C: GetFileExt

/* Return a string pointer to a filename's extension */
char* GetFileExt(char* fileName)
{
    /* Initialize return pointer
    (will contain address of the filename string's extension,
    at the location of the '.' character) */
    char* extPtr = NULL;

    do
    {
        /* If current position of the filename string is the '.' character,
        update return pointer */
        if (*fileName == '.')
        {
            extPtr = fileName;
        }

    /* Continue until we reach the end of the filename string
    (accounts for '.'s appearing in filenames before the extension) */
    } while (*fileName++ != '\0');

    /* Return */
    return extPtr;
}