RTC-SCM-CLI: how to find out if a file in my sandbox already belongs to an active changeset ?

I'm writing a wrapper tool around RTC-SCM-CLI

Our requirement is that, during checkin of a file, the user should have the option
- to create a new changeset [or]
- select any other active changeset that is already present in that component

Once the user checks in a file into a changeset, as long as that changeset remains active, it is not possible for the user to link this file to another changeset during his subsequent checkin operations on that file. It would lead to the below error:

Cannot check-in <file> because it is already being changed in another active change set.
Instead of picking a specific change set, try allowing the check-in to pick the correct change set.

Now, my question is, how the user can be prevented in getting into this situation ?
Is there a CLI command available which will let me know if a file in my sandbox already belongs to an active changeset of a component, given its relative path in the sandbox ?
(Once I have this information, then it is easier for me to force the user to either store his changes into that active changeset [or] close that active changeset and open a new one)

Thanks for your help.