Undo

Nvim :help pages, generated from source using the tree-sitter-vimdoc parser.

Undo and redo

The basics are explained in section 02.5 of the user manual.

1. Undo and redo commands undo-commands

<Undo> or undo <Undo> u u Undo [count] changes.

:u :un :undo :u[ndo] Undo one change. E830 :u[ndo] {N} Jump to after change number {N}. See undo-branches for the meaning of {N}.

:u[ndo]! Undo one change and remove it from undo history. E5767 :u[ndo]! {N} Like ":u[ndo] {N}", but forget all changes in the current undo branch up until {N}. You may only use ":undo! {N}" to move backwards in the same undo branch, not to redo or switch to a different undo branch.

CTRL-R CTRL-R Redo [count] changes which were undone.

:red :redo redo :red[o] Redo one change which was undone.

U U Undo all latest changes on one line, the line where the latest change was made. U itself also counts as a change, and thus U undoes a previous U.

The last changes are remembered. You can use the undo and redo commands above to revert the text to how it was before each change. You can also apply the changes again, getting back the text before the undo.

The "U" command is treated by undo/redo just like any other command. Thus a "u" command undoes a "U" command and a 'CTRL-R' command redoes it again. When mixing "U", "u" and 'CTRL-R' you will notice that the "U" command will restore the situation of a line to before the previous "U" command. This may be confusing. Try it out to get used to it. The "U" command will always mark the buffer as changed. When "U" changes the buffer back to how it was without changes, it is still considered changed. Use "u" to undo changes until the buffer becomes unchanged.

2. Two ways of undo undo-two-ways

How undo and redo commands work depends on the 'u' flag in 'cpoptions'. There is the Vim way ('u' excluded) and the Vi-compatible way ('u' included). In the Vim way, "uu" undoes two changes. In the Vi-compatible way, "uu" does nothing (undoes an undo).

'u' excluded, the Vim way: You can go back in time with the undo command. You can then go forward again with the redo command. If you make a new change after the undo command, the redo will not be possible anymore.

'u' included, the Vi-compatible way: The undo command undoes the previous change, and also the previous undo command. The redo command repeats the previous undo command. It does NOT repeat a change command, use "." for that.

Examples Vim way Vi-compatible way

"uu" two times undo no-op "u CTRL-R" no-op two times undo

Rationale: Nvi uses the "." command instead of CTRL-R. Unfortunately, this is not Vi compatible. For example "dwdwu." in Vi deletes two words, in Nvi it does nothing.

3. Undo blocks undo-blocks

One undo command normally undoes a typed command, no matter how many changes that command makes. This sequence of undo-able changes forms an undo block. Thus if the typed key(s) call a function, all the commands in the function are undone together.

If you want to write a function or script that doesn't create a new undoable change but joins in with the previous change use this command:

:undoj :undojoin E790 :undoj[oin] Join further changes with the previous undo block. Warning: Use with care, it may prevent the user from properly undoing changes. Don't use this after undo or redo.

This is most useful when you need to prompt the user halfway through a change. For example in a function that calls getchar(). Do make sure that there was a related change before this that you must join with.

This doesn't work by itself, because the next key press will start a new change again. But you can do something like this:

:undojoin | delete

After this a "u" command will undo the delete command and the previous change. undo-break undo-close-block To do the opposite, use a new undo block for the next change, in Insert mode use CTRL-G u. This is useful if you want an insert command to be undoable in parts. E.g., for each sentence. i_CTRL-G_u

Setting the value of 'undolevels' also closes the undo block. Even when the new value is equal to the old value. Use g:undolevels to explicitly read and write only the global value of 'undolevels'.

let &g:undolevels = &g:undolevels

Note that the similar-looking assignment let &undolevels=&undolevels does not preserve the global option value of 'undolevels' in the event that the local option has been set to a different value. For example:

" Start with different global and local values for 'undolevels'.
let &g:undolevels = 1000
let &l:undolevels = 2000
" This assignment changes the global option to 2000:
let &undolevels = &undolevels

4. Undo branches undo-branches undo-tree

Above we only discussed one line of undo/redo. But it is also possible to branch off. This happens when you undo a few changes and then make a new change. The undone changes become a branch. You can go to that branch with the following commands.

This is explained in the user manual: usr_32.txt.

