx --idle
-@opindex -i
-@opindex -u
-@opindex --idle
-@cindex idle time
-After the login time, print the number of hours and minutes that the
-user has been idle.  @samp{.} means the user was active in last minute.
-@samp{old} means the user was idle for more than 24 hours.
-
-@item -l
-@itemx --lookup
-@opindex -l
-@opindex --lookup
-Attempt to canonicalize hostnames found in utmp through a DNS lookup.  This
-is not the default because it can cause significant delays on systems with
-automatic dial-up internet access.
-
-@item -H
-@itemx --heading
-@opindex -H
-@opindex --heading
-Print a line of column headings.
-
-@item -w
-@itemx -T
-@itemx --mesg
-@itemx --message
-@itemx --writable
-@opindex -w
-@opindex -T
-@opindex --mesg
-@opindex --message
-@opindex --writable
-@cindex message status
-@pindex write@r{, allowed}
-After each login name print a character indicating the user's message status:
-
-@display
-@samp{+} allowing @code{write} messages
-@samp{-} disallowing @code{write} messages
-@samp{?} cannot find terminal device
-@end display
-
-@end table
-
-
-@node System context
-@chapter System context
-
-@cindex system context
-@cindex context, system
-@cindex commands for system context
-
-This section describes commands that print or change system-wide
-information.
-
-@menu
-* date invocation::             Print or set system date and time.
-* uname invocation::            Print system information.
-* hostname invocation::         Print or set system name.
-* hostid invocation::           Print numeric host identifier.
-@end menu
-
-
-@node date invocation
-@section @code{date}: Print or set system date and time
-
-@pindex date
-@cindex time, printing or setting
-@cindex printing the current time
-
-Synopses:
-
-@example
-date [@var{option}]@dots{} [+@var{format}]
-date [-u|--utc|--universal] @c this avoids a newline in the output
-[ MMDDhhmm[[CC]YY][.ss] ]
-@end example
-
-Invoking @code{date} with no @var{format} argument is equivalent to invoking
-@samp{date '+%a %b %e %H:%M:%S %Z %Y'}.
-
-@findex strftime @r{and @code{date}}
-@cindex time formats
-@cindex formatting times
-If given an argument that starts with a @samp{+}, @code{date} prints the
-current time and date (or the time and date specified by the
-@code{--date} option, see below) in the format defined by that argument,
-which is the same as in the @code{strftime} function.  Except for
-directives, which start with @samp{%}, characters in the format string
-are printed unchanged.  The directives are described below.
-
-@menu
-* Time directives::             %[HIklMprsSTXzZ]
-* Date directives::             %[aAbBcdDhjmUwWxyY]
-* Literal directives::          %[%nt]
-* Padding::                     Pad with zeroes, spaces (%_), or nothing (%-).
-* Setting the time::            Changing the system clock.
-* Options for date::            Instead of the current time.
-* Examples of date::            Examples.
-@end menu
-
-@node Time directives
-@subsection Time directives
-
-@cindex time directives
-@cindex directives, time
-
-@code{date} directives related to times.
-
-@table @samp
-@item %H
-hour (00@dots{}23)
-@item %I
-hour (01@dots{}12)
-@item %k
-hour ( 0@dots{}23)
-@item %l
-hour ( 1@dots{}12)
-@item %M
-minute (00@dots{}59)
-@item %p
-locale's AM or PM
-@item %r
-time, 12-hour (hh:mm:ss [AP]M)
-@item %s
-@cindex epoch, seconds since
-@cindex seconds since the epoch
-@cindex beginning of time
-seconds since the epoch, i.e., 1 January 1970 00:00:00 UTC (a
-GNU extension).
-Note that this value is the number of seconds between the epoch
-and the current date as defined by the localtime system call.
-It isn't changed by the @samp{--date} option.
-@item %S
-second (00@dots{}60)
-@item %T
-time, 24-hour (hh:mm:ss)
-@item %X
-locale's time representation (%H:%M:%S)
-@item %z
-RFC-822 style numeric time zone (e.g., -0600 or +0100), or nothing if no
-time zone is determinable.  This value reflects the @emph{current} time
-zone.  It isn't changed by the @samp{--date} option.
-@item %Z
-time zone (e.g., EDT), or nothing if no time zone is
-determinable.
-Note that this value reflects the @emph{current} time zone.
-It isn't changed by the @samp{--date} option.
-@end table
-
-
-@node Date directives
-@subsection Date directives
-
-@cindex date directives
-@cindex directives, date
-
-@code{date} directives related to dates.
-
-@table @samp
-@item %a
-locale's abbreviated weekday name (Sun@dots{}Sat)
-@item %A
-locale's full weekday name, variable length (Sunday@dots{}Saturday)
-@item %b
-locale's abbreviated month name (Jan@dots{}Dec)
-@item %B
-locale's full month name, variable length (January@dots{}December)
-@item %c
-locale's date and time (Sat Nov 04 12:02:33 EST 1989)
-@item %C
-century (year divided by 100 and truncated to an integer) (00@dots{}99)
-@item %d
-day of month (01@dots{}31)
-@item %D
-date (mm/dd/yy)
-@item %h
-same as %b
-@item %j
-day of year (001@dots{}366)
-@item %m
-month (01@dots{}12)
-@item %U
-week number of year with Sunday as first day of week (00@dots{}53).
-Days in a new year preceding the first Sunday are in week zero.
-@item %V
-week number of year with Monday as first day of the week as a decimal
-(01@dots{}53). If the week containing January 1 has four or more days in
-the new year, then it is considered week 1; otherwise, it is week 53 of
-the previous year, and the next week is week 1. (See the ISO 8601: 1988
-standard.)
-@item %w
-day of week (0@dots{}6) with 0 corresponding to Sunday
-@item %W
-week number of year with Monday as first day of week (00@dots{}53).
-Days in a new year preceding the first Monday are in week zero.
-@item %x
-locale's date representation (mm/dd/yy)
-@item %y
-last two digits of year (00@dots{}99)
-@item %Y
-year (1970@dots{}.)
-@end table
-
-
-@node Literal directives
-@subsection Literal directives
-
-@cindex literal directives
-@cindex directives, literal
-
-@code{date} directives that produce literal strings.
-
-@table @samp
-@item %%
-a literal %
-@item %n
-a newline
-@item %t
-a horizontal tab
-@end table
-
-
-@node Padding
-@subsection Padding
-
-@cindex numeric field padding
-@cindex padding of numeric fields
-@cindex fields, padding numeric
-
-By default, @code{date} pads numeric fields with zeroes, so that, for
-example, numeric months are always output as two digits. GNU @code{date}
-recognizes the following numeric modifiers between the @samp{%} and the
-directive.
-
-@table @samp
-@item -
-(hyphen) do not pad the field; useful if the output is intended for
-human consumption.
-@item _
-(underscore) pad the field with spaces; useful if you need a fixed
-number of characters in the output, but zeroes are too distracting.
-@end table
-
-@noindent
-These are GNU extensions.
