Automated Jobs and Library Jobs
I received an IM late yesterday evening (my time) from “James” (via the Web) asking what the difference is between an automated job and a library job. Unfortunately, I wasn’t around to answer it (I started work about 2 AM PDT today, and the IM was from about 9:30 PM PDT yesterday), but it’s rare I get asked something I can flip an answer to off the top of my head, so…
I’m assuming this is in the context of the Device Test Manager (DTM) in the Windows Logo Kit (WLK). That is a derivative of a larger internal-use product we call WTT (Windows Test Technologies), so I’ll assume the same answer applies to both, because I’m sure it does (and if I’m wrong, feel free to correct me).
If you’re a programmer, the fastest rough analogy is that an Automated Job is like a C / C++ “main” while the Library job is like a “function” in the runtime library (or some DLL, etc). The important difference here being that a job can “call” a library job and pass it parameters, while you cannot “call” an automated job- you can schedule it (and give it parameters) just like you can invoke a program (and give it parameters) from a command shell- but we don’t have analogs like piping and redirection of I/O etc in this execution environment.
They are a lot alike- both can be scheduled and given run-time parameters, and possess fairly similar capabilities.
So why not make all Automated jobs Library Jobs? One strong reason is that Automated Jobs can be constrained [have a set of circumstances spelled out to detail the requirements for running the job- one common one in device testing is the presence of a particular kind of hardware, for instance] while library jobs cannot. Another one I use occasionally perhaps ventures into the realm of the political- making a job an automated job so that it doesn’t wind up being called as a library job if you expect such a usage to have untoward consequences.
The best practice, especially initially, is to make most jobs library jobs- this gives you the most flexibility as you combine them later. You can work on them in pieces and then combine the pieces fairly easily.
Well, James- if you’re still searching for that answer, perhaps this will help. If not, maybe it will help someone else later.
