Question

I need to use sed to convert all occurences of ##XXX## to ${XXX}. X could be any alphabetic character or ‘_’. I know that I need to use something like:

's/##/\${/g' 

But of course that won’t work properly, as it will convert ##FOO## to ${FOO${

Answer 1

Here’s a shot at a better replacement regex:

's/##\([a-zA-Z_]\+\)##/${\1}/g' 

Or if you assume exactly three characters :

's/##\([a-zA-Z_]\{3\}\)##/${\1}/g'