1 | /* Copyright (C) 1992-2022 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 Lesser General Public |
6 | License as published by the Free Software Foundation; either |
7 | version 2.1 of the 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 | Lesser General Public License for more details. |
13 | |
14 | You should have received a copy of the GNU Lesser General Public |
15 | License along with the GNU C Library; if not, see |
16 | <https://www.gnu.org/licenses/>. */ |
17 | |
18 | /* This file implements the `flock' function in terms of the POSIX.1 `fcntl' |
19 | locking mechanism. In 4BSD, these are two incompatible locking mechanisms, |
20 | perhaps with different semantics? */ |
21 | |
22 | #include <errno.h> |
23 | #include <unistd.h> |
24 | #include <fcntl.h> |
25 | #include <sys/file.h> |
26 | |
27 | /* Apply or remove an advisory lock, according to OPERATION, |
28 | on the file FD refers to. */ |
29 | int |
30 | __flock (int fd, int operation) |
31 | { |
32 | struct flock lbuf; |
33 | |
34 | switch (operation & ~LOCK_NB) |
35 | { |
36 | case LOCK_SH: |
37 | lbuf.l_type = F_RDLCK; |
38 | break; |
39 | case LOCK_EX: |
40 | lbuf.l_type = F_WRLCK; |
41 | break; |
42 | case LOCK_UN: |
43 | lbuf.l_type = F_UNLCK; |
44 | break; |
45 | default: |
46 | __set_errno (EINVAL); |
47 | return -1; |
48 | } |
49 | |
50 | lbuf.l_whence = SEEK_SET; |
51 | lbuf.l_start = lbuf.l_len = 0L; /* Lock the whole file. */ |
52 | |
53 | return __fcntl (fd, (operation & LOCK_NB) ? F_SETLK : F_SETLKW, &lbuf); |
54 | } |
55 | |
56 | weak_alias (__flock, flock) |
57 | |