Get list of variables whose name matches a certain pattern

Question

In bash

echo ${!X*} 

will print all the names of the variables whose name starts with 'X'.
Is it possible to get the same with an arbitrary pattern, e.g. get all the names of the variables whose name contains an 'X' in any position?

Answer 1

Use the builtin command compgen:

compgen -A variable | grep X 

Answer 2

This should do it:

env | grep ".*X.*" 

Edit: sorry, that looks for X in the value too. This version only looks for X in the var name

env | awk -F "=" '{print $1}' | grep ".*X.*" 

As Paul points out in the comments, if you're looking for local variables too, env needs to be replaced with set:

set | awk -F "=" '{print $1}' | grep ".*X.*"