lockf.c raw

   1  #include <unistd.h>
   2  #include <fcntl.h>
   3  #include <errno.h>
   4  
   5  int 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  }
  31  
  32  weak_alias(lockf, lockf64);
  33