Batch update cb field based on user group

How do I update a specific CB field based for members of a specific User group? The batch tools under Members are fixed. Perhaps CB Auto actions? But how in that case?

Select all users Group = A and set CB_Field = X

At this time there's no batch functionality for fields. Best I can suggest is a Field action in CB Auto Actions acting on the after user login trigger so it'll change the field after they login. There's the Internal Users trigger in CB Auto Actions which will loop every user through your auto action that could also work, but that's a very heavy operation. As for limiting it to a specific usergroup simply use the Access parameter of the auto action.

Thanks! You mention an Internal Users trigger? Could you please give a little bit more on how set it up? The site is very, very little used, perhaps one or two access per day, and in total only 250 users. Perhaps the action won't be that heavy...?

Internal Users loops your entire userbase through the auto action. It's not about how many users you've active per day, but how many you have total. So if you've 10,000 users they will all be sent through the auto action. It has no batching functionality at this time so this can be a very heavy operation. To use it add the Internal Users trigger to your auto action then run the URL provided in CB Auto Actions > Parameters; typically you'd schedule it with CRON for regularly ran tasks. However I think in your case the after login approach should be fine.