The dirname function takes a pointer to a character string that
    contains a UNIX pathname and returns a pointer to a string that
    is a pathname of the parent directory of that file. Trailing
    slash (/)  characters in the path are not counted as part of the
    path.

    This function returns a pointer to the string "." (dot), when the
    path argument:

    o  Does not contain a slash (/).

    o  Is a NULL pointer.

    o  Points to an empty string.

    The dirname function can modify the string pointed to by the path
    argument.

    The dirname and basename functions together yield a complete
    pathname. The expression dirname(path) obtains the pathname of
    the directory where basename(path) is found.

    See also basename.