popen

=========== popen

What is it?

The popen package provides a simple shell-like syntax inside python for running external commands.

Features:

• Chaining (aka. piping) as Sh('ls') | 'sort'
• Redirect stderr to stdout as Sh('make').include_stderr | 'wc'
• Redirect output to file as Sh('ls') > '~/listing.txt'
• Iteration over output lines as for line in Sh('ls'):
• Streaming input into commands in the chain as Sh.pipe('~/listing.txt').Sh('grep', '-q', 'code').returncode
• Expands special characters (~*!?)
• Expands env vars ($HOME) as print Sh('ls', '$USER', '~/*')
• Properly splits strings ('echo "hole in one"' becomes ['echo', 'hole in one'])
• Or iterable arguments (Sh('ls', '-l') | ['wc', '-l'] > '/dev/null')

===== TL;DR

Installation:

.. code-block:: SH

pip install popen

Example:

.. code-block:: PY

from popen import Sh
for line in Sh('du', '~/') | 'head -n 10' | 'sort -n':
    print('GOT', line)

===== Usage

Simples usage, run a command and iterate the output lines:

.. code-block:: PY

from popen import Sh
for line in Sh('ls', '-la', '~'):
    print line

Piping that output to a file:

.. code-block:: PY

Sh('ls', '-la', '~') > '~/listing'

Note that special characters like ~ are expanded, as are environment variables (e.g. $HOME).

Chaining commands is trivial, here with append instead of write to file:

.. code-block:: PY

Sh('ls') | Sh('sort') >> '~/listing'

But the right hand side of | can be very flexible, as it employs lexical splitter on string input or takes an iterable:

.. code-block:: PY

Sh('ls', '-la', '~') | 'sort -c' | ['uniq', '-c'] | 'tail' | Sh('wc') > '~/listing'

To run a command and let output go to stdout, ask for the return code:

.. code-block:: PY

cmd = Sh('ls') | 'grep polka'
print cmd.returncode

To pipe a string into a command, wrap in an iterable:

.. code-block:: PY

print Sh.pipe(['this is a \nmulti line\nstring.']) | 'wc'