tee-like behavior in Python

[Dave Angel]

On 05/09/2012 11:35 AM, Florian Lindner wrote:
> Hello,
>
> how can I achieve a behavior like tee in Python?
>
> * execute an application
> * leave the output to stdout and stderr untouched
> * but capture both and save it to a file (resp. file-like object)
>
> I have this code
>
> proc = subprocess.Popen(shlex.split(cmd), stdout = subprocess.PIPE,
> stderr=subprocess.STDOUT)
> while True:
>     out = proc.stdout.readline()
>     if out == '' and proc.poll() != None:
>        break
>     sys.stdout.write(out)
>     logfile.write(out)
>
> This works so far but always buffers a couple of lines and outputs
> them en bloc. The final output is like it is desired but with a
> significant delay. Is there a way around that?
>
> Thanks,
>
> Florian
Chances are that other program is buffering its output.  Many programs
check if they're running on a tty, and turn off buffering for
interactive use.  But redirect them into a pipe, and they'll run as
efficiently as possible, which includes buffering the output.



-- 

DaveA