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 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).

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 "=".

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