1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
|
: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.
.. 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.
.. _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`. With no argument, :meth:`do_help` lists all available help
topics (that is, all commands with corresponding :meth:`help_\*` methods), 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:`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.)
|
