I am new to perl (5 days as of today), and I seek the wisdom of the perl monks. I am writing a script, run from cron, that monitors whether or not a host on the network is pingable. I think I have the the core part of the script functioning well, but I am unsure of some of the other parts. As documented in the code, my first concern has to do with the creation and checking of a lock file used to detrmine if the previous execution of the script finished. My second concern is of the system calls made and general perl worthiness of the code. To sum up, I'd like some peer review of my first REAL baby. (note: this code is based off of someone else's previous work, but is entirely re-written to be more efficeint, (I hope)). Thanks for your time. 
#!/usr/bin/perl -w
# Run this perl code from cron every 5 minutes
# 0,5,10,15,20,25,30,35,40,45,50,55 * * * * /.ping_hosts.pl 2>&1 
#
# Problem: Any user on localhost can stop the repeated execution
# of this script by creating the lock_file. If I create a
# non-predictable name for the lock file, how does the script know
# what the previous lock_file name was?

$lock_file = "/tmp/ping_hosts.lock";

sub test_for_lock { # Check if last run has finished
    my $lock_file = shift(@_);
    if (-e $lock_file) {
         system("touch $lock_file");
        die "Process lock file, ${tattle}, still exists (Old process s
+till running?)\n";
    }
    else { system("/bin/touch $lock_file") }
}

sub ping_hosts {
    my $timeout = 2;
    my @hosts = qw(host1 host2 host3 host4);
    foreach $ws (@hosts) {
        $result = qx(/usr/sbin/ping $ws $timeout);
        unless ($result =~ m/alive/) {
            print "$ws did not respond to ping within the $timeout sec
+ond timeout period\n";
            notify_admins($ws);
        } 
    }
}

sub notify_admins { # Called from ping_hosts()
    # Similar problem with $nfile as with $lock_file
    my $nfile = "/tmp/${ws}.notify";
    my $ws = shift(@_);
    my $admins = "admin1\@mailhost.com, " .
         "18005551212\@page.com, " .
         "admin2\@mailhost.com, " .
         "19005551212\@page.com";
         # root, aka script owner, already getting notified by cron
    unless (-e $nfile) {
        open(MAIL, "|/bin/mailx $admins") or die "Can't fork for mailx
+: $!\n";
        print MAIL "$ws doesn't respond to ping\n";
        close(MAIL);
        system("/bin/touch $nfile");
    }    
}

### MAIN ###
test_for_lock($lock_file);
ping_hosts();
system("/bin/rm $lock_file");

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In reply to lock files vs. non-predictable file names by RuphSkunk

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