Installing¶

First you need to make sure you have Python 2.7 or Python 3.3+, pip, and setuptools. Then you can just use pip to install from PyPI.

sudo pip install <package_name>

pip install cmd2

pip install -U git+git://github.com/python-cmd2/cmd2.git

sudo apt-get install python-cmd2

sudo apt-get install python3-cmd2

Upgrading cmd2¶

Upgrade an already installed cmd2 to the latest version from PyPI:

pip install -U cmd2

This will upgrade to the newest stable version of cmd2 and will also upgrade any dependencies if necessary.

Uninstalling cmd2¶

If you wish to permanently uninstall cmd2, this can also easily be done with pip:

pip uninstall cmd2

Script files¶

Text files can serve as scripts for your cmd2-based application, with the load, save, and edit commands.

Cmd.do_load(file_path=None)¶

Runs commands in script at file or URL.

Usage: load [file_path]

Parameters:	file_path – str - a file path or URL pointing to a script (default: value stored in default_file_name)
Returns:	bool - True implies application should stop, False to continue like normal

Script should contain one command per line, just like command would be typed in console.

Cmd.do_save(arg)¶

Saves command(s) from history to file.

Usage: save [N] [file_path]

Parameters:	arg – str - [N] [filepath]

• N - Number of command (from history), or * for all commands in history (default: most recent command)
• file_path - location to save script of command(s) to (default: value stored in default_file_name)

Cmd.do_edit(arg)¶

Edit a file or command in a text editor.

Usage: edit [N]|[file_path]

Parameters:	arg – str - [N]|[file_path]

• N - Number of command (from history), or * for all commands in history (default: most recent command)
• file_path - path to a file to open in editor

The editor used is determined by the editor settable parameter. “set editor (program-name)” to change or set the EDITOR environment variable.

The optional arguments are mutually exclusive. Either a command number OR a file name can be supplied. If neither is supplied, the most recent command in the history is edited.

Edited commands are always run after the editor is closed.

Edited files are run on close if the autorun_on_edit settable parameter is True.

Comments¶

Comments are omitted from the argument list before it is passed to a do_ method. By default, both Python-style and C-style comments are recognized; you may change this by overriding app.commentGrammars with a different pyparsing grammar.

Comments can be useful in Script files, but would be pointless within an interactive session.

def do_speak(self, arg):
    self.stdout.write(arg + '\n')

(Cmd) speak it was /* not */ delicious! # Yuck!
it was  delicious!

Commands at invocation¶

You can send commands to your app as you invoke it by including them as extra arguments to the program. cmd2 interprets each argument as a separate command, so you should enclose each command in quotation marks if it is more than a one-word command.

cat@eee:~/proj/cmd2/example$ python example.py "say hello" "say Gracie" quit
hello
Gracie
cat@eee:~/proj/cmd2/example$

Output redirection¶

As in a Unix shell, output of a command can be redirected:

• sent to a file with >, as in mycommand args > filename.txt
• piped (|) as input to operating-system commands, as in mycommand args | wc
• sent to the paste buffer, ready for the next Copy operation, by ending with a bare >, as in mycommand args >.. Redirecting to paste buffer requires software to be installed on the operating system, pywin32 on Windows or xclip on *nix.

If your application depends on mathematical syntax, > may be a bad choice for redirecting output - it will prevent you from using the greater-than sign in your actual user commands. You can override your app’s value of self.redirector to use a different string for output redirection:

class MyApp(cmd2.Cmd):
    redirector = '->'

(Cmd) say line1 -> out.txt
(Cmd) say line2 ->-> out.txt
(Cmd) !cat out.txt
line1
line2

Python¶

The py command will run its arguments as a Python command. Entered without arguments, it enters an interactive Python session. That session can call “back” to your application with cmd(""). Through self, it also has access to your application instance itself which can be extremely useful for debugging. (If giving end-users this level of introspection is inappropriate, the locals_in_py parameter can be set to False and removed from the settable dictionary. See see Other user-settable parameters)

(Cmd) py print("-".join("spelling"))
s-p-e-l-l-i-n-g
(Cmd) py
Python 2.6.4 (r264:75706, Dec  7 2009, 18:45:15)
[GCC 4.4.1] on linux2
Type "help", "copyright", "credits" or "license" for more information.
(CmdLineApp)

    py <command>: Executes a Python command.
    py: Enters interactive Python mode.
    End with `Ctrl-D` (Unix) / `Ctrl-Z` (Windows), `quit()`, 'exit()`.
    Non-python commands can be issued with `cmd("your command")`.

