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flock
Langue: en
Version: 4 Feb 2006 (ubuntu - 07/07/09)
Section: 1 (Commandes utilisateur)
NAME
flock - Manage locks from shell scriptsSYNOPSIS
flock [-sxon] [-w timeout] lockfile [-c] command...flock [-sxun] [-w timeout] fd
DESCRIPTION
This utility manages flock(2) locks from within shell scripts or the command line.
The first form wraps the lock around the executing a command, in a manner similar to su(1) or newgrp(1). It locks a specified file, which is created (assuming appropriate permissions), if it does not already exist.
The second form is convenient inside shell scripts, and is usually used the following manner:
(
flock -s 200
# ... commands executed under lock ...
) 200>/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, however, 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 holding 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 hold ing 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 © 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 PARTICULAR PURPOSE.
SEE ALSO
flock(2)AVAILABILITY
The flock command is part of the util-linux-ng package and is available from ftp://ftp.kernel.org/pub/linux/utils/util-linux-ng/.Contenus ©2006-2023 Benjamin Poulain
Design ©2006-2023 Maxime Vantorre