fcntl.c

   1 #define _FILE_OFFSET_BITS 64
   2 #include <stdio.h>
   3 #include <fcntl.h>
   4 #include <sys/types.h>
   5 #include <sys/wait.h>
   6
   7 int main(void)
   8 {
   9         struct flock lock;
  10         int status;
  11         int fd = open("conftest.dat", O_CREAT|O_RDWR, 0600);
  12         lock.l_type = F_WRLCK;
  13         lock.l_whence = SEEK_SET;
  14         lock.l_start = 0;
  15         lock.l_len = 1;
  16         lock.l_pid = 0;
  17
  18         fcntl(fd,F_SETLK,&lock);
  19         if (fork() == 0) {
  20                 lock.l_start = 1;
  21                 exit(fcntl(fd,F_SETLK,&lock) != 0);
  22         }
  23         wait(&status);
  24         unlink("conftest.dat");
  25         if (WEXITSTATUS(status)) {
  26                 perror("lock");
  27                 exit(1);
  28         } else {
  29                 printf("OK\n");
  30         }
  31         exit(WEXITSTATUS(status));
  32 }