-
-Here is an example illustrating the differences:
-
-@example
-date +%d/%m -d "Feb 1"
-@result{} 01/02
-date +%-d/%-m -d "Feb 1"
-@result{} 1/2
-date +%_d/%_m -d "Feb 1"
-@result{}  1/ 2
-@end example
-
-
-@node Setting the time
-@subsection Setting the time
-
-@cindex setting the time
-@cindex time setting
-@cindex appropriate privileges
-
-If given an argument that does not start with @samp{+}, @code{date} sets
-the system clock to the time and date specified by that argument (as
-described below).  You must have appropriate privileges to set the
-system clock.  The @samp{--date} and @samp{--set} options may not be
-used with such an argument.  The @samp{--universal} option may be used
-with such an argument to indicate that the specified time and date are
-relative to Coordinated Universal Time rather than to the local time
-zone.
-
-The argument must consist entirely of digits, which have the following
-meaning:
-
-@table @samp
-@item MM
-month
-@item DD
-day within month
-@item hh
-hour
-@item mm
-minute
-@item CC
-first two digits of year (optional)
-@item YY
-last two digits of year (optional)
-@item ss
-second (optional)
-@end table
-
-The @samp{--set} option also sets the system clock; see the next section.
-
-
-@node Options for date
-@subsection Options for @code{date}
-
-@cindex @code{date} options
-@cindex options for @code{date}
-
-The program accepts the following options.  Also see @ref{Common options}.
-
-@table @samp
-
-@item -d @var{datestr}
-@itemx --date=@var{datestr}
-@opindex -d
-@opindex --date
-@cindex parsing date strings
-@cindex date strings, parsing
-@cindex arbitrary date strings, parsing
-@opindex yesterday
-@opindex tomorrow
-@opindex next @var{day}
-@opindex last @var{day}
-Display the time and date specified in @var{datestr} instead of the
-current time and date.  @var{datestr} can be in almost any common
-format.  It can contain month names, time zones, @samp{am} and @samp{pm},
-@samp{yesterday}, @samp{ago}, @samp{next}, etc.  @xref{Date input formats}.
-
-@item -f @var{datefile}
-@itemx --file=@var{datefile}
-@opindex -f
-@opindex --file
-Parse each line in @var{datefile} as with @samp{-d} and display the
-resulting time and date.  If @var{datefile} is @samp{-}, use standard
-input.  This is useful when you have many dates to process, because the
-system overhead of starting up the @code{date} executable many times can
-be considerable.
-
-@item -I[@var{timespec}]
-@itemx --iso-8601[=@var{timespec}]
-@opindex -I[@var{timespec}]
-@opindex --iso-8601[=@var{timespec}]
-Display the date using the ISO 8601 format, @samp{%Y-%m-%d}.
-
-The optional argument @var{timespec} specifies the number of additional
-terms of the time to include.  It can be one of the following:
-@table @samp
-@item auto
-The default behavior: print just the date.
-
-@item hours
-Append the hour of the day to the date.
-
-@item minutes
-Append the hours and minutes.
-
-@item seconds
-Append the hours, minutes, and seconds.
-@end table
-
-If showing any time terms, then include the time zone using the format
-@samp{%z}.
-
-@item -R
-@itemx --rfc-822
-@opindex -R
-@opindex --rfc-822
-Display the time and date using the RFC-822-conforming
-format, @samp{%a, %_d %b %Y %H:%M:%S %z}.
-
-@item -r @var{file}
-@itemx --reference=@var{file}
-@opindex -r
-@opindex --reference
-Display the time and date reference according to the last modification
-time of @var{file}, instead of the current time and date.
-
-@item -s @var{datestr}
-@itemx --set=@var{datestr}
-@opindex -s
-@opindex --set
-Set the time and date to @var{datestr}.  See @samp{-d} above.
-
-@item -u
-@itemx --utc
-@itemx --universal
-@opindex -u
-@opindex --utc
-@opindex --universal
-@cindex Coordinated Universal Time
-@cindex UTC
-@cindex Greenwich Mean Time
-@cindex GMT
-Use Coordinated Universal Time (@sc{utc}) by operating as if the
-@env{TZ} environment variable were set to the string @samp{UTC0}.
-Normally, @command{date} operates in the time zone indicated by
-@env{TZ}, or the system default if @env{TZ} is not set.  Coordinated
-Universal Time is often called ``Greenwich Mean Time'' (@sc{gmt}) for
-historical reasons.
-@end table
-
-
-@node Examples of date
-@subsection Examples of @code{date}
-
-@cindex examples of @code{date}
-
-Here are a few examples.  Also see the documentation for the @samp{-d}
-option in the previous section.
-
-@itemize @bullet
-
-@item
-To print the date of the day before yesterday:
-
-@example
-date --date='2 days ago'
-@end example
-
-@item
-To print the date of the day three months and one day hence:
-@example
-date --date='3 months 1 day'
-@end example
-
-@item
-To print the day of year of Christmas in the current year:
-@example
-date --date='25 Dec' +%j
-@end example
-
-@item
-To print the current full month name and the day of the month:
-@example
-date '+%B %d'
-@end example
-
-But this may not be what you want because for the first nine days of
-the month, the @samp{%d} expands to a zero-padded two-digit field,
-for example @samp{date -d 1may '+%B %d'} will print @samp{May 01}.
-
-@item
-To print a date without the leading zero for one-digit days
-of the month, you can use the (GNU extension) @code{-} modifier to suppress
-the padding altogether.
-@example
-date -d 1may '+%B %-d
-@end example
-
-@item
-To print the current date and time in the format required by many
-non-GNU versions of @code{date} when setting the system clock:
-@example
-date +%m%d%H%M%Y.%S
-@end example
-
-@item
-To set the system clock forward by two minutes:
-@example
-date --set='+2 minutes'
-@end example
-
-@item
-To print the date in the format specified by RFC-822,
-use @samp{date --rfc}.  I just did and saw this:
-
-@example
-Mon, 25 Mar 1996 23:34:17 -0600
-@end example
-
-@item
-To convert a date string to the number of seconds since the epoch
-(which is 1970-01-01 00:00:00 UTC), use the @samp{--date} option with
-the @samp{%s} format.  That can be useful in sorting and/or graphing
-and/or comparing data by date.  The following command outputs the
-number of the seconds since the epoch for the time two minutes after the
-epoch:
-
-@example
-date --date='1970-01-01 00:02:00 +0000' +%s
-120
-@end example
-
-If you do not specify time zone information in the date string,
-@command{date} uses your computer's idea of the time zone when
-interpreting the string.  For example, if your computer's time zone is
-that of Cambridge, Massachusetts, which was then 5 hours (i.e., 18,000
-seconds) behind UTC:
-
-@example
-# local time zone used
-date --date='1970-01-01 00:02:00' +%s
-18120
-@end example
-
-@item
-If you're sorting or graphing dated data, your raw date values may be
-represented as seconds since the epoch.  But few people can look at
-the date @samp{946684800} and casually note ``Oh, that's the first second
-of the year 2000 in Greenwich, England.''
