Re: Most efficient method to call a system routine and capture it's output

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#263

From: Darren Dunham
Date: Fri, 19 Jul 2002 15:54

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Ralph SOBEK <sobek@iritremovespam.fr> wrote:
> 	What is the most efficient method to call a system routine
> repeatedly and capture it's short output?

> 	Supposedly, in loop:

> #1	system @cmd;

> is efficient.  But using backquotes:

> #2	(my $sum = `@cmd 2>/dev/null`) =~ s/\s+.*$//;

> captures the output correctly, but is horrendously slow, if repeated a
> couple of thousand times.  For 35,000 files count about SIX hours!

Number of files may be relevant, but /usr/ucb/sum will run in time
proportional to the size of the files.  If those are huge files, that
may be normal.  You can't run faster than 'sum' takes, and I would
imagine any inefficiency in the perl is *swamped* by the time the sum
takes.

How long does it take outside of perl?

find /your/directory/here -exec /usr/ucb/sum {} \;
 
> 	Is there a possibility to prepare the fork in #1 in such a way
> as to recover the forks output afterwards?  It may help to know that
> the output consists only of two numbers.

> 	In fact, in the above I am using File::Find to recursively
> checksum a file structure.  @cmd[0] = '/usr/ucb/sum' and @cmd[1] is
> the file path.

-- 
Darren Dunham                                           ddunham@taos.com
Unix System Administrator                    Taos - The SysAdmin Company
Got some Dr Pepper?                           San Francisco, CA bay area
         < This line left intentionally blank to confuse you. >

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From: Darren Dunham <ddunham@redwood.taos.com>
Subject: Re: Most efficient method to call a system routine and capture it's output
Newsgroups: comp.lang.perl.misc,fr.comp.lang.perl
References: <ausn2ib8ny.fsf@irit.irit.fr> <aud6tjbw4d.fsf@irit.irit.fr>
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