Removing duplicate rows in vi?

Question

I have a text file that contains a long list of entries (one on each line). Some of these are duplicates, and I would like to know if it is possible (and if so, how) to remove

Answer 1

This version only removes repeated lines that are contigous. I mean, only deletes consecutive repeated lines. Using the given map the function does note mess up with blank lines. But if change the REGEX to match start of line ^ it will also remove duplicated blank lines.

" function to delete duplicate lines
function! DelDuplicatedLines()
    while getline(".") == getline(line(".") - 1)
        exec 'norm! ddk'
    endwhile
    while getline(".") == getline(line(".") + 1)
        exec 'norm! dd'
    endwhile
endfunction
nnoremap d :g/./call DelDuplicatedLines()