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, cre
ating it if
necessary, and removing the file on exit unless explicitly
told not to.
While holding the lock, it executes a command with optional
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
to constitute a lock.
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
In no event will lockf break a lock that is held by another


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:
EX_TEMPFAIL The specified lock file was already locked by
another pro
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) failed unexpected


flock(2), sysexits(3)


A lockf utility first appeared in FreeBSD 2.2.


John Polstra <jdp@polstra.com>.
BSD July 7, 1998
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