5.10.1 Cmd Objects

A Cmd instance has the following methods:

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 intro class member).

If the readline module is loaded, input will automatically inherit bash-like history-list editing (e.g. Ctrl-P scrolls back to the last command, Ctrl-N forward to the next one, Ctrl-F moves the cursor to the right non-destructively, Ctrl-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 containing only the character "?" is dispatched to the method do_help(). As another special case, a line containing only the character "!" is dispatched to the method do_shell (if such a method is defined).

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.

onecmd (str)

Interpret the argument as though it had been typed in in response to the prompt.

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.

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.

precmd ()

Hook method executed just before the input prompt is issued. This method is a stub in Cmd; it exists to be overridden by subclasses.

postcmd ()

Hook method executed just after a command dispatch is finished. This method is a stub in Cmd; it exists to be overridden by subclasses.

preloop ()

Hook method executed once when cmdloop() is called. This method is a stub in Cmd; it exists to be overridden by subclasses.

postloop ()

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 "=".