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[glibc.git] / sysdeps / posix / flock.c
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1 /* Copyright (C) 1992, 1995, 1996, 1997 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
4 The GNU C Library is free software; you can redistribute it and/or
5 modify it under the terms of the GNU Library General Public License as
6 published by the Free Software Foundation; either version 2 of the
7 License, or (at your option) any later version.
9 The GNU C Library is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 Library General Public License for more details.
14 You should have received a copy of the GNU Library General Public
15 License along with the GNU C Library; see the file COPYING.LIB. If not,
16 write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
17 Boston, MA 02111-1307, USA. */
19 /* This file implements the `flock' function in terms of the POSIX.1 `fcntl'
20 locking mechanism. In 4BSD, these are two incompatible locking mechanisms,
21 perhaps with different semantics? */
23 #include <errno.h>
24 #include <unistd.h>
25 #include <fcntl.h>
26 #include <sys/file.h>
28 /* Apply or remove an advisory lock, according to OPERATION,
29 on the file FD refers to. */
30 int
31 __flock (fd, operation)
32 int fd;
33 int operation;
35 struct flock lbuf;
37 switch (operation & ~LOCK_NB)
39 case LOCK_SH:
40 lbuf.l_type = F_RDLCK;
41 break;
42 case LOCK_EX:
43 lbuf.l_type = F_WRLCK;
44 break;
45 case LOCK_UN:
46 lbuf.l_type = F_UNLCK;
47 break;
48 default:
49 __set_errno (EINVAL);
50 return -1;
53 lbuf.l_whence = SEEK_SET;
54 lbuf.l_start = lbuf.l_len = 0L; /* Lock the whole file. */
56 return __fcntl (fd, (operation & LOCK_NB) ? F_SETLK : F_SETLKW, &lbuf);
59 weak_alias (__flock, flock)