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


lockf — execute a command while holding a file lock


lockf [−ks] [−t seconds] file command [arguments]


The lockf utility acquires an exclusive lock on a file, creating it if necessary. 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.

The following options are supported:


Causes the lock file to be kept (not removed) after the command completes.


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.

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


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


The specified lock file was already locked by another process.


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


There was an error on the lockf command line.


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


flock(2), sysexits(3)


A lockf utility first appeared in FreeBSD 2.2.


John Polstra <jdp [AT]>.

BSD July 7, 1998 BSD