if (output_file_name) {
output = fopen (output_file_name, "w");
if (output == NULL) {
fprintf (stderr, "Error opening %s for writing: %s\n",
output_file_name, strerror (errno));
if (output_file_name) {
output = fopen (output_file_name, "w");
if (output == NULL) {
fprintf (stderr, "Error opening %s for writing: %s\n",
output_file_name, strerror (errno));