books/apue/hole.c

   1 /*
   2  * Creates a file with a hole
   3  */
   4
   5 #include <stdio.h>
   6 #include <fcntl.h>
   7 #include <unistd.h>
   8 #include <stdlib.h>
   9 #include <sys/stat.h>
  10 #include <sys/types.h>
  11
  12 char buf1[] = "abcdefghij";
  13 char buf2[] = "ABCDEFGHIJ";
  14
  15 int main(void)
  16 {
  17         int fd;
  18
  19         if ((fd = creat("file.hole", 0666)) < 0) {
  20                 perror("creat()");
  21                 exit(1);
  22         }
  23
  24         if (write(fd, buf1, 10) != 10) {
  25                 perror("buf1 write error");
  26                 exit(1);
  27         }
  28         /* offset now == 10 */
  29
  30         if (lseek(fd, 40, SEEK_SET) == -1) {
  31                 perror("lseek()");
  32                 exit(1);
  33         }
  34         /* offset now == 40 */
  35
  36         if (write(fd, buf2, 10) != 10) {
  37                 perror("buff2 write error");
  38                 exit(1);
  39         }
  40         /* offset now == 50 */
  41
  42         return 0;
  43 }