How to merge two multi-line blocks of text in Vim?

An elegant and concise Ex command solving the issue can be obtained by combining the :global, :move, and :join commands. Assuming that the first block of lines starts on the first line of the buffer, and that the cursor is located on the line immediately preceding the first line of the second block, the command is as follows.

:1,g/^/''+m.|-j!

For detailed explanation of this technique, see my answer to an essentially the same question “How to achieve the “paste -d '␣'” behavior out of the box in Vim?”.


Here's how I'd do it (with the cursor on the first line):

qama:5<CR>y$'a$p:5<CR>dd'ajq3@a

You need to know two things:

  • The line number on which the first line of the second group starts (5 in my case), and
  • the number of lines in each group (3 in my example).

Here's what's going on:

  • qa records everything up to the next q into a "buffer" in a.
  • ma creates a mark on the current line.
  • :5<CR> goes to the next group.
  • y$ yanks the rest of the line.
  • 'a returns to the mark, set earlier.
  • $p pastes at the end of the line.
  • :5<CR> returns to the second group's first line.
  • dd deletes it.
  • 'a returns to the mark.
  • jq goes down one line, and stops recording.
  • 3@a repeats the action for each line (3 in my case)

You can certainly do all this with a single copy/paste (using block-mode selection), but I'm guessing that's not what you want.

If you want to do this with just Ex commands

:5,8del | let l=split(@") | 1,4s/$/\=remove(l,0)/

will transform

work it 
make it 
do it 
makes us 
harder
better
faster
stronger
~

into

work it harder
make it better
do it faster
makes us stronger
~

UPDATE: An answer with this many upvotes deserves a more thorough explanation.

In Vim, you can use the pipe character (|) to chain multiple Ex commands, so the above is equivalent to

:5,8del
:let l=split(@")
:1,4s/$/\=remove(l,0)/

Many Ex commands accept a range of lines as a prefix argument - in the above case the 5,8 before the del and the 1,4 before the s/// specify which lines the commands operate on.

del deletes the given lines. It can take a register argument, but when one is not given, it dumps the lines to the unnamed register, @", just like deleting in normal mode does. let l=split(@") then splits the deleted lines into a list, using the default delimiter: whitespace. To work properly on input that had whitespace in the deleted lines, like:

more than 
hour 
our 
never 
ever
after
work is
over
~

we'd need to specify a different delimiter, to prevent "work is" from being split into two list elements: let l=split(@","\n").

Finally, in the substitution s/$/\=remove(l,0)/, we replace the end of each line ($) with the value of the expression remove(l,0). remove(l,0) alters the list l, deleting and returning its first element. This lets us replace the deleted lines in the order in which we read them. We could instead replace the deleted lines in reverse order by using remove(l,-1).


To join blocks of line, you have to do the following steps:

  1. Go to the third line: jj
  2. Enter visual block mode: CTRL-v
  3. Anchor the cursor to the end of the line (important for lines of differing length): $
  4. Go to the end: CTRL-END
  5. Cut the block: x
  6. Go to the end of the first line: kk$
  7. Paste the block here: p

The movement is not the best one (I'm not an expert), but it works like you wanted. Hope there will be a shorter version of it.

Here are the prerequisits so this technique works well:

  • All lines of the starting block (in the example in the question abc and def) have the same length XOR
  • the first line of the starting block is the longest, and you don't care about the additional spaces in between) XOR
  • The first line of the starting block is not the longest, and you additional spaces to the end.

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