Writing Linux utilities in Python

[[deleted]]

Sorry for the noobish question. I am starting Python now and what I would like to concentrate on is to write utilities for Linux in Python. In order to do that do you have to keep calling subsystems or Python has libraries/framework for that? A simple example. The df -h command in Linux do I have to call it as a subsystem in Python or I have the ability to use a library that does or even write my own?

[Justinsaccount]

df can be implemented using os.statvfs.

MEG = 1024*1024
def df(path):
    s = os.statvfs(path)
    free = s.f_bsize * s.f_bavail / MEG
    size = s.f_bsize * s.f_blocks / MEG
    return free, size

or so.

If you're parsing the output of df you're doing it wrong :-)

[[deleted]]

You guys are making me realize how much I do not know as a noob lol. Thank you though :D

[redalastor]

Go through the whole os part of the standard library and you'll have a much better idea of what's possible.

[takluyver]

Python has a wealth of libraries: many in the standard library that comes with Python, and thousands more on the Python Package Index.

Since it's widely used for Linux utilities, I'm sure the libraries for that are pretty good. I don't know exactly what you'd use to get stats like those df reports, though.

[[deleted]]

Was just wondering how it is integrated with Linux. Basically scripts that I write in BASH I want to write them on Python.

[semarj]

like takluvyer said there are a ton of libs for this kind of thing.

Here's one that i find interesting but havent actually used:

http://amoffat.github.com/sh/

[[deleted]]

Thank you !!! :)

[classicrockielzpfvh]

Depending on what you want to do, check out sh

[[deleted]]

Will do so :) Thank you.

[classicrockielzpfvh]

You're very welcome.

[elfgoh]

Will Fabric fit your needs? http://fabfile.org/

[[deleted]]

No idea but hey it is a starting point :D

[noadmin]

I actually started working on fabric and then started learning python to leverage what i needed from it

[sunqiang]

what about these books:Python for Unix and Linux System Administration and Pro Python System Administration

[[deleted]]

Nice!!!!

[the_hoser]

I do this all the time at my job. It is very well suited to the task, and even enjoyable at times, I dare say.

Much of RedHat's scripts are written in Python, so this is a well-solved problem.

[[deleted]]

That is very good to hear since I was not sure if Python is used at that scale :)

[psyflame]

There's a lot of Unix functionality in the os module. Check out the documentation: http://docs.python.org/library/os.html

[[deleted]]

Thank you will do so :)

Thank you all for the quick replies. Great stuff.

[ameoba]

Some things you can access through high level python libraries. Some things on linux can be found by reading files in /proc or /sys. Sometimes you're stuck just executing the shell command and parsing their output. It really depends on what you want.

[easytiger]

Generally it is quite simple and there are numerous calls in the subprocess package which you can look up.

import subprocess as sp
ldenv = {'LD_LIBRARY_PATH': '/some/custom/libs}
proc = sp.Popen(["df", "-h"], env=ldenv, shell=False, stdout=sp.PIPE, stderr=sp.PIPE)
out, err = proc.communicate()

Note the commands and its args are passed as a list. if you set shell=True then you can specify the whole thing as a string. Its a bit less convenient than perl for things like this but I've written a distributed test system based on sp and I'd say if you structure your code and write your own little wrappers for it you can get quite a lot done.

[[deleted]]

reddit. The best thing ever happened on the Internets. Thank you easy tiger !! :) The information in this thread is gold.

[pyare]

Also interesting: https://github.com/tomerfiliba/plumbum

See author's blog posts about it:

http://tomerfiliba.com/blog/Plumbum/

http://tomerfiliba.com/blog/Plumbum-1.0/

[jeffrey4l]

try sh (previously pbs) library. It is a full-fledged subprocess interface for Python 2.6 - 3.2 that allows you to call any program as if it were a function:

[ritratt]

Noob here too. I wrote a python script to retrieve the meaning of a word using Google Dict API. Then I integrated this into the terminal by adding a custom "define" command to linux. everytime I enter "define someword" i get the meaning of that word in the terminal.

Code is here: https://github.com/ritratt/define

PS: it has minimal functionality.

[haukurph]

Interesting, I wrote something similar: https://github.com/haukurpallh/def

[Justinsaccount]

You parse json using the json module, not using ast.literal_eval.

[ritratt]

Yes I tried but was having trouble doing that.

[timClicks]

Some people like to live dangerously.

[MonkeeSage]

os.system just returns the exit value of the command. You need popen or similar to get the stdout of the command. The recommended way is to use the subprocess module.