diff.txt For Vim version 7.4. Last change: 2014 Oct 31LINK


diff vimdiff gvimdiff diff-modeLINK

This file describes the +diff feature: Showing differences between two,

three or four versions of the same file.

The basics are explained in section 08.7 of the user manual.

1. Starting diff mode vimdiff

2. Viewing diffs view-diffs

3. Jumping to diffs jumpto-diffs

4. Copying diffs copy-diffs

5. Diff options diff-options

{not in Vi}


1. Starting diff mode

The easiest way to start editing in diff mode is with the "vimdiff" command.

This starts Vim as usual, and additionally sets up for viewing the differences

between the arguments.

vimdiff file1 file2 [file3 [file4]]

This is equivalent to:

vim -d file1 file2 [file3 [file4]]

You may also use "gvimdiff" or "vim -d -g". The GUI is started then.

You may also use "viewdiff" or "gviewdiff". Vim starts in readonly mode then.

"r" may be prepended for restricted mode (see -Z).

The second and following arguments may also be a directory name. Vim will

then append the file name of the first argument to the directory name to find

the file.

This only works when a standard "diff" command is available. See 'diffexpr'.

Diffs are local to the current tab page tab-page. You can't see diffs with

a window in another tab page. This does make it possible to have several

diffs at the same time, each in their own tab page.

What happens is that Vim opens a window for each of the files. This is like

using the -O argument. This uses vertical splits. If you prefer horizontal

splits add the -o argument:

vimdiff -o file1 file2 [file3 [file4]]

If you always prefer horizontal splits include "horizontal" in 'diffopt'.

In each of the edited files these options are set:

'diff' on

'scrollbind' on

'cursorbind' on

'scrollopt' includes "hor"

'wrap' off

'foldmethod' "diff"

'foldcolumn' value from 'diffopt', default is 2

These options are set local to the window. When editing another file they are

reset to the global value.

The options can still be overruled from a modeline when re-editing the file.

However, 'foldmethod' and 'wrap' won't be set from a modeline when 'diff' is


The differences shown are actually the differences in the buffer. Thus if you

make changes after loading a file, these will be included in the displayed

diffs. You might have to do ":diffupdate" now and then, not all changes are

immediately taken into account.

In your .vimrc file you could do something special when Vim was started in

diff mode. You could use a construct like this:

if &diff

setup for diff mode


setup for non-diff mode


While already in Vim you can start diff mode in three ways.


:diffs[plit] {filename} :diffs :diffsplitLINK

Open a new window on the file {filename}. The options are set

as for "vimdiff" for the current and the newly opened window.

Also see 'diffexpr'.

:difft :diffthisLINK

:difft[his] Make the current window part of the diff windows. This sets

the options like for "vimdiff".

:diffp[atch] {patchfile} E816 :diffp :diffpatchLINK

Use the current buffer, patch it with the diff found in

{patchfile} and open a buffer on the result. The options are

set as for "vimdiff".

{patchfile} can be in any format that the "patch" program

understands or 'patchexpr' can handle.

Note that {patchfile} should only contain a diff for one file,

the current file. If {patchfile} contains diffs for other

files as well, the results are unpredictable. Vim changes

directory to /tmp to avoid files in the current directory

accidentally being patched. But it may still result in

various ".rej" files to be created. And when absolute path

names are present these files may get patched anyway.

To make these commands use a vertical split, prepend :vertical. Examples:

:vert diffsplit main.c~

:vert diffpatch /tmp/diff

If you always prefer a vertical split include "vertical" in 'diffopt'.


There can be up to four buffers with 'diff' set.

Since the option values are remembered with the buffer, you can edit another

file for a moment and come back to the same file and be in diff mode again.

:diffo :diffoffLINK

:diffo[ff] Switch off diff mode for the current window. Resets related

options also when 'diff' was not set.

:diffo[ff]! Switch off diff mode for the current window and in all windows

in the current tab page where 'diff' is set. Resetting

related options only happens in a window that has 'diff' set,

if the current window does not have 'diff' set then no options

in it are changed.

The ":diffoff" command resets the relevant options to the values they had when

using :diffsplit, :diffpatch , :diffthis. or starting Vim in diff mode.

Otherwise they are set to their default value:

'diff' off

'scrollbind' off

'cursorbind' off

'scrollopt' without "hor"

'wrap' on

'foldmethod' "manual"

'foldcolumn' 0


2. Viewing diffs view-diffsLINK

The effect is that the diff windows show the same text, with the differences

highlighted. When scrolling the text, the 'scrollbind' option will make the

text in other windows to be scrolled as well. With vertical splits the text

should be aligned properly.

The alignment of text will go wrong when:

- 'wrap' is on, some lines will be wrapped and occupy two or more screen


- folds are open in one window but not another

- 'scrollbind' is off

- changes have been made to the text

- "filler" is not present in 'diffopt', deleted/inserted lines makes the

alignment go wrong

All the buffers edited in a window where the 'diff' option is set will join in

the diff. This is also possible for hidden buffers. They must have been

edited in a window first for this to be possible.

:DiffOrig diff-original-fileLINK

Since 'diff' is a window-local option, it's possible to view the same buffer

in diff mode in one window and "normal" in another window. It is also

possible to view the changes you have made to a buffer since the file was

loaded. Since Vim doesn't allow having two buffers for the same file, you

need another buffer. This command is useful:

command DiffOrig vert new | set bt=nofile | r ++edit # | 0d_

\ | diffthis | wincmd p | diffthis

(this is in vimrc_example.vim). Use ":DiffOrig" to see the differences

between the current buffer and the file it was loaded from.

A buffer that is unloaded cannot be used for the diff. But it does work for

hidden buffers. You can use ":hide" to close a window without unloading the

buffer. If you don't want a buffer to remain used for the diff do ":set

nodiff" before hiding it.

