check if a filehandle is STDOUT when using use strict;

ISAI student has asked for the wisdom of the Perl Monks concerning the following question:

Hello all. I am rewriting a subroutine, in which a check if a filehandle is in fact STDOUT is performed.

When not using use strict, the answer is very simple. However, bare word is anallowed when use strict is applied . Would ( $bar == \*STDOUT ) do?

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Re: check if a filehandle is STDOUT when using use strict; by bart (Canon) on Dec 31, 2012 at 11:22 UTC
I seriously doubt if comparing to \STDOUT will do. After all, a filehandle is a special entry in a typeglob, it's not just a plain scalar that you can compare. It's not even a reference. But you can always use fileno, and applying the snippet of code on the page, you can do: `if(fileno($fh)==fileno(STDOUT)) { # ... }` [download] And yes, `fileno(STDOUT)` is allowed by strict. There could be a bit of a problem if `$fh` is a tied filehandle instead of a physical handle. In that case, fileno will return -1, which is different from the default* value for STDOUT, which is 1. If you tie STDOUT too, then you're in trouble.	[reply] [d/l] [select]
Re^2: check if a filehandle is STDOUT when using use strict; by ISAI student (Scribe) on Jan 01, 2013 at 06:56 UTC
It's a physical handle. Thanks!	[reply]
Re: check if a filehandle is STDOUT when using use strict; by zwon (Abbot) on Dec 31, 2012 at 10:39 UTC
It depends on what do you mean by filehandle is in fact STDOUT. E.g. consider the following: `$ perl -E'open my $foo, "<&=1"; say $foo->fileno; say $foo == \*STDOUT + ? "STDOUT" : "Not STDOUT"' 1 Not STDOUT` [download]	[reply] [d/l]
Re^2: check if a filehandle is STDOUT when using use strict; by ISAI student (Scribe) on Dec 31, 2012 at 10:49 UTC
I can assume that it gets assigned the value of \STDOUT `I.E. $file= \STDOUT ;`	[reply] [d/l]
Re: check if a filehandle is STDOUT when using use strict; by mhearse (Chaplain) on Jan 01, 2013 at 17:58 UTC
`#!/usr/bin/env perl use strict; print "PID: " . $$, "\n"; open STDOUT, ">/tmp/returntozork" or die $!; while (1) { sleep 10; }` [download] `PID: 3868 shell> ls -l /proc/3868/fd/ lrwx------. 64 Jan 1 09:55 2 -> /dev/pts/0 l-wx------. 64 Jan 1 09:55 1 -> /tmp/returntozork lrwx------. 64 Jan 1 09:55 0 -> /dev/pts/0` [download]	[reply] [d/l] [select]

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