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

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From: arnold <at> skeeve.com
To: adam.danischewski <at> gmail.com, 28304 <at> debbugs.gnu.org
Subject: bug#28304: Feature Request - Quit on Non Match
Date: Thu, 31 Aug 2017 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

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