I have a string that is always 3 characters... the first one and the last one are always the same.
Is there a simple way to only display the one in the middle? (which is the only one that changes)
Yes, try doing this, and pick your preferred method =) :
With bash parameter expansion :
You could also use
For variety, here's one way with
If your grep doesn't support perl (
These alternatives only work for one-line input.