22.1.1 Cmd Objects
A Cmd instance has the following methods:
-
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 intro class member).
If the readline module is loaded, input will automatically
inherit bash-like history-list editing (e.g. Control-P
scrolls back to the last command, Control-N forward to the next
one, Control-F moves the cursor to the right non-destructively,
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 do_foo(). As a special case,
a line beginning with the character "?" is dispatched to
the method do_help(). As another special case, a line
beginning with the character "!" is dispatched to the
method do_shell() (if such a method is defined).
This method will return when the postcmd() method returns a
true value. The stop argument to postcmd() is the
return value from the command's corresponding do_*() method.
If completion is enabled, completing commands will be done
automatically, and completing of commands args is done by calling
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 Cmd inherit a predefined do_help().
This method, called with an argument 'bar' , invokes the
corresponding method help_bar(). With no argument,
do_help() lists all available help topics (that is, all
commands with corresponding help_*() methods), and also lists
any undocumented commands.
-
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 precmd() and 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 do_*() method for the command str, the return
value of that method is returned, otherwise the return value from the
default() method is returned.
-
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 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.
completedefault( |
text, line, begidx, endidx) |
-
Method called to complete an input line when no command-specific
complete_*() method is available. By default, it returns an
empty list.
-
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 Cmd; it exists to be overridden by
subclasses. The return value is used as the command which will be
executed by the onecmd() method; the precmd()
implementation may re-write the command or simply return line
unchanged.
-
Hook method executed just after a command dispatch is finished. This
method is a stub in 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 postcmd(); this will be the
return value of the 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.
-
Hook method executed once when cmdloop() is called. This
method is a stub in Cmd; it exists to be overridden by
subclasses.
-
Hook method executed once when cmdloop() is about to return.
This method is a stub in Cmd; it exists to be overridden by
subclasses.
Instances of Cmd subclasses have some public instance variables:
- prompt
-
The prompt issued to solicit input.
- identchars
-
The string of characters accepted for the command prefix.
- lastcmd
-
The last nonempty command prefix seen.
- intro
-
A string to issue as an intro or banner. May be overridden by giving
the cmdloop() method an argument.
- doc_header
-
The header to issue if the help output has a section for documented
commands.
- misc_header
-
The header to issue if the help output has a section for miscellaneous
help topics (that is, there are help_*() methods without
corresponding do_*() methods).
- undoc_header
-
The header to issue if the help output has a section for undocumented
commands (that is, there are do_*() methods without
corresponding help_*() methods).
- ruler
-
The character used to draw separator lines under the help-message
headers. If empty, no ruler line is drawn. It defaults to
"=".
- use_rawinput
-
A flag, defaulting to true. If true, cmdloop() uses
raw_input() to display a prompt and read the next command;
if false, sys.stdout.write() and
sys.stdin.readline() are used. (This means that by
importing readline, on systems that support it, the
interpreter will automatically support Emacs-like line editing
and command-history keystrokes.)
Release 2.5.2, documentation updated on 21st February, 2008.
See About this document... for information on suggesting changes.
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