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

Question

What I have is this:

progname=${0%.*}
progname=${progname##*/}

Can this be nested (or not) into one line, i.e. a single expression?

I'm trying to strip the path and extension off of a script name so that only the base name is left. The above two lines work fine. My 'C' nature is simply driving me to obfuscate these even more.

Answer 1

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.

Answer 2

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.

Answer 3

The following option has worked for me:

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

Output is:

par2