csplit: add the --suppress-matched option

With --suppress-matched, the lines that match the pattern will not be
printed in the output files.  I.E. the first line from the second
and subsequent splits will be suppressed.

* src/csplit.c: process_regexp(),process_line_count(): Don't output the
matched lines.  Since csplit includes "up to but not including" matched
lines in each split, the first line (in the next group) is the matched
line - so just skip it.
main(): Handle new option.
usage(): Mention new option.
* doc/coreutils.texi (csplit invocation): Mention new option, examples.
* tests/misc/csplit-suppress-matched.pl: New test script.
* tests/local.mk: Reference the new test.
* NEWS: Mention new feature.

1 files changed, 25 insertions, 0 deletions

diff --git a/doc/coreutils.texi b/doc/coreutils.texi
index 4cfe4c50c..8e4bacfb7 100644
--- a/doc/coreutils.texi
+++ b/doc/coreutils.texi
@@ -3607,6 +3607,12 @@ long instead of the default 2.
 @opindex --keep-files
 Do not remove output files when errors are encountered.
 
+@item --suppress-matched
+@opindex --suppress-matched
+Do not output lines matching the specified @var{pattern}.
+I.E. suppress the boundary line from the start of the second
+and subsequent splits.
+
 @item -z
 @itemx --elide-empty-files
 @opindex -z
@@ -3683,6 +3689,25 @@ $ head xx*
 14
 @end example
 
+Example of splitting input by empty lines:
+
+@example
+$ csplit --suppress-matched @var{input.txt} '/^$/' '@{*@}'
+@end example
+
+@c
+@c TODO: "uniq" already supports "--group".
+@c        when it gets the "--key" option, uncomment this example.
+@c
+@c Example of splitting input file, based on the value of column 2:
+@c
+@c @example
+@c $ cat @var{input.txt} |
+@c       sort -k2,2 |
+@c       uniq --group -k2,2 |
+@c       csplit -m '/^$/' '@{*@}'
+@c @end example
+
 @node Summarizing files
 @chapter Summarizing files