NAME

flock — Provide locking API for shell scripts

SYNOPSIS

flock

[-dnosvx] [-w timeout] lockfile|lockdir [-c command] | [command ...]

flock

[-dnsuvx] [-w timeout] lockfd

DESCRIPTION

The flock utility provides flock(2) access to the command line or scripts. The first form locks a file or directory while the command provided is executed. If the file or directory does not exist, then a file is created.

The second form can use an arbitrary file descriptor 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.

EXIT STATUS

The flock utility exits 0 on success, and >0 if an error occurs.

SEE ALSO

shlock(1), flock(2)

HISTORY

An flock utility appeared in NetBSD 6.1.