LOCKF(1)		  BSD General Commands Manual		      LOCKF(1)

NAME
     lockf -- execute a command while holding a file lock

SYNOPSIS
     lockf [-ks] [-t seconds] file command [arguments]

DESCRIPTION
     The lockf utility acquires an exclusive lock on a file, creating it if
     necessary, and removing the file on exit unless explicitly told not to.
     While holding the lock, it executes a command with optional arguments.
     After the command completes, lockf releases the lock, and removes the
     file unless the -k option is specified.  BSD-style locking is used, as
     described in flock(2); the mere existence of the file is not considered
     to constitute a lock.

     If the lockf utility is being used to facilitate concurrency between a
     number of processes, it is recommended that the -k option be used.  This
     will guarantee lock ordering, as well as implement a performance enhanced
     algorithm which minimizes CPU load associated with concurrent unlink,
     drop and re-acquire activity.  It should be noted that if the -k option
     is not used, then no guarantees around lock ordering can be made.

     The following options are supported:

     -k 	 Causes the lock file to be kept (not removed) after the com-
		 mand completes.

     -s 	 Causes lockf to operate silently.  Failure to acquire the
		 lock is indicated only in the exit status.

     -t seconds  Specifies a timeout for waiting for the lock.	By default,
		 lockf waits indefinitely to acquire the lock.	If a timeout
		 is specified with this option, lockf will wait at most the
		 given number of seconds before giving up.  A timeout of 0 may
		 be given, in which case lockf will fail unless it can acquire
		 the lock immediately.	When a lock times out, command is not
		 executed.

     In no event will lockf break a lock that is held by another process.

EXIT STATUS
     If lockf successfully acquires the lock, it returns the exit status pro-
     duced by command.	Otherwise, it returns one of the exit codes defined in
     sysexits(3), as follows:

     EX_TEMPFAIL   The specified lock file was already locked by another
		   process.

     EX_CANTCREAT  The lockf utility was unable to create the lock file, e.g.,
		   because of insufficient access privileges.

     EX_USAGE	   There was an error on the lockf command line.

     EX_OSERR	   A system call (e.g., fork(2)) failed unexpectedly.

     EX_SOFTWARE   The command did not exit normally, but may have been sig-
		   naled or stopped.

SEE ALSO
     flock(2), sysexits(3)

HISTORY
     A lockf utility first appeared in FreeBSD 2.2.

AUTHORS
     John Polstra 

BSD				 July 7, 1998				   BSD