determine if os.system() is done

[Martin Franklin]

Xah Lee wrote:
> suppose i'm calling two system processes, one to unzip, and one to
> “tail” to get the last line. How can i determine when the first
> process is done?
> 
> Example:
> 
> subprocess.Popen([r"/sw/bin/gzip","-d","access_log.4.gz"]);
> 
> last_line=subprocess.Popen([r"/usr/bin/tail","-n 1","access_log.4"],
> stdout=subprocess.PIPE).communicate()[0]
> 
> of course, i can try workarounds something like os.system("gzip -d
> thiss.gz && tail thiss"), but i wish to know if there's non-hack way to
> determine when a system process is done.
> 
>  Xah
>  xah at xahlee.org
> ∑ http://xahlee.org/
> 



I think the idea is you wait for the first call to subprocess.call to
finish before executing the second...



http://docs.python.org/lib/node231.html


call( 	*args, **kwargs)
   Run command with arguments. *Wait for command to complete*, then
   return the returncode attribute.

   The arguments are the same as for the Popen constructor. Example:

   retcode = call(["ls", "-l"])