#!/usr/bin/env perl

# for https://perlmonks.org/?node_id=1231710
# author: bliako
# 27/03/2019
# WARNING: it writes and deletes file 'xyz' in local dir

use strict;
use warnings;

sub spawner {
	my ($cmd, $timeout) = @_;
	print "spawner starting.\n";
	my $pid = fork();
	if( ! $pid ){
		print "spawner in child.\n";
		eval {
			local $SIG{ALRM} = sub { die "alarm blah blah" };
			alarm $timeout;
			print "starting system command.\n";
			`$cmd`;
			print "system command ended.\n";
			alarm 0;
		};
		if( $@ =~ /^alarm blah blah/ ){ die "spawner: child timed out" }
		elsif( $@ ){ die "spawner: something wrong with eval block which spawns '$cmd'" }
		exit 0;
	}
	print "spawner ending.\n";
}

spawner('rm -f xyz; sleep 5; touch xyz', 2);

wait();

if( -e 'xyz' ){ print "command seems to have terminated on its own will.\n"; }
else { print "command has timed out.\n"; }