cmd2

cmd2 is a tool for writing command-line interactive applications for Python 2.7 and Python 3.3+. It is based on the Python Standard Library's cmd module, and can be used any place cmd is used simply by importing cmd2 instead. It is pure Python code with the only 3rd-party dependencies being on six and pyparsing.

The latest documentation for cmd2 can be read online here: https://cmd2.readthedocs.io/en/latest/

See the Installation Instructions in the cmd2 documentation for instructions on installing, upgrading, and uninstalling cmd2.

Bug reports may be submitted directly to the issue tracker. Pull Requests are welcome, see the Contributor's Guide for more information.

Feature Support

cmd2 provides the following features, in addition to those already existing in cmd:

• Searchable command history
• Load commands from file, save to file, edit commands in file
• Multi-line commands
• Case-insensitive commands
• Special-character shortcut commands (beyond cmd's @ and !)
• Settable environment parameters
• Parsing commands with flags
• Redirection to file with >, >>; input from file with <
• Bare >, >> with no filename send output to paste buffer
• Pipe output to shell commands with |
• Simple transcript-based application testing
• Unicode character support (Python 3 only)
• Tab completion of file system paths for edit, load, pyscript, save, and shell commands
• Integrated Python scripting capability via pyscript and py commands
• (Optional) Embedded IPython shell integration via optional opt-in ipy command

Instructions for implementing each feature follow.

• Searchable command history

  All commands will automatically be tracked in the session's history, unless the command is listed in Cmd's excludeFromHistory attribute. The history is accessed through the history, list, and run commands. If you wish to exclude some of your custom commands from the history, append their names to the list at Cmd.ExcludeFromHistory.

• Load commands from file, save to file, edit commands in file

  Type help load, help save, help edit for details.

• Multi-line commands

  Any command accepts multi-line input when its name is listed in Cmd.multilineCommands. The program will keep expecting input until a line ends with any of the characters in Cmd.terminators . The default terminators are ; and /n (empty newline).

• Case-insensitive commands

  All commands are case-insensitive, unless Cmd.caseInsensitive is set to False.

• Special-character shortcut commands (beyond cmd's "@" and "!")

  To create a single-character shortcut for a command, update Cmd.shortcuts.

• Settable environment parameters

  To allow a user to change an environment parameter during program execution, append the parameter's name to `Cmd.settable``

• Parsing commands with optparse options (flags)

  @options([make_option('-m', '--myoption', action="store_true", help="all about my option")])
  def do_myfunc(self, arg, opts):
      if opts.myoption:
          #TODO: Do something useful
          pass

  See Python standard library's optparse documentation: https://docs.python.org/3/library/optparse.html

Tutorials

A couple tutorials on using cmd2 exist:

• A detailed PyCon 2010 talk by Catherine Devlin, the original author
  • http://pyvideo.org/pycon-us-2010/pycon-2010--easy-command-line-applications-with-c.html
• A nice brief step-by-step tutorial
  • https://kushaldas.in/posts/developing-command-line-interpreters-using-python-cmd2.html

Example Application

Example cmd2 application (examples/example.py):

'''A sample application for cmd2.'''

from cmd2 import Cmd, make_option, options

class CmdLineApp(Cmd):
    multilineCommands = ['orate']
    Cmd.shortcuts.update({'&': 'speak'})
    maxrepeats = 3
    Cmd.settable.append('maxrepeats')

    # Setting this true makes it run a shell command if a cmd2/cmd command doesn't exist
    # default_to_shell = True

    @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:], 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')
            # self.stdout.write is better than "print", because Cmd can be
            # initialized with a non-standard output destination

    do_say = do_speak     # now "say" is a synonym for "speak"
    do_orate = do_speak   # another synonym, but this one takes multi-line input

if __name__ == '__main__':
    c = CmdLineApp()
    c.cmdloop()

The following is a sample session running example.py. Thanks to Cmd2's built-in transcript testing capability, it also serves as a test suite for example.py when saved as exampleSession.txt. Running

python example.py -t exampleSession.txt

will run all the commands in the transcript against example.py, verifying that the output produced matches the transcript.

example/exampleSession.txt:

(Cmd) help

Documented commands (type help <topic>):
========================================
_relative_load  help     orate  pyscript  save  shell      speak
cmdenvironment  history  pause  quit      say   shortcuts
edit            load     py     run       set   show

(Cmd) help say
Repeats what you tell me to.
Usage: speak [options] arg

Options:
  -h, --help            show this help message and exit
  -p, --piglatin        atinLay
  -s, --shout           N00B EMULATION MODE
  -r REPEAT, --repeat=REPEAT
                        output [n] times

(Cmd) say goodnight, Gracie
goodnight, Gracie
(Cmd) say -ps --repeat=5 goodnight, Gracie
OODNIGHT, GRACIEGAY
OODNIGHT, GRACIEGAY
OODNIGHT, GRACIEGAY
(Cmd) set maxrepeats 5
maxrepeats - was: 3
now: 5
(Cmd) say -ps --repeat=5 goodnight, Gracie
OODNIGHT, GRACIEGAY
OODNIGHT, GRACIEGAY
OODNIGHT, GRACIEGAY
OODNIGHT, GRACIEGAY
OODNIGHT, GRACIEGAY
(Cmd) hi
-------------------------[1]
help
-------------------------[2]
help say
-------------------------[3]
say goodnight, Gracie
-------------------------[4]
say -ps --repeat=5 goodnight, Gracie
-------------------------[5]
set maxrepeats 5
-------------------------[6]
say -ps --repeat=5 goodnight, Gracie
(Cmd) run 4
say -ps --repeat=5 goodnight, Gracie

OODNIGHT, GRACIEGAY
OODNIGHT, GRACIEGAY
OODNIGHT, GRACIEGAY
OODNIGHT, GRACIEGAY
OODNIGHT, GRACIEGAY
(Cmd) orate Four score and
> seven releases ago
> our BDFL
> blah blah blah
Four score and
seven releases ago
our BDFL
blah blah blah
(Cmd) & look, a shortcut!
look, a shortcut!
(Cmd) show color
colors: /(True|False)/
(Cmd) set prompt "---> "
prompt - was: (Cmd)
now: --->
---> say goodbye
goodbye

Note how a regular expression /(True|False)/ is used near the end for output of the show color command since colored text is currently not available for cmd2 on Windows. Regular expressions can be used anywhere within a transcript file simply by embedding them within two forward slashes, /.