Say I have a string file name `aa.bb.cc.xx.txt` 
I would like to remove the first content between . and . (remove .xx) before the .txt to have `aa.bb.cc.txt`. 

I don't want to use rev, cut and rev because this uses 3 commands

```
echo 'aa.bb.cc.xx.rpm' |rev | cut -d '.' --complement -s -f 2 |rev

```

Is there any better solution by using bash?
Thanks