os.popen does not seem to catch stdout

[kyosohma at gmail.com]

On Nov 7, 12:17 pm, "gregpin... at gmail.com" <gregpin... at gmail.com>
wrote:
> On Nov 7, 11:31 am, kyoso... at gmail.com wrote:
>
>
>
> > On Nov 7, 7:58 am, zane.selv... at gmail.com wrote:
>
> > > Hi there,
>
> > > I've been banging my head against this for a day, and I can't take it
> > > anymore.  It's probably a stupid error, but I don't see where.
>
> > > I'm trying to use Python to call an external program, and then catch
> > > and process the output of that program.  Seems simple enough.  The
> > > command I'm trying to run, in the test, is:
>
> > > "/Users/zane/svn/stress/satstress/satstress -r1.561e+06 -a5 -s45000 -
> > > e0 -R6.709e+08 -g1.31472 -m1.8987e+27 -Q57100.1 -n0.333355 -Y9.29881e
> > > +09 -k1e+22 -Z1.19173 -z-6.293e-05 -V0.309434 -v-2.903e-05 -W1.81305 -
> > > w-0.00418645 -U0.474847 -u-0.00276624 -C /tmp/18_tmp.gen -b 60"
>
> > > When I run it at my zsh prompt, I get the expected output.
>
> > > If I let ss_cmd equal the above string within ipython (or the standard
> > > python interactive interpreter):
>
> > > ss_outlines = os.popen(ss_cmd).readlines()
>
> > > ss_outlines contains the same output I saw when I ran the command at
> > > my zsh prompt, one line per list element, as expected.
>
> > > However, when I try doing the same thing from within a program, it
> > > fails.  ss_outlines is an empty list.
>
> > > I've tried using subprocess.Popen(), and subprocess.call(), and
> > > subprocess.check_call(), and all have yielded similar results.  I did
> > > find, however, that the return value python is getting from the
> > > program I'm calling is different from what I get at the command line
> > > (I get 0, python gets -11).
>
> > > Does this ring a bell for anyone?
>
> > > I'm using Python 2.5.1 on a Mac running OS X 10.5.
>
> > I think when you use subprocess.Popen, you need to do something set
> > the shell to True to get it to behave like running from a command
> > prompt:
>
> > subprocess.Popen('some command', shell=True)
>
> > Seehttp://docs.python.org/lib/node529.htmlformore details.
>
> > You'll also find a fairly interesting thread on this topic here:
>
> >http://mail.python.org/pipermail/chicago/2005-November/000141.htmlhtt...
>
> > This seems to be a recipe on it:
>
> >http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/440554
>
> > Mike
>
> That's right, and I think you also want to put the whole command in a
> list or tuple, one item for each arg.  I don't know why though.
>
> -Greg

I've never had to put the command into a list or tuple...but you're
welcome to try it that way.

Mike