214 lines
8.2 KiB
ReStructuredText
214 lines
8.2 KiB
ReStructuredText
|
|
:mod:`cmd` --- Support for line-oriented command interpreters
|
|
=============================================================
|
|
|
|
.. module:: cmd
|
|
:synopsis: Build line-oriented command interpreters.
|
|
.. sectionauthor:: Eric S. Raymond <esr@snark.thyrsus.com>
|
|
|
|
|
|
The :class:`Cmd` class provides a simple framework for writing line-oriented
|
|
command interpreters. These are often useful for test harnesses, administrative
|
|
tools, and prototypes that will later be wrapped in a more sophisticated
|
|
interface.
|
|
|
|
.. seealso::
|
|
|
|
Latest version of the `cmd module Python source code
|
|
<http://svn.python.org/view/python/branches/release27-maint/Lib/cmd.py?view=markup>`_
|
|
|
|
.. class:: Cmd([completekey[, stdin[, stdout]]])
|
|
|
|
A :class:`Cmd` instance or subclass instance is a line-oriented interpreter
|
|
framework. There is no good reason to instantiate :class:`Cmd` itself; rather,
|
|
it's useful as a superclass of an interpreter class you define yourself in order
|
|
to inherit :class:`Cmd`'s methods and encapsulate action methods.
|
|
|
|
The optional argument *completekey* is the :mod:`readline` name of a completion
|
|
key; it defaults to :kbd:`Tab`. If *completekey* is not :const:`None` and
|
|
:mod:`readline` is available, command completion is done automatically.
|
|
|
|
The optional arguments *stdin* and *stdout* specify the input and output file
|
|
objects that the Cmd instance or subclass instance will use for input and
|
|
output. If not specified, they will default to :data:`sys.stdin` and
|
|
:data:`sys.stdout`.
|
|
|
|
If you want a given *stdin* to be used, make sure to set the instance's
|
|
:attr:`use_rawinput` attribute to ``False``, otherwise *stdin* will be
|
|
ignored.
|
|
|
|
.. versionchanged:: 2.3
|
|
The *stdin* and *stdout* parameters were added.
|
|
|
|
|
|
.. _cmd-objects:
|
|
|
|
Cmd Objects
|
|
-----------
|
|
|
|
A :class:`Cmd` instance has the following methods:
|
|
|
|
|
|
.. method:: Cmd.cmdloop([intro])
|
|
|
|
Repeatedly issue a prompt, accept input, parse an initial prefix off the
|
|
received input, and dispatch to action methods, passing them the remainder of
|
|
the line as argument.
|
|
|
|
The optional argument is a banner or intro string to be issued before the first
|
|
prompt (this overrides the :attr:`intro` class member).
|
|
|
|
If the :mod:`readline` module is loaded, input will automatically inherit
|
|
:program:`bash`\ -like history-list editing (e.g. :kbd:`Control-P` scrolls back
|
|
to the last command, :kbd:`Control-N` forward to the next one, :kbd:`Control-F`
|
|
moves the cursor to the right non-destructively, :kbd:`Control-B` moves the
|
|
cursor to the left non-destructively, etc.).
|
|
|
|
An end-of-file on input is passed back as the string ``'EOF'``.
|
|
|
|
An interpreter instance will recognize a command name ``foo`` if and only if it
|
|
has a method :meth:`do_foo`. As a special case, a line beginning with the
|
|
character ``'?'`` is dispatched to the method :meth:`do_help`. As another
|
|
special case, a line beginning with the character ``'!'`` is dispatched to the
|
|
method :meth:`do_shell` (if such a method is defined).
|
|
|
|
This method will return when the :meth:`postcmd` method returns a true value.
|
|
The *stop* argument to :meth:`postcmd` is the return value from the command's
|
|
corresponding :meth:`do_\*` method.
|
|
|
|
If completion is enabled, completing commands will be done automatically, and
|
|
completing of commands args is done by calling :meth:`complete_foo` with
|
|
arguments *text*, *line*, *begidx*, and *endidx*. *text* is the string prefix
|
|
we are attempting to match: all returned matches must begin with it. *line* is
|
|
the current input line with leading whitespace removed, *begidx* and *endidx*
|
|
are the beginning and ending indexes of the prefix text, which could be used to
|
|
provide different completion depending upon which position the argument is in.
|
|
|
|
All subclasses of :class:`Cmd` inherit a predefined :meth:`do_help`. This
|
|
method, called with an argument ``'bar'``, invokes the corresponding method
|
|
:meth:`help_bar`, and if that is not present, prints the docstring of
|
|
:meth:`do_bar`, if available. With no argument, :meth:`do_help` lists all
|
|
available help topics (that is, all commands with corresponding
|
|
:meth:`help_\*` methods or commands that have docstrings), and also lists any
|
|
undocumented commands.
