def complete(text, state):
    """On tab press, return the next possible completion"""
    global completion_results
    if state == 0:
        line = readline.get_line_buffer()
        if line.startswith(':'):
            # Control command completion
            completion_results = complete_control_command(line, text)
        else:
            if line.startswith('!') and text and line.startswith(text):
                dropped_exclam = True
                text = text[1:]
            else:
                dropped_exclam = False
            completion_results = []
            # Complete local paths
            completion_results += complete_local_path(text)
            # Complete from history
            l = len(text)
            completion_results += [w + ' ' for w in history_words if
                                   len(w) > l and w.startswith(text)]
            if readline.get_begidx() == 0:
                # Completing first word from $PATH
                completion_results += [w + ' ' for w in user_commands_in_path
                                           if len(w) > l and w.startswith(text)]
            completion_results = remove_dupes(completion_results)
            if dropped_exclam:
                completion_results = ['!' + r for r in completion_results]

    if state < len(completion_results):
        return completion_results[state]
    completion_results = None
    return None
On tab press, return the next possible completion