how to start a new process while the other ist running on

Keith Dart kdart at kdart.com
Wed Dec 22 22:25:18 CET 2004


On 2004-12-22, Erik Geiger <Erik.geiger at gmx.de> wrote:
> Donn Cave schrieb:
>
>> In article <cqbh6m$ttc$1 at online.de>, Erik Geiger <Erik.geiger at gmx.de>
>> wrote:
> [...]
>> > Thats what I've tried, but it did not work. Maybe it's because I want to
>> > start something like su -c '/path/to/skript $parameter1 $parameter2' 
>> > user
>
>> Unfortunately this particular case kind of dilutes the advantages
>> of spawnv.  In the common case, parameter1 et al. would be submitted
>> directly as the parameter list.  I believe it may be clearer to start
>> with to think about the spawnv() function -
>>    os.spawnv(os.P_NOWAIT, path, [cmdname, parameter1, parameter2])
>> 
>> If one of the parameters is itself another command, then of course
>> it has to be rendered as a string
>>    os.spawnv(os.P_NOWAIT, '/bin/su', ['su', '-c', '%s %s %s' % (cmd,
>>       parameter1, parameter2)])
>> so you have almost as much work to scan the parameters for shell
>> metacharacters as you would have with system().
>> 
>>    Donn Cave, donn at u.washington.edu
> OK, thats too high for me ;-)
>
> Is the %s the variable for the following commands/parameters? If I have
> three parameters, I'll need one more %s? Where to write the user for the su
> command?
>
> Well, I've given up ;-)
>

Hey, don't give up. There is help. ;-) guess...

There is a package called pyNMS (http://sourceforge.net/projects/pynms)
That has a module called "proctools", and also one called "sudo". Once
you set up sudo correctly, you can do what you want easily. 

However, be aware that proctools spawns a process with the subprocess
stdio connected to _your_ parent process, and does not inherit the stdio
of the parent. So, if the subprocess writes a lot of stuff you must read
it, or the subprocess will block. However, there is some (perhaps buggy)
support for asynchronous operation where those reads happen
automatically (on Linux). 




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   Keith Dart <kdart at kdart.com>
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