-
-@example
-date --date='2000-01-01 UTC' +%s
-946684800
-@end example
-
-To convert such an unwieldy number of seconds back to
-a more readable form, use a command like this:
-
-@smallexample
-# local time zone used
-date -d '1970-01-01 UTC 946684800 seconds' +"%Y-%m-%d %T %z"
-1999-12-31 19:00:00 -0500
-@end smallexample
-
-@end itemize
-
-
-@node uname invocation
-@section @code{uname}: Print system information
-
-@pindex uname
-@cindex print system information
-@cindex system information, printing
-
-@code{uname} prints information about the machine and operating system
-it is run on.  If no options are given, @code{uname} acts as if the
-@code{-s} option were given. Synopsis:
-
-@example
-uname [@var{option}]@dots{}
-@end example
-
-If multiple options or @code{-a} are given, the selected information is
-printed in this order:
-
-@example
-@var{sysname} @var{nodename} @var{release} @var{osversion} @var{machine}
-@end example
-
-The @var{osversion}, at least, may well be multiple words.  For example:
-
-@example
-uname -a
-@result{} Linux hayley 1.0.4 #3 Thu May 12 18:06:34 1994 i486
-@end example
-
-
-The program accepts the following options.  Also see @ref{Common options}.
-
-@table @samp
-
-@item -a
-@itemx --all
-@opindex -a
-@opindex --all
-Print all of the below information.
-
-@item -m
-@itemx --machine
-@opindex -m
-@opindex --machine
-@cindex machine type
-@cindex hardware type
-Print the machine (hardware) type.
-
-@item -n
-@itemx --nodename
-@opindex -n
-@opindex --nodename
-@cindex hostname
-@cindex node name
-@cindex network node name
-Print the machine's network node hostname.
-
-@item -p
-@itemx --processor
-@opindex -p
-@opindex --processor
-@cindex host processor type
-Print the machine's processor type
-
-@item -r
-@itemx --release
-@opindex -r
-@opindex --release
-@cindex operating system release
-@cindex release of operating system
-Print the operating system release.
-
-@item -s
-@itemx --sysname
-@opindex -s
-@opindex --sysname
-@cindex operating system name
-@cindex name of operating system
-Print the operating system name.
-
-@item -v
-@opindex -v
-@cindex operating system version
-@cindex version of operating system
-Print the operating system version.
-
-@end table
-
-@node hostname invocation
-@section @code{hostname}: Print or set system name
-
-@pindex hostname
-@cindex setting the hostname
-@cindex printing the hostname
-@cindex system name, printing
-@cindex appropriate privileges
-
-With no arguments, @code{hostname} prints the name of the current host
-system.  With one argument, it sets the current host name to the
-specified string.  You must have appropriate privileges to set the host
-name. Synopsis:
-
-@example
-hostname [@var{name}]
-@end example
-
-The only options are @samp{--help} and @samp{--version}.  @xref{Common
-options}.
-
-
-@node hostid invocation
-@section @code{hostid}: Print numeric host identifier.
-
-@pindex hostid
-@cindex printing the host identifier
-
-@code{hostid} prints the numeric identifier of the current host
-in hexadecimal.  This command accepts no arguments.
-The only options are @samp{--help} and @samp{--version}.
-@xref{Common options}.
-
-For example, here's what it prints on one system I use:
-
-@example
-$ hostid
-1bac013d
-@end example
-
-On that system, the 32-bit quantity happens to be closely
-related to the system's Internet address, but that isn't always
-the case.
-
-
-@node Modified command invocation
-@chapter Modified command invocation
-
-@cindex modified command invocation
-@cindex invocation of commands, modified
-@cindex commands for invoking other commands
-
-This section describes commands that run other commands in some context
-different than the current one: a modified environment, as a different
-user, etc.
-
-@menu
-* chroot invocation::           Modify the root directory.
-* env invocation::              Modify environment variables.
-* nice invocation::             Modify scheduling priority.
-* nohup invocation::            Immunize to hangups.
-* su invocation::               Modify user and group id.
-@end menu
-
-
-@node chroot invocation
-@section @code{chroot}: Run a command with a different root directory
-
-@pindex chroot
-@cindex running a program in a specified root directory
-@cindex root directory, running a program in a specified
-
-@code{chroot} runs a command with a specified root directory.
-On many systems, only the super-user can do this.
-Synopses:
-
-@example
-chroot @var{newroot} [@var{command} [@var{args}]@dots{}]
-chroot @var{option}
-@end example
-
-Ordinarily, filenames are looked up starting at the root of the
-directory structure, i.e., @file{/}.  @code{chroot} changes the root to
-the directory @var{newroot} (which must exist) and then runs
-@var{command} with optional @var{args}.  If @var{command} is not
-specified, the default is the value of the @env{SHELL} environment
-variable or @code{/bin/sh} if not set, invoked with the @samp{-i} option.
-
-The only options are @samp{--help} and @samp{--version}.  @xref{Common
-options}.
-
-Here are a few tips to help avoid common problems in using chroot.
-To start with a simple example, make @var{command} refer to a statically
-linked binary.  If you were to use a dynamically linked executable, then
-you'd have to arrange to have the shared libraries in the right place under
-your new root directory.
-
-For example, if you create a statically linked `ls' executable,
-and put it in /tmp/empty, you can run this command as root:
-
-@example
-$ chroot /tmp/empty /ls -Rl /
-@end example
-
-Then you'll see output like this:
-
-@example
-/:
-total 1023
--rwxr-xr-x    1 0        0         1041745 Aug 16 11:17 ls
-@end example
-
-If you want to use a dynamically linked executable, say @code{bash},
-then first run @samp{ldd bash} to see what shared objects it needs.
-Then, in addition to copying the actual binary, also copy the listed
-files to the required positions under your intended new root directory.
-Finally, if the executable requires any other files (e.g., data, state,
-device files), copy them into place, too.
-
-
-@node env invocation
-@section @code{env}: Run a command in a modified environment
-
-@pindex env
-@cindex environment, running a program in a modified
-@cindex modified environment, running a program in a
-@cindex running a program in a modified environment
-
-@code{env} runs a command with a modified environment.  Synopses:
-
-@example
-env [@var{option}]@dots{} [@var{name}=@var{value}]@dots{} @c
-[@var{command} [@var{args}]@dots{}]
-env
-@end example
-
-Arguments of the form @samp{@var{variable}=@var{value}} set
-the environment variable @var{variable} to value @var{value}.
-@var{value} may be empty (@samp{@var{variable}=}).  Setting a variable
-to an empty value is different from unsetting it.
-
-@vindex PATH
-The first remaining argument specifies the program name to invoke; it is
-searched for according to the @env{PATH} environment variable.  Any
-remaining arguments are passed as arguments to that program.
-
-@cindex environment, printing
-
-If no command name is specified following the environment
-specifications, the resulting environment is printed.  This is like
-specifying a command name of @code{printenv}.
-
-The program accepts the following options.  Also see @ref{Common options}.
-
-@table @samp
-
-@item -u @var{name}
-@itemx --unset=@var{name}
-@opindex -u
-@opindex -unset
-Remove variable @var{name} from the environment, if it was in the
-environment.
-
-@item -
-@itemx -i
-@itemx --ignore-environment
-@opindex -
-@opindex -i
-@opindex --ignore-environment
-Start with an empty environment, ignoring the inherited environment.
