[GRASSLIST:1517] Re: multiple terminal sessions

[Ed Davison]

On Thu, 2003-10-16 at 20:18, Glynn Clements wrote:
> Ed Davison wrote:
> 
> > I have noticed that a user cannot login to a grass session more than
> > once and that is understood.
> > 
> > But, I would like to run multiple xterms to work on various aspects of a
> > coverage at the same time.  For example, right now I have a large data
> > load taking place but I would like to be able to do other things with
> > layers and maps that are not being loaded (the load will likely take
> > about 6 hours even on my fast computer).
> > 
> > I see that in tcltkgrass (which I do not use) that it can launch
> > multiple xterms and get things done that way.  
> > 
> > I have tried this myself and everytime I launch an xterm (either with
> > "xterm &" or with "exec xterm") they come up with their own environment
> > that is NOT capable of using GRASS.
> > 
> > How do I do this with just an xterm without having to use tcltkgrass?
> 
> First, if you try to run multiple GRASS commands concurrently within
> the same mapset, the behaviour is undefined (and may include
> corrupting your data). GRASS doesn't perform any locking on the files
> which it uses, i.e. the files which comprise the maps, the WIND file
> (which stores the current region), $GISRC (which stores various
> session parameters such as the active monitor) etc.
> 
> Although tcltkgrass spawns xterms for some commands (typically those
> which may attempt to interact with the user via a terminal), all
> commands are run sequentially; it won't attempt to start a new command
> before the previous command has completed.
> 
> Having said all of that:
> 

[full explanation cut out[

Thanks for the very informative rundown on how to get this to work. I
did not realize that there were files that were being modified, like
WIND, that would effect other processes. I can see this now.  

The main thing that I wanted to do was to be able to draw maps on a
display while the data load was working.  I can try this with what you
have laid out but it seems safe to say that I might cause other problems
the first time I zoom or set a region that might effect the data load.

The safest thing to do would probably be to create another user and use
that user to create maps from the same coverage that I am working on.
That way there would be no other potential problems.

But, I have to say that your explanation should enable me to run "batch
files" and create various GRASS output's without having to launch an
entire GRASS process to do it.

Thanks again.

Ed Davison