new: _abs(), _getrelease(), _printfl(), _printfs(), _printfc(), _unprintf(), _substr()
rm : _download(), _email()

    _abs(): calculate the absolute value of a number
    _getrelease(): print debian|ubuntu release version
    _printfl(): print a line with a centered text
    _printfs(): print a line with a [+] as prefix
    _printfs(): print a line with a $ as prefix
    _unprintf(): print \b for as many as the len string
    _substr(): calculate substrings

    _download(), _email(): where too big to be functions