Python-os. Command Execution

ALAN GAULD alan.gauld at btinternet.com
Sat Feb 19 11:04:02 CET 2011



> when user click install, It will start one GUI  installation script and
> exit my application
> 
> This my task.. The problem  was the installation script started but
> control will be transfered  to
> 
> other window ... when installation finished the GUI application will  be 
>closed..
> 
> code:
> 
> os.system("ls -l") &  root.destroy
> 

First question is, why are you using the bitwise and operator to manage 
execution status. This is Python not C. Use clear logic that erflects 
what you are trying to do.( Especially if you only post code fragments.)

if os.system('ls -l') != 0 : root.destroy()

Is much more obvious in intent.

> when execute a command "ls -l " and application will be  closed

Only if os.system returns an error code

> os.system("top") & root.destroy
> 
> Control will  the transferred to the other-window, "top" closed means
> application will be  closed.. plz..help me..

I have no idea what other window you are referring to. Is it the 
OS console that top runs in? Have you checked the return code 
of os.system to see if it returns cleanly (ie a 0) or if it returns an error?

You might find it better to use the subprocess module instead of 
os.system. There is more flexibilityy and control available there.

> I checked also the command as background  process.. like os.system("top
> &") & root.destroy

And what happened?

We need a bit more context and you need to do a bity more debugging.
Starting with getting rid of the bitwise and "trick" from C. All it does 
here is make it hard to understand whats happening.

HTH,

Alan G.
Author of the Learn to Program web site
http://www.alan-g.me.uk/



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