Question 3 version 3 -- Corrected

int main(int argc, char * argv[])
{ int s, conn[2];
  if (argc != 2)
  { fprintf(stderr, "usage: %s filename\n", argv[0]);
    exit(1); }
  pipe(conn);
  int p = fork();
  if (p == 0)
  { close(2);
    dup(conn[1]);
    execlp("cc", "cc", argv[1], NULL);
    fprintf(stderr, "execlp failed\n");
    exit(1); }
  close(conn[1]);
  int r = open("errors.txt", O_WRONLY | O_CREAT | O_TRUNC, 0600);
  if (r < 0)
  { fprintf(stderr, "error creating errors.txt\n");
    exit(1); }
  char buff[1024];
  int errors = 0;
  while (1)
  { int n = read(conn[0], buff, 1024);
    if (n > 0)
      errors = 1;
    else
      break;
    write(2, buff, n);
    write(r, buff, n); }
  if (! errors)
  { printf("no errors\n");
    execl("a.out", "a.out", NULL); } }