Re: [edlug] Perl - Only run n instances of script?

[Lee Kindness <lkindness@xxx.xxx.xxx>]

David R. Baird writes:
 > Instead of writing a single lock file, you could write to 4. If 
 > all 4 exist, then lock them out. 
 > 
 > Or write the pids to a single file, and remove them when the 
 > script ends. Lock them out if there are 4 pids. 

Aha, I see what you mean. Something along the lines of:

#!/usr/bin/perl -w

use Fcntl ':flock';

$LOCK1 = '/tmp/xxx.lock.1';
$LOCK2 = '/tmp/xxx.lock.2';
$LOCK3 = '/tmp/xxx.lock.3';
$LOCK4 = '/tmp/xxx.lock.4';

open LOCK1, ">$LOCK1" or die;
open LOCK2, ">$LOCK2" or die;
open LOCK3, ">$LOCK3" or die;
open LOCK4, ">$LOCK4" or die;

while( (flock LOCK1, LOCK_EX | LOCK_NB ||
	flock LOCK2, LOCK_EX | LOCK_NB ||
	flock LOCK3, LOCK_EX | LOCK_NB ||
	flock LOCK4, LOCK_EX | LOCK_NB) == 0 )
  {
    print "Waiting for lock\n";
    sleep 5;
  }

print "Got lock\n";
sleep 60; # do work
print "Releasing lock\n";

close LOCK4;
close LOCK3;
close LOCK2;
close LOCK1;

exit;

Thanks, L.
-
----------------------------------------------------------------------
You can find the EdLUG mailing list FAQ list at:
http://www.edlug.org.uk/list_faq.html