lckdo(1)lckdo(1)NAME
lckdo - run a program with a lock held
SYNOPSIS
lckdo [options] {lockfile} {program} [arguments]
DESCRIPTION
lckdo runs a program with a lock held, in order to prevent multiple processes from running in parallel. Use just like nice or nohup.
Now that util-linux contains a similar command named flock, lckdo is deprecated, and will be removed from some future version of moreutils.
OPTIONS -w If the lock is already held by another process, wait for it to complete instead of failing immediately.
-W {sec}
The same as -w but wait not more than sec seconds.
-e Execute the program directly without forking and waiting (keeps an extra file descriptor open).
-E {nnn}
Set the file descriptor number to keep open when exec()ing (implies -e).
-n Do not create the lock file if it does not exist.
-q Produce no output if lock is already held.
-s Lock in shared (read) mode.
-x Lock in exclusive (write) mode (default).
-t Test for lock existence.
EXIT STATUS
If the lock was successfully acquired, the return value is that of the program invoked by lckdo. If the lock couldn't be acquired, EX_TEMP-
FAIL is returned. If there was a problem opening/creating or locking the lock file, EX_CANTCREAT or EX_OSERR will be returned.
AUTHOR
Michael Tokarev
2007-08-15 lckdo(1)
Check Out this Related Man Page
LOCKF(1) BSD General Commands Manual LOCKF(1)NAME
lockf -- execute a command while holding a file lock
SYNOPSIS
lockf [-kns] [-t seconds] file command [arguments]
DESCRIPTION
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 command completes.
-s Causes lockf to operate silently. Failure to acquire the lock is indicated only in the exit status.
-n Causes lockf to fail if the specified lock file does not exist. If -n is not specified, lockf will create file if necessary.
-t seconds Specifies a timeout for waiting for the lock. By default, lockf waits indefinitely to acquire the lock. If a timeout is speci-
fied 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 process.
EX_CANTCREAT The lockf utility was unable to create the lock file, e.g., because of insufficient access privileges.
EX_UNAVAILABLE
The -n option is specified and the specified lock file does not exist.
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 signaled or stopped.
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