GNU bug report logs - #23185
GNU grep matching discrepancy between -a/--text and not.

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Shlomi Fish <shlomif <at> shlomifish.org>
To: bug-grep <at> gnu.org
Subject: GNU grep matching discrepancy between -a/--text and not.
Date: Sat, 2 Apr 2016 15:00:12 +0300

Hi all,

as can be seen in this repository:

https://github.com/shlomif/gnu-grep-trailing-space-and-CR-on-riddles.he-false-match

GNU grep says a document it suspects to be binary matches without -a/--text and
doesn't match it or return results with that flag applied. perl sides with the
latter.

I'm on Mageia linux x86-64 v6 and have built GNU grep from the latest git
commit ( c767ed70eca9a82d76f07dcdbcaafa21ec7f86d6 ) to test.

Regards,

	Shlomi Fish

P.S: it seems the build system uses gperf but configure does not verify that it
exists in the path.

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Message #10 received at 23185-done <at> debbugs.gnu.org (full text, mbox):

From: Paul Eggert <eggert <at> cs.ucla.edu>
To: Shlomi Fish <shlomif <at> shlomifish.org>, 23185-done <at> debbugs.gnu.org
Subject: Re: bug#23185: GNU grep matching discrepancy between -a/--text and
 not.
Date: Tue, 5 Apr 2016 23:56:22 -0700

[Message part 1 (text/plain, inline)]

Thanks for pointing out the seeming inconsistency. The documentation mentions 
the issue but is perhaps not clear enough, so I installed the attached patch.

The input file contains NUL bytes and so is treated as binary data, and the grep 
documentation (secton "File and Directory Selection", option "--binary-files") 
says "When processing binary data, ‘grep’ may treat non-text bytes as line 
terminators". This behavior was added to GNU grep in release 2.21 dated 2014, 
partly for performance reasons.

There are two instances in riddle.he of a space followed by a NUL byte, so

  grep -P '[ \t]\r?$' riddles.he

finds a match when the $ matches just before the NUL byte.

-a is one way to get the behavior you evidently expected. Another (perhaps 
better) way is -z. The command:

  grep -zP '[ \t]\r?\n' riddles.he

outputs nothing and exits with status 1.

[0001-Give-another-example-of-binary-file-processing.patch (text/x-diff, attachment)]

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