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author | Paul Eggert <eggert@cs.ucla.edu> | 2004-09-09 23:02:12 +0000 |
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committer | Paul Eggert <eggert@cs.ucla.edu> | 2004-09-09 23:02:12 +0000 |
commit | 86a87a157d96998ec49c4b9dbd3cf35bd10668a4 (patch) | |
tree | ab6171d672ba564d2a9bf6be45153ebafadf9b55 /doc/coreutils.texi | |
parent | b0b7a0164efd6897413973ab8a3c46e471a42d60 (diff) | |
download | coreutils-86a87a157d96998ec49c4b9dbd3cf35bd10668a4.tar.xz |
(sort invocation): -u disables the last-resort
comparison, too. Revamp its description.
Diffstat (limited to 'doc/coreutils.texi')
-rw-r--r-- | doc/coreutils.texi | 46 |
1 files changed, 20 insertions, 26 deletions
diff --git a/doc/coreutils.texi b/doc/coreutils.texi index b624e1840..ec995bb7f 100644 --- a/doc/coreutils.texi +++ b/doc/coreutils.texi @@ -3123,10 +3123,21 @@ works. @vindex LC_ALL @vindex LC_COLLATE -A pair of lines is compared as follows: if any key fields have -been specified, @command{sort} compares each pair of fields, in the +@cindex sort stability +@cindex sort's last-resort comparison +A pair of lines is compared as follows: +@command{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. +If no key fields are specified, @command{sort} uses a default key of +the entire line. Finally, as a last resort when all keys compare +equal, @command{sort} compares entire lines as if no ordering options +other than @option{--reverse} (@option{-r}) were specified. The +@option{--stable} (@option{-s}) option disables this @dfn{last-resort +comparison} so that lines in which all fields compare equal are left +in their original relative order. The @option{--unique} +(@option{-u}) option also disables the last-resort comparison. + Unless otherwise specified, all comparisons use the character collating sequence specified by the @env{LC_COLLATE} locale.@footnote{If you use a non-@acronym{POSIX} locale (e.g., by setting @env{LC_ALL} @@ -3139,18 +3150,6 @@ Second, it has undefined behavior if @env{LC_CTYPE} (or @env{LANG}, if you get undefined behavior if @env{LC_CTYPE} is @code{ja_JP.PCK} but @env{LC_COLLATE} is @code{en_US.UTF-8}. } -If any of the global options @samp{bdfgiMnr} are given but no key fields -are specified, @command{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), @command{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} @command{sort} (as specified for all @sc{gnu} utilities) has no limit 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} @@ -3349,18 +3348,11 @@ files. @opindex -s @opindex --stable @cindex sort stability -@cindex disabling sort's last-resort comparison - -Make @command{sort} stable by disabling the last-resort -comparison that is performed in some cases. -By default, when lines compare equal based on command line options -that affect ordering, those lines are ordered using -a @dfn{last-resort comparison} that takes the entire -line as the key and acts as if no ordering options were specified. -But if @option{--reverse} (@option{-r}) was specified along with other -ordering options, then the last-resort comparison does use @option{--reverse}. -In any case, when no ordering option is specified or when only -@option{--reverse} is specified, the last-resort comparison is not performed. +@cindex sort's last-resort comparison + +Make @command{sort} stable by disabling its last-resort comparison. +This option has no effect if no fields or global ordering options +other than @option{--reverse} (@option{-R}) are specified. @item -S @var{size} @itemx --buffer-size=@var{size} @@ -3426,6 +3418,8 @@ 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. +This option also disables the default last-resort comparison. + The commands @code{sort -u} and @code{sort | uniq} are equivalent, but this equivalence does not extend to arbitrary @command{sort} options. For example, @code{sort -n -u} inspects only the value of the initial |