subprocess escaping POpen?!

[Jean-Michel Pichavant]

Chris Withers wrote:
> Hi All,
>
> I have a script that does the following:
>
> from subprocess import Popen,PIPE,STDOUT
>
> def execute(command,cwd):
>     return Popen(
>         command,
>         stderr=STDOUT,
>         stdout=PIPE,
>         universal_newlines=True,
>         cwd=cwd,
>         shell=True,
>         ).communicate()[0]
>
> captured = execute('svn up .')
>
> Now, if the subversion update requires authentication credentials, it 
> manages to write to the console running the above script, *and* read 
> input from it too.
>
> This is a bit baffling to me, I thought Popen.communicate() was 
> happily hoovering all the output to stdout and stderr into the result 
> returned from communicate?
>
> And, indeed, if I change the script instead to do:
>
> import sys
> f = open('test.py','w')
> f.write('import sys; sys.stderr.write("Hello!\\n")')
> f.close()
> captured = execute('test.py')
>
> ...then the output is indeed captured. So, what is svn doing 
> differently? How is it escaping its jail?
>
> Chris
>
You did not redirect stdin, so it is expected you can still read input 
from the console. And it looks like svn is writting the credentials 
prompt on stderr.

You may want to look at http://pysvn.tigris.org/docs/pysvn.html though.

JM