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FLOCK(1) NetBSD General Commands Manual FLOCK(1)
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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 pro-
vided 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.
Provide debugging output.
-n, --nb, --nonblock
Don't block and fail immediately if the lock could not be
Close the file before executing the command. This is useful
if the child forks and should not be holding the lock.
Obtain a shared lock.
Unlock an existing lock. This is available only for a file
On error print an explanation of the failure.
-w, --wait, --timeout seconds
Fail if the lock could not be obtained after seconds.
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.
NetBSD 9.99 October 4, 2019 NetBSD 9.99