>>> import os
>>> os.uname()
('Linux', 'eee', '2.6.31-19-generic', '#56-Ubuntu SMP Thu Jan 28 01:26:53 UTC 2010', 'i686')
>>> cmd("say --piglatin {os}".format(os=os.uname()[0]))
inuxLay
>>> self.prompt
'(Cmd) '
>>> self.prompt = 'Python was here > '
>>> quit()
Python was here >

Using the py command is tightly integrated with your main cmd2 application and any variables created or changed will persist for the life of the application:

(Cmd) py x = 5
(Cmd) py print(x)
5

IPython (optional)¶

If IPython is installed on the system and the cmd2.Cmd class is instantiated with use_ipython=True, then the optional ipy command will be present:

from cmd2 import Cmd
class App(Cmd):
    def __init__(self):
        Cmd.__init__(self, use_ipython=True)

The ipy command enters an interactive IPython session. Similar to an interactive Python session, this shell can access your application instance via self. However, the ipy shell cannot call “back” to your application with cmd("") and any changes made will not persist between sessions or back in the main application.

IPython provides many advantages, including:

• Comprehensive object introspection
• Input history, persistent across sessions
• Caching of output results during a session with automatically generated references
• Extensible tab completion, with support by default for completion of python variables and keywords

The object introspection and tab completion make IPython particularly efficient for debugging as well as for interactive experimentation and data analysis.

Searchable command history¶

All cmd-based applications have access to previous commands with the up- and down- cursor keys.

All cmd-based applications on systems with the readline module also provide bash-like history list editing.

cmd2 makes a third type of history access available, consisting of these commands:

Cmd.do_history(instance, arg)¶

history [arg]: lists past commands issued

no arg: list all

arg is integer: list one history item, by index

arg is string: string search

arg is /enclosed in forward-slashes/: regular expression search

Usage: history [options] (limit on which commands to include)

Options:

-h, --help	show this help message and exit
-s, --script	Script format; no separation lines

Cmd.do_list(arg)¶

list [arg]: lists command(s) from history in a flexible/searchable way.

Parameters:	arg – str - behavior varies as follows:

• no arg -> list most recent command
• arg is integer -> list one history item, by index
• a..b, a:b, a:, ..b -> list spans from a (or start) to b (or end)
• arg is string -> list all commands matching string search
• arg is /enclosed in forward-slashes/ -> regular expression search

Cmd.do_run(arg)¶

run [arg]: re-runs an earlier command

Parameters:	arg – str - determines which command is re-run, as follows:

• no arg -> run most recent command
• arg is integer -> run one history item, by index
• arg is string -> run most recent command by string search
• arg is /enclosed in forward-slashes/ -> run most recent by regex

Quitting the application¶

cmd2 pre-defines a quit command for you. It’s trivial, but it’s one less thing for you to remember.

Abbreviated commands¶

cmd2 apps will accept shortened command names so long as there is no ambiguity. Thus, if do_divide is defined, then divid, div, or even d will suffice, so long as there are no other commands defined beginning with divid, div, or d.

This behavior can be turned off with app.abbrev (see Other user-settable parameters)

Misc. pre-defined commands¶

Several generically useful commands are defined with automatically included do_ methods.

Cmd.do_quit(arg)¶

Exits this application.

Cmd.do_pause(text)¶

Displays the specified text then waits for the user to press <Enter>.

Usage: pause [text]

Parameters:	text – str - Text to display to the user (default: blank line)

Cmd.do_shell(command)¶

Execute a command as if at the OS prompt.

