How to use python and popen4 to capture stdout and stderr from a command

This is my OLD blog. I've copied this post over to my NEW blog at:

http://www.saltycrane.com/blog/2007/03/how-to-use-python-and-popen4-to-capture_12/

You should be redirected in 2 seconds.

You can use popen to capture stdout from a command:

import os
stdout = os.popen("dir asdkfhqweiory")
print stdout.read()

And your output will be something like:

>>> ================================ RESTART ================================
 >>> 
  Volume in drive C has no label.
  Volume Serial Number is XXXXXXXX
 
  Directory of C:\Python25
 
 
 >>> 

If you wanted the error message, popen won't give it to you. To capture both stdout and stderr, use popen4:

import os

(dummy, stdout_and_stderr) = os.popen4("dir asdkfhqweiory")
print stdout_and_stderr.read()

This will give you the following output (which includes the error message):

>>> ================================ RESTART ================================
 >>> 
  Volume in drive C has no label.
  Volume Serial Number is XXXXXXXX
 
  Directory of C:\Python25
 
 File Not Found
 
 >>> 

See http://docs.python.org/lib/os-newstreams.html for more information.