-
-@end table
-
-
-@node nice invocation
-@section @code{nice}: Run a command with modified scheduling priority
-
-@pindex nice
-@cindex modifying scheduling priority
-@cindex scheduling priority, modifying
-@cindex priority, modifying
-@cindex appropriate privileges
-
-@code{nice} prints or modifies the scheduling priority of a job.
-Synopsis:
-
-@example
-nice [@var{option}]@dots{} [@var{command} [@var{arg}]@dots{}]
-@end example
-
-If no arguments are given, @code{nice} prints the current scheduling
-priority, which it inherited.  Otherwise, @code{nice} runs the given
-@var{command} with its scheduling priority adjusted.  If no
-@var{adjustment} is given, the priority of the command is incremented by
-10.  You must have appropriate privileges to specify a negative
-adjustment.  The priority can be adjusted by @code{nice} over the range
-of -20 (the highest priority) to 19 (the lowest).
-
-@cindex conflicts with shell built-ins
-@cindex built-in shell commands, conflicts with
-Because most shells have a built-in command by the same name, using the
-unadorned command name in a script or interactively may get you
-different functionality than that described here.
-
-The program accepts the following option.  Also see @ref{Common options}.
-
-@table @samp
-@item -n @var{adjustment}
-@itemx -@var{adjustment}
-@itemx --adjustment=@var{adjustment}
-@opindex -n
-@opindex --adjustment
-@opindex -@var{adjustment}
-Add @var{adjustment} instead of 10 to the command's priority.
-@end table
-
-
-@node nohup invocation
-@section @code{nohup}: Run a command immune to hangups
-
-@pindex nohup
-@cindex hangups, immunity to
-@cindex immunity to hangups
-@cindex logging out and continuing to run
-
-@flindex nohup.out
-@code{nohup} runs the given @var{command} with hangup signals ignored,
-so that the command can continue running in the background after you log
-out. Synopsis:
-
-@example
-nohup @var{command} [@var{arg}]@dots{}
-@end example
-
-@flindex nohup.out
-@code{nohup} increases the scheduling priority of @var{command} by 5, so
-it has a slightly smaller chance to run.  If standard output is a terminal,
-it and standard error are redirected so that they are appended to the
-file @file{nohup.out}; if that cannot be written to, they are appended
-to the file @file{$HOME/nohup.out}.  If that cannot be written to, the
-command is not run.
-
-If @code{nohup} creates either @file{nohup.out} or
-@file{$HOME/nohup.out}, it creates it with no ``group'' or ``other''
-access permissions.  It does not change the permissions if the output
-file already existed.
-
-@code{nohup} does not automatically put the command it runs in the
-background; you must do that explicitly, by ending the command line
-with an @samp{&}.
-
-The only options are @samp{--help} and @samp{--version}.  @xref{Common
-options}.
-
-
-@node su invocation
-@section @code{su}: Run a command with substitute user and group id
-
-@pindex su
-@cindex substitute user and group ids
-@cindex user id, switching
-@cindex super-user, becoming
-@cindex root, becoming
-
-@code{su} allows one user to temporarily become another user.  It runs a
-command (often an interactive shell) with the real and effective user
-id, group id, and supplemental groups of a given @var{user}. Synopsis:
-
-@example
-su [@var{option}]@dots{} [@var{user} [@var{arg}]@dots{}]
-@end example
-
-@cindex passwd entry, and @code{su} shell
-@flindex /bin/sh
-@flindex /etc/passwd
-If no @var{user} is given, the default is @code{root}, the super-user.
-The shell to use is taken from @var{user}'s @code{passwd} entry, or
-@file{/bin/sh} if none is specified there.  If @var{user} has a
-password, @code{su} prompts for the password unless run by a user with
-effective user id of zero (the super-user).
-
-@vindex HOME
-@vindex SHELL
-@vindex USER
-@vindex LOGNAME
-@cindex login shell
-By default, @code{su} does not change the current directory.
-It sets the environment variables @env{HOME} and @env{SHELL}
-from the password entry for @var{user}, and if @var{user} is not
-the super-user, sets @env{USER} and @env{LOGNAME} to @var{user}.
-By default, the shell is not a login shell.
-
-Any additional @var{arg}s are passed as additional arguments to the
-shell.
-
-@cindex @samp{-su}
-GNU @code{su} does not treat @file{/bin/sh} or any other shells specially
-(e.g., by setting @code{argv[0]} to @samp{-su}, passing @code{-c} only
-to certain shells, etc.).
-
-@findex syslog
-@code{su} can optionally be compiled to use @code{syslog} to report
-failed, and optionally successful, @code{su} attempts.  (If the system
-supports @code{syslog}.)  However, GNU @code{su} does not check if the
-user is a member of the @code{wheel} group; see below.
-
-The program accepts the following options.  Also see @ref{Common options}.
-
-@table @samp
-@item -c @var{command}
-@itemx --command=@var{command}
-@opindex -c
-@opindex --command
-Pass @var{command}, a single command line to run, to the shell with
-a @code{-c} option instead of starting an interactive shell.
-
-@item -f
-@itemx --fast
-@opindex -f
-@opindex --fast
-@flindex .cshrc
-@cindex file name pattern expansion, disabled
-@cindex globbing, disabled
-Pass the @code{-f} option to the shell.  This probably only makes sense
-if the shell run is @code{csh} or @code{tcsh}, for which the @code{-f}
-option prevents reading the startup file (@file{.cshrc}).  With
-Bourne-like shells, the @code{-f} option disables file name pattern
-expansion (globbing), which is not likely to be useful.
-
-@item -
-@itemx -l
-@itemx --login
-@opindex -
-@opindex -l
-@opindex --login
-@c other variables already indexed above
-@vindex TERM
-@vindex PATH
-@cindex login shell, creating
-Make the shell a login shell.  This means the following.  Unset all
-environment variables except @env{TERM}, @env{HOME}, and @env{SHELL}
-(which are set as described above), and @env{USER} and @env{LOGNAME}
-(which are set, even for the super-user, as described above), and set
-@env{PATH} to a compiled-in default value.  Change to @var{user}'s home
-directory.  Prepend @samp{-} to the shell's name, intended to make it
-read its login startup file(s).
-
-@item -m
-@itemx -p
-@itemx --preserve-environment
-@opindex -m
-@opindex -p
-@opindex --preserve-environment
-@cindex environment, preserving
-@flindex /etc/shells
-@cindex restricted shell
-Do not change the environment variables @env{HOME}, @env{USER},
-@env{LOGNAME}, or @env{SHELL}.  Run the shell given in the environment
-variable @env{SHELL} instead of the shell from @var{user}'s passwd
-entry, unless the user running @code{su} is not the superuser and
-@var{user}'s shell is restricted.  A @dfn{restricted shell} is one that
-is not listed in the file @file{/etc/shells}, or in a compiled-in list
-if that file does not exist.  Parts of what this option does can be
-overridden by @code{--login} and @code{--shell}.
-
-@item -s @var{shell}
-@itemx --shell=@var{shell}
-@opindex -s
-@opindex --shell
-Run @var{shell} instead of the shell from @var{user}'s passwd entry,
-unless the user running @code{su} is not the superuser and @var{user}'s
-shell is restricted (see @samp{-m} just above).
