Bash variable substitution on find's output through exec
It took me a while to get the question. Basically you are asking if something like:
echo "${test.png%.png}"could be used to get the word test.
The answer is no. The string manipulation operators starting with ${ are a subset of the parameter substitution operators. They work only on variables, not with string literals, meaning you need to store the string in a variable before. Like this:
img="test.png"echo "${img%.png}"Just for travellers from Google, I would use rename for this particular task. (As the OP already mentioned in his question). The command could look like this:
find -name '*png' -execdir rename 's/\.png/_copy.png/' {} +