FLOCK(1) | General Commands Manual | FLOCK(1)

# 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.

August 18, 2014 | NetBSD 8.1