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392 lines
15 KiB
Plaintext
*undo.txt* For Vim version 7.4. Last change: 2014 May 24
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VIM REFERENCE MANUAL by Bram Moolenaar
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Undo and redo *undo-redo*
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The basics are explained in section |02.5| of the user manual.
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1. Undo and redo commands |undo-commands|
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2. Two ways of undo |undo-two-ways|
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3. Undo blocks |undo-blocks|
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4. Undo branches |undo-branches|
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5. Undo persistence |undo-persistence|
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6. Remarks about undo |undo-remarks|
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==============================================================================
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1. Undo and redo commands *undo-commands*
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<Undo> or *undo* *<Undo>* *u*
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u Undo [count] changes.
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*:u* *:un* *:undo*
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:u[ndo] Undo one change.
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*E830*
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:u[ndo] {N} Jump to after change number {N}. See |undo-branches|
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for the meaning of {N}.
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*CTRL-R*
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CTRL-R Redo [count] changes which were undone.
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*:red* *:redo* *redo*
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:red[o] Redo one change which was undone.
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*U*
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U Undo all latest changes on one line, the line where
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the latest change was made. |U| itself also counts as
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a change, and thus |U| undoes a previous |U|.
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The last changes are remembered. You can use the undo and redo commands above
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to revert the text to how it was before each change. You can also apply the
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changes again, getting back the text before the undo.
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The "U" command is treated by undo/redo just like any other command. Thus a
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"u" command undoes a "U" command and a 'CTRL-R' command redoes it again. When
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mixing "U", "u" and 'CTRL-R' you will notice that the "U" command will
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restore the situation of a line to before the previous "U" command. This may
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be confusing. Try it out to get used to it.
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The "U" command will always mark the buffer as changed. When "U" changes the
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buffer back to how it was without changes, it is still considered changed.
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Use "u" to undo changes until the buffer becomes unchanged.
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==============================================================================
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2. Two ways of undo *undo-two-ways*
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How undo and redo commands work depends on the 'u' flag in 'cpoptions'.
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There is the Vim way ('u' excluded) and the Vi-compatible way ('u' included).
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In the Vim way, "uu" undoes two changes. In the Vi-compatible way, "uu" does
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nothing (undoes an undo).
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'u' excluded, the Vim way:
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You can go back in time with the undo command. You can then go forward again
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with the redo command. If you make a new change after the undo command,
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the redo will not be possible anymore.
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'u' included, the Vi-compatible way:
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The undo command undoes the previous change, and also the previous undo command.
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The redo command repeats the previous undo command. It does NOT repeat a
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change command, use "." for that.
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Examples Vim way Vi-compatible way ~
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"uu" two times undo no-op
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"u CTRL-R" no-op two times undo
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Rationale: Nvi uses the "." command instead of CTRL-R. Unfortunately, this
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is not Vi compatible. For example "dwdwu." in Vi deletes two
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words, in Nvi it does nothing.
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==============================================================================
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3. Undo blocks *undo-blocks*
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One undo command normally undoes a typed command, no matter how many changes
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that command makes. This sequence of undo-able changes forms an undo block.
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Thus if the typed key(s) call a function, all the commands in the function are
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undone together.
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If you want to write a function or script that doesn't create a new undoable
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change but joins in with the previous change use this command:
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*:undoj* *:undojoin* *E790*
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:undoj[oin] Join further changes with the previous undo block.
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Warning: Use with care, it may prevent the user from
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properly undoing changes. Don't use this after undo
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or redo.
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This is most useful when you need to prompt the user halfway through a change.
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For example in a function that calls |getchar()|. Do make sure that there was
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a related change before this that you must join with.
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This doesn't work by itself, because the next key press will start a new
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change again. But you can do something like this: >
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:undojoin | delete
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After this an "u" command will undo the delete command and the previous
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change.
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To do the opposite, break a change into two undo blocks, in Insert mode use
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CTRL-G u. This is useful if you want an insert command to be undoable in
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parts. E.g., for each sentence. |i_CTRL-G_u|
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Setting the value of 'undolevels' also breaks undo. Even when the new value
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is equal to the old value.
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==============================================================================
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4. Undo branches *undo-branches* *undo-tree*
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Above we only discussed one line of undo/redo. But it is also possible to
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branch off. This happens when you undo a few changes and then make a new
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change. The undone changes become a branch. You can go to that branch with
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the following commands.
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This is explained in the user manual: |usr_32.txt|.
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*:undol* *:undolist*
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:undol[ist] List the leafs in the tree of changes. Example:
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number changes when saved ~
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88 88 2010/01/04 14:25:53
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108 107 08/07 12:47:51
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136 46 13:33:01 7
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166 164 3 seconds ago
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The "number" column is the change number. This number
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continuously increases and can be used to identify a
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specific undo-able change, see |:undo|.
