#!/usr/bin/perl

use strict; use warnings;
use Data::Dumper;


print "".localtime(),"\n";
my $pid = fork;
die "fork failed\n" if !defined $pid;
if ($pid == 0) { # child
    print "child is $$\n";
    exec "/bin/sleep", "4";
    die "exec failed:$!\n";
}
else { # parent

    # there is no code in the parent to kill the child if the alarm is called
    $SIG{ALRM} = sub {
        print( "Alarm triggered, making system call in $$\n" );
        unlink('/doesnt/exist');  # this will definitely fail
    };

    alarm(2);
    my $pid = wait;
    my $status = $?;
    print "return value from child is $pid and status was $status\n";
}
print "".localtime(),"\n";

##</code><code>##

Sat Sep 29 09:04:00 2007
child is 26171
Alarm triggered, making system call in 26170
return value from child is -1 and status was -1
Sat Sep 29 09:04:02 2007

##</code><code>##


#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <signal.h>
#include <unistd.h>

void alarm_sig(int sig)
{
    int rt;

    puts("in alarm_sig");
    if ((rt = unlink("/doesnt/exist")) == -1) {
        perror("unlink failed");
    }
}

int main()
{
    int rt;

    signal(SIGALRM, alarm_sig);
    alarm(2);
    rt = system("sleep 4");
    printf("return value from system %d\n", rt);

}

##</code><code>##

in alarm_sig
unlink failed: No such file or directory
return value from system 0