1#include <unistd.h>
2#include <fcntl.h>
3#include <errno.h>
4
5int lockf(int fd, int op, off_t size)
6{
7 struct flock l = {
8 .l_type = F_WRLCK,
9 .l_whence = SEEK_CUR,
10 .l_len = size,
11 };
12 switch (op) {
13 case F_TEST:
14 l.l_type = F_RDLCK;
15 if (fcntl(fd, F_GETLK, &l) < 0)
16 return -1;
17 if (l.l_type == F_UNLCK || l.l_pid == getpid())
18 return 0;
19 errno = EACCES;
20 return -1;
21 case F_ULOCK:
22 l.l_type = F_UNLCK;
23 case F_TLOCK:
24 return fcntl(fd, F_SETLK, &l);
25 case F_LOCK:
26 return fcntl(fd, F_SETLKW, &l);
27 }
28 errno = EINVAL;
29 return -1;
30}