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From: ziegast@eng.umd.edu (Eric W. Ziegast)
Newsgroups: comp.lang.perl
Subject: Re: How can I capture STDERR from a command executed externally
Message-ID: <1991May23.204119.23595@eng.umd.edu>
Date: 23 May 91 20:41:19 GMT
References: <4352@inews.intel.com> <1991May23.055849.6100@jpl-devvax.jpl.nasa.gov>
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Reply-To: ziegast@eng.umd.edu (Eric W. Ziegast)
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Organization: College of Engineering, Maryversity of Uniland, College Park
Lines: 35

(Larry Wall) writes:
> You're making this all much too hard.  Just say
> 
> open(TMP, "ls -h 2>&1 |");
> while (<TMP>) {
>     tr/+/%/;
>     print;
> }

The above method will merge STDERR into STDOUT.  In his book, Larry also
shows another way of doing this where STDERR and STDOUT are still handled
seperately.

	# Before your command: redirects STDERR
	open(SAVEERR, ">&STDERR");
	open(STDERR, "> stderr_output_filename");
	
	# Commands you would have used normally
	# Ex: open(TMP, "ls -h");
	
	#After your command: restores STDERR
	close STDERR;
	open(STDERR, ">&SAVEERR");

After this, you can open the file "stderr_output_filename" and
read what was sent to STDERR.  If you just want to get rid of STDERR, use
/dev/null for a filename.

The same process would work with STDOUT with a few minor file handle changes.
	s/ERR/OUT/g

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| Eric W. Ziegast      Internet: ziegast@eng.umd.edu |
| Univ. of Merryland   Phonenet: Eric@[301.405.3689] |
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