Greetings and hallucinations Anonymous One,
Consdier the following code:

#!/usr/bin/perl -w
                                                                      
+          
use File::Basename;
use strict;
use warnings;
use diagnostics;
                                                                      
+          
my $pid=$$;
                                                                      
+          
my $name=basename($0);
                                                                      
+          
my $pidfile="/var/tmp/" . $name . "." . $pid;
                                                                      
+          
printf "I'm going to use: %s\n",$pidfile;
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When this is run it yields:

--$  perl procpid.pl
I'm going to use: /var/tmp/procpid.pl.1974
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There is more than one way to do this but that's one way. Further to actually assert the "lock" you would add the following:

use FileHandle; # Add this with the rest of the uses
:
: # do the filename calculation steps shown above
:
my $fh=new FileHandle("> $pidfile") or die $!;
print $fh "$$"; # Or whatever you want to write
undef $fh; #automatically closes the file
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Do you want to get rid of the ".pl" part of the name? Do this:

$pidfile =~ s/\.pl//;
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Enjoy!

---

Peter L. Berghold -- Unix Professional Peter at Berghold dot Net
	Dog trainer, dog agility exhibitor, brewer of fine Belgian style ales. Happiness is a warm, tired, contented dog curled up at your side and a good Belgian ale in your chalice.