tests/small-cat.c

   1 // A small "cat" utility that copies stdin to stdout.
   2 // It does only one 4K read from stdin, and writes it to stdout in as few
   3 // write()s as possible.
   4 // This gives a controlled number of operations, which makes testing the
   5 // random operations more robust.
   6
   7 #include <stdio.h>  // printf(), perror()
   8 #include <unistd.h> // read(), write()
   9
  10 const size_t BUFSIZE = 4092;
  11
  12 int main(void)
  13 {
  14         char buf[BUFSIZE];
  15         ssize_t r, w, pos;
  16
  17         r = read(0, buf, BUFSIZE);
  18         if (r < 0) {
  19                 perror("Read error in small-cat");
  20                 return 1;
  21         }
  22
  23         pos = 0;
  24         while (r > 0) {
  25                 w = write(1, buf + pos, r);
  26                 if (w <= 0) {
  27                         perror("Write error in small-cat");
  28                         return 2;
  29                 }
  30
  31                 pos += w;
  32                 r -= w;
  33         }
  34
  35         return 0;
  36 }