http://www.perlmonks.org?node_id=833643

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---

#!/usr/bin/perl
use strict;
use warnings;

system("clear");

my ( $who_am_i, $countdown_pid, $checking_pid );
$countdown_pid = fork();
if ( $countdown_pid == 0 ) {
    $who_am_i = "countdown process";
}
elsif ($countdown_pid) {
    $checking_pid = fork();
    if ( $checking_pid == 0 ) {
        $who_am_i = "checking process";
    }
    elsif ($checking_pid) {
        $who_am_i = "controlling process";
    }
    else {
        die "Error forking: $!";
    }
}
else {
    die "Error forking: $!";
}

for ($who_am_i) {
    if ($who_am_i eq "countdown process") {
        sleep_count( 3, 'Verifying with Nagios that resin is down: ' )
+;
    }
    if ($who_am_i eq "checking process") {
        my $test_check = `/bin/ps -u dramaya`;
        my $counter    = 0;
        while ( $test_check =~ /vi/ ) {
            if ( $counter == 310 ) {
                die "Could not verify if resin is down\n";
            }
            $test_check = `/bin/ps -u dramaya`;
            sleep 10;
            $counter++;
        }
    }
    if ($who_am_i eq "controlling process") {
        # Wait on the "checking process" to complete.
        waitpid($checking_pid, 0);
        # Kill countdown timer
        kill(9, $countdown_pid);
        waitpid($countdown_pid, 0);
   }

}

print "$countdown_pid $checking_pid\n";

sub sleep_count {
    my $minutes   = shift;
    my $string    = shift;
    my $countdown = $minutes * 60;    # in secs.

    $| = 1;

    my $beg_time = time;
    my $end_time = $beg_time + $countdown;

    for ( ; ; ) {
        my $time = time;
        last if ( $time >= $end_time );
        printf(
            "\r[ %02d:%02d ] $string",
            ( $end_time - $time ) / (60) % 60,
            ( $end_time - $time ) % 60,
        );
        sleep(1);
    }
}
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