How (Not) To Ask A Question

What "doesn't work"? What do you mean by "filehandler is used"? What did you expect that to do? Why would you expect it to do that? How much wood would a woodchuck chuck if a woodchuck could chuck wood?

First, my confusion: "filehandler" is something that handles files, and "filehandle" is a handle to a (or token for a) file. You have a filehandle.

Second, the solution: Using fileno works fine for files. On Linux/unix, it probably works for sockets, fifos, and many other things. On no platform does it work for IO::String or handles to a string buffer (e.g., open OUT, '>', \$buffer). If you are only worried about real files, that's fine.

Instead, you will pretty much need to keep the state seperate. For example, using a symref:

my $fh;
open $fh, "<", "/etc/shadow" or $fh = undef;
if ($fh) {
  # do stuff
}
[download]

Personally, I just merge it all:

if (open my $fh, "<", "/etc/shadow")
{
  # do stuff.
  close $fh;
}
[download]

if ( OUT ) {
    print OUT " bla bla\n" ;
}
[download]

if (defined fileno(OUT)) {
    print OUT "bla bla\n";
}
[download]

    --k.

any idea of the diff between yours and mine? I've always used *HANDLE:

use strict;
use warnings;
open(OUT, ">test.txt") or die "Can't open file to write, $!.";
if(defined fileno *OUT){
    print "File handle is valid.";
}else{
    print "Nope.";
}
close OUT;
[download]

if (*STDOUT{IO}) {
    print "it's used\n";
}
[download]