Path: csiph.com!x330-a1.tempe.blueboxinc.net!usenet.pasdenom.info!aioe.org!feeder.news-service.com!xlned.com!feeder5.xlned.com!newsfeed.xs4all.nl!newsfeed6.news.xs4all.nl!xs4all!post.news.xs4all.nl!not-for-mail
DomainKey-Signature: a=rsa-sha1; c=nofws; d=rebertia.com; s=google; h=mime-version:sender:in-reply-to:references:date :x-google-sender-auth:message-id:subject:from:to:cc:content-type :content-transfer-encoding; b=QXc350R7Xq3snOELVVgFNAZjm3jITKSrxYIyzDv06WwK7tsQH2Dc9CYJ13o/cqqyGg aS1J+TtA3SNMgBJYPPQjvJpYY16YY72NzVc74YOxwqnZ073gRNc2G2LrHHvDxpcLcShc cv1kqHgWt/UI7ovJdwcpbaH/YHUU4kQDMSkbw=
MIME-Version: 1.0
Sender: chris@rebertia.com
In-Reply-To: <BANLkTiktJHy2yrkdaGD3o-CCJ2i4CgtBsA@mail.gmail.com>
References: <BANLkTiktJHy2yrkdaGD3o-CCJ2i4CgtBsA@mail.gmail.com>
Date: Sat, 21 May 2011 12:38:54 -0700
Subject: Re: Problem in using subprocess module and communicate()
From: Chris Rebert <clp2@rebertia.com>
To: vijay swaminathan <swavijay@gmail.com>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: quoted-printable
Cc: python-list@python.org
Precedence: list
Newsgroups: comp.lang.python
Message-ID: <mailman.1887.1306006743.9059.python-list@python.org>
Lines: 81
NNTP-Posting-Host: 82.94.164.166
Xref: x330-a1.tempe.blueboxinc.net comp.lang.python:5934

On Sat, May 21, 2011 at 8:56 AM, vijay swaminathan <swavijay@gmail.com> wro=
te:
> Hi=C2=A0 Gurus,
>
> I'm having some problem in using the communicate() along with the
> subprocess.I would like to invoke a command prompt and pass=C2=A0 on a .b=
at file
> to execute. I went through the subprocess module and understood that usin=
g
> communicate, we can send the send data to stdin.
>
> According to the documentation
> http://docs.python.org/library/subprocess.html#subprocess.call, it says,
>
> if you want to send data to the process=E2=80=99s stdin, you need to crea=
te the
> Popen object with stdin=3DPIPE.
>
> so based on this, I have used the below function but it does not seem to
> work. Am I missing something here?
>
> import subprocess
> import threading
> import time
>
> def runMonitor(command):
> =C2=A0=C2=A0=C2=A0 retcode =3D subprocess.Popen([command, '\k', 'dir'],

Shouldn't that be /k, not \k?

> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 cwd=3D
> 'C:\Python26\WorkSpace\FunctionExamples\src',

Sidenote: You really should use forward-slashes in paths like this (or
double-up the backslashes).

> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 stdin =3D subprocess.PIPE,
> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 creationflags=3Dsubprocess.CREATE_NEW_CON=
SOLE)
>
> =C2=A0=C2=A0=C2=A0 retcode.wait()
>
> =C2=A0=C2=A0=C2=A0 retcode.communicate('scripts_to_execute.bat')

Several issues here:
- .wait() waits for the subprocess to terminate; there's reason for
the shell to terminate here, so your program will hang forever on the
.wait() call.
- It makes no sense to call .communicate() after .wait(), since the
subprocess will have already terminated; you can't communicate with a
dead process.
- .communicate() blocks until the subprocess terminates anyway, so
calling .wait() is pointless.
- I would think a newline is needed in you input to the shell. When
one runs a command in the shell manually, one presses Enter after
typing it, no?
- `retcode` seems a rather poor variable name, since it's holding a
Popen object rather than an integer exit code.

Putting this all together, here's an improved version:

def runMonitor(command):
    proc =3D subprocess.Popen([command, '/k', 'dir'],
        cwd=3D'C:/Python26/WorkSpace/FunctionExamples/src',
        stdin=3Dsubprocess.PIPE,
        creationflags=3Dsubprocess.CREATE_NEW_CONSOLE)
    input_data =3D 'scripts_to_execute.bat\n' + 'exit\n'
    stdout_data, stderr_data =3D proc.communicate(input_data)

I can't test it since I don't run Windows.

Cheers,
Chris
--
http://rebertia.com