How to build a conditional assignment in bash?

If you want a way to define defaults in a shell script, use code like this:

: ${VAR:="default"}

Yes, the line begins with ':'. I use this in shell scripts so I can override variables in ENV, or use the default.

This is related because this is my most common use case for that kind of logic. ;]

As per Jonathan's comment:

variable=$(( 1 == 1 ? 1 : 0 ))  

EDIT:

I revised the original answer which just echo'd the value of the condition operator, it didn't actually show any assignment.