Python Pluggable Shell Interface
Project description
Python Pluggable Shell Interface, or pypsi, is a framework for developing command line based shell interfaces, akin to bash or csh.
Pypsi was designed around the Python cmd module. The Python cmd module is fine for small projects with a limited number of commands and features. However, as the interface grows, maintainability and extensibility becomes increasingly hard. Adding features such as argument parsing after a few commands have been implemented is exectremely time consuming.
Pypsi is targetted towards both rapid prototype interfaces and large stable shells. The bootstraping code is very small with very little boilerplate. Pypsi ships with a great deal of capabilities box of the box, all of which can be used or ignore. Pypsi is pluggable which allows commands, features, and plugins be developed independently in their own source files and/or Python classes. This results in a very clean source repository. The actual code to setup and run the shell is exetremely small, on the order of ~20-50 lines of code.
Pypsi, at its core, is pluggable. There are many hooks that allow plugin authors to extend and modify the core behavior of pypsi. Commands are isolated classes that make distribution, sharing, and modifing easy.
Caveats
The only major caveat when using pypsi is that it only supports Python 3. Python 3 is the future.
Releases
The pypsi source code is located on GitHub <https://github.com/ameily/pypsi> and on PyPI <https://pypi.python.org/pypi/pypsi>. The latest version can also be install via pip:
pip install pypsi
Features
The following capabilities ship with pypsi and are available out of the box.
I/O redirection
String-based pipes
Flexible API
Tab completion
Multiplatform
Minimal dependencies
Colors
Session tips and message of the day (MOTD)
Automated help, usage messages, and argument parsing
Word wrapping
Term highlighting (grep)
Tables
Prompt wizards
cmd plugin to migrate existing cmd commands into pypsi
Demo
The demo.py source file can be run to show off some of the base commands and features that ship with pypsi (the demo.py file can be downloaded from the git repo at https://github.com/ameily/pypsi/blob/master/demo.py). The commands displayed below are all optional: pypsi does not require the use of any command or plugin.
Variables
pypsi)> var name = "Paul" pypsi)> var house = "Atredis" pypsi)> echo My name is $name, and I belong to House $house My name is Paul, and I belong to House Atredis pypsi)> var -l name Paul house Atredis pypsi)> var -d name pypsi)> echo $name pypsi)> var name = "Paul $house" pypsi)> echo $name Paul Atredis
I/O redirection
pypsi)> echo Hello
Hello
pypsi)> echo Hello > output.txt
pypsi)> echo Goodbye
pypsi)> xargs -I{} "echo line: {}" < output.txt
line: Hello
line: Goodbye
pypsi)> cat output.txt | grep ll
Hello
System commands
Allows execution of external applications. Command mimics Python’s os.system() function.
pypsi)> ls pypsi: ls: command not found pypsi)> system ls include/ src/ README.md pypsi)> system ls | system grep md README.md
Fallback command
Allows the developer to set which command gets called if one does not exist in the current shell. This is very useful, for example, if you want to fallback on any OS installed executables. In this example, the fallback command is system.
pypsi)> ls include/ src/ README.md
Command chaining
pypsi)> echo Hello && echo --bad-arg && echo goodbye Hello echo: unrecgonized arguments: --bad-arg pypsi)> echo Hello ; echo --bad-arg ; echo goodbye Hello echo: unrecgonized arguments: --bad-arg goodbye pypsi)> echo --bad-arg || echo first failed echo: unrecgonized arguments: --bad-arg first failed
Multiline commands
pypsi)> echo Hello, \ > Dave Hello, Dave pypsi)> echo This \ > is \ > pypsi \ > and it rocks This is pypsi and it rocks
Macros
Macros are analogous to functions in bash. They provide the ability to create new commands in the shell.
pypsi)> macro hello > echo Hello, $1 > echo Goodbye from macro $0 > end pypsi)> hello Adam Hello, Adam Goodbye from macro hello
License
pypsi is released under the BSD 3-Clause license.
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