How to left and right strip at the same time?

Question

I use ${parameter#word} and ${parameter%word} to remove prefix and postfix of string.

$ x=2012-hello.jpg
$ y=${x#*-}
$ z=${y%.*}
$ echo $z
hello

How can I do them at once instead of two.

Answer 1

It is not possible with parameter expansion, but it is possible with regular expression matching:

x=2012-hello.jpg
[[ $x =~ .*-(.*)\.jpg ]] && echo ${BASH_REMATCH[1]}

Answer 2

If you are OK with using sed instead of parameter expansion:

x=2012-hello.jpg
$ z="$(sed -e 's/.*-\(.*\)\..*/\1/' <<<"$x")"
$ echo "$z"
hello