[GRASS-user] Re: Using temp files in Grass Script

[Johannes Radinger]

-------- Original-Nachricht --------
> Datum: Thu, 19 May 2011 07:11:47 +0100
> Von: Glynn Clements <glynn at gclements.plus.com>
> An: "Johannes Radinger" <JRadinger at gmx.at>
> CC: grass-user at lists.osgeo.org
> Betreff: Re: [GRASS-user] Re: Using temp files in Grass Script

> 
> Johannes Radinger wrote:
> 
> > > Using an exit handler ensures that the temporary map gets removed
> > > regardless of how the script terminates (e.g. if it terminates due to
> > > an exception).
> > 
> > Thank you for your nice examples how to do that with tmp files and the
> exit handler.
> > 
> > Just some questions:
> > 
> > 1) is the PID also used on windows systems? so can it be integrated
> > in a script which also windows users want to use?
> 
> Yes.
> 
> > Is it correct that the PID is the same value for running the whole
> > script one time?
> 
> Yes.
> 
> > 2) what exactly does the "global tmpmap"?
> 
> First, it should have been "global tmp_map", not "global tmpmap".
> 
> "global" declares a variable as global, so that any assignment to that
> variable within the function modifies the global variable rather than
> creating a local variable with that name.
> 
> In order to assign a global variable from within a function, it must
> be explicitly declared "global". A "global" statement isn't required
> to read a global variable.
> 
> In this case, tmp_map must be global so that the name generated within
> main() can be used from within cleanup().
> 
> > 3)I've got a lot of tmp-files which will be created during the
> > process, so is there and option to tell the g.remove that all maps
> > containing .tmp.%d' % os.getpid() in the end should be removed
> > instead of typing all the tmp map files into the list of g.remove.
> 
> You could use g.mremove to remove multiple maps based upon a pattern,
> but I would recommend specifying all of the temporary maps explicitly. 
> 
> If an option for a GRASS command accepts multiple values (e.g. all of
> g.remove's options), you can pass a Python list via
> grass.run_command(), e.g..
> 
> 	grass.run_command('g.remove', rast = [tmp1, tmp2, tmp3])
> 
> > 4) so the whole thing works that in the end all the tmp maps are
> > deleted after the processing of the script and after an exception
> > etc.
> 
> An exit handler registered using atexit.register() will be run when
> the script terminates, whether due to reaching the end of the script,
> calling sys.exit(), an uncaught exception, Ctrl-C/Ctrl-Z, etc.
> 
> The only situation where it won't be run is if the Python interpreter
> crashes (or is terminated with SIGKILL on Unix, etc), which can't
> realistically be handled by any means.
> 
> -- 
> Glynn Clements <glynn at gclements.plus.com>
> _______________________________________________
> grass-user mailing list
> grass-user at lists.osgeo.org
> http://lists.osgeo.org/mailman/listinfo/grass-user


Okay I think I managed to do everything according to your really good explanation (Thank you!). Here how I implemented the tmp maps including the  PID and deleting it via the cleanup and a list containing all tmp maps:

tmp_map_rast = None
tmp_map_vect = None

def cleanup():
    if (tmp_map_rast or tmp_map_vect) and not flags['a']:
        grass.run_command("g.remove", 
                rast = tmp_map_rast,
                vect = tmp_map_vect,
                quiet = True)


def main():
    
    #global variables for cleanup
    global tmp_map_rast
    tmp_map_rast = [f + str(os.getpid()) for f in['rast1_tmp_', 'rast2_tmp_', 'rast3_tmp_']]

    global tmp_map_vect
    tmp_map_vect = [f + str(os.getpid()) for f in['vect1_tmp_', 'vect2_tmp_', 'vect3_tmp_']]

if __name__ == "__main__":
    options, flags = grass.parser()
    atexit.register(cleanup)
    sys.exit(main())


I tried it once and it worked! I hope it a good way how i did it, but probably there is always something to make better. Anyway thanks a lot!

/Johannes

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