LOCKF(1) BSD General Commands Manual LOCKF(1)NAMElockf — execute a command while holding a file lock
SYNOPSISlockf [-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.
SEE ALSOflock(2), sysexits(3)HISTORY
A lockf utility first appeared in FreeBSD 2.2.
John Polstra ⟨firstname.lastname@example.org⟩
BSD July 7, 1998 BSD