books/apue/buf-files.c

   1 /*
   2  * Print buffering for various standard I/O streams
   3  */
   4
   5 #include <stdio.h>
   6 #include <stdlib.h>
   7
   8 void pr_stdio(const char *name, FILE *fp)
   9 {
  10         printf("stream = %s, ", name);
  11
  12         if (fp->_flags & _IONBF)
  13                 printf("unbuffered");
  14         else if (fp->_flags & _IOLBF)
  15                 printf("line buffered");
  16         else
  17                 printf("fully buffered");
  18
  19         printf("\n");
  20 }
  21
  22 int main(void)
  23 {
  24         FILE *fp;
  25
  26         fputs("enter any character\n", stdout);
  27         if (getchar() == EOF) {
  28                 perror("getchar()");
  29                 exit(1);
  30         }
  31         fputs("one line to standard error\n", stderr);
  32
  33         pr_stdio("stdin", stdin);
  34         pr_stdio("stdout", stdout);
  35         pr_stdio("stderr", stderr);
  36
  37         if ((fp = fopen("/etc/passwd", "r")) == NULL) {
  38                 fprintf(stderr, "fopen() error");
  39                 exit(1);
  40         }
  41         if (getc(fp) == EOF) {
  42                 fprintf(stderr, "getc() error");
  43                 exit(1);
  44         }
  45
  46         pr_stdio("/etc/passwd", fp);
  47         fclose(fp);
  48
  49         return 0;
  50 }