#!/usr/bin/perl -w

#Here's a simple module that lets you run a "forever" kind 
#of script, and know it will die at a time you specify.

#This could be better, but it does what I need.

#Edit: Added note about hooking $SIG{INT} for cleanup to
#POD comments

package Until;

=head1 NAME

Until.pm

=head1 SYNOPSIS

    use Until "16:30";

    sub cleanup {
        # do whatever you need to do on exit
    }

    $SIG{INT}=\&cleanup;

    while(1) {
        # do something...
    }

=head1 DESCRIPTION

This simple module forks, and the child process returns.  The parent
process waits for the designated end time, then kills the child process.

=cut

use strict;

sub import
{
    my $stopTime=$_[-1];

    die "Arg 1 ($stopTime) must be hh:mm" unless $stopTime=~/^(\d\d?):(\d\d)$/;
    print "Running until $stopTime\n";

    my ($h,$m)=($1,$2);
    my $endMinutes=$h*60+$m;

    my $pid;

    if(!($pid=fork)) {
        # did fork fail?
        die "Error forking ($!)" if !defined $pid;

        # child process
        return;
    }
    else {
        my $currMinutes;
        do {
            my ($h, $m)=(localtime)[2,1];
            $currMinutes=$h*60+$m;
            sleep(5) unless $currMinutes<$endMinutes;
        } while($currMinutes < $endMinutes);

        # kill child process
        my $result=kill "INT",$pid;
        print "Killed child process $pid (result $result)\n";

        exit;
    }
}

1;