-
-@end table
-
-@cindex wheel group, not supported
-@cindex group wheel, not supported
-@cindex fascism
-@heading Why GNU @code{su} does not support the @samp{wheel} group
-
-(This section is by Richard Stallman.)
-
-@cindex Twenex
-@cindex MIT AI lab
-Sometimes a few of the users try to hold total power over all the
-rest.  For example, in 1984, a few users at the MIT AI lab decided to
-seize power by changing the operator password on the Twenex system and
-keeping it secret from everyone else.  (I was able to thwart this coup
-and give power back to the users by patching the kernel, but I
-wouldn't know how to do that in Unix.)
-
-However, occasionally the rulers do tell someone.  Under the usual
-@code{su} mechanism, once someone learns the root password who
-sympathizes with the ordinary users, he or she can tell the rest.  The
-``wheel group'' feature would make this impossible, and thus cement the
-power of the rulers.
-
-I'm on the side of the masses, not that of the rulers.  If you are
-used to supporting the bosses and sysadmins in whatever they do, you
-might find this idea strange at first.
-
-
-@node Delaying
-@chapter Delaying
-
-@cindex delaying commands
-@cindex commands for delaying
-
-@c Perhaps @code{wait} or other commands should be described here also?
-
-@menu
-* sleep invocation::            Delay for a specified time.
-@end menu
-
-
-@node sleep invocation
-@section @code{sleep}: Delay for a specified time
-
-@pindex sleep
-@cindex delay for a specified time
-
-@code{sleep} pauses for an amount of time specified by the sum of
-the values of the command line arguments.
-Synopsis:
-
-@example
-sleep @var{number}[smhd]@dots{}
-@end example
-
-@cindex time units
-Each argument is a number followed by an optional unit; the default
-is seconds.  The units are:
-
-@table @samp
-@item s
-seconds
-@item m
-minutes
-@item h
-hours
-@item d
-days
-@end table
-
-Historical implementations of @code{sleep} have required that
-@var{number} be an integer.  However, GNU @code{sleep} accepts
-arbitrary floating point numbers.
-
-The only options are @samp{--help} and @samp{--version}.  @xref{Common
-options}.
-
-
-@node Numeric operations
-@chapter Numeric operations
-
-@cindex numeric operations
-These programs do numerically-related operations.
-
-@menu
-* factor invocation::              Show factors of numbers.
-* seq invocation::                 Print sequences of numbers.
-@end menu
-
-
-@node factor invocation
-@section @code{factor}: Print prime factors
-
-@pindex factor
-@cindex prime factors
-
-@code{factor} prints prime factors.  Synopses:
-
-@example
-factor [@var{number}]@dots{}
-factor @var{option}
-@end example
-
-If no @var{number} is specified on the command line, @code{factor} reads
-numbers from standard input, delimited by newlines, tabs, or spaces.
-
-The only options are @samp{--help} and @samp{--version}.  @xref{Common
-options}.
-
-The algorithm it uses is not very sophisticated, so for some inputs
-@code{factor} runs for a long time.  The hardest numbers to factor are
-the products of large primes.  Factoring the product of the two largest 32-bit
-prime numbers takes over 10 minutes of CPU time on a 400MHz Pentium II.
-
-@example
-$ p=`echo '4294967279 * 4294967291'|bc`
-$ factor $p
-18446743979220271189: 4294967279 4294967291
-@end example
-
-In contrast, @code{factor} factors the largest 64-bit number in just
-over a tenth of a second:
-
-@example
-$ factor `echo '2^64-1'|bc`
-18446744073709551615: 3 5 17 257 641 65537 6700417
-@end example
-
-@node seq invocation
-@section @code{seq}: Print numeric sequences
-
-@pindex seq
-@cindex numeric sequences
-@cindex sequence of numbers
-
-@code{seq} prints a sequence of numbers to standard output.  Synopses:
-
-@example
-seq [@var{option}]@dots{} [@var{first} [@var{increment}]] @var{last}@dots{}
-@end example
-
-@code{seq} prints the numbers from @var{first} to @var{last} by
-@var{increment}.  By default, @var{first} and @var{increment} are both 1,
-and each number is printed on its own line.  All numbers can be reals,
-not just integers.
-
-The program accepts the following options.  Also see @ref{Common options}.
-
-@table @samp
-@item -f @var{format}
-@itemx --format=@var{format}
-@opindex -f @var{format}
-@opindex --format=@var{format}
-@cindex formatting of numbers in @code{seq}
-Print all numbers using @var{format}; default @samp{%g}.
-@var{format} must contain exactly one of the floating point
-output formats @samp{%e}, @samp{%f}, or @samp{%g}.
-
-@item -s @var{string}
-@itemx --separator=@var{string}
-@cindex separator for numbers in @code{seq}
-Separate numbers with @var{string}; default is a newline.
-The output always terminates with a newline.
-
-@item -w
-@itemx --equal-width
-Print all numbers with the same width, by padding with leading zeroes.
-(To have other kinds of padding, use @samp{--format}).
-
-@end table
-
-If you want to use @code{seq} to print sequences of large integer values,
-don't use the default @samp{%g} format since it can result in
-loss of precision:
-
-@example
-$ seq 1000000 1000001
-1e+06
-1e+06
-@end example
-
-Instead, you can use the format, @samp{%1.f},
-to print large decimal numbers with no exponent and no decimal point.
-
-@example
-$ seq --format=%1.f 1000000 1000001
-1000000
-1000001
-@end example
-
-If you want hexadecimal output, you can use @code{printf}
-to perform the conversion:
-
-@example
-$ printf %x'\n' `seq -f %1.f 1048575 1024 1050623`
-fffff
-1003ff
-1007ff
-@end example
-
-For very long lists of numbers, use xargs to avoid
-system limitations on the length of an argument list:
-
-@example
-$ seq -f %1.f 1000000 | xargs printf %x'\n' |tail -3
-f423e
-f423f
-f4240
-@end example
-
-To generate octal output, use the printf @code{%o} format instead
-of @code{%x}.  Note however that using printf works only for numbers
-smaller than @code{2^32}:
-
-@example
-$ printf "%x\n" `seq -f %1.f 4294967295 4294967296`
-ffffffff
-bash: printf: 4294967296: Numerical result out of range
-@end example
-
-On most systems, seq can produce whole-number output for values up to
-@code{2^53}, so here's a more general approach to base conversion that
-also happens to be more robust for such large numbers.  It works by
-using @code{bc} and setting its output radix variable, @var{obase},
-to @samp{16} in this case to produce hexadecimal output.
-
-@example
-$ (echo obase=16; seq -f %1.f 4294967295 4294967296)|bc
-FFFFFFFF
-100000000
-@end example
-
-Be careful when using @code{seq} with a fractional @var{increment},
-otherwise you may see surprising results.  Most people would expect to
-see @code{0.3} printed as the last number in this example:
-
-@example
-$ seq -s' ' 0 .1 .3
-0 0.1 0.2
-@end example
-
-But that doesn't happen on most systems because @code{seq} is
-implemented using binary floating point arithmetic (via the C
-@code{double} type) -- which means some decimal numbers like @code{.1}
-cannot be represented exactly.  That in turn means some nonintuitive
-conditions like @code{.1 * 3 > .3} will end up being true.
