1.\" 2.\" Copyright (C) 1998 John D. Polstra. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 13.\" THIS SOFTWARE IS PROVIDED BY JOHN D. POLSTRA AND CONTRIBUTORS ``AS IS'' AND 14.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 15.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 16.\" ARE DISCLAIMED. IN NO EVENT SHALL JOHN D. POLSTRA OR CONTRIBUTORS BE LIABLE 17.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 18.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 19.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 20.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 21.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 22.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 23.\" SUCH DAMAGE. 24.\" 25.\" $FreeBSD$ 26.\" 27.Dd July 7, 1998 28.Os 29.Dt LOCKF 1 30.Sh NAME 31.Nm lockf 32.Nd execute a command while holding a file lock 33.Sh SYNOPSIS 34.Nm 35.Op Fl ks 36.Op Fl t Ar seconds 37.Ar file 38.Ar command 39.Op Ar arguments 40.Sh DESCRIPTION 41The 42.Nm 43utility acquires an exclusive lock on a 44.Ar file , 45creating it if necessary, 46.Bf Em 47and removing the file on exit unless explicitly told not to. 48.Ef 49While holding the lock, it executes a 50.Ar command 51with optional 52.Ar arguments . 53After the 54.Ar command 55completes, 56.Nm 57releases the lock, and removes the 58.Ar file 59unless the 60.Fl k 61option is specified. 62.Bx Ns -style 63locking is used, as described in 64.Xr flock 2 ; 65the mere existence of the 66.Ar file 67is not considered to constitute a lock. 68.Pp 69The following options are supported: 70.Bl -tag -width ".Fl t Ar seconds" 71.It Fl k 72Causes the lock file to be kept (not removed) after the command 73completes. 74.It Fl s 75Causes 76.Nm 77to operate silently. 78Failure to acquire the lock is indicated only in the exit status. 79.It Fl t Ar seconds 80Specifies a timeout for waiting for the lock. 81By default, 82.Nm 83waits indefinitely to acquire the lock. 84If a timeout is specified with this option, 85.Nm 86will wait at most the given number of 87.Ar seconds 88before giving up. 89A timeout of 0 may be given, in which case 90.Nm 91will fail unless it can acquire the lock immediately. 92When a lock times out, 93.Ar command 94is 95.Em not 96executed. 97.El 98.Pp 99In no event will 100.Nm 101break a lock that is held by another process. 102.Sh EXIT STATUS 103If 104.Nm 105successfully acquires the lock, it returns the exit status produced by 106.Ar command . 107Otherwise, it returns one of the exit codes defined in 108.Xr sysexits 3 , 109as follows: 110.Bl -tag -width ".Dv EX_CANTCREAT" 111.It Dv EX_TEMPFAIL 112The specified lock file was already locked by another process. 113.It Dv EX_CANTCREAT 114The 115.Nm 116utility 117was unable to create the lock file, e.g., because of insufficient access 118privileges. 119.It Dv EX_USAGE 120There was an error on the 121.Nm 122command line. 123.It Dv EX_OSERR 124A system call (e.g., 125.Xr fork 2 ) 126failed unexpectedly. 127.El 128.Sh SEE ALSO 129.Xr flock 2 , 130.Xr sysexits 3 131.Sh HISTORY 132A 133.Nm 134utility first appeared in 135.Fx 2.2 . 136.Sh AUTHORS 137.An John Polstra Aq jdp@polstra.com 138