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From: merlyn@iwarp.intel.com (Randal L. Schwartz)
Newsgroups: comp.lang.perl
Subject: Re: pager pipes
Message-ID: <1991Feb17.024739.17286@iwarp.intel.com>
Date: 17 Feb 91 02:47:39 GMT
References: <1991Feb16.210445.7760@convex.com>
Sender: news@iwarp.intel.com
Reply-To: merlyn@iwarp.intel.com (Randal L. Schwartz)
Organization: Stonehenge; netaccess via Intel, Beaverton, Oregon, USA
Lines: 33
In-Reply-To: tchrist@convex.COM (Tom Christiansen)

In article <1991Feb16.210445.7760@convex.com>, tchrist@convex (Tom Christiansen) writes:
| I was trying to set up an automatic pager for STDOUT, and 
| it doesn't seem to work.  If I choose a different handle,
| it's fine.  Any clues?
| 
|     $pager = $ENV{'PAGER'} || 'more';
|     open(STDOUT, "| $pager") || die "can't reopen STDOUT to $pager: $!";
|     open(STDERR, ">&PIPE") || die "dup failed: $!";
|     system 'ps t';
|     system 'grep nada nonesuch';
|     while (<>) { print; }
|     close(STDOUT) || die "close failed: $!";
| 
| Notice that I never die of a bad dup even though there is no
| PIPE handle.  If you %s/STDOUT/PIPE/g and add an appropriate
| select, it all works fine.  This is under both 3.044 and 4.0beta.

Arrrgh... Think about what $pager's stdout is at the time of the fork!

This works:

	open(TMP,"| $pager");  # $pager's stdout is Perl's stdout
	open(STDOUT, ">&TMP"); # Perl's stdout is now the pager's stdin
	close(TMP); # no need for this anymore

(The appropriate error checking is left as an exercise to the reader.)

print "Just another Perl hacker,"
-- 
/=Randal L. Schwartz, Stonehenge Consulting Services (503)777-0095 ==========\
| on contract to Intel's iWarp project, Beaverton, Oregon, USA, Sol III      |
| merlyn@iwarp.intel.com ...!any-MX-mailer-like-uunet!iwarp.intel.com!merlyn |
\=Cute Quote: "Intel: putting the 'backward' in 'backward compatible'..."====/