A program that takes an error number and outputs the correct error message that matches it.

err_message.c

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

#define ONE_ARG 2
#define DECIMAL 10

typedef enum { FALSE, TRUE } BOOLEAN;

BOOLEAN str_to_int(const char input[], int * output)
{
        char * end;
        long lresult;

        /* extract the number */
        lresult = strtol(input, &end, DECIMAL);
        /* was there non-numeric data ? */
        if(*end)
        {
                fprintf(stderr, "Error: non-numeric data entered.\n");
                return FALSE;
        }
        /* is the value outside the range of an int */
        if(lresult < INT_MIN || lresult > INT_MAX)
        {
                fprintf(stderr, "Error: the number was outside the valid"
                                " range for an int.\n");
                return FALSE;
        }
        *output = lresult;
        return TRUE;
}

int main(int argc, char ** argv)
{
        int err_code;
        /* check that there is only one argument */
        if(argc != ONE_ARG)
        {
                fprintf(stderr, "Error: please provide a single number "
                                "to get an error message for.\n");
                return EXIT_FAILURE;
        }
        /* extract the number from argv[1] */
        if(!str_to_int(argv[1], &err_code))
        {
                return EXIT_FAILURE;
        }
        /* output the error message */
        printf("%s\n", strerror(err_code));
        return EXIT_SUCCESS;
}