An dynamically extensible CMD based command shell
- Python 2.7.13
Setup a virtualenv either with virtualenv or pyenv.
virtualenv:
virtualenv ~/ENV2
pyenv:
pyenev virtualenv 2.7.13 ENV2
First you must install cloudmesh_client. You must do this before working with cloudmesh cmd5. At this time it is best to use pip:
pip install cloudmesh_client
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/common.git git clone https://github.com/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.
To install them simply to the following:
cd ~/github/common python setup.py install pip install . cd ~/github/cmd5 python setup.py install pip install . cd ~/github/extstreet python setup.py install pip install .
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
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
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/ext/command/COMMANDNAME.py
An example for the bar command is presented at:
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.