Delegator.py — Subprocesses for Humans 2.0

Delegator.py is a simple library for dealing with subprocesses, inspired by both envoy <https://github.com/kennethreitz/envoy>_ and pexpect <http://pexpect.readthedocs.io>_ (in fact, it depends on it!).

This module features two main functions delegator.run() and delegator.chain(). One runs commands, blocking or non-blocking, and the other runs a chain of commands, separated by the standard unix pipe operator: |.

Basic Usage

Basic run functionality:

.. code:: pycon

>>> c = delegator.run('ls')
>>> print c.out
README.rst   delegator.py

>>> c = delegator.run('long-running-process', block=False)
>>> c.pid
35199
>>> c.block()
>>> c.return_code
0

Commands can be passed in as lists as well (e.g. ['ls', '-lrt']), for parameterization.

Basic chain functionality:

.. code:: pycon

Can also be called with ([['fortune'], ['cowsay']]).

or, delegator.run('fortune').pipe('cowsay')

c = delegator.chain('fortune | cowsay') print c.out _______________________________________ / Our swords shall play the orators for | us. | | | \ -- Christopher Marlowe / --------------------------------------- \ ^^ \ (oo)_____ (__)\ )/ ||----w | || ||

Expect functionality is built-in too, on non-blocking commands:

.. code:: pycon

>>> c.expect('Password:')
>>> c.send('PASSWORD')
>>> c.block()

Other functions:

.. code:: pycon

>>> c.kill()
>>> c.send('SIGTERM', signal=True)

# Only available when block=True, otherwise, use c.out.
>>> c.err
''

# Direct access to pipes.
>>> c.std_err
<open file '<fdopen>', mode 'rU' at 0x10a5351e0>

# Adjust environment variables for the command (existing will be overwritten).
>>> c = delegator.chain('env | grep NEWENV', env={'NEWENV': 'FOO_BAR'})
>>> c.out
NEWENV=FOO_BAR