lockf(1)

NAME

lockf - execute a command while holding a file lock

SYNOPSIS

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

DESCRIPTION

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

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 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
executed.

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

process.

EXIT STATUS

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

cess.

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

ly.

SEE ALSO

flock(2), sysexits(3)

HISTORY

A lockf utility first appeared in FreeBSD 2.2.

AUTHORS

John Polstra <jdp@polstra.com>.

BSD July 7, 1998

BSD