text: #include <fcntl.h>
  #include <stdio.h>
  #include <stdlib.h>
  #include <unistd.h>
  
  const char *test_file = "/tmp/test_segment_lock";
  
  int main() {
    int file_desc;
    int byte_count;
    char *byte_to_write = "A";
    struct flock region_1;
    struct flock region_2;
    int res;
  
    file_desc = open(test_file, O_RDWR | O_CREAT, 0666);
    if (!file_desc) {
      fprintf(stderr, "Unable to open %s for read/write\n", test_file);
      exit(EXIT_FAILURE);
    }
  
    for (byte_count = 0; byte_count < 100; byte_count++) {
      (void)write(file_desc, byte_to_write, 1);
    }
  
    region_1.l_type = F_RDLCK;
    region_1.l_whence = SEEK_SET;
    region_1.l_start = 10;
    region_1.l_len = 20;
  
    region_2.l_type = F_WRLCK;
    region_2.l_whence = SEEK_SET;
    region_2.l_start = 40;
    region_2.l_len = 10;
  
    printf("Process %d is locking file\n", getpid());
  
    res = fcntl(file_desc, F_SETLK, &region_1);
    if (res == -1)
      fprintf(stderr, "Failed to lock region 1\n");
  
    res = fcntl(file_desc, F_SETLK, &region_2);
    if (res == -1)
      fprintf(stderr, "Failed to lock region 2\n");
  
    sleep(60);
  
    printf("Process %d is closing file\n", getpid());
    close(file_desc);
  
    return 0;
  }
  