Features requiring application changes

Multiline commands

Command input may span multiple lines for the commands whose names are listed in the parameter app.multilineCommands. These commands will be executed only after the user has entered a terminator. By default, the command terminators is ;; replacing or appending to the list app.terminators allows different terminators. A blank line is always considered a command terminator (cannot be overridden).

Parsed statements

cmd2 passes arg to a do_ method (or default) as a ParsedString, a subclass of string that includes an attribute parsed. parsed is a pyparsing.ParseResults object produced by applying a pyparsing grammar applied to arg. It may include:

Name of the command called
Full input exactly as typed.
Character used to end a multiline command
Remnant of input after terminator
def do_parsereport(self, arg):
    self.stdout.write(arg.parsed.dump() + '\n')
(Cmd) parsereport A B /* C */ D; E
['parsereport', 'A B  D', ';', 'E']
- args: A B  D
- command: parsereport
- raw: parsereport A B /* C */ D; E
- statement: ['parsereport', 'A B  D', ';']
    - args: A B  D
    - command: parsereport
    - terminator: ;
- suffix: E
- terminator: ;

If parsed does not contain an attribute, querying for it will return None. (This is a characteristic of pyparsing.ParseResults.)

The parsing grammar and process currently employed by cmd2 is stable, but is likely significantly more complex than it needs to be. Future cmd2 releases may change it somewhat (hopefully reducing complexity).

(Getting arg as a ParsedString is technically “free”, in that it requires no application changes from the cmd standard, but there will be no result unless you change your application to use arg.parsed.)

Environment parameters

Your application can define user-settable parameters which your code can reference. Create them as class attributes with their default values, and add them (with optional documentation) to settable.

from cmd2 import Cmd
class App(Cmd):
    degrees_c = 22
    sunny = False
    settable = Cmd.settable + '''degrees_c temperature in Celsius
    def do_sunbathe(self, arg):
        if self.degrees_c < 20:
            result = "It's {temp} C - are you a penguin?".format(temp=self.degrees_c)
        elif not self.sunny:
            result = 'Too dim.'
            result = 'UV is bad for your skin.'
        self.stdout.write(result + '\n')
app = App()
(Cmd) set --long
degrees_c: 22                  # temperature in Celsius
sunny: False                   #
(Cmd) sunbathe
Too dim.
(Cmd) set sunny yes
sunny - was: False
now: True
(Cmd) sunbathe
UV is bad for your skin.
(Cmd) set degrees_c 13
degrees_c - was: 22
now: 13
(Cmd) sunbathe
It's 13 C - are you a penguin?

Commands with flags

All do_ methods are responsible for interpreting the arguments passed to them. However, cmd2 lets a do_ methods accept Unix-style flags. It uses optparse to parse the flags, and they work the same way as for that module.

Flags are defined with the options decorator, which is passed a list of optparse-style options, each created with make_option. The method should accept a second argument, opts, in addition to args; the flags will be stripped from args.

@options([make_option('-p', '--piglatin', action="store_true", help="atinLay"),
    make_option('-s', '--shout', action="store_true", help="N00B EMULATION MODE"),
    make_option('-r', '--repeat', type="int", help="output [n] times")
def do_speak(self, arg, opts=None):
    """Repeats what you tell me to."""
    arg = ''.join(arg)
    if opts.piglatin:
        arg = '%s%say' % (arg[1:].rstrip(), arg[0])
    if opts.shout:
        arg = arg.upper()
    repetitions = opts.repeat or 1
    for i in range(min(repetitions, self.maxrepeats)):
(Cmd) say goodnight, gracie
goodnight, gracie
(Cmd) say -sp goodnight, gracie
(Cmd) say -r 2 --shout goodnight, gracie

options takes an optional additional argument, arg_desc. If present, arg_desc will appear in place of arg in the option’s online help.

@options([make_option('-t', '--train', action='store_true', help='by train')],
         arg_desc='(from city) (to city)')
def do_travel(self, arg, opts=None):
    'Gets you from (from city) to (to city).'
(Cmd) help travel
Gets you from (from city) to (to city).
Usage: travel [options] (from-city) (to-city)

  -h, --help   show this help message and exit
  -t, --train  by train

Controlling how arguments are parsed for commands with flags

There are three functions which can globally effect how arguments are parsed for commands with flags:


Allows user of cmd2 to choose between POSIX and non-POSIX splitting of args for @options commands.

Parameters:val – bool - True => POSIX, False => Non-POSIX

Allows user of cmd2 to choose whether to automatically strip outer-quotes when POSIX_SHLEX is False.

Parameters:val – bool - True => strip quotes on args and option args for @option commands if POSIX_SHLEX is False.

Allows user of cmd2 to choose between passing @options commands an argument string or list of arg strings.

Parameters:val – bool - True => arg is a list of strings, False => arg is a string (for @options commands)


Since optparse has been deprecated since Python 3.2, the cmd2 developers plan to replace optparse with argparse at some point in the future. We will endeavor to keep the API as identical as possible when this change occurs.

poutput, pfeedback, perror

Standard cmd applications produce their output with self.stdout.write('output') (or with print, but print decreases output flexibility). cmd2 applications can use self.poutput('output'), self.pfeedback('message'), and self.perror('errmsg') instead. These methods have these advantages:

  • More concise
    • .pfeedback() destination is controlled by quiet parameter.


Text output can be colored by wrapping it in the colorize method.

Cmd.colorize(val, color)

Given a string (val), returns that string wrapped in UNIX-style special characters that turn on (and then off) text color and style. If the colors environment parameter is False, or the application is running on Windows, will return val unchanged. color should be one of the supported strings (or styles): red/blue/green/cyan/magenta, bold, underline


Controls whether self.pfeedback('message') output is suppressed; useful for non-essential feedback that the user may not always want to read. quiet is only relevant if app.pfeedback is sometimes used.


Presents numbered options to user, as bash select.

app.select is called from within a method (not by the user directly; it is app.select, not app.do_select).

Cmd.select(opts, prompt='Your choice? ')

Presents a numbered menu to the user. Modelled after the bash shell’s SELECT. Returns the item chosen.

Argument opts can be:

a single string -> will be split into one-word options
a list of strings -> will be offered as options
a list of tuples -> interpreted as (value, text), so that the return value can differ from the text advertised to the user
def do_eat(self, arg):
    sauce = self.select('sweet salty', 'Sauce? ')
    result = '{food} with {sauce} sauce, yum!'
    result = result.format(food=arg, sauce=sauce)
    self.stdout.write(result + '\n')
(Cmd) eat wheaties
    1. sweet
    2. salty
Sauce? 2
wheaties with salty sauce, yum!