/* 
 * Simple contrived example of formatted I/O on files:
 * Read integers from input, sum, write partial sums to output file.
 * Filenames given as command-line arguments.
 */
#include <stdio.h>

int main(int argc, char *argv[]) {
	if (argc != 3) {
		printf("arguments:  infile outfile\n");
		return 1;
	}
	FILE * infile = fopen(argv[1], "r");
	if (infile == NULL) {
		printf("cannot open input\n");
		return 1;
	}
	FILE * outfile = fopen(argv[2], "w");
	if (outfile == NULL) {
		printf("cannot open output\n");
		return 1;
	}

	int n;
	int sum = 0;
	while (fscanf(infile, "%d", &n) == 1) {
		sum += n;
		fprintf(outfile, "%d\n", sum);
	}
	/* loop ends either on EOF or on bad input */
	if (!feof(infile)) {
		/* if not EOF, must be bad input */
		printf("error in input\n");
		fclose(infile);
		fclose(outfile);
		return 1;
	}
	printf("%d\n", sum);

	fclose(infile);
	fclose(outfile);
	return 0;
}