Hi Scott,
The CLI command for running a query is "im issues". As part of that command you can pass in a query name or a query definition to narrow down the list of items to what you are looking for, in this case the tasks with assigned user = xyz
The query definition format can be a bit tricky, so a good way to start is to set up a regular query with all the filters you want in the GUI, then look at the history tab of that query to see it in "query definition" format.
Of course once you have the query built in the gui you can always use the query name in order to run the im issues command, but sometimes you need to programmatically alter the definition to make a lot of similar queries or something like that.
Hope that helps,
Matt
