Question

Why this simple script:

#! perl -w

use strict;
use warnings;
$| = 1;

my $LOCKFILE = "$0.lock";

sub mklock {
    open my $lf, ">", $LOCKFILE;
    print $lf $$;
    close $lf;
}

sub rmlock { unlink $LOCKFILE; }

sub clean_exit { rmlock;  exit 0; }

sub work {
    print "working...";
    sleep 10;
    # although `sleep 1 foreach (1..10);`
    # *does* interrupt---between `sleep`s--see my answer
    print "done.\n"
}

$SIG{INT} = "clean_exit";

mklock;
work;
rmlock;

works on Debian but not on Windows?

• on Windows, the Ctrl+C is ignored when this script is working
• on Debian, clean exit is performed as expected
• with $SIG{INT} = \&clean_exit;, the behavior seems the same
• (if I do the same with SIGHUP ($SIG{HUP} = "clean_exit";), window is closed but clean exit is not performed anyway)

(Well, I admit that it’s Strawberry perl 5, version 14, subversion 2 (v5.14.2) built for MSWin32-x86-multi-thread on Windows 7 amd64 -vs- perl, v5.10.1 (*) built for x86_64-linux-gnu-thread-multi on the Debian 6.0.4 box, but I doubt it matters for such basic stuff. Edit: I just checked it on similar box with ActiveState perl 5.12 and it’s the same, so apparently the problem is not isolated to Strawberry.)

I know perlport says it clear,

Don’t count on signals or %SIG for anything.

but there must be a way… (Plus, I would like to understand.)

So what should be done differently?

Answer 1

After adding some more printing, I found out that actually, the code does work, except that it does not interrupt during sleep.

So just changing sleep 60 to more “realistic” sleep 1 foreach (1..10); brings much more acceptable behavior.

It still does work differently on Windows than on *nix, of course.