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, 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-
-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
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 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
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.
A lockf utility first appeared in FreeBSD 2.2.
BSD July 7, 1998 BSD