src/misc/lockf.c

   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 }