Question

I know I can select the lines and use something like

:w ! sort | uniq -c

Is there a better solution?

Answer 1

With vimscript it is easy to do that:

if getline(line_number_1) ==# getline(line_number_2)
   echo 'hello'
endif

where *line_number_1* and *line_number_2* are integers. You can compute the current line number with line('.').

See :help getline() and help line(). Broader documentation is help eval.txt.