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d614a753 | 1 | /* Copyright (C) 1992-2020 Free Software Foundation, Inc. |
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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 | |
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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. | |
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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 | |
41bdb6e2 | 12 | Lesser General Public License for more details. |
478b92f0 | 13 | |
41bdb6e2 | 14 | You should have received a copy of the GNU Lesser General Public |
59ba27a6 | 15 | License along with the GNU C Library; if not, see |
5a82c748 | 16 | <https://www.gnu.org/licenses/>. */ |
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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 | ||
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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 | |
bd2260a2 | 30 | __flock (int fd, int operation) |
28f540f4 RM |
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: | |
c4029823 | 46 | __set_errno (EINVAL); |
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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) |