Usage: shell command

Parameters:	command – str - shell command to execute

( ! is a shortcut for shell; thus !ls is equivalent to shell ls.)

Transcript-based testing¶

If the entire transcript (input and output) of a successful session of a cmd2-based app is copied from the screen and pasted into a text file, transcript.txt, then a transcript test can be run against it:

python app.py --test transcript.txt

Any non-whitespace deviations between the output prescribed in transcript.txt and the actual output from a fresh run of the application will be reported as a unit test failure. (Whitespace is ignored during the comparison.)

Regular expressions can be embedded in the transcript inside paired / slashes. These regular expressions should not include any whitespace expressions.

Case-insensitivity¶

By default, all cmd2 command names are case-insensitive; sing the blues and SiNg the blues are equivalent. To change this, set App.case_insensitive to False.

Whether or not you set case_insensitive, please do not define command method names with any uppercase letters. cmd2 expects all command methods to be lowercase.

Shortcuts¶

Special-character shortcuts for common commands can make life more convenient for your users. Shortcuts are used without a space separating them from their arguments, like !ls. By default, the following shortcuts are defined:

?

help

!

shell: run as OS-level command

@

load script file

@@

load script file; filename is relative to current script location

To define more shortcuts, update the dict App.shortcuts with the {‘shortcut’: ‘command_name’} (omit do_):

class App(Cmd2):
    Cmd2.shortcuts.update({'*': 'sneeze', '~': 'squirm'})

Default to shell¶

Every cmd2 application can execute operating-system level (shell) commands with shell or a ! shortcut:

(Cmd) shell which python
/usr/bin/python
(Cmd) !which python
/usr/bin/python

However, if the parameter default_to_shell is True, then every command will be attempted on the operating system. Only if that attempt fails (i.e., produces a nonzero return value) will the application’s own default method be called.

(Cmd) which python
/usr/bin/python
(Cmd) my dog has fleas
sh: my: not found
*** Unknown syntax: my dog has fleas

Timing¶

Setting App.timing to True outputs timing data after every application command is executed. The user can set this parameter during application execution. (See Other user-settable parameters)

Echo¶

If True, each command the user issues will be repeated to the screen before it is executed. This is particularly useful when running scripts.

Debug¶

Setting App.debug to True will produce detailed error stacks whenever the application generates an error. The user can set this parameter during application execution. (See Other user-settable parameters)

Other user-settable parameters¶

A list of all user-settable parameters, with brief comments, is viewable from within a running application with:

(Cmd) set --long
abbrev: True                   # Accept abbreviated commands
autorun_on_edit: True          # Automatically run files after editing
case_insensitive: True         # upper- and lower-case both OK
colors: True                   # Colorized output (*nix only)
continuation_prompt: >         # On 2nd+ line of input
debug: False                   # Show full error stack on error
default_file_name: command.txt # for ``save``, ``load``, etc.
echo: False                    # Echo command issued into output
editor: vim                    # Program used by ``edit``
feedback_to_output: False      # include nonessentials in `|`, `>` results
locals_in_py: True             # Allow access to your application in py via self
prompt: (Cmd)                  # The prompt issued to solicit input
quiet: False                   # Don't print nonessential feedback
timing: False                  # Report execution times

Any of these user-settable parameters can be set while running your app with the set command like so:

set abbrev False

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:

command

Name of the command called

raw

Full input exactly as typed.

terminator

Character used to end a multiline command

suffix

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
        sunny'''
    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.'
        else:
            result = 'UV is bad for your skin.'
        self.stdout.write(result + '\n')
app = App()
app.cmdloop()

(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)):
        self.stdout.write(arg)
        self.stdout.write('\n')

(Cmd) say goodnight, gracie
goodnight, gracie
(Cmd) say -sp goodnight, gracie
OODNIGHT, GRACIEGAY
(Cmd) say -r 2 --shout goodnight, gracie
GOODNIGHT, GRACIE
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)

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

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.

color¶

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 paramter 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

quiet¶

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.

select¶

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(options, prompt='Your choice? ')¶

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

Argument options 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!