Parallel processing through tcl script - multithreading

Question

Need solution for parallel processing in tcl (windows).
I tried with thread, still not able to achieve desired output.
To simplify My requirement I am giving a simple example as following.
Requirement:
I want to run notepad.exe without effecting my current execution of flow. From main thread control should go to called thread, start notepad.exe and come back to main thread with out closing the notepad .
Tried:(Tcl script)
package require Thread
set a 10
proc test_thread {b} {
puts "in procedure $b"
set tid [thread::create] ;# Create a thread
return $tid
}
puts "main thread"
puts [thread::id]
set ttid [test_thread $a]
thread::send $ttid {exec c:/windows/system32/notepad.exe &}
puts "end"
Getting Output:
running notepad without showing any log.
when closing notepad application I am getting following output.
main thread
tid0000000000001214
in procedure 10
end
Desired output:
main thread
tid0000000000001214
in procedure 10
---->> control should go to thread and run notepad.exe with out effecting main thread flow.
<<-------
end
So kindly help to solve this issue and if appart from thread concept any other is there let me know.

Answer 1

You're using a synchronous thread::send. It's the version that is most convenient for when you want to get a value back, but it does wait. You probably should be using the asynchronous version:
thread::send -async $ttid {exec c:/windows/system32/notepad.exe &}
# ^^^^^^ This flag here is what you need to add
However it is curious that the exec call is behaving as you describe at all; the & at the end should make it effectively asynchronous anyway. Unless there's some sort of nasty interaction with how Windows is interpreting asynchronous subprocess creation in this case.