GNU bug report logs - #28304
Feature Request - Quit on Non Match

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

From: Adam Danischewski <adam.danischewski <at> gmail.com>
To: bug-grep <at> gnu.org
Subject: Feature Request - Quit on Non Match
Date: 2017年8月31日 10:43:30 -0400

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I've been writing parsers and it would be really nice if grep could do the
following:
*grep --quit-nm 1 -Pno "^[ \t\f]*#.*$" <(sed -n '2,$p' gen_ent.bsh)*
If you:
*grep -m 1 -Pno "^[ \t\f]*#.*$" <(sed -n '2,$p' gen_ent.bsh)*
Only the first match of the header block gets printed, yet it would be nice
if grep in O(n), could simply be on the look out for the first failure to
match the -o context and quit at --quit-nm non-match occurrences.

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Message #8 received at 28304 <at> debbugs.gnu.org (full text, mbox):

From: arnold <at> skeeve.com
To: adam.danischewski <at> gmail.com, 28304 <at> debbugs.gnu.org
Subject: Re: bug#28304: Feature Request - Quit on Non Match
Date: 2017年8月31日 08:53:30 -0600

Adam Danischewski <adam.danischewski <at> gmail.com> wrote:
> I've been writing parsers and it would be really nice if grep could do the
> following:
>
> *grep --quit-nm 1 -Pno "^[ \t\f]*#.*$" <(sed -n '2,$p' gen_ent.bsh)*
>
> If you:
> *grep -m 1 -Pno "^[ \t\f]*#.*$" <(sed -n '2,$p' gen_ent.bsh)*
>
> Only the first match of the header block gets printed, yet it would be nice
> if grep in O(n), could simply be on the look out for the first failure to
> match the -o context and quit at --quit-nm non-match occurrences.
I may be misunderstanding what you want, but something like
	awk '/pattern to match/ { print ; continue }
		{ exit 0}' file
might do what I think you want - exit on first non match.
If gawk can do the same matching you're doing with grep -Pno, that
is a different question.
HTH,
Arnold

Message #11 received at 28304 <at> debbugs.gnu.org (full text, mbox):

From: Adam Danischewski <adam.danischewski <at> gmail.com>
To: arnold <at> skeeve.com
Cc: 28304 <at> debbugs.gnu.org
Subject: Re: bug#28304: Feature Request - Quit on Non Match
Date: 2017年8月31日 13:50:49 -0400

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Yes, awk can handle it except for maybe very large files. I was trying to
keep it restricted to grep, grep is already counting matches with -m but
maybe GNU views this direction as becoming too programmatic from what the
original vision of grep is?
awk '{if(0ドル~/^[ \t\f#]+/)print 0ドル;else exit}' gen_ent.bsh
Thanks anyway,
 +AMD
On Thu, Aug 31, 2017 at 10:53 AM, <arnold <at> skeeve.com> wrote:
> Adam Danischewski <adam.danischewski <at> gmail.com> wrote:
>
> > I've been writing parsers and it would be really nice if grep could do
> the
> > following:
> >
> > *grep --quit-nm 1 -Pno "^[ \t\f]*#.*$" <(sed -n '2,$p' gen_ent.bsh)*
> >
> > If you:
> > *grep -m 1 -Pno "^[ \t\f]*#.*$" <(sed -n '2,$p' gen_ent.bsh)*
> >
> > Only the first match of the header block gets printed, yet it would be
> nice
> > if grep in O(n), could simply be on the look out for the first failure to
> > match the -o context and quit at --quit-nm non-match occurrences.
>
> I may be misunderstanding what you want, but something like
>
> awk '/pattern to match/ { print ; continue }
> { exit 0}' file
>
> might do what I think you want - exit on first non match.
>
> If gawk can do the same matching you're doing with grep -Pno, that
> is a different question.
>
> HTH,
>
> Arnold
>

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