VIM Removing duplicate lines [duplicate]

Question

I have an issue regarding editing strings using VIM, I currently have the following strings:

The red fox.

The red fox.

The blue fish.

The blue fish.

Question: how do I remove the duplicates? and lets say that I have a minimum of 500 lines with duplicates

Expected result:

The red fox.

The blue fish.

Answer 1

If you do not need to preserve the order of the lines you can do:

:sort u

i.e. sort all lines and remove duplicates.

Answer 2

If you don't want to sort lines:

:g/^\(.*\)$\n\1/d

Explanation:

:g/^\(.*\)$\n\1/d
 g/            /d   # Delete the lines matching the regexp
   ^\(.*\)$         # Match a whole line and put it in substitution register 1
           \n\1     # Match substitution register 1 preceded by new line