-
-To work around that in the above example, use a slightly larger number as
-the @var{last} value:
-
-@example
-$ seq -s' ' 0 .1 .31
-0 0.1 0.2 0.3
-@end example
-
-In general, when using an @var{increment} with a fractional part, where
-(@var{last} - @var{first}) / @var{increment} is (mathematically) a whole
-number, specify a slightly larger (or smaller, if @var{increment} is negative)
-value for @var{last} to ensure that @var{last} is the final value printed
-by seq.
-
-@node File permissions
-@chapter File permissions
-@include perm.texi
-
-@include getdate.texi
-
-@c              What's GNU?
-@c              Arnold Robbins
-@node Opening the software toolbox
-@chapter Opening the Software Toolbox
-
-This chapter originally appeared in @cite{Linux Journal}, volume 1,
-number 2, in the @cite{What's GNU?} column. It was written by Arnold
-Robbins.
-
-@menu
-* Toolbox introduction::        Toolbox introduction
-* I/O redirection::             I/O redirection
-* The who command::             The @command{who} command
-* The cut command::             The @command{cut} command
-* The sort command::            The @command{sort} command
-* The uniq command::            The @command{uniq} command
-* Putting the tools together::  Putting the tools together
-@end menu
-
-
-@node Toolbox introduction
-@unnumberedsec Toolbox Introduction
-
-This month's column is only peripherally related to the GNU Project, in
-that it describes a number of the GNU tools on your GNU/Linux system and how they
-might be used.  What it's really about is the ``Software Tools'' philosophy
-of program development and usage.
-
-The software tools philosophy was an important and integral concept
-in the initial design and development of Unix (of which Linux and GNU are
-essentially clones).  Unfortunately, in the modern day press of
-Internetworking and flashy GUIs, it seems to have fallen by the
-wayside.  This is a shame, since it provides a powerful mental model
-for solving many kinds of problems.
-
-Many people carry a Swiss Army knife around in their pants pockets (or
-purse).  A Swiss Army knife is a handy tool to have: it has several knife
-blades, a screwdriver, tweezers, toothpick, nail file, corkscrew, and perhaps
-a number of other things on it.  For the everyday, small miscellaneous jobs
-where you need a simple, general purpose tool, it's just the thing.
-
-On the other hand, an experienced carpenter doesn't build a house using
-a Swiss Army knife.  Instead, he has a toolbox chock full of specialized
-tools---a saw, a hammer, a screwdriver, a plane, and so on.  And he knows
-exactly when and where to use each tool; you won't catch him hammering nails
-with the handle of his screwdriver.
-
-The Unix developers at Bell Labs were all professional programmers and trained
-computer scientists.  They had found that while a one-size-fits-all program
-might appeal to a user because there's only one program to use, in practice
-such programs are
-
-@enumerate a
-@item
-difficult to write,
-
-@item
-difficult to maintain and
-debug, and
-
-@item
-difficult to extend to meet new situations.
-@end enumerate
-
-Instead, they felt that programs should be specialized tools.  In short, each
-program ``should do one thing well.''  No more and no less.  Such programs are
-simpler to design, write, and get right---they only do one thing.
-
-Furthermore, they found that with the right machinery for hooking programs
-together, that the whole was greater than the sum of the parts.  By combining
-several special purpose programs, you could accomplish a specific task
-that none of the programs was designed for, and accomplish it much more
-quickly and easily than if you had to write a special purpose program.
-We will see some (classic) examples of this further on in the column.
-(An important additional point was that, if necessary, take a detour
-and build any software tools you may need first, if you don't already
-have something appropriate in the toolbox.)
-
-@node I/O redirection
-@unnumberedsec I/O Redirection
-
-Hopefully, you are familiar with the basics of I/O redirection in the
-shell, in particular the concepts of ``standard input,'' ``standard output,''
-and ``standard error''.  Briefly, ``standard input'' is a data source, where
-data comes from.  A program should not need to either know or care if the
-data source is a disk file, a keyboard, a magnetic tape, or even a punched
-card reader.  Similarly, ``standard output'' is a data sink, where data goes
-to.  The program should neither know nor care where this might be.
-Programs that only read their standard input, do something to the data,
-and then send it on, are called @dfn{filters}, by analogy to filters in a
-water pipeline.
-
-With the Unix shell, it's very easy to set up data pipelines:
-
-@smallexample
-program_to_create_data | filter1 | .... | filterN > final.pretty.data
-@end smallexample
-
-We start out by creating the raw data; each filter applies some successive
-transformation to the data, until by the time it comes out of the pipeline,
-it is in the desired form.
-
-This is fine and good for standard input and standard output.  Where does the
-standard error come in to play?  Well, think about @command{filter1} in
-the pipeline above.  What happens if it encounters an error in the data it
-sees?  If it writes an error message to standard output, it will just
-disappear down the pipeline into @command{filter2}'s input, and the
-user will probably never see it.  So programs need a place where they can send
-error messages so that the user will notice them.  This is standard error,
-and it is usually connected to your console or window, even if you have
-redirected standard output of your program away from your screen.
-
-For filter programs to work together, the format of the data has to be
-agreed upon.  The most straightforward and easiest format to use is simply
-lines of text.  Unix data files are generally just streams of bytes, with
-lines delimited by the @sc{ascii} @sc{lf} (Line Feed) character,
-conventionally called a ``newline'' in the Unix literature. (This is
-@code{'\n'} if you're a C programmer.)  This is the format used by all
-the traditional filtering programs.  (Many earlier operating systems
-had elaborate facilities and special purpose programs for managing
-binary data.  Unix has always shied away from such things, under the
-philosophy that it's easiest to simply be able to view and edit your
-data with a text editor.)
-
-OK, enough introduction. Let's take a look at some of the tools, and then
-we'll see how to hook them together in interesting ways.   In the following
-discussion, we will only present those command line options that interest
-us.  As you should always do, double check your system documentation
-for the full story.
-
-@node The who command
-@unnumberedsec The @command{who} Command
-
-The first program is the @command{who} command.  By itself, it generates a
-list of the users who are currently logged in.  Although I'm writing
-this on a single-user system, we'll pretend that several people are
-logged in:
-
-@example
-$ who
-@print{} arnold   console Jan 22 19:57
-@print{} miriam   ttyp0   Jan 23 14:19(:0.0)
-@print{} bill     ttyp1   Jan 21 09:32(:0.0)
-@print{} arnold   ttyp2   Jan 23 20:48(:0.0)
-@end example
-
-Here, the @samp{$} is the usual shell prompt, at which I typed @samp{who}.
-There are three people logged in, and I am logged in twice.  On traditional
-Unix systems, user names are never more than eight characters long.  This
-little bit of trivia will be useful later.  The output of @command{who} is nice,
-but the data is not all that exciting.
