books/apue/buf-prov.c

   1 /*
   2  * This program proves the behaivor of  buffered, line-buffered
   3  * and unbufferd I/O. Read the comments to understand it.
   4  */
   5
   6 #include <stdio.h>
   7 #include <unistd.h>
   8 #include <stdlib.h>
   9
  10 int main(void)
  11 {
  12         char c;
  13         FILE *file;
  14
  15         /*
  16          * stdout is line-buffered, it means the that data is flushed
  17          * when a new-line char is found. So, you should see the line
  18          * bellow.
  19          */
  20         fprintf(stdout, "stdout is line-buffered\n");
  21
  22         /* ... and you shouldn't see the next line */
  23         fprintf(stdout, "--- The hidden line ---");
  24
  25         /* stderr is unbuffered, you will see the line */
  26         fprintf(stderr, "this is stderr in action");
  27
  28         /*
  29          * opens a file and write-data in it. When we call pause()
  30          * you'll see that nothing was written to the file.
  31          */
  32         file = fopen("./buf_test.txt", "w+");
  33         if (file) {
  34                 fprintf(file, "File contents\nFully buffered\n");
  35         } else {
  36                 perror("fopen()");
  37                 exit(1);
  38         }
  39
  40         read(0, &c, 1);
  41         return 0;
  42 }