issuing dos commands from inside ruby on rails controller in the same dos session
What you are proposing could be possible if Rails was friendlier about forked processes.  A cleaner and better solution would be to write a python daemon that you could query so that you don't incur the startup penalty.  (This could be a web-service or a daemon you communicate with standard network sockets or whatever).
Here is my scenario.
I have a ajax call in my web site to find the elevation at particular point. Once this point comes into an action of a controller in Ruby on rails, I have to use python on command line to find the elevation.
The following sequence of commands in DOS does that for me.

python (starts a python session)
import arcpy (takes a lot of time)
function call (very fast).

Now if I put this into a script and run it, I do get the result, but its very slow, because the 'import' step takes a lot of time. But the actual function takes less than a second. 
As all this is suppose to happen behind an Ajax call on ror web site, such a large delay is unacceptable.
Question:
Is it possible for me in  Ror to open a 'command line session' when the application loads and issue the first two commands, and then use this session every time a request comes in a controller's action, and issue the third command, and return its output?
If yes can someone please post some samples?
Thanks
Shaunak