:undol :undolist :undol[ist] List the leafs in the tree of changes. Example:

number changes when saved

88 88 2010/01/04 14:25:53 108 107 08/07 12:47:51 136 46 13:33:01 7 166 164 3 seconds ago

The "number" column is the change number. This number continuously increases and can be used to identify a specific undo-able change, see :undo. The "changes" column is the number of changes to this leaf from the root of the tree. The "when" column is the date and time when this change was made. The four possible formats are: N seconds ago HH:MM:SS hour, minute, seconds MM/DD HH:MM:SS idem, with month and day YYYY/MM/DD HH:MM:SS idem, with year The "saved" column specifies, if this change was written to disk and which file write it was. This can be used with the :later and :earlier commands. For more details use the undotree() function.

g- g- Go to older text state. With a count repeat that many times. :ea :earlier :earlier {count} Go to older text state {count} times. :earlier {N}s Go to older text state about {N} seconds before. :earlier {N}m Go to older text state about {N} minutes before. :earlier {N}h Go to older text state about {N} hours before. :earlier {N}d Go to older text state about {N} days before.

:earlier {N}f Go to older text state {N} file writes before. When changes were made since the last write ":earlier 1f" will revert the text to the state when it was written. Otherwise it will go to the write before that. When at the state of the first file write, or when the file was not written, ":earlier 1f" will go to before the first change.

g+ g+ Go to newer text state. With a count repeat that many times. :lat :later :later {count} Go to newer text state {count} times. :later {N}s Go to newer text state about {N} seconds later. :later {N}m Go to newer text state about {N} minutes later. :later {N}h Go to newer text state about {N} hours later. :later {N}d Go to newer text state about {N} days later.

:later {N}f Go to newer text state {N} file writes later. When at the state of the last file write, ":later 1f" will go to the newest text state.

Note that text states will become unreachable when undo information is cleared for 'undolevels'.

Don't be surprised when moving through time shows multiple changes to take place at a time. This happens when moving through the undo tree and then making a new change.

EXAMPLE

Start with this text:

one two three

Delete the first word by pressing "x" three times:

ne two three

e two three

two three

Now undo that by pressing "u" three times:

e two three

ne two three

one two three

Delete the second word by pressing "x" three times:

one wo three

one o three

one three

Now undo that by using "g-" three times:

one o three

one wo three

two three

You are now back in the first undo branch, after deleting "one". Repeating "g-" will now bring you back to the original text:

e two three

ne two three

one two three

Jump to the last change with ":later 1h":

one three

And back to the start again with ":earlier 1h":

one two three

Note that using "u" and CTRL-R will not get you to all possible text states while repeating "g-" and "g+" does.

5. Undo persistence undo-persistence persistent-undo

When unloading a buffer Vim normally destroys the tree of undos created for that buffer. By setting the 'undofile' option, Vim will automatically save your undo history when you write a file and restore undo history when you edit the file again.

The 'undofile' option is checked after writing a file, before the BufWritePost autocommands. If you want to control what files to write undo information for, you can use a BufWritePre autocommand:

au BufWritePre /tmp/* setlocal noundofile

Vim saves undo trees in a separate undo file, one for each edited file, using a simple scheme that maps filesystem paths directly to undo files. Vim will detect if an undo file is no longer synchronized with the file it was written for (with a hash of the file contents) and ignore it when the file was changed after the undo file was written, to prevent corruption. An undo file is also ignored if its owner differs from the owner of the edited file, except when the owner of the undo file is the current user. Set 'verbose' to get a message about that when opening a file.

Location of the undo files is controlled by the 'undodir' option, by default they are saved to the dedicated directory in the application data folder.

You can also save and restore undo histories by using ":wundo" and ":rundo" respectively: :wundo :rundo :wundo[!] {file} Write undo history to {file}. When {file} exists and it does not look like an undo file (the magic number at the start of the file is wrong), then this fails, unless the ! was added. If it exists and does look like an undo file it is overwritten. If there is no undo-history, nothing will be written. Implementation detail: Overwriting happens by first deleting the existing file and then creating a new file with the same name. So it is not possible to overwrite an existing undofile in a write-protected directory.

:rundo {file} Read undo history from {file}.

