Grammar for commands found in the overall input files.

def command():
        """ Grammar for commands found in the overall input files. """
        return (
            OneOrMore(
                Word(approved_printables+' ').setResultsName('command',
                    listAllMatches=True) ^
                Grammar.__command_input_output.setResultsName('_in',
                    listAllMatches=True)
                )
            )