Removing unneeded information in filename using bash script

I need to remove everything before and after a name in bash script, the following are examples

test_3123_123_testone-2.cpp
abc_3123_12312_a.cpp
johnchase_4123123123_123123123_johnc-1.cpp

I would need them simply change into

testone.cpp
a.cpp
johnc.cpp

But having trouble with regex and trying to get this setup properly, any advice would be great!

>Solution :

the text right before .cpp but ignoring any dashes(-2) if they exist behind it.

Do exactly that. Write it from the end.

• "before .cpp" -> so .cpp must be last
• "ignoring any dashes" – so there is a dash(-2)
  • "if they exist behind it" – the dash is optional
• "the text" – so match the text.

var=test_3123_123_testone-2.cpp
[[ "$var" =~ ([^_-]*)(-[0-9]+)?.cpp$ ]]
echo ${BASH_REMATCH[1]}.cpp