Can ${var} parameter expansion expressions be nested in bash?

If by nest, you mean something like this:

#!/bin/bash

export HELLO="HELLO"
export HELLOWORLD="Hello, world!"

echo ${${HELLO}WORLD}

Then no, you can't nest ${var} expressions. The bash syntax expander won't understand it.

However, if I understand your problem right, you might look at using the basename command - it strips the path from a given filename, and if given the extension, will strip that also. For example, running basename /some/path/to/script.sh .sh will return script.

An old thread but perhaps the answer is the use of Indirection:${!PARAMETER}

For e.g., consider the following lines:

H="abc"
PARAM="H"
echo ${!PARAM} #gives abc

Bash supports indirect expansion:

$ FOO_BAR="foobar"
$ foo=FOO
$ foobar=${foo}_BAR
$ echo ${foobar}
FOO_BAR
$ echo ${!foobar}
foobar

This should support the nesting you are looking for.

The following option has worked for me:

NAME="par1-par2-par3"
echo $(TMP=${NAME%-*};echo ${TMP##*-})

Output is:

par2