Cat

#include <stdio.h>
int main(int argc, const char * argv[]) {
  int c;
  if (argc > 1) {
    if (freopen(argv[1], "r", stdin) == NULL) {
      perror(argv[1]);
      return 1;
    }
  }
  while ((c = getchar()) != EOF && putchar(c))
    ;
  return 0;
}