-
-@node The cut command
-@unnumberedsec The @command{cut} Command
-
-The next program we'll look at is the @command{cut} command.  This program
-cuts out columns or fields of input data.  For example, we can tell it
-to print just the login name and full name from the @file{/etc/passwd}
-file.  The @file{/etc/passwd} file has seven fields, separated by
-colons:
-
-@example
-arnold:xyzzy:2076:10:Arnold D. Robbins:/home/arnold:/bin/bash
-@end example
-
-To get the first and fifth fields, we would use @command{cut} like this:
-
-@example
-$ cut -d: -f1,5 /etc/passwd
-@print{} root:Operator
-@dots{}
-@print{} arnold:Arnold D. Robbins
-@print{} miriam:Miriam A. Robbins
-@dots{}
-@end example
-
-With the @option{-c} option, @command{cut} will cut out specific characters
-(i.e., columns) in the input lines.  This command looks like it might be
-useful for data filtering.
-
-
-@node The sort command
-@unnumberedsec The @command{sort} Command
-
-Next we'll look at the @command{sort} command.  This is one of the most
-powerful commands on a Unix-style system; one that you will often find
-yourself using when setting up fancy data plumbing.
-
-The @command{sort}
-command reads and sorts each file named on the command line.  It then
-merges the sorted data and writes it to standard output.  It will read
-standard input if no files are given on the command line (thus
-making it into a filter).  The sort is based on the character collating
-sequence or based on user-supplied ordering criteria.
-
-
-@node The uniq command
-@unnumberedsec The @command{uniq} Command
-
-Finally (at least for now), we'll look at the @command{uniq} program.  When
-sorting data, you will often end up with duplicate lines, lines that
-are identical.  Usually, all you need is one instance of each line.
-This is where @command{uniq} comes in. The @command{uniq} program reads its
-standard input, which it expects to be sorted.  It only prints out one
-copy of each duplicated line.  It does have several options.  Later on,
-we'll use the @option{-c} option, which prints each unique line, preceded
-by a count of the number of times that line occurred in the input.
-
-
-@node Putting the tools together
-@unnumberedsec Putting the Tools Together
-
-Now, let's suppose this is a large ISP server system with dozens of users
-logged in.  The management wants the system administrator to write a program that will
-generate a sorted list of logged in users.  Furthermore, even if a user
-is logged in multiple times, his or her name should only show up in the
-output once.
-
-The administrator could sit down with the system documentation and write a C
-program that did this. It would take perhaps a couple of hundred lines
-of code and about two hours to write it, test it, and debug it.
-However, knowing the software toolbox, the administrator can instead start out
-by generating just a list of logged on users:
-
-@example
-$ who | cut -c1-8
-@print{} arnold
-@print{} miriam
-@print{} bill
-@print{} arnold
-@end example
-
-Next, sort the list:
-
-@example
-$ who | cut -c1-8 | sort
-@print{} arnold
-@print{} arnold
-@print{} bill
-@print{} miriam
-@end example
-
-Finally, run the sorted list through @command{uniq}, to weed out duplicates:
-
-@example
-$ who | cut -c1-8 | sort | uniq
-@print{} arnold
-@print{} bill
-@print{} miriam
-@end example
-
-The @command{sort} command actually has a @option{-u} option that does what
-@command{uniq} does. However, @command{uniq} has other uses for which one
-cannot substitute @samp{sort -u}.
-
-The administrator puts this pipeline into a shell script, and makes it available for
-all the users on the system (@samp{#} is the system administrator,
-or @code{root}, prompt):
-
-@example
-# cat > /usr/local/bin/listusers
-who | cut -c1-8 | sort | uniq
-^D
-# chmod +x /usr/local/bin/listusers
-@end example
-
-There are four major points to note here.  First, with just four
-programs, on one command line, the administrator was able to save about two
-hours worth of work.  Furthermore, the shell pipeline is just about as
-efficient as the C program would be, and it is much more efficient in
-terms of programmer time.  People time is much more expensive than
-computer time, and in our modern ``there's never enough time to do
-everything'' society, saving two hours of programmer time is no mean
-feat.
-
-Second, it is also important to emphasize that with the
-@emph{combination} of the tools, it is possible to do a special
-purpose job never imagined by the authors of the individual programs.
-
-Third, it is also valuable to build up your pipeline in stages, as we did here.
-This allows you to view the data at each stage in the pipeline, which helps
-you acquire the confidence that you are indeed using these tools correctly.
-
-Finally, by bundling the pipeline in a shell script, other users can use
-your command, without having to remember the fancy plumbing you set up for
-them. In terms of how you run them, shell scripts and compiled programs are
-indistinguishable.
-
-After the previous warm-up exercise, we'll look at two additional, more
-complicated pipelines.  For them, we need to introduce two more tools.
-
-The first is the @command{tr} command, which stands for ``transliterate.''
-The @command{tr} command works on a character-by-character basis, changing
-characters. Normally it is used for things like mapping upper case to
-lower case:
-
-@example
-$ echo ThIs ExAmPlE HaS MIXED case! | tr '[A-Z]' '[a-z]'
-@print{} this example has mixed case!
-@end example
-
-There are several options of interest:
-
-@table @code
-@item -c
-work on the complement of the listed characters, i.e.,
-operations apply to characters not in the given set
-
-@item -d
-delete characters in the first set from the output
-
-@item -s
-squeeze repeated characters in the output into just one character.
-@end table
-
-We will be using all three options in a moment.
-
-The other command we'll look at is @command{comm}.  The @command{comm}
-command takes two sorted input files as input data, and prints out the
-files' lines in three columns.  The output columns are the data lines
-unique to the first file, the data lines unique to the second file, and
-the data lines that are common to both.  The @option{-1}, @option{-2}, and
-@option{-3} command line options @emph{omit} the respective columns. (This is
-non-intuitive and takes a little getting used to.)  For example:
-
-@example
-$ cat f1
-@print{} 11111
-@print{} 22222
-@print{} 33333
-@print{} 44444
-$ cat f2
-@print{} 00000
-@print{} 22222
-@print{} 33333
-@print{} 55555
-$ comm f1 f2
-@print{}         00000
-@print{} 11111
-@print{}                 22222
-@print{}                 33333
-@print{} 44444
-@print{}         55555
-@end example
-
-The single dash as a filename tells @command{comm} to read standard input
-instead of a regular file.
-
-Now we're ready to build a fancy pipeline.  The first application is a word
-frequency counter.  This helps an author determine if he or she is over-using
-certain words.
-
-The first step is to change the case of all the letters in our input file
-to one case.  ``The'' and ``the'' are the same word when doing counting.
-
-@example
-$ tr '[A-Z]' '[a-z]' < whats.gnu | ...
-@end example
-
-The next step is to get rid of punctuation.  Quoted words and unquoted words
-should be treated identically; it's easiest to just get the punctuation out of
-the way.
-
-@smallexample
-$ tr '[A-Z]' '[a-z]' < whats.gnu | tr -cd '[A-Za-z0-9_ \012]' | ...
-@end smallexample
-
-The second @command{tr} command operates on the complement of the listed
-characters, which are all the letters, the digits, the underscore, and
-the blank.  The @samp{\012} represents the newline character; it has to
-be left alone.  (The @sc{ascii} tab character should also be included for
-good measure in a production script.)
-
-At this point, we have data consisting of words separated by blank space.
-The words only contain alphanumeric characters (and the underscore).  The
-next step is break the data apart so that we have one word per line. This
-makes the counting operation much easier, as we will see shortly.
