How to schedule system calls with Python

TerryP bigboss1964 at gmail.com
Thu Oct 15 22:15:05 CEST 2009


On Oct 15, 7:42 pm, Jeremy <jlcon... at gmail.com> wrote:
> I need to write a Python script that will call some command line
> programs (using os.system).  I will have many such calls, but I want
> to control when the calls are made.  I won't know in advance how long
> each program will run and I don't want to have 10 programs running
> when I only have one or two processors.  I want to run one at a time
> (or two if I have two processors), wait until it's finished, and then
> call the next one.
>
> How can I use Python to schedule these commands?
>
> Thanks,
> Jeremy

External programs are not system calls; external programs are invoked
through system calls; for example system() is a function call which
when implemented under UNIX systems invokes some form of fork() and
exec(), and likely spawn() under Windows NT.

If you want simple sequenceal execution of external programs, use a
suitable blocking function to execute them (like system) combined with
a simple loop over the sequence of commands to run.


for prog in ['cmd1', 'cmd2', 'cmd3']:
    os.system(prog)

blah.



For anything more detailed (or complex) in response, try being more
detailed yourself ;).



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