You can use these in autocommands to explicitly specify the name of the history file. E.g.:

au BufReadPost * call ReadUndo()
au BufWritePost * call WriteUndo()
func ReadUndo()
  if filereadable(expand('%:h') .. '/UNDO/' .. expand('%:t'))
    rundo %:h/UNDO/%:t
  endif
endfunc
func WriteUndo()
  let dirname = expand('%:h') .. '/UNDO'
  if !isdirectory(dirname)
    call mkdir(dirname)
  endif
  wundo %:h/UNDO/%:t
endfunc

You should keep 'undofile' off, otherwise you end up with two undo files for every write.

You can use the undofile() function to find out the file name that Vim would use.

Note that while reading/writing files and 'undofile' is set most errors will be silent, unless 'verbose' is set. With :wundo and :rundo you will get more error messages, e.g., when the file cannot be read or written.

NOTE: undo files are never deleted by Vim. You need to delete them yourself.

Reading an existing undo file may fail for several reasons: E822 It cannot be opened, because the file permissions don't allow it. E823 The magic number at the start of the file doesn't match. This usually means it is not an undo file. E824 The version number of the undo file indicates that it's written by a newer version of Vim. You need that newer version to open it. Don't write the buffer if you want to keep the undo info in the file. "File contents changed, cannot use undo info" The file text differs from when the undo file was written. This means the undo file cannot be used, it would corrupt the text. This also happens when 'encoding' differs from when the undo file was written. E825 The undo file does not contain valid contents and cannot be used. "Not reading undo file, owner differs" The undo file is owned by someone else than the owner of the text file. For safety the undo file is not used.

Writing an undo file may fail for these reasons: E828 The file to be written cannot be created. Perhaps you do not have write permissions in the directory. "Cannot write undo file in any directory in 'undodir'" None of the directories in 'undodir' can be used. "Will not overwrite with undo file, cannot read" A file exists with the name of the undo file to be written, but it cannot be read. You may want to delete this file or rename it. "Will not overwrite, this is not an undo file" A file exists with the name of the undo file to be written, but it does not start with the right magic number. You may want to delete this file or rename it. "Skipping undo file write, nothing to undo" There is no undo information to be written, nothing has been changed or 'undolevels' is negative. E829 An error occurred while writing the undo file. You may want to try again.

6. Remarks about undo undo-remarks

The number of changes that are remembered is set with the 'undolevels' option. If it is zero, the Vi-compatible way is always used. If it is negative no undo is possible. Use this if you are running out of memory.

clear-undo When you set 'undolevels' to -1 the undo information is not immediately cleared, this happens at the next change. To force clearing the undo information you can use these commands:

:let old_undolevels = &l:undolevels
:setlocal undolevels=-1
:exe "normal a \<BS>\<Esc>"
:let &l:undolevels = old_undolevels
:unlet old_undolevels

Note use of &l:undolevels to explicitly read the local value of 'undolevels' and the use of :setlocal to change only the local option (which takes precedence over the corresponding global option value). Saving the option value via the use of &undolevels is unpredictable; it reads either the local value (if one has been set) or the global value (otherwise). Also, if a local value has been set, changing the option via :set undolevels will change both the global and local values, requiring extra work to save and restore both values.

Marks for the buffer ('a to 'z) are also saved and restored, together with the text.

When all changes have been undone, the buffer is not considered to be changed. It is then possible to exit Vim with ":q" instead of ":q!". Note that this is relative to the last write of the file. Typing "u" after ":w" actually changes the buffer, compared to what was written, so the buffer is considered changed then.

When manual folding is being used, the folds are not saved and restored. Only changes completely within a fold will keep the fold as it was, because the first and last line of the fold don't change.

The numbered registers can also be used for undoing deletes. Each time you delete text, it is put into register "1. The contents of register "1 are shifted to "2, etc. The contents of register "9 are lost. You can now get back the most recent deleted text with the put command: '"1P'. (also, if the deleted text was the result of the last delete or copy operation, 'P' or 'p' also works as this puts the contents of the unnamed register). You can get back the text of three deletes ago with '"3P'.

redo-register If you want to get back more than one part of deleted text, you can use a special feature of the repeat command ".". It will increase the number of the register used. So if you first do '"1P', the following "." will result in a '"2P'. Repeating this will result in all numbered registers being inserted.

Example: If you deleted text with 'dd....' it can be restored with '"1P....'.

If you don't know in which register the deleted text is, you can use the :display command. An alternative is to try the first register with '"1P', and if it is not what you want do 'u.'. This will remove the contents of the first put, and repeat the put command for the second register. Repeat the 'u.' until you got what you want.