Well, ctokens should probably have a '-q' option and an exit status to
tell if the tokens are valid.  If I were you, I'd add that and then
use it.
The only complexity is how you handle tokens that are expiring in say
10 minutes; perhaps ctokens should have a second option to make exit
status depend on if tokens are valid for > x minutes.

-- 
        Greg Troxel <gdt_at_ir.bbn.com>