From 38cdb01a32ba386a42c370be8371a8bf884eacce Mon Sep 17 00:00:00 2001 From: Pádraig Brady Date: Wed, 24 Nov 2010 08:37:23 +0000 Subject: doc: add alternatives for field processing not supported by cut * doc/coreutils.texi (cut invocation): Remove the tr -s '[:blank:]' example, as it doesn't handle leading and trailing blanks. Add `awk` examples for common field processing operations often asked about. Also document a `join` hack, to achieve the same thing. Note the join options are ordered so as to be compatible with other systems. --- doc/coreutils.texi | 23 +++++++++++++++++++---- 1 file changed, 19 insertions(+), 4 deletions(-) (limited to 'doc') diff --git a/doc/coreutils.texi b/doc/coreutils.texi index b89147ea8..ea35afe29 100644 --- a/doc/coreutils.texi +++ b/doc/coreutils.texi @@ -5506,11 +5506,26 @@ Select for printing 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 @option{--only-delimited} (@option{-s}) option is specified. -Note @command{cut} does not support specifying runs of whitespace as a -delimiter, so to achieve that common functionality one can pre-process -with @command{tr} like: + +Note @command{awk} supports more sophisticated field processing, +and by default will use (and discard) runs of blank characters to +separate fields, and ignore leading and trailing blanks. +@example +@verbatim +awk '{print $2}' # print the second field +awk '{print $NF-1}' # print the penultimate field +awk '{print $2,$1}' # reorder the first two fields +@end verbatim +@end example + +In the unlikely event that @command{awk} is unavailable, +one can use the @command{join} command, to process blank +characters as @command{awk} does above. @example -tr -s '[:blank:]' '\t' | cut -f@dots{} +@verbatim +join -a1 -o 1.2 - /dev/null # print the second field +join -a1 -o 1.2,1.1 - /dev/null # reorder the first two fields +@end verbatim @end example @item -d @var{input_delim_byte} -- cgit v1.2.3-54-g00ecf