Small command line application to translate error numbers to readable messages. You can supply multiple error numbers via command line arguments. If zero arguments are supplied, the app asks for an error number interactively.

error.c

#include <stdio.h>
#include <string.h>

void print_error(int);

int main(int argc, char *argv[])
{
	int err_num;
	if(argc > 1) {
		while(--argc > 0 && ++argv) {
			if(err_num = atoi(*argv))
				print_error(err_num);
			else
				printf("warning: '%s' is not a valid error number\n", *argv);
                }
        } else {
		printf("input error code: ");
		scanf("%d", &err_num);
		print_error(err_num);
	}
	return 0;
}

void print_error(int err_num)
{
	printf("%d: %s\n", err_num, strerror(err_num));
}