Date: Tue, 10 Jun 2008 01:44:36 +1000 (EST) From: Ian Smith <smithi@nimnet.asn.au> To: Bill Campbell <freebsd@celestial.com> Cc: Jos Chrispijn <jos@webrz.net>, Wojciech Puchar <wojtek@wojtek.tensor.gdynia.pl>, Raphael Becker <rabe@uugrn.org>, freebsd-questions@freebsd.org Subject: Re: Grep Guru Message-ID: <Pine.BSF.3.96.1080610001213.15342A-100000@gaia.nimnet.asn.au> In-Reply-To: <20080608231711.053E310656E1@hub.freebsd.org>
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On Sun, 8 Jun 2008 16:07:12 -0700 Bill Campbell <freebsd@celestial.com> wrote:
> On Mon, Jun 09, 2008, Raphael Becker wrote:
> >On Sun, Jun 08, 2008 at 10:15:50PM +0200, Wojciech Puchar wrote:
> >> find . -type f -print0|xargs -0 grep <grepoptions> <text to search>
> >
> >There's no more need for find | xargs
> >
> >Try:
> >
> >find . -type -f -exec grep <grepoptions> <text to search> {} \+
> >
> >-exec foo {} \+ behaves like xargs foo
> >-exec foo {} \; exec foo for every file
Thanks for this kick; I'd missed or misunderstood using {} \+
> The issue here is that grep execs grep for each file found while
> xargs batches the files.
If find(1) is to be believed, so does -exec utility [argument ...] {} +
> This is of particular importance if one wants to see the file
> names in the output. In relation to this, if one wants to be
> sure that grep always generates the file name, insure that it
> always gets at least two files as arguments:
>
> find . -type f -print0 | xargs -0 grep pattern /dev/null
Another good clue. Many ways to do anything; I've often used such as:
% find /sys/ -name "*.[chm]" -exec egrep -Hi 'CPUFREQ_[GS]ET' {} \;
which has grep print the filenames, rather than using -print with find,
but I've just now run the above find, then using \+ instead, twice each,
and am pleased to learn that the latter method runs ~4 times faster in
real time and is even lighter on the system:
% time find /sys/ -name "*.[chm]" -exec grep -Hi 'CPUFREQ_[GS]ET' {} \;
/sys/kern/kern_cpu.c:static int cpufreq_settings_sysctl(SYSCTL_HANDLER_ARGS);
[.. etc ..]
20.524u 46.205s 4:03.91 27.3% 79+201k 5698+0io 0pf+0w
% time find /sys/ -name "*.[chm]" -exec grep -Hi 'CPUFREQ_[GS]ET' {} \+
1.756u 3.058s 1:07.51 7.1% 81+290k 7148+0io 13pf+0w
% time find /sys/ -name "*.[chm]" -exec grep -Hi 'CPUFREQ_[GS]ET' {} \;
21.742u 44.382s 3:57.99 27.7% 79+200k 7144+0io 0pf+0w
% time find /sys/ -name "*.[chm]" -exec grep -Hi 'CPUFREQ_[GS]ET' {} \+
1.651u 3.134s 0:58.39 8.1% 75+267k 7149+0io 10pf+0w
(Ignore sloth; poor 300MHz Celeron already busy dumping /usr over nfs :)
> FWIW, I have learned about gnu-grep's -r option reading this
> thread, which I had not noticed previously. I guess that just
> goes to show that old habits die hard :-).
When you're on a good thing :) but always plenty new tricks to learn.
cheers, Ian
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