Here's what my goal is:

I have an application that controls a printer. It can be given arguments to affect its behavior. It prints status messages to STDOUT. It is not written in Perl.

I would like my daemon script to spawn children, each one of which is an incarnation of this print app, run with its own arguments. I would like the output of each child to print to its own file in realtime (i.e. not buffered) so I can tail -f to see what a given printer is up to at any given time. The daemon should also listen for signals and terminate the children nicely.

Here's what I've got so far:

For testing purposes, replace the print app with this:

#!/usr/bin/perl -w

use strict;

while (1) {
    print localtime() . "\n";
    sleep 1;
}
[download]

Here is how far I've gotten with the daemon:

#!/usr/bin/perl -w

use strict;
use POSIX;
use IO::File;

my $time_to_die = 0;

my $pid = fork;
exit if $pid;
die "Couldn't fork: $!" unless defined $pid;
print "daemon pid = $$\n";

POSIX::setsid() or die "Can't start a new session: $!";

for my $n (1 .. 5) {
    my $pid;
    my $logfile = $n . '.log';

    if ($pid = fork) {
        print "child pid = $pid\n";
    }
    else {

        my $fh = IO::File->new;
        $fh->open("> $logfile") or warn "Couldn't open $logfile: $!\n"
+;
        open (STDOUT, ">&" . fileno($fh)) or warn "Couldn't redirect S
+TDOUT to $logfile: $!\n";
        STDOUT->autoflush(1);

        $SIG{INT} = "IGNORE";

        my $command = ("/home/brasey/daemon/timer");
        exec $command;
    }
}

until ($time_to_die) {
    $SIG{INT} = $SIG{TERM} = $SIG{HUP} = \&sig_handler;
    sleep;
}

exit 0;

sub sig_handler {
    print "time to die\n";
    $time_to_die = 1;
    kill ('HUP', -$$);
}
[download]

(Also linked here)

Here's the skinny:

Basically, it all works, but output is buffered. I've tried these methods:

$| = 1;
$^F = 10000;
STDOUT->autoflush(1);
[download]

Where have I gone wrong?

Bob

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