I wrote a function, the function is used to add comments to some lines, the content is as follows:

func Add(x)
  call setline(a:x+1, "\  //**************************************************************")
  call setline(a:x+2, "\  // **** Note ****")
  call setline(a:x+3, "\  //**************************************************************")

When I use the Add(100) function in vi, I want the content of the 100th line to remain unchanged, and 3 additional lines are used to add text.

1 Answer 1


Use append() function instead as described in :h setline() help section.

It accepts the line number and and either a text line or a list of text lines that would be inserted/appended after given line number.

func! AddCommentHeader(lnum) abort
    let comment_header = 
                \'//******* Note *****************************************',
    let lnum = a:lnum < 1 ? line('.') : a:lnum

    call append(lnum, comment_header)

nnoremap gci :<C-U>call AddCommentHeader(v:count)<CR>

In the example above there is a function that accepts a line number to insert a comment header after. If the line number is 0 or basically less then 1 it would insert comment header right after the current line:

let lnum = a:lnum < 1 ? line('.') : a:lnum

This is ternary operator condition ? return if true : return if false.

The mapping after function maps gci to call a function. There are 2 interesting things there <C-U> and v:count:

  • we would like to provide a count you prepend your mapping with to a function, like if I want to add comment header after line 100 I would do 100gci -- this is what built-in v:count variable for.
  • we don't want default range to be applied to our function which we call from within commandline mode :call ... if we provide a count for it. Try for example to type 100: and see your command line is prefilled with :.,.+99 <--- this thing we delete with <C-U> in the mapping:
    nnoremap gci :<C-U>call AddCommentHeader(v:count)<CR>


Don't forget to use K mapping to call builtin help on a function under cursor. Also :h function-list might be useful.

  • Your answer is very helpful, thank you very much. Commented Mar 20, 2021 at 9:47

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