Python script + v4lctl

[Gabriel Genellina]

En Mon, 20 Oct 2008 06:15:34 -0200, Gatis <gatisl at inbox.lv> escribió:

> I wrote script that in case of some event takes picture using usb
> webcam [Creative Live! Cam Vista IM (VF0420)] and command line utility
> v4lctl (from package xawtv).
> Problem1:
> To catch error and info messages from script I used:
> sys.stdout = open('/tmp/log','a')
> sys.stderr=sys.stdout
> All writes to log file well, except v4lctl error messages. If script
> is run from commandline, than v4lctl error messages are shown there.
> How to catch these messages?

Use the subprocess module to invoke the external program; see  
http://docs.python.org/library/subprocess.html specially the examples at  
the end.

> Problem2:
> When script is run from /etc/init.d (in runlevel 2) during boot, no
> pictures are taken. I can't tell error message, because of Problem1.
> If I execute now v4lctl from commandline (while my script is running
> in background), picture is taken.

Once you start using subprocess, you could write to some file what you get  
 from the communicate() method - the error messages, if any, should be  
there.

-- 
Gabriel Genellina