How to delete text in a file based on regular expression using vim

Question

I have an XML file like this:

<fruit><apple>100</apple><banana>200</banana></fruit>
<fruit><apple>150</apple><banana>250</banana></fruit>

Now I want delete all the text in the file except the words in tag apple. That is, the file should contain:

100
150

How can I achive this?

Answer 1

:%s/.*apple>\(.*\)<\/apple.*/\1/

That should do what you need. Worked for me.

Basically just grabbing everything up to and including the tag, then backreferences everything between the apple begin and end tag, and matches to the rest of the line. Replaces it with the first backreference, which was the stuff between the apple tags.