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#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
int lockf(int fd, int op, off_t size)
{
struct flock l = {
.l_type = F_WRLCK,
.l_whence = SEEK_CUR,
.l_len = size,
};
switch (op) {
case F_TEST:
l.l_type = F_RDLCK;
if (fcntl(fd, F_GETLK, &l) < 0)
return -1;
if (l.l_type == F_UNLCK || l.l_pid == getpid())
return 0;
errno = EACCES;
return -1;
case F_ULOCK:
l.l_type = F_UNLCK;
case F_TLOCK:
return fcntl(fd, F_SETLK, &l);
case F_LOCK:
return fcntl(fd, F_SETLKW, &l);
}
errno = EINVAL;
return -1;
}
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