/**
 * Program to sum integers read from file.
 */
#include <stdio.h>
#include <stdlib.h>

int main(int argc, char* argv[]) {

    int input;
    int sum = 0;
    FILE* infile;

    if (argc < 2) {
        fprintf(stderr, "need parameter:  input filename\n");
        return EXIT_FAILURE;
    }

    infile = fopen(argv[1], "r");
    if (infile == NULL) {
        fprintf(stderr, "cannot open input file %s\n", argv[1]);
        return EXIT_FAILURE;
    }

    while(fscanf(infile, "%d", &input) == 1) {
        sum += input;
    }
    /* if fscanf did not return 1 for any reason other than EOF, error */
    if (!feof(infile)) {
        fprintf(stderr, "invalid input value\n");
        fclose(infile);
        return EXIT_FAILURE;
    }
    fclose(infile);

    printf("sum is %d\n", sum);
    return EXIT_SUCCESS;
}