I seemed to have gotten a bit off track and though I found out some interesting details about perl (never can learn too many of those!), I didn't really figure out how to get a file-handle for use with 'ioctl', from 'STDOUT'.

Let's assume that STDOUT may or may not point to the same TTY device as '/dev/tty' -- but for my purposes, assume that it isn't -- but that it is pointing to some tty-style window.

ioctl stays it takes a file handle. So how do I 'massage' STDOUT to get it's underlying file handle in a way that works for ioctl?

Here's code that demonstrates the problem: 

#!/usr/bin/perl -w
use strict;
use feature ':5.10';

{ no warnings "all";
  $SIG{__WARN__} = sub { };    #pretend "no warnings" works
  require "sys/ioctl.ph";
}

sub getwinsize (;$) {
  my $recheck=$_[0];
  my $winsize=0;
  state ($maxcols, $maxrows);

  return ($maxcols,$maxrows) if $maxcols && $maxrows && !$recheck;

  my $err = ioctl STDOUT, &TIOCGWINSZ, $winsize;
 
  unless ($err) {  
    print STDERR "ERROR: ioctl on STDOUT: $!\n";
    $err = ioctl fileno(STDOUT), &TIOCGWINSZ, $winsize;
    unless ($err) {
      print STDERR "ERROR: ioctl on fileno(STDOUT): $!\n";
    } else {
      printf STDERR "ioctl on fileno(STDOUT) worked\n";
    }
  } else {
    printf STDERR "ioctl on STDOUT worked\n";
  }

  my ($rows, $cols, $unused1, $unused2) = unpack "S!4", $winsize;

  printf STDERR "(rows=%u, cols=%u)\n", $rows//0, $cols//0;

  ($maxcols, $maxrows) = ($cols || -1, $rows || -1);
}

my ($rows,$cols) = getwinsize;

print "rows=$rows, cols=$cols\n";

# vim: ts=2: sw=2

[download]
and here's the output I get: 
ERROR: ioctl on STDOUT: Bad address
ERROR: ioctl on fileno(STDOUT): Bad file descriptor
(rows=0, cols=0)
rows=-1, cols=-1

[download]
Ideas? Bug?

In reply to Don't understand why can't get 'size' assoc w/STDOUT by perl-diddler

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