strtol.c

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

void
old (char *str)
{
    long num;

    num = atol (str);

    printf ("ATOL\n----\n");
    printf ("Your number is %ld\n", num);
}

void
new (char *str)
{
    long num;
    char *ptr;

    num = strtol (str, &ptr, 0);

    printf ("\nSTRTOL\n------\n");
    if (errno)
    {
        fprintf (stderr, "Error: %s\n", strerror (errno));
      	return;
    }

    printf ("Your number is %ld\n", num);
    printf ("And the end pointer was %s\n", ptr);
}

int
main (void)
{
    char *str;

    printf ("Input a string: ");
    scanf ("%ms", &str);

    old (str);
    new (str);

    return 0;
}