.\"	$NetBSD: flock.1,v 1.10 2014/08/18 09:45:52 christos Exp $
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.\" This code is derived from software contributed to The NetBSD Foundation
.\" by Christos Zoulas.
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.Dd August 18, 2014
.Dt FLOCK 1
.Os
.Sh NAME
.Nm flock
.Nd Provide locking API for shell scripts
.Sh SYNOPSIS
.Nm
.Op Fl dnosvx
.Op Fl w Ar timeout
.Ar lockfile|lockdir
.Op Fl c Ar command
|
.Op Ar command ...
.Nm
.Op Fl dnsuvx
.Op Fl w Ar timeout
.Ar lockfd
.Sh DESCRIPTION
The
.Nm
utility provides
.Xr 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.
.Pp
The second form can use an arbitrary file descriptor that is provided from a
shell script for example:
.Bd -literal
(
	flock -s 100
	# commands to be executed under the lock
) 100> /path/to/lockfile
.Ed
.Pp
The following options are available:
.Bl -tag -width "XXXXXXXXXXXXXXXXX"
.It Fl c Ar command
Pass a command to a the shell.
.It Fl d , Fl Fl debug
Provide debugging output.
.It Fl n , Fl Fl nb , Fl Fl nonblock
Don't block and fail immediately if the lock could not be obtained.
.It Fl o , Fl Fl close
Close the file before executing the command.
This is useful if the child forks and should not be holding the lock.
.It Fl s , Fl Fl shared
Obtain a shared lock.
.It Fl u , Fl Fl unlock
Unlock an existing lock.
This is available only for a file descriptor.
.It Fl v , Fl Fl verbose
On error print an explanation of the failure.
.It Fl w , Fl Fl wait , Fl Fl timeout Ar seconds
Fail if the lock could not be obtained after
.Ar seconds .
.It Fl x , Fl Fl exclusive
Obtain an exclusive lock.
This is the default.
.El
.Sh EXIT STATUS
.Ex -std
.Sh SEE ALSO
.Xr shlock 1 ,
.Xr flock 2
.Sh HISTORY
An
.Nm
utility appeared in
.Nx 6.1 .