Get list of extensions logged into queue

Is it possible to get a list of which extensions are logged into which queues? Can this be taking from the database or sqlite file?

In its most basic form, from the Asteirsk CLI:

queue show

and/or

queue show xxxx

where xxxx is the queue number

Ok I will try that, but is there a way to get this via the REST API to be able to use the data in a system I’m developing?

I doubt it, but you should be able to get the information from querying AMI.