How to delete all Lines not starting with.. [Notepad++]

Question

I've got a rather large file (Over 1GB) which I'm trying to filter out the mass of. I'd like to delete all lines not containing a specific url in them.

I'm unsure how I'd do this and am not familiar with expressions in Notepad++ so as basic of an answer as possible would be great.

Edit: I'd like to do this for multiple files at once so if possible using the find in files tab would be best.

Answer 1

You could do:

1. Search the lines that contain the url:
   in the search box, give your url and in the tab "marks" click on Mark lines then search all
2. Then in menu Search > Bookmark > invert bookmarks
3. Then in menu Search > Bookmark > Remove bookmarked lines.

I haven't an english version of Noptepad++ so the name of functions could be a little bit different.