-
-@smallexample
-$ tr '[A-Z]' '[a-z]' < whats.gnu | tr -cd '[A-Za-z0-9_ \012]' |
-> tr -s '[ ]' '\012' | ...
-@end smallexample
-
-This command turns blanks into newlines.  The @option{-s} option squeezes
-multiple newline characters in the output into just one.  This helps us
-avoid blank lines. (The @samp{>} is the shell's ``secondary prompt.''
-This is what the shell prints when it notices you haven't finished
-typing in all of a command.)
-
-We now have data consisting of one word per line, no punctuation, all one
-case.  We're ready to count each word:
-
-@smallexample
-$ tr '[A-Z]' '[a-z]' < whats.gnu | tr -cd '[A-Za-z0-9_ \012]' |
-> tr -s '[ ]' '\012' | sort | uniq -c | ...
-@end smallexample
-
-At this point, the data might look something like this:
-
-@example
-  60 a
-   2 able
-   6 about
-   1 above
-   2 accomplish
-   1 acquire
-   1 actually
-   2 additional
-@end example
-
-The output is sorted by word, not by count!  What we want is the most
-frequently used words first.  Fortunately, this is easy to accomplish,
-with the help of two more @command{sort} options:
-
-@table @code
-@item -n
-do a numeric sort, not a textual one
-
-@item -r
-reverse the order of the sort
-@end table
-
-The final pipeline looks like this:
-
-@smallexample
-$ tr '[A-Z]' '[a-z]' < whats.gnu | tr -cd '[A-Za-z0-9_ \012]' |
-> tr -s '[ ]' '\012' | sort | uniq -c | sort -nr
-@print{}  156 the
-@print{}   60 a
-@print{}   58 to
-@print{}   51 of
-@print{}   51 and
-@dots{}
-@end smallexample
-
-Whew!  That's a lot to digest.  Yet, the same principles apply. With six
-commands, on two lines (really one long one split for convenience), we've
-created a program that does something interesting and useful, in much
-less time than we could have written a C program to do the same thing.
-
-A minor modification to the above pipeline can give us a simple spelling
-checker!  To determine if you've spelled a word correctly, all you have to
-do is look it up in a dictionary.  If it is not there, then chances are
-that your spelling is incorrect.  So, we need a dictionary.
-The conventional location for a dictionary is @file{/usr/dict/words}.
-On my GNU/Linux system,@footnote{Redhat Linux 6.1, for the November 2000
-revision of this article.}
-this is a is a sorted, 45,402 word dictionary.
-
-Now, how to compare our file with the dictionary?  As before, we generate
-a sorted list of words, one per line:
-
-@smallexample
-$ tr '[A-Z]' '[a-z]' < whats.gnu | tr -cd '[A-Za-z0-9_ \012]' |
-> tr -s '[ ]' '\012' | sort -u | ...
-@end smallexample
-
-Now, all we need is a list of words that are @emph{not} in the
-dictionary.  Here is where the @command{comm} command comes in.
-
-@smallexample
-$ tr '[A-Z]' '[a-z]' < whats.gnu | tr -cd '[A-Za-z0-9_ \012]' |
-> tr -s '[ ]' '\012' | sort -u |
-> comm -23 - /usr/dict/words
-@end smallexample
-
-The @option{-2} and @option{-3} options eliminate lines that are only in the
-dictionary (the second file), and lines that are in both files.  Lines
-only in the first file (standard input, our stream of words), are
-words that are not in the dictionary.  These are likely candidates for
-spelling errors.  This pipeline was the first cut at a production
-spelling checker on Unix.
-
-There are some other tools that deserve brief mention.
-
-@table @command
-@item grep
-search files for text that matches a regular expression
-
-@item egrep
-like @command{grep}, but with more powerful regular expressions
-
-@item wc
-count lines, words, characters
-
-@item tee
-a T-fitting for data pipes, copies data to files and to standard output
-
-@item sed
-the stream editor, an advanced tool
-
-@item awk
-a data manipulation language, another advanced tool
-@end table
-
-The software tools philosophy also espoused the following bit of
-advice: ``Let someone else do the hard part.''  This means, take
-something that gives you most of what you need, and then massage it the
-rest of the way until it's in the form that you want.
-
-To summarize:
-
-@enumerate 1
-@item
-Each program should do one thing well.  No more, no less.
-
-@item
-Combining programs with appropriate plumbing leads to results where
-the whole is greater than the sum of the parts.  It also leads to novel
-uses of programs that the authors might never have imagined.
-
-@item
-Programs should never print extraneous header or trailer data, since these
-could get sent on down a pipeline. (A point we didn't mention earlier.)
-
-@item
-Let someone else do the hard part.
-
-@item
-Know your toolbox!  Use each program appropriately. If you don't have an
-appropriate tool, build one.
-@end enumerate
-
-As of this writing, all the programs we've discussed are available via
-anonymous @command{ftp} from: @*
-@uref{ftp://gnudist.gnu.org/textutils/textutils-1.22.tar.gz}.  (There may
-be more recent versions available now.)
-
-None of what I have presented in this column is new. The Software Tools
-philosophy was first introduced in the book @cite{Software Tools}, by
-Brian Kernighan and P.J. Plauger (Addison-Wesley, ISBN 0-201-03669-X).
-This book showed how to write and use software tools.  It was written in
-1976, using a preprocessor for FORTRAN named @command{ratfor} (RATional
-FORtran).  At the time, C was not as ubiquitous as it is now; FORTRAN
-was.  The last chapter presented a @command{ratfor} to FORTRAN
-processor, written in @command{ratfor}. @command{ratfor} looks an awful
-lot like C; if you know C, you won't have any problem following the
-code.
-
-In 1981, the book was updated and made available as @cite{Software Tools
-in Pascal} (Addison-Wesley, ISBN 0-201-10342-7).  The first book is
-still in print; the second, alas, is not.  Both books are well worth
-reading if you're a programmer.  They certainly made a major change in
-how I view programming.
-
-Initially, the programs in both books were available (on 9-track tape)
-from Addison-Wesley.  Unfortunately, this is no longer the case,
-although the @command{ratfor} versions are available from
-@uref{http://cm.bell-labs.come/who/bwk, Brian Kernighan's home page},
-and you might be able to find copies of the Pascal versions floating
-around the Internet.  For a number of years, there was an active
-Software Tools Users Group, whose members had ported the original
-@command{ratfor} programs to essentially every computer system with a
-FORTRAN compiler.  The popularity of the group waned in the middle 1980s
-as Unix began to spread beyond universities.
-
-With the current proliferation of GNU code and other clones of Unix programs,
-these programs now receive little attention; modern C versions are
-much more efficient and do more than these programs do.  Nevertheless, as
-exposition of good programming style, and evangelism for a still-valuable
-philosophy, these books are unparalleled, and I recommend them highly.
-
-Acknowledgment: I would like to express my gratitude to Brian Kernighan
-of Bell Labs, the original Software Toolsmith, for reviewing this column.
-
-@include doclicense.texi
-
-@node Index
-@unnumbered Index
-
-@printindex cp
-
-@shortcontents
-@contents
-@bye
-
-@c Local variables:
-@c texinfo-column-for-description: 32
-@c End: