written by :	Stephen J. Friedl
              Software Consultant
		Southern California USA
              steve@unixwiz.net
		http://www.unixwiz.net/tools/

	===================================================================
	======== This software is in the public domain, and can be ========
	======== used by anybody for any purpose                   ========
	===================================================================

	Lockrun: This program is used to launch a program out with a lockout
	so that only one can run at a time. It's mainly intended for use out
	of cron so that our five-minute running jobs which run long don't get
	walked on. We find this a *lot* with Cacti jobs which just get hung
	up: it's better to miss a polling period than to stack them up and
	slow each other down.

	So we use a file which is used for locking: this program attempts to
	lock the file, and if the lock exists, we have to either exit with
	an error, or wait for it to release.

		lockrun --lockfile=FILE -- my command here

 COMMAND LINE
 ------------

 --lockfile=F

	Specify the name of a file which is used for locking. The file is
	created if necessary (with mode 0666), and no I/O of any kind is
	done. The file is never removed.

 --maxtime=N

	The script being controlled should run for no more than <N> seconds,
	and if it's beyond that time, we should report it to the standard
	error (which probably gets routed to the user via cron's email).

 --wait

	When a lock is hit, we normally exit with error, but --wait causes
	it to loop until the lock is released.

 --sleep=N
 
	When using --wait, will sleep <N> seconds between attempts to acquire
	the lock.

 --retries=N

	When using --wait, will try only <N> attempts of acquiring the lock.
 
 --verbose

	Show a bit more runtime debugging.

 --quiet

	Don't show "run is locked" error if things are busy; keeps cron from
	overwhelming you with messages if lockrun overlap is not uncommon.

 --

	Mark the end of the options: the command to run follows.
	

 VERSION HISTORY

 1.1.3 2014/11/03; now handle exit status correctly (thanks to Richard Faasen)
 1.1.2 2013/04/26; now we use lockf() if the platform supports it
 1.1.1 2012/09/05; added setsid() to make the controlled process a process
			group leader
 1.1.0 2012/09/05; added --version and --help; added --retries (thanks Dov Murik)
 1.0.3 2010/11/20; added --quiet parameter
 1.0.2 2009/06/25; added lockf() support for Solaris 10 (thanks Michal Bella)
 1.0.1 2006/06/03; initial release