Update.
[glibc.git] / io / lockf.c
blob7bf90c9b5935295cb77850525d159cd88f4e3372
1 /* Copyright (C) 1994, 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 #include <sys/types.h>
20 #include <unistd.h>
21 #include <fcntl.h>
22 #include <errno.h>
23 #include <string.h>
25 /* lockf is a simplified interface to fcntl's locking facilities. */
27 int
28 lockf (int fd, int cmd, off_t len)
30 struct flock fl;
32 memset ((char *) &fl, '\0', sizeof (fl));
34 switch (cmd)
36 case F_TEST:
37 /* Test the lock: return 0 if FD is unlocked or locked by this process;
38 return -1, set errno to EACCES, if another process holds the lock. */
39 if (fcntl (fd, F_GETLK, &fl) < 0)
40 return -1;
41 if (fl.l_type == F_UNLCK || fl.l_pid == getpid ())
42 return 0;
43 __set_errno (EACCES);
44 return -1;
46 case F_ULOCK:
47 fl.l_type = F_UNLCK;
48 cmd = F_SETLK;
49 break;
50 case F_LOCK:
51 fl.l_type = F_WRLCK;
52 cmd = F_SETLKW;
53 break;
54 case F_TLOCK:
55 fl.l_type = F_WRLCK;
56 cmd = F_SETLK;
57 break;
59 default:
60 __set_errno (EINVAL);
61 return -1;
64 /* lockf is always relative to the current file position. */
65 fl.l_whence = SEEK_CUR;
66 fl.l_start = 0;
68 fl.l_len = len;
70 return fcntl (fd, cmd, &fl);