Incomplete behaviour of System Exec VI when part of a LabVIEW web service

Question

Background
I would like to execute arbitrary command line commands via a LabVIEW web service.
Problem
I have a LabVIEW project (attached) with a VI boot.vi that takes a string as an argument, which is handed over to the System Exec VI.
This boot.vi works nicely: when I execute it with a string "test", it nicely executes my Ruby program "test.rb" because (i) I put the path of my the directory inside which test.rb resides into my PATH system variable and (ii) ".rb" endings are associated with Ruby programs on my PC. Similary, I can hand over the string "PATH", and it displays my PATH system variable.
However, if I build and deplay boot.vi as a LabVIEW webservice, the situation looks differently:
- the URL "http://localhost:8080/serviceManager/boot/PATH" works fine: the content of my PATH system variable is correctly displayed in the browser window as expected.
- However, the URL "http://localhost:8080/serviceManager/boot/test" does not work as expected. The following error message (coming Standard Error output of the System Exec VI) is displayed: 'test' is not recognized as an internal or external command, operable program or batch file.
My conclusion
System Exec VI does make correct use of the search paths in the PATH system variable only when NOT executed as part of a web service. This is the case although even in a web service, the content the PATH system variable is KNOWN to the System Exec VI. Strange!
Question
Am I doing something wrong? Or is there a work-around?
Attachments:
serviceManager.zip ‏7 KB

Answer 1

I just wanted to add my experiences to this thread.  We have a similar web application, and in fact it seems like we followed many of the same trials with the Internet Toolkit and G Web Server.
As of today, I have migrated our GWS/cgi based application to use web services and the LabVIEW 2009 built-in web server.  It was a fairly straightforward move, though I did run into difficulties bridging the gap between our "normal" application instance and that of the web server that holds the web service VI's.
Now I'm looking to move to LabVIEW 2010 and right away running into some problems.  While our web application has individual pages served depending on the web service called, it also uses a common pool of static web pages.  Typically these would install to the traditional "web root" folder and would be served from there.
LabVIEW 2010 has the "Application Web Server" set up as a service that starts with the system.  That seems to work fine.  It also hosts its own configuration page through the "System Web Server" on port 3580.  This too seems to work, but has very few configuration options available.
I have also spotted this article that discusses serving static pages from the Application Web Server:
http://digital.ni.com/public.nsf/allkb/2D926638796FB20E8625778F00572966
I believe I can drill down into the web server configuration (.conf) files and set things appropriately, but I think there should be more documentation available from NI describing the configuration options and how to support these in a deployed web application.
James