FLOCK(1) User Commands FLOCK(1)
flock - acquire a file lock and then execute a command with the lock
flock [ --shared | --timeout=seconds ] lockfile command ..
Acquire a file lock using the flock(2) system call and then execute the
given command with the lock held. Depending on the options given, the
lock can be either exclusive or shared, and the behavior in the event
of lock contention can be specified as either waiting indefinitely for
the lock to become available (the default), or failing if the lock does
not become available after a specific time, which can be specified as
zero to make the command not wait at all.
Acquire a shared lock. Acquiring a shared lock does not stop
others from acquiring a shared lock, but it will stop others
from acquiring an exclusive lock. Conversely, acquiring an
exclusive lock (the default) stops both exclusive and shared
attempts to acquire the lock. Typically, a shared lock is used
if a command is just going to read the locked data, and an
exclusive lock is used if the command might write to it.
Abort if the lock cannot be acquired before n seconds. For a
completely non-blocking attempt to acquire a lock, specify
--timeout=0. The timer applies only to the attempt to acquire
the lock. As soon as the lock is acquired, the timeout is can-
celled. The command to be run is not subject to the timeout.
EXAMPLES (invoking some imaginary programs)
flock /etc/passwd read-and-write-to-passwd
flock --shared /etc/passwd just-read-something-from-passwd
flock --timeout=0 /sys /usr/local/bin/update-hotplug /sys
Written by Adam J. Richter
flock (util-linux) November 2004 FLOCK(1)
Man(1) output converted with