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The "changes" column is the number of changes to this
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leaf from the root of the tree.
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The "when" column is the date and time when this
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change was made. The four possible formats are:
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N seconds ago
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HH:MM:SS hour, minute, seconds
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MM/DD HH:MM:SS idem, with month and day
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YYYY/MM/DD HH:MM:SS idem, with year
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The "saved" column specifies, if this change was
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written to disk and which file write it was. This can
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be used with the |:later| and |:earlier| commands.
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For more details use the |undotree()| function.
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*g-*
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g- Go to older text state. With a count repeat that many
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times.
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*:ea* *:earlier*
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:earlier {count} Go to older text state {count} times.
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:earlier {N}s Go to older text state about {N} seconds before.
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:earlier {N}m Go to older text state about {N} minutes before.
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:earlier {N}h Go to older text state about {N} hours before.
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:earlier {N}d Go to older text state about {N} days before.
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:earlier {N}f Go to older text state {N} file writes before.
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When changes were made since the last write
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":earlier 1f" will revert the text to the state when
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it was written. Otherwise it will go to the write
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before that.
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When at the state of the first file write, or when
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the file was not written, ":earlier 1f" will go to
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before the first change.
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*g+*
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g+ Go to newer text state. With a count repeat that many
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times.
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*:lat* *:later*
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:later {count} Go to newer text state {count} times.
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:later {N}s Go to newer text state about {N} seconds later.
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:later {N}m Go to newer text state about {N} minutes later.
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:later {N}h Go to newer text state about {N} hours later.
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:later {N}d Go to newer text state about {N} days later.
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:later {N}f Go to newer text state {N} file writes later.
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When at the state of the last file write, ":later 1f"
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will go to the newest text state.
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Note that text states will become unreachable when undo information is cleared
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for 'undolevels'.
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Don't be surprised when moving through time shows multiple changes to take
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place at a time. This happens when moving through the undo tree and then
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making a new change.
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EXAMPLE
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Start with this text:
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one two three ~
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Delete the first word by pressing "x" three times:
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ne two three ~
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e two three ~
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two three ~
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Now undo that by pressing "u" three times:
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e two three ~
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ne two three ~
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one two three ~
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Delete the second word by pressing "x" three times:
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one wo three ~
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one o three ~
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one three ~
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Now undo that by using "g-" three times:
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one o three ~
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one wo three ~
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two three ~
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You are now back in the first undo branch, after deleting "one". Repeating
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"g-" will now bring you back to the original text:
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e two three ~
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ne two three ~
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one two three ~
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Jump to the last change with ":later 1h":
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one three ~
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And back to the start again with ":earlier 1h":
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one two three ~
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Note that using "u" and CTRL-R will not get you to all possible text states
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while repeating "g-" and "g+" does.
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==============================================================================
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5. Undo persistence *undo-persistence* *persistent-undo*
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When unloading a buffer Vim normally destroys the tree of undos created for
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that buffer. By setting the 'undofile' option, Vim will automatically save
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your undo history when you write a file and restore undo history when you edit
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the file again.
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The 'undofile' option is checked after writing a file, before the BufWritePost
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autocommands. If you want to control what files to write undo information
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for, you can use a BufWritePre autocommand: >
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au BufWritePre /tmp/* setlocal noundofile
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Vim saves undo trees in a separate undo file, one for each edited file, using
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a simple scheme that maps filesystem paths directly to undo files. Vim will
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detect if an undo file is no longer synchronized with the file it was written
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for (with a hash of the file contents) and ignore it when the file was changed
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after the undo file was written, to prevent corruption. An undo file is also
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ignored if its owner differs from the owner of the edited file, except when
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the owner of the undo file is the current user. Set 'verbose' to get a
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message about that when opening a file.
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Location of the undo files is controlled by the 'undodir' option, by default
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they are saved to the dedicated directory in the application data folder.
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You can also save and restore undo histories by using ":wundo" and ":rundo"
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respectively:
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*:wundo* *:rundo*
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:wundo[!] {file}
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Write undo history to {file}.
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When {file} exists and it does not look like an undo file
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(the magic number at the start of the file is wrong), then
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this fails, unless the ! was added.
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If it exists and does look like an undo file it is
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overwritten. If there is no undo-history, nothing will be
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written.
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Implementation detail: Overwriting happens by first deleting
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the existing file and then creating a new file with the same
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name. So it is not possible to overwrite an existing undofile
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in a write-protected directory.
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:rundo {file} Read undo history from {file}.