|
|
|
|
|
|
.. method:: Cmd.onecmd(str)
|
|
|
|
Interpret the argument as though it had been typed in response to the prompt.
|
|
This may be overridden, but should not normally need to be; see the
|
|
:meth:`precmd` and :meth:`postcmd` methods for useful execution hooks. The
|
|
return value is a flag indicating whether interpretation of commands by the
|
|
interpreter should stop. If there is a :meth:`do_\*` method for the command
|
|
*str*, the return value of that method is returned, otherwise the return value
|
|
from the :meth:`default` method is returned.
|
|
|
|
|
|
.. method:: Cmd.emptyline()
|
|
|
|
Method called when an empty line is entered in response to the prompt. If this
|
|
method is not overridden, it repeats the last nonempty command entered.
|
|
|
|
|
|
.. method:: Cmd.default(line)
|
|
|
|
Method called on an input line when the command prefix is not recognized. If
|
|
this method is not overridden, it prints an error message and returns.
|
|
|
|
|
|
.. method:: Cmd.completedefault(text, line, begidx, endidx)
|
|
|
|
Method called to complete an input line when no command-specific
|
|
:meth:`complete_\*` method is available. By default, it returns an empty list.
|
|
|
|
|
|
.. method:: Cmd.precmd(line)
|
|
|
|
Hook method executed just before the command line *line* is interpreted, but
|
|
after the input prompt is generated and issued. This method is a stub in
|
|
:class:`Cmd`; it exists to be overridden by subclasses. The return value is
|
|
used as the command which will be executed by the :meth:`onecmd` method; the
|
|
:meth:`precmd` implementation may re-write the command or simply return *line*
|
|
unchanged.
|
|
|
|
|
|
.. method:: Cmd.postcmd(stop, line)
|
|
|
|
Hook method executed just after a command dispatch is finished. This method is
|
|
a stub in :class:`Cmd`; it exists to be overridden by subclasses. *line* is the
|
|
command line which was executed, and *stop* is a flag which indicates whether
|
|
execution will be terminated after the call to :meth:`postcmd`; this will be the
|
|
return value of the :meth:`onecmd` method. The return value of this method will
|
|
be used as the new value for the internal flag which corresponds to *stop*;
|
|
returning false will cause interpretation to continue.
|
|
|
|
|
|
.. method:: Cmd.preloop()
|
|
|
|
Hook method executed once when :meth:`cmdloop` is called. This method is a stub
|
|
in :class:`Cmd`; it exists to be overridden by subclasses.
|
|
|
|
|
|
.. method:: Cmd.postloop()
|
|
|
|
Hook method executed once when :meth:`cmdloop` is about to return. This method
|
|
is a stub in :class:`Cmd`; it exists to be overridden by subclasses.
|
|
|
|
Instances of :class:`Cmd` subclasses have some public instance variables:
|
|
|
|
|
|
.. attribute:: Cmd.prompt
|
|
|
|
The prompt issued to solicit input.
|
|
|
|
|
|
.. attribute:: Cmd.identchars
|
|
|
|
The string of characters accepted for the command prefix.
|
|
|
|
|
|
.. attribute:: Cmd.lastcmd
|
|
|
|
The last nonempty command prefix seen.
|
|
|
|
|
|
.. attribute:: Cmd.intro
|
|
|
|
A string to issue as an intro or banner. May be overridden by giving the
|
|
:meth:`cmdloop` method an argument.
|
|
|
|
|
|
.. attribute:: Cmd.doc_header
|
|
|
|
The header to issue if the help output has a section for documented commands.
|
|
|
|
|
|
.. attribute:: Cmd.misc_header
|
|
|
|
The header to issue if the help output has a section for miscellaneous help
|
|
topics (that is, there are :meth:`help_\*` methods without corresponding
|
|
:meth:`do_\*` methods).
|
|
|
|
|
|
.. attribute:: Cmd.undoc_header
|
|
|
|
The header to issue if the help output has a section for undocumented commands
|
|
(that is, there are :meth:`do_\*` methods without corresponding :meth:`help_\*`
|
|
methods).
|
|
|
|
|
|
.. attribute:: Cmd.ruler
|
|
|
|
The character used to draw separator lines under the help-message headers. If
|
|
empty, no ruler line is drawn. It defaults to ``'='``.
|
|
|
|
|
|
.. attribute:: Cmd.use_rawinput
|
|
|
|
A flag, defaulting to true. If true, :meth:`cmdloop` uses :func:`raw_input` to
|
|
display a prompt and read the next command; if false, :meth:`sys.stdout.write`
|
|
and :meth:`sys.stdin.readline` are used. (This means that by importing
|
|
:mod:`readline`, on systems that support it, the interpreter will automatically
|
|
support :program:`Emacs`\ -like line editing and command-history keystrokes.)
|
|
|