in reply to Re: Can't close STDIN/STDOUT/STDERR
in thread Can't close STDIN/STDOUT/STDERR

Ah! It appears to originate from Net::OpenSSH. (Thanks Google)

Anyway, it's a fair warning. Programs expect to be provided a STDIN, STDOUT and STDERR, and you don't provide them. Don't close them. Instead, redirect them to /dev/null.

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Re^3: Can't close STDIN/STDOUT/STDERR
by brp4h (Acolyte) on Feb 09, 2010 at 21:20 UTC
    I tried that (redirect to /dev/null) and it broke my program... I'm not well-versed enough in Perl to know why. Could you give me an example of how I should do it?
[reply]
[d/l]
      You can find samples of how to redirect file handles in open:

      open STDOUT, '>', "/dev/null" or die "Can't redirect STDOUT: $!";

[reply]
[d/l]
          close(READER) or die "can't close READER: $!";

    open STDIN,  '<',  '/dev/null' or die "can't open STDIN: $!\n";
    open STDOUT, '>',  '/dev/null' or die "can't open STDOUT: $!\n";
    open STDERR, '>&', \*STDOUT'   or die "can't dup STDOUT: $!\n";

      [download]
[reply]
[d/l]

        What does this syntax do:

        open STDERR, '>&', \*STDOUT'

        because this simpler syntax seems to work:

             1  use strict;
     2  use warnings;
     3  use 5.010;
     4
     5  open my $SAVE_STDOUT, '>&', 'STDOUT';  #<--quoted bareword
     6  open STDOUT, '>', 'data1.txt';
     7  say 'hello world';
     8
     9  open my $SAVE_STDERR, '>&', 'STDERR';  #<--quoted bareword
    10  open STDERR, '>', 'errors.txt';
    11  warn "my warning message";
    12
    13  open STDOUT, '>&', $SAVE_STDOUT;
    14  open STDERR, '>&', $SAVE_STDERR;
    15  say 'goodbye';
    16  warn 'my warning message #2';

--output:--
goodbye
my warning message #2 at 2perl.pl line 16.

$cat data1.txt
hello world

$cat errors.txt
my warning message at 2perl.pl line 11.

        [download]
        EDIT: In fact, I just tried using STDOUT and STDERR as the third argument to open() without quotes around them, and that works too: the output is the same.
[reply]
[d/l]

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