How to display a sign before the line number gutter?

Question

I'd like to display some characters in left side of the line number gutter just like the vim-syntastic plugin does to show the errors.

back when I was starting to learn vim I saw a plugin doing just that (it displayed the marks per line) I don't really remember which plugin it was as I was just blindly installing everything back then.

Is this doable using vimscirpt or should I use other scripting language like python or something?

Answer 1

I think you are looking for :h :sign:

Here is an example that places a sign "piet", displayed with the text ">>", in    
line 23 of the current file: >
    :sign define piet text=>> texthl=Search
    :exe ":sign place 2 line=23 name=piet file=" . expand("%:p")

For example these two lines give this on my setup (notice the sign >> on the 23rd line):