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:
-k Causes the lock file to be kept (not removed) after the command
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.
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:
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) failed unexpectedly.
flock(2), sysexits(3)
A lockf utility first appeared in FreeBSD 2.2.
John Polstra <jdp@polstra.com>.
FreeBSD 5.2.1 July 7, 1998 FreeBSD 5.2.1 [ Back ] |
