In Vim, how to remove all lines that are duplicate somewhere

Question

I have a file that contains lines as follows:

one one
one one
two two two
one one
three three
one one
three three
four

I want to remove all occurrences of the duplicate lines from the file and leave only the non-duplicate lines. So, in the example above, the result should be:

two two two
four

I saw this answer to a similar looking question. I tried to modify the ex one-liner as given below:

:syn clear Repeat | g/^\(.*\)\n\ze\%(.*\n\)*\1$/exe 'syn match Repeat "^' . escape(getline ('.'), '".\^$*[]') . '$"' | d

But it does not remove all occurrences of the duplicate lines, it removes only some occurrences.

How can I do this in vim? or specifically How can I do this with ex in vim?

To clarify, I am not looking for sort u.

Answer 1

if you are on linux box with awk available, this line works for your needs:

:%!awk '{a[$0]++}END{for(x in a)if(a[x]==1)print x}'

Answer 2

If you have access to UNIX-style commands, you could do:

:%!sort | uniq -u

The -u option to the uniq command performs the task you require. From the uniq command's help text:

   -u, --unique
          only print unique lines

I should note however that this answer assumes that you don't mind that the output doesn't match any sort order that your input file might have already.