/*
 * Program to read integers from a file, double them, and write the
 * results to a file.  Names of files are supplied as command-line 
 * arguments.  (Yes, it's silly, but it's an example of using fscanf
 * and fprintf.)
 */
#include <stdio.h>
#include <string.h>

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

	int num;
	FILE *infile;
	FILE *outfile;

	if (argc < 3) {
		fprintf(stderr, "usage:  %s infile outfile\n", argv[0]);
		return 1;
	}

	infile = fopen(argv[1], "r");
	if (infile == NULL) {
		fprintf(stderr, "unable to open input file %s\n", argv[1]);
		return 1;
	}

	outfile = fopen(argv[2], "w");
	if (outfile == NULL) {
		fprintf(stderr, "unable to open output file %s\n", argv[2]);
		return 1;
	}

	while ( (fscanf(infile, "%d", &num)) == 1 ) {
        fprintf(outfile, "%d\n", 2*num);
	}
    /* TODO:
       should check here to see that we stopped at EOF rather than because of
       an error 
     */
	fclose(infile);
	fclose(outfile);

	return 0;
}