How to determine subprocess.Popen() failed when shell=True

[Chris Rebert]

On Mon, May 17, 2010 at 1:45 PM,  <python at bdurham.com> wrote:
> Windows version of Python 2.6.4: Is there any way to determine if
> subprocess.Popen() fails when using shell=True?
>
> Popen() successfully fails when shell=False
>
>>>> import subprocess
>>>> p = subprocess.Popen( 'Nonsense.application', shell=False )
> Traceback (most recent call last):
>  File "<pyshell#258>", line 1, in <module>
>    p = subprocess.Popen( 'Nonsense.application' )
>  File "C:\Python26\lib\subprocess.py", line 621, in __init__
>    errread, errwrite)
>  File "C:\Python26\lib\subprocess.py", line 830, in
> _execute_child
>    startupinfo)
> WindowsError: [Error 2] The system cannot find the file specified
>
> But when shell=True, there appears to be no way to determine if a
> Popen() call was successful or not.
>
>>>> p = subprocess.Popen( 'Nonsense.application', shell=True )
>>>> p
> <subprocess.Popen object at 0x0275FF90>
>>>> p.pid
> 6620
>>>> p.returncode
>>>>

I don't have a Windows box to test on, but have you tried p.wait()?
Worked for me on *nix:
$ python
Python 2.6.5 (r265:79063, May 11 2010, 13:15:13)
[GCC 4.2.1 (Apple Inc. build 5659)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> from subprocess import Popen
>>> a = Popen("nonsense", shell=True)
>>> /bin/sh: nonsense: command not found

>>> a.returncode
>>> a.wait()
127
>>> a.returncode
127

Cheers,
Chris
--
http://blog.rebertia.com