| 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.
HISTORY
 An flock utility appeared in NetBSD 6.1.