sarge 0.1

The sarge package provides a wrapper for subprocess which provides command pipeline functionality.

This package leverages subprocess to provide easy-to-use cross-platform command pipelines with a Posix flavour: you can have chains of commands using ;, &, pipes using | and |&, and redirection.

Here’s a taster (example suggested by Kenneth Reitz’s Envoy documentation):

>>> from sarge import capture_stdout
>>> p = capture_stdout('fortune|cowthink')
>>> p.returncode
0
>>> p.commands
[Command('fortune'), Command('cowthink')]
>>> p.returncodes
[0, 0]
>>> print(p.stdout.text)
 ____________________________________
( The last thing one knows in        )
( constructing a work is what to put )
( first.                             )
(                                    )
( -- Blaise Pascal                   )
 ------------------------------------
        o   ^__^
         o  (oo)\_______
            (__)\       )\/\
                ||----w |
                ||     ||

The capture_stdout function is a convenient form of an underlying function, run. You can also use conditionals:

>>> from sarge import run
>>> p = run('false && echo foo')
>>> p.commands
[Command('false')]
>>> p.returncodes
[1]
>>> p.returncode
1
>>> p = run('false || echo foo')
foo
>>> p.commands
[Command('false'), Command('echo foo')]
>>> p.returncodes
[1, 0]
>>> p.returncode
0

The conditional logic is being done by sarge and not the shell – which means you can use the identical code on Windows. Here’s an example of some more involved use of pipes, which also works identically on Posix and Windows:

>>> cmd = 'echo foo | tee stdout.log 3>&1 1>&2 2>&3 | tee stderr.log > %s' % os.devnull
>>> p = run(cmd)
>>> p.commands
[Command('echo foo'), Command('tee stdout.log'), Command('tee stderr.log')]
>>> p.returncodes
[0, 0, 0]
>>>
vinay@eta-oneiric64:~/projects/sarge$ cat stdout.log
foo
vinay@eta-oneiric64:~/projects/sarge$ cat stderr.log
foo

In the above example, the first tee invocation swaps its stderr and stdout – see this post for a longer explanation of this somewhat esoteric usage.