What is indirect expansion? What does ${!var*} mean?

Question

I\'m reading \"Bash Guide for Beginners\". It says:

If the first character of PARAMETER is an exclamation point, Bash uses the

Answer 1

Yes, it searches for all possible expansions of variables after the !. If you had done:

echo ${!NP*}

you would get only NPX_PLUGIN_PATH.

Consider the following example:

:~> export myVar="hi"
:~> echo ${!my*}
    myVar
:~> export ${!my*}="bye"
:~> echo $myVar
    bye