EDIT: I've gotten some help from Splunk support team and now can get oneshot blocking calls working using the url below:
https://localhost:8089/services/search/jobs?exec_mode=oneshot&output_mode=json&search="search index=_internal | head 10"
however it is unclear to me how I would invoke a oneshot REST call to a saved service. I'm guessing it would look something like the url below but haven't had any success after playign with a few combinations usually a '404 not found':
https://localhost:8089/saved/searches/{name}?exec_mode=oneshot&output_mode=json
can someone help please?
