Python Shell Toolkit (SHTK)

Python SHTK is a python module that seeks to make replacing shell scripts with Python scripts an easier process. Python has a number of syntax advantages over traditional shell scripting languages such as BASH, including:

• Classes
• Modules
• With statements
• Try/Except statements
• Async and await for coroutines

The module and package oriented structure of Python's toolchain enables broad code re-use and redistribution. Python also benefits from a wide selection of built-in modules, and expands itself via the wide assortment of packages that can be quickly installed using its built-in package manager.

Finally, built-in automated test harnesses and long-standing code-quality integrations make it easy to review, document, test, and maintain its libraries.

SHTK is written with the assumption that you want to run more than one command. Towards this end, improvements over Python's built-in subprocess library include:

• Much shorter code -- designed to be as close to BASH as possible
• Easy piping of stdout to other commands' stdin
• Easy redirects to files
• Shell objects to track and manage cwd and environment variables
• An evaluate() function that returns the text a command wrote to stdout
• Optional NonzeroExitCodeException raised in response to non-zero exit codes
• Connects commands to sys.stdin, sys.stdout, and sys.stderr by default

The author's primary intended use cases for Python SHTK include replacing BASH scripts that automate builds of disk images, docker containers, and system configurations.

Installation

Using pip you can install shtk as follows:

pip3 install shtk

Or you can install the module from source as follows:

pip3 install .

Tests

To run the automated tests, run the following command from the project's root directory:

pip3 install coverage
python3 run_tests.py

Documentation

The documentation is publically available at https://shtk.readthedocs.org

To build the documentation from source, run the following which generates documention in ./docs/html/index.html

cd docs
make html
cd ..

Examples

import shtk

sh = shtk.Shell.get_shell()

ls = sh.command('ls')
wc = sh.command('wc')
cat = sh.command('cat')
sleep = sh.command('sleep')
touch = sh.command('touch')

#touch tmp.txt
sh(touch('tmp.txt'))

#cat tmp.txt
sh(cat('tmp.txt'))

#cat tmp.txt | wc -l
sh(cat('tmp.txt') | wc('-l'))

#wc -l < tmp.txt
sh(wc('-l').stdin('tmp.txt'))

#ls | wc -l > /dev/null
sh(ls | wc('-l').stdout(None))

#ls | wc -l > tmp.txt
sh(ls | wc('-l').stdout('tmp.txt'))

#ls | wc -l >> tmp.txt
sh(ls | wc('-l').stdout('tmp.txt', mode='a'))

with open('test_file1.txt', 'w') as fout:
    msg = """
abc
xyz
The quick brown fox jumps over the lazy dog.
""".lstrip()
    print(msg, file=fout)

try:
    # ls test_file2.txt 2> /dev/null | wc -l
    sh(
        ls('test_file2.txt').stderr('/dev/null') | wc('-l')
    )
except shtk.NonzeroExitCodeException:
    print("Caught a failure")

sh(
    ls('test_file1.txt')
)

#echo $(ls | wc -l)
print(sh.evaluate(ls | wc('-l')).strip())

More examples can be found in the source code's examples directory, but they're still under construction.