/*
 * Program to read numbers from a file and write to two files.
 *
 * Input:  text file "numbers.txt" containing integers.
 *
 * Output:  text files "odds.txt", "evens.txt" containing odd and
 *   even numbers, respectively, from "numbers.txt".
 */
#include <stdio.h>
#include <stdlib.h>

int main(void) {

	FILE * nums;
	FILE * odds;
	FILE * evens;

	int input;

	/* open input file and check result */
	nums = fopen("numbers.txt", "r");
	if (nums == NULL) {
		printf("unable to open input file\n");
		exit(1);
	}

	/* open output files and check result */
	odds = fopen("odds.txt", "w");
	evens = fopen("evens.txt", "w");
	if ((odds == NULL) || (evens == NULL)) {
		printf("unable to open output file\n");
		exit(1);
	}

	/* read numbers from input file and copy to output files */
	while (fscanf(nums, "%d", &input) == 1) {
		if ((input % 2) == 0) {
			fprintf(evens, "%d\n", input);
		}
		else {
			fprintf(odds, "%d\n", input);
		}
	}

	/* close files */
	fclose(nums);
	fclose(odds);
	fclose(evens);

	printf("Goodbye!\n");
	return 0;
}