1.\"- 2.\" Copyright (c) 2007 Dag-Erling Co�dan Sm�rgrav 3.\" All rights reserved. 4.\" 5.\" Redistribution and use in source and binary forms, with or without 6.\" modification, are permitted provided that the following conditions 7.\" are met: 8.\" 1. Redistributions of source code must retain the above copyright 9.\" notice, this list of conditions and the following disclaimer. 10.\" 2. Redistributions in binary form must reproduce the above copyright 11.\" notice, this list of conditions and the following disclaimer in the 12.\" documentation and/or other materials provided with the distribution. 13.\" 14.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 15.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 16.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 17.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 18.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 19.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 20.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 21.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 22.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 23.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 24.\" SUCH DAMAGE. 25.\" 26.\" $FreeBSD$ 27.\" 28.Dd May 10, 2007 29.Dt FLOPEN 3 30.Os 31.Sh NAME 32.Nm flopen 33.Nd "Reliably open and lock a file" 34.Sh LIBRARY 35.Lb libutil 36.Sh SYNOPSIS 37.In sys/fcntl.h 38.In libutil.h 39.Ft int 40.Fn flopen "const char *path" "int flags" 41.Ft int 42.Fn flopen "const char *path" "int flags" "mode_t mode" 43.Sh DESCRIPTION 44The 45.Fn flopen 46function opens or creates a file and acquires an exclusive lock on it. 47It is essentially equivalent with calling 48.Fn open 49with the same parameters followed by an 50.Fn fcntl 51.Dv F_SETLK 52or 53.Dv F_SETLKW 54operation with lock type 55.Dv F_WRLCK , 56except that 57.Fn flopen 58will attempt to detect and handle races that may occur between opening 59/ creating the file and locking it. 60Thus, it is well suited for opening lock files, PID files, spool 61files, mailboxes and other kinds of files which are used for 62synchronization between processes. 63.Pp 64If 65.Va flags 66includes 67.Dv O_NONBLOCK 68and the file is already locked, 69.Fn flopen 70will fail and set 71.Va errno 72to 73.Dv EWOULDBLOCK . 74.Pp 75As with 76.Fn open , 77the additional 78.Va mode 79argument is required if 80.Va flags 81includes 82.Dv O_CREAT . 83.Sh RETURN VALUES 84If successful, 85.Fn flopen 86returns a valid file descriptor. 87Otherwise, it returns -1, and sets 88.Va errno 89as described in 90.Xr fcntl 2 91and 92.Xr open 2 . 93.Sh SEE ALSO 94.Xr errno 2 , 95.Xr fcntl 2 , 96.Xr open 2 97.Sh HISTORY 98The 99.Fn flopen 100function first appeared in 101.Fx 6.3 . 102.Sh AUTHORS 103.An -nosplit 104The 105.Nm 106function and this manual page were written by 107.An Dag-Erling Sm\(/orgrav Aq des@FreeBSD.org . 108