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You can use these in autocommands to explicitly specify the name of the
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history file. E.g.: >
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au BufReadPost * call ReadUndo()
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au BufWritePost * call WriteUndo()
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func ReadUndo()
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if filereadable(expand('%:h'). '/UNDO/' . expand('%:t'))
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rundo %:h/UNDO/%:t
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endif
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endfunc
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func WriteUndo()
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let dirname = expand('%:h') . '/UNDO'
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if !isdirectory(dirname)
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call mkdir(dirname)
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endif
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wundo %:h/UNDO/%:t
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endfunc
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You should keep 'undofile' off, otherwise you end up with two undo files for
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every write.
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You can use the |undofile()| function to find out the file name that Vim would
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use.
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Note that while reading/writing files and 'undofile' is set most errors will
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be silent, unless 'verbose' is set. With :wundo and :rundo you will get more
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error messages, e.g., when the file cannot be read or written.
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NOTE: undo files are never deleted by Vim. You need to delete them yourself.
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Reading an existing undo file may fail for several reasons:
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*E822* It cannot be opened, because the file permissions don't allow it.
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*E823* The magic number at the start of the file doesn't match. This usually
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means it is not an undo file.
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*E824* The version number of the undo file indicates that it's written by a
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newer version of Vim. You need that newer version to open it. Don't
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write the buffer if you want to keep the undo info in the file.
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"File contents changed, cannot use undo info"
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The file text differs from when the undo file was written. This means
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the undo file cannot be used, it would corrupt the text. This also
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happens when 'encoding' differs from when the undo file was written.
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*E825* The undo file does not contain valid contents and cannot be used.
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"Not reading undo file, owner differs"
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The undo file is owned by someone else than the owner of the text
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file. For safety the undo file is not used.
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Writing an undo file may fail for these reasons:
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*E828* The file to be written cannot be created. Perhaps you do not have
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write permissions in the directory.
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"Cannot write undo file in any directory in 'undodir'"
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None of the directories in 'undodir' can be used.
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"Will not overwrite with undo file, cannot read"
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A file exists with the name of the undo file to be written, but it
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cannot be read. You may want to delete this file or rename it.
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"Will not overwrite, this is not an undo file"
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A file exists with the name of the undo file to be written, but it
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does not start with the right magic number. You may want to delete
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this file or rename it.
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"Skipping undo file write, nothing to undo"
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There is no undo information to be written, nothing has been changed
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or 'undolevels' is negative.
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*E829* An error occurred while writing the undo file. You may want to try
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again.
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==============================================================================
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6. Remarks about undo *undo-remarks*
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The number of changes that are remembered is set with the 'undolevels' option.
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If it is zero, the Vi-compatible way is always used. If it is negative no
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undo is possible. Use this if you are running out of memory.
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*clear-undo*
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When you set 'undolevels' to -1 the undo information is not immediately
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cleared, this happens at the next change. To force clearing the undo
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information you can use these commands: >
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:let old_undolevels = &undolevels
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:set undolevels=-1
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:exe "normal a \<BS>\<Esc>"
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:let &undolevels = old_undolevels
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:unlet old_undolevels
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Marks for the buffer ('a to 'z) are also saved and restored, together with the
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text.
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When all changes have been undone, the buffer is not considered to be changed.
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It is then possible to exit Vim with ":q" instead of ":q!".
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Note that this is relative to the last write of the file. Typing "u" after
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":w" actually changes the buffer, compared to what was written, so the buffer
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is considered changed then.
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When manual |folding| is being used, the folds are not saved and restored.
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Only changes completely within a fold will keep the fold as it was, because
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the first and last line of the fold don't change.
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The numbered registers can also be used for undoing deletes. Each time you
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delete text, it is put into register "1. The contents of register "1 are
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shifted to "2, etc. The contents of register "9 are lost. You can now get
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back the most recent deleted text with the put command: '"1P'. (also, if the
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deleted text was the result of the last delete or copy operation, 'P' or 'p'
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also works as this puts the contents of the unnamed register). You can get
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back the text of three deletes ago with '"3P'.
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*redo-register*
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If you want to get back more than one part of deleted text, you can use a
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special feature of the repeat command ".". It will increase the number of the
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register used. So if you first do ""1P", the following "." will result in a
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'"2P'. Repeating this will result in all numbered registers being inserted.
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Example: If you deleted text with 'dd....' it can be restored with
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'"1P....'.
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If you don't know in which register the deleted text is, you can use the
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:display command. An alternative is to try the first register with '"1P', and
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if it is not what you want do 'u.'. This will remove the contents of the
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first put, and repeat the put command for the second register. Repeat the
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'u.' until you got what you want.
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vim:tw=78:ts=8:ft=help:norl:
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