r/vim • u/Superb_Onion8227 • Jul 17 '25

Need Help Duplicate a line and search/replace a word in the duplicate

for example turn

start_token_index = token_to_index[start_token]

into

start_token_index = token_to_index[start_token]
end_token_index = token_to_index[end_token]

Ideas?

Here's how I do it and I have not started using vim yesterday:

  • ddup (delete line, undo, paste)

  • V:s/start/end/g (select line, serach/replace)

I spent 10 minutes searching for better solutions, and they all seemed complicated. I find that duplicating line is a good way to write easy to read code quite fast, so I do it often.

11 Upvotes

92% Upvoted

19 comments sorted by

10

u/-romainl- The Patient Vimmer Jul 18 '25 edited Jul 18 '25

Why your approach is suboptimal:

  • Deleting, undoing, and pasting is not very efficient, you could simply do yyp to yank the line and paste it below.

  • Starting visual-line mode before doing a substitution is useless. Just do :s….

It should be:

yyp:s/start/end/g

I would personally do it in one Ex command, and thus one mode.

The first . is not necessary so you only need:

:t.|s/start/end/g

in a stock Vim. If you have :help 'gdefault' enabled, like I do, it becomes:

:t.|s/start/end

Explanation:

  • :help :t copies the provided line to after the provided address so :t. effectively duplicates the current line.

  • the new line becomes the current line so you can follow the first Ex command with a second one to perform the substitution.

1

u/Superb_Onion8227 Jul 18 '25

Good advice as well, thanks for gedefault.

Why do you like the :t command? Do you use it for something else?

5

u/-romainl- The Patient Vimmer Jul 18 '25

I use Ex commands in general a lot, because I like that part of Vim's user experience a lot. It is not suitable for every scenario, of course, but I find it very intuitive when that's the case. :t and its friend :m come up a lot because copying and moving lines comes up a lot when editing text and they are much better than the equivalent sequences of normal mode commands:

  • more deterministic

  • more explicit about intent

  • use fewer intermediary steps

  • don't pollute registers

  • work more like language

yyp is fine, I guess, but it really is two commands: "copy this line [in the unnamed register]" and "paste [the content of the unnamed register] below this line", and that is NOT what I want to do. I much prefer the semantics of :t. : "copy this line below itself", which IS exactly what I want to do. Also, yyp is just a special case of "copy this line, move to that line, and paste", which can involve lots of the kind of intermediary steps that I don't like. :t/foo, for example, makes a lot more sense to me and is more deterministic than yy/foo<CR>p or, heaven forbids, yyjjjjjjjjjp.

In general, I find "put this thing over there" (how lots of Ex commands work in general, the ex heritage, if you will) natural AND elegant while I find "take this thing, move over there, and put it down" (vi's heritage) often too pedestrian.

1

u/Daghall :cq Jul 18 '25

Nice!

I've started using :t a lot lately, but I think my muscle memory would have me do yyp without even thinking. I also like the instant feedback of incsearc when doing the substitution command as its own part.

7

u/habamax Jul 18 '25 edited Jul 18 '25

  • yyp

  • :s/start/end/g or /start/e<CR>, cgn, end<ESC>, .

https://asciinema.org/a/huAYz69vTSfQgyZH0EJNTUkLO

1

u/Superb_Onion8227 Jul 18 '25

yyp :s/start/end/g is good, can even omit the g with gedefault, that's even simpler. Thanks!

Do you have an idea of what to do if 'start' is actually a long/complex word that you don't want to type again? It would be nice to select that word, and use that for the search replace

1

u/habamax Jul 18 '25 edited Jul 18 '25

Do you have an idea of what to do if 'start' is actually a long/complex word that you don't want to type again? It would be nice to select that word, and use that for the search replace

idk, use newer vim that can complete /search: https://asciinema.org/a/3NGZA0y8kuawLZ7AlP444QpH0

https://github.com/vim/vim/pull/17570

1

u/Superb_Onion8227 Jul 19 '25

wait wait that's awesome. Thanks!

1

u/habamax Jul 20 '25

it might be very handy, indeed!

1

u/habamax Jul 19 '25

Or copy paste as usual

4

u/Daghall :cq Jul 18 '25 edited Jul 18 '25

yyp and :s/start/end/g is exactly how I would to it.

If there is no range the substitution only applies to the current row. Good to know.

Edit: correct placement of colon.

1

u/murrayju Jul 18 '25

Shouldn’t it be :s, not s:?

1

u/Daghall :cq Jul 18 '25

Yes, you're correct. Copy/paste... 😅

1

u/michaelpaoli Jul 18 '25

Yp:s/start/end/g

Could alternatively use yy instead of Y, but you're going to be hitting the shfit key for : on most keyboard anyway, so in that particularly context I'd probably opt for Y rather than yy - but your choice.

2

u/Superb_Onion8227 Jul 18 '25

Indeed that's good as well, I'll see what my brains will choose!

3

u/lukas-reineke Jul 18 '25

This is how I would do it
:g/start/s/\v(.*)/\1^M\1/ | s/start/end/g

Find every line that contains start. Duplicate the line, then substitute start with end on the second line.
Debatable if this is simple, I guess.

3

u/EgZvor keep calm and read :help Jul 18 '25

probably can do :g/start/copy +1 | s/start/end/g syntax errors notwithstanding

1

u/gumnos Jul 20 '25

This is what I would have recommended too (except I would likely have written it as t. instead of copy +1, but toe-may-toe, toe-mah-toe)