popen function of os and subprocess modules

banu varun.nagpaal at gmail.com
Wed Oct 28 15:15:55 CET 2009


On Oct 28, 3:02 pm, Jon Clements <jon... at googlemail.com> wrote:
> On 28 Oct, 13:39, banu <varun.nagp... at gmail.com> wrote:
>
>
>
> > Hi,
> > I am a novice in python. I was trying to write a simple script on
> > Linux (python 3.0) that does the following
>
> > #cd directory
> > #ls -l
>
> > I use the following code, but it doesn't work:
>
> > import os
> > directory = '/etc'
> > pr = os.popen('cd %s' % directory,'w')
> > pr.close()
> > pr = os.popen('ls -l','w')                                      #
> > prints the content of present folder and not '/etc'
> > pr.close()
>
> > Can anyone suggest me how to fix this simple script? Also what is the
> > use of read(), readlines() and write() functions?
>
> > Now, I also read in the online python documentation that os.popen is
> > deprecated and no longer recommended in pyhton 3.0. Instead they ask
> > to use subprocess.popen. I am not able to figure out how to accomplish
> > my task with subprocess.poepn also. Can anyone suggest please?
>
> > Regards
> > Varun
>
> If you're only trying to get the contents of a directory, there are
> more suitable functions - you don't need a separate process. The popen*
> () commands are deprecated.
>
> Try using os.listdir() - can't remember off the top of my head if
> that's been moved to os.path.listdir() in the 3.* series, but a read
> of the doc's will set you straight.
>
> Ditto for read() and write().
>
> If you describe what you're trying to achieve, maybe we can help more.
>
> Also, if you're using 3.0, may I suggest moving to 3.1?
>
> hth,
>
> Jon.

Thanks for the reply Jon
Basically I need to move into a folder and then need to execute some
shell commands(make etc.) in that folder. I just gave 'ls' for the
sake of an example. The real problem I am facing is, how to stay in
the folder after popen('cd directory') finishes. It seems trivial, but
I am not able to do it.

Varun



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