1 /* Copyright (C) 1994, 1996, 1997, 1998, 2000 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
3
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.
8
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.
13
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 see <http://www.gnu.org/licenses/>. */
17
18 #include <features.h>
19 #include <sys/types.h>
20 #include <fcntl.h>
21 #include <unistd.h>
22 #include <errno.h>
23 #include <string.h>
24
25 /* lockf is a simplified interface to fcntl's locking facilities. */
26
lockf(int fd,int cmd,off_t len)27 int lockf (int fd, int cmd, off_t len)
28 {
29 struct flock fl;
30
31 memset ((char *) &fl, '\0', sizeof (fl));
32
33 /* lockf is always relative to the current file position. */
34 fl.l_whence = SEEK_CUR;
35 fl.l_start = 0;
36 fl.l_len = len;
37
38 switch (cmd)
39 {
40 case F_TEST:
41 /* Test the lock: return 0 if FD is unlocked or locked by this process;
42 return -1, set errno to EACCES, if another process holds the lock. */
43 fl.l_type = F_RDLCK;
44 if (fcntl (fd, F_GETLK, &fl) < 0)
45 return -1;
46 if (fl.l_type == F_UNLCK || fl.l_pid == getpid ())
47 return 0;
48 __set_errno(EACCES);
49 return -1;
50
51 case F_ULOCK:
52 fl.l_type = F_UNLCK;
53 cmd = F_SETLK;
54 break;
55 case F_LOCK:
56 fl.l_type = F_WRLCK;
57 cmd = F_SETLKW;
58 break;
59 case F_TLOCK:
60 fl.l_type = F_WRLCK;
61 cmd = F_SETLK;
62 break;
63
64 default:
65 __set_errno(EINVAL);
66 return -1;
67 }
68
69 return fcntl(fd, cmd, &fl);
70 }
71 libc_hidden_def(lockf)
72