Cat

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>

int     main(int c, char *v[])
{
  while (c == 1 && read(0, *v, 1) && write(1, *v, 1));
  while (c != 1 && *(++v) && (((*v)[0] == 45 && !(*v)[1] && !(c = 0)) ||
                    ((c = open(*v, O_RDONLY))) != -1))
    while ((read(c, *v, 1) && write(1, *v, 1)) || (c && close(c) && 0));
  return (0);
}