Cloudmesh cmd5

An dynamically extensible CMD based command shell

Requirements

• Python 2.7.13

Installation from source

Setup a virtualenv either with virtualenv or pyenv.

virtualenv:

virtualenv ~/ENV2

pyenv:

pyenev virtualenv 2.7.13 ENV2

Now you need to get two source directories. We assume yo place them in ~/github:

mkdir ~/github
cd ~/github
git clone https://github.com/cloudmesh/cloudmesh.common.git
git clone https://github.com/cloudmesh/cloudmesh.cmd5.git
git clone https://github.com/cloudmesh/cloudmesh.bar.git

The cmd5 repository contains the shell, while the extbar directory contains the sample commands foo and bar. The common library contains some useful classes and methods that we also share with other cloudmesh code.

To install them from source simply to the following. The cloudmesh.bar example you want as source as you want to modify the code at one point:

cd ~/github/cloudmesh.common
python setup.py install
pip install .
cd ~/github/cloudmesh.cmd5
python setup.py install
pip install .
cd ~/github/cloudmesh.bar
python setup.py install
pip install .

Instalation from pip

To install cmd5 from pip please use:

pip install cloudmesh.cmd5

The cloudmesh.bar repository you want to download as source so you can learn how to write your own commands:

mkdir ~/github
cd ~/github
git clone https://github.com/cloudmesh/cloudmesh.bar.git

Commands are shared in the cloudmesh namespace:

Execution

to run the shell you can activate it with the cms command. cms stands for cloudmesh shell:

(ENV2) $ cms

It will print the banner and enter the shell:

+-------------------------------------------------------+
|   ____ _                 _                     _      |
|  / ___| | ___  _   _  __| |_ __ ___   ___  ___| |__   |
| | |   | |/ _ \| | | |/ _` | '_ ` _ \ / _ \/ __| '_ \  |
| | |___| | (_) | |_| | (_| | | | | | |  __/\__ \ | | | |
|  \____|_|\___/ \__,_|\__,_|_| |_| |_|\___||___/_| |_| |
+-------------------------------------------------------+
|                  Cloudmesh CMD5 Shell                 |
+-------------------------------------------------------+

cms>

To see the list of commands you can say:

cms> help

To see the manula page for a specific command, please use:

help COMMANDNAME

Extension

One of the most important features of CMD5 is its ability to extend it with new commands. This is done via packaged name spaces. This is defined in the setup.py file of your enhancement. The best way to create an enhancement is to take a look at the code in

• https://github.com/cloudmesh/cloudmesh.bar.git

Simply copy the code and modify the bar and foo commands to fit yor needs.

Wraning: do not copy the .git directory

It is important that all objects are defined in the command itself and that no global variables be use in order to allow each shell command to stand alone. Naturally you should develop API libraries outside of the cloudmesh shell command and reuse them in order to keep the command code as small as possible. We place the command in:

cloudmsesh/COMMANDNAME/command/COMMANDNAME.py

An example for the bar command is presented at:

• https://github.com/cloudmesh/cloudmesh.bar/blob/master/cloudmesh/bar/command/bar.py

It shows how simple the command definition is (bar.py):

from __future__ import print_function
from cloudmesh.shell.command import command
from cloudmesh.shell.command import PluginCommand

class BarCommand(PluginCommand):

    @command
    def do_bar(self, args, arguments):
        """
        ::

          Usage:
                command -f FILE
                command FILE
                command list
          This command does some useful things.
          Arguments:
              FILE   a file name
          Options:
              -f      specify the file
        """
        print(arguments)

An important difference to other CMD solutions is that our commands can leverage (besides the standrad definition), docopts as a way to define the manual page. This allows us to use arguments as dict and use simple if conditions to interpret the command. Using docopts has the advantage that contributors are forced to think about the command and its options and document them from the start. Previously we used not to use docopts and argparse was used. However we noticed that for some contributions the lead to commands that were either not properly documented or the developers delivered ambiguous commands that resulted in confusion and wrong ussage by the users. Hence, we do recommend that you use docopts.

The transformation is enabled by the @command decorator that takes also the manual page and creates a proper help message for the shell automatically. Thus there is no need to introduce a sepaarte help method as would normally be needed in CMD.