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

int main(int argc, char *argv[])
{
    int errorNumber = -1;
    const char *message;

    if (argc > 1) {
        errorNumber = atoi(argv[1]);
    }

    errno = 0;
    message = strerror(errorNumber);

    printf("errno = %d after strerror(%d) returned ", errno, errorNumber);
    if (message == NULL) {
        printf("NULL\n");
    } else {
        printf("\"%s\"\n", message);
    }

    return EXIT_SUCCESS;
}