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
FLOCK(1) H. Peter Anvin FLOCK(1)NAME
flock - Manage locks from shell scripts
SYNOPSIS
flock [-sxon] [-w timeout] lockfile [-c] command...
flock [-sxon] [-w timeout] lockdir [-c] command...
flock [-sxun] [-w timeout] fd
DESCRIPTION
This utility manages flock(2) locks from within shell scripts or the command line.
The first and second forms wraps the lock around the executing a command, in a manner similar to su(1) or newgrp(1). It locks a specified
file or directory, which is created (assuming appropriate permissions), if it does not already exist.
The third form is convenient inside shell scripts, and is usually used the following manner:
(
flock -n 9
# ... commands executed under lock ...
) 9>/var/lock/mylockfile
The mode used to open the file doesn't matter to flock; using > or >> allows the lockfile to be created if it does not already exist, how-
ever, write permission is required; using < requires that the file already exists but only read permission is required.
By default, if the lock cannot be immediately acquired, flock waits until the lock is available.
OPTIONS -s, --shared
Obtain a shared lock, sometimes called a read lock.
-x, -e, --exclusive
Obtain an exclusive lock, sometimes called a write lock. This is the default.
-u, --unlock
Drop a lock. This is usually not required, since a lock is automatically dropped when the file is closed. However, it may be
required in special cases, for example if the enclosed command group may have forked a background process which should not be hold-
ing the lock.
-n, --nb, --nonblock
Fail (with an exit code of 1) rather than wait if the lock cannot be immediately acquired.
-w, --wait, --timeout seconds
Fail (with an exit code of 1) if the lock cannot be acquired within seconds seconds. Decimal fractional values are allowed.
-o, --close
Close the file descriptor on which the lock is held before executing command. This is useful if command spawns a child process
which should not be holding the lock.
-c, --command command
Pass a single command to the shell with -c.
-h, --help
Print a help message.
AUTHOR
Written by H. Peter Anvin <hpa@zytor.com>.
COPYRIGHT
Copyright (C) 2003-2006 H. Peter Anvin.
This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICU-
LAR PURPOSE.
SEE ALSO flock(2)AVAILABILITY
The flock command is part of the util-linux package and is available from ftp://ftp.kernel.org/pub/linux/utils/util-linux/.
flock utility 4 Feb 2006 FLOCK(1)