How to detect termination of a background lnx invoked from a MSF function

[Farshid]

I am invoking a lnx function on the background from a msf function. I would like check the termination of the background job and perform some operation on the output of that lnx function inside the msf file. I used the fact that "who" command show the status of the lnx output variables as busy to detect the termination of lnx (see the code below).

--------------------------------
Function [result] = myfun(c,d)
[a,l] = (define sl2sb, { background})(m,d);
while(1)
[c] === who;
display c;
if (index(c,"a -- busy") == -1)
exit;
else
pause(2)
endif
endwhile
c= a+2;
d = l+1;
endFunction
----------------------------------

The msf function never terminates
(get caught in the while loop) since even after the background lnx is terminated the "who" command keep showing busy status for the lnx outputs.

Note that this does not happen if I invoke the background lnx from the xmath command line (and not from the msf function), as soon as the lnx terminates, "who" shows the return value not the busy status.

Any hint on what is done wrongly above?

Is there a better way to achieve the same result (detecting termination of a background lnx invoked from a msf function)?

Thanks,

[jdigiova]

Hello,

The reason the msf is getting caught in the while loop is because the background lnx function has NOT terminated. The background process is running in the same thread as Xmath. Therefore the background process gets called and begins to execute. Then because it is a background process the Xmath commands are free to interupt the function. This is where we go into the while loop. The pause function does not put the process to sleep so we stay in the while loop and the background function is starved, never finishes, and we are stuck in the while loop. Note: This does not have to do with calling the lnx from an msf. If you cut and paste the code (excluding the function declaration and endfunction) into the Xmath command window you should still end up in a n
ever ending loop.

Therefore the underlying cause of the problem is that the background process does not run in a seperate thread then the Xmath functions. The background process is designed to run in-between Xmath commands. This assumes that there is some break in the commands that will allow the background process to execute.

I recommend running the lnx as a foreground process to insure that it gets executed. Since a background process and Xmath use the same thread running the lnx function in the foreground should not and any time to your overall execution time.

Joe D.
National Instruments