Different behaviour between spawn and exec

[ton...@googlemail.com]

I have been experimenting with launching scripts from within a main
script which is being run from within a wish console. I have found
significant performance differences of these sub-scripts, which are
generating and processing snmp information by performing an exec on a
net-snmp application.

If I exec the sub-script from within the main script I get 'normal'
performance i.e. snmp messages are generated at 0.3 second intervals.

exec tclsh sub-script.tcl

If I spawn the sub-script from within the main script then the sub-
script's interaction with net-snmp increases from 0.3sec to 3sec
intervals

exp_spawn tclsh sub-script.tcl

With exec I get better performance but I am unable to see updates on
the console. With exp_spawn I am able to see the updates on the
console but I get poor performance.

Has anybody got any ideas of a way forward on this?