flock
—
Provide locking API for shell scripts
flock |
[-dnosvx ] [-w
timeout]
file|directory
command [args
...] |
flock |
[-dnosvx ] [-w
timeout]
file|directory
-c command |
flock |
[-dnsuvx ] [-w
timeout] number |
The flock
utility provides
flock(2) access to the command
line or scripts. The first two forms lock the specified
file or directory while the
provided command is executed. If the path does not exist, then a file of that
name is created with mode 0600.
The third form can use an arbitrary file descriptor
number that is provided from a shell script for
example:
(
flock -s 100
# commands to be executed under the lock
) 100> /path/to/lockfile
The following options are available:
-c
command
- Pass a command to a the shell.
-d
,
-
-debug
- Provide debugging output.
-n
,
-
-nb
,
-
-nonblock
- Don't block and fail immediately if the lock could not be obtained.
-o
,
-
-close
- Close the file before executing the command. This is useful if the child
forks and should not be holding the lock.
-s
,
-
-shared
- Obtain a shared lock.
-u
,
-
-unlock
- Unlock an existing lock. This is available only for a file
descriptor.
-v
,
-
-verbose
- On error print an explanation of the failure.
-w
,
-
-wait
,
-
-timeout
seconds
- Fail if the lock could not be obtained after
seconds.
-x
,
-
-exclusive
- Obtain an exclusive lock. This is the default.
The flock
utility exits 0 on success,
and >0 if an error occurs.
An flock
utility appeared in NetBSD
6.1.