Popen to get stdout and stderr for ffmpeg - No such file or directory ?

[Rhodri James]

On Tue, 19 Apr 2011 00:07:46 +0100, goldtech <goldtech at worldpost.com>  
wrote:

> Trying to learn how to run a linux command and get the stdout and
> stderr. I'm trying the following:
>
>>>> cmd3 = r'ffmpeg -i /home/giga/Desktop/Guitar1.flv'
>>>> p = Popen(cmd3, stdout=PIPE, stderr=PIPE)
>
> Traceback (most recent call last):
>   File "<pyshell#73>", line 1, in <module>
>     p = Popen(cmd3, stdout=PIPE, stderr=PIPE)
>   File "/usr/lib/python2.6/subprocess.py", line 623, in __init__
>     errread, errwrite)
>   File "/usr/lib/python2.6/subprocess.py", line 1141, in
> _execute_child
>     raise child_exception
> OSError: [Errno 2] No such file or directory


This is something that catches everyone!  From the Fine Manual  
(http://docs.python.org/library/subprocess.html#using-the-subprocess-module):

> On Unix, with shell=False (default): In this case, the Popen class
> uses os.execvp() to execute the child program. args should normally
> be a sequence. If a string is specified for args, it will be used
> as the name or path of the program to execute; this will only work
> if the program is being given no arguments.

What you actually want is more like:

p = Popen(('ffmpeg', '-i', '/home/giga/Desktop/Guitar1.flv'),
           stdout=PIPE, stderr=PIPE)

The manual gives you an example of using shlex to split a string
into tokens if you'd rather do it that way.

-- 
Rhodri James *-* Wildebeest Herder to the Masses