SHLOCK(1)						    InterNetNews Documentation							 SHLOCK(1)

NAME

       shlock - Create lock files for use in shell scripts

SYNOPSIS

       shlock [-b|-c|-u] -f name -p pid

DESCRIPTION

       shlock tries to create a lock file named name and write the process ID pid into it.  If the file already exists, shlock will read the
       process ID from the file and test to see whether the process is currently running.  If the process exists, then the file will not be
       created.  shlock exits with a zero status if it could create the lock file, or non-zero if the file refers to a currently active process.

OPTIONS

       -b  Process IDs are normally read and written in ASCII.	If the -b flag is used, then they will be written as a binary int.

       -c  If the -c flag is used, then shlock will not create a lock file, but will instead use the file to see if the lock is held by another
	   program.  If the lock is valid, the program will exit with a non-zero status; if the lock is not valid (i.e. invoking shlock without
	   the flag would have succeeded), then the program will exit with a zero status.

       -f name
	   name is the name of the lock file shlock attempts to create.  If the file already exists, it will read the process ID from the file and
	   exit with a non-zero status if this process is currently active.

       -p pid
	   pid is the process ID to write into the file name.

       -u  For compatibility with other systems, the -u flag is accepted as a synonym for -b since binary locks are used by many UUCP packages.

EXAMPLES

       The following example shows how shlock would be used within a shell script:

	   LOCK=<pathrun in inn.conf>/LOCK.send
	   trap 'rm -f ${LOCK} ; exit 1' 1 2 3 15
	   if shlock -p $$ -f ${LOCK} ; then
	       # Do appropriate work.
	   else
	       echo "Locked by `cat ${LOCK}`"
	   fi

HISTORY

       Written by Rich $alz <rsalz@uunet.uu.net> for InterNetNews after a description of HDB UUCP locking given by Peter Honeyman, and improved by
       Berend Reitsma to solve a race condition.  Converted to POD by Julien Elie.

       $Id: shlock.pod 8357 2009-02-27 17:56:00Z iulius $

INN 2.5.2							    2009-05-21								 SHLOCK(1)