:diffu :diffupdateLINK

:diffu[pdate][!] Update the diff highlighting and folds.

Vim attempts to keep the differences updated when you make changes to the

text. This mostly takes care of inserted and deleted lines. Changes within a

line and more complicated changes do not cause the differences to be updated.

To force the differences to be updated use:


If the ! is included Vim will check if the file was changed externally and

needs to be reloaded. It will prompt for each changed file, like :checktime

was used.

Vim will show filler lines for lines that are missing in one window but are

present in another. These lines were inserted in another file or deleted in

this file. Removing "filler" from the 'diffopt' option will make Vim not

display these filler lines.

Folds are used to hide the text that wasn't changed. See folding for all

the commands that can be used with folds.

The context of lines above a difference that are not included in the fold can

be set with the 'diffopt' option. For example, to set the context to three


:set diffopt=filler,context:3

The diffs are highlighted with these groups:

hl-DiffAdd DiffAdd Added (inserted) lines. These lines exist in

this buffer but not in another.

hl-DiffChange DiffChange Changed lines.

hl-DiffText DiffText Changed text inside a Changed line. Vim

finds the first character that is different,

and the last character that is different

(searching from the end of the line). The

text in between is highlighted. This means

that parts in the middle that are still the

same are highlighted anyway. Only "iwhite" of

'diffopt' is used here.

hl-DiffDelete DiffDelete Deleted lines. Also called filler lines,

because they don't really exist in this



3. Jumping to diffs jumpto-diffsLINK

Two commands can be used to jump to diffs:


[c Jump backwards to the previous start of a change.

When a count is used, do it that many times.


]c Jump forwards to the next start of a change.

When a count is used, do it that many times.

It is an error if there is no change for the cursor to move to.


4. Diff copying copy-diffs E99 E100 E101 E102 E103LINK


There are two commands to copy text from one buffer to another. The result is

that the buffers will be equal within the specified range.

:diffg :diffgetLINK

:[range]diffg[et] [bufspec]

Modify the current buffer to undo difference with another

buffer. If [bufspec] is given, that buffer is used. If

[bufspec] refers to the current buffer then nothing happens.

Otherwise this only works if there is one other buffer in diff


See below for [range].

:diffpu :diffput E793LINK

:[range]diffpu[t] [bufspec]

Modify another buffer to undo difference with the current

buffer. Just like ":diffget" but the other buffer is modified

instead of the current one.

When [bufspec] is omitted and there is more than one other

buffer in diff mode where 'modifiable' is set this fails.

See below for [range].


[count]do Same as ":diffget" without range. The "o" stands for "obtain"

("dg" can't be used, it could be the start of "dgg"!). Note:

this doesn't work in Visual mode.

If you give a [count], it is used as the [bufspec] argument

for ":diffget".


[count]dp Same as ":diffput" without range. Note: this doesn't work in

Visual mode.

If you give a [count], it is used as the [bufspec] argument

for ":diffput".

When no [range] is given, the diff at the cursor position or just above it is

affected. When [range] is used, Vim tries to only put or get the specified

lines. When there are deleted lines, this may not always be possible.

There can be deleted lines below the last line of the buffer. When the cursor

is on the last line in the buffer and there is no diff above this line, the

":diffget" and "do" commands will obtain lines from the other buffer.

To be able to get those lines from another buffer in a [range] it's allowed to

use the last line number plus one. This command gets all diffs from the other



Note that deleted lines are displayed, but not counted as text lines. You

can't move the cursor into them. To fill the deleted lines with the lines

from another buffer use ":diffget" on the line below them.


When the buffer that is about to be modified is read-only and the autocommand

that is triggered by FileChangedRO changes buffers the command will fail.

The autocommand must not change buffers.

The [bufspec] argument above can be a buffer number, a pattern for a buffer

name or a part of a buffer name. Examples:

:diffget Use the other buffer which is in diff mode

:diffget 3 Use buffer 3

:diffget v2 Use the buffer which matches "v2" and is in

diff mode (e.g., "file.c.v2")


5. Diff options diff-optionsLINK

Also see 'diffopt' and the "diff" item of 'fillchars'.


The 'diffexpr' option can be set to use something else than the standard

"diff" program to compare two files and find the differences.

When 'diffexpr' is empty, Vim uses this command to find the differences

between file1 and file2:

diff file1 file2 > outfile

The ">" is replaced with the value of 'shellredir'.

The output of "diff" must be a normal "ed" style diff. Do NOT use a context

diff. This example explains the format that Vim expects:


> bbb


< 111




> ggg

The "1a2" item appends the line "bbb".

The "4d4" item deletes the line "111".

The "7c7" item replaces the line "GGG" with "ggg".

When 'diffexpr' is not empty, Vim evaluates it to obtain a diff file in the

format mentioned. These variables are set to the file names used:

v:fname_in original file

v:fname_new new version of the same file

v:fname_out resulting diff file

Additionally, 'diffexpr' should take care of "icase" and "iwhite" in the

'diffopt' option. 'diffexpr' cannot change the value of 'lines' and


Example (this does almost the same as 'diffexpr' being empty):

set diffexpr=MyDiff()

function MyDiff()

let opt = ""

if &diffopt =~ "icase"

let opt = opt . "-i "


if &diffopt =~ "iwhite"

let opt = opt . "-b "


silent execute "!diff -a --binary " . opt . v:fname_in . " " . v:fname_new .

\ " > " . v:fname_out


The "-a" argument is used to force comparing the files as text, comparing as

binaries isn't useful. The "--binary" argument makes the files read in binary

mode, so that a CTRL-Z doesn't end the text on DOS.

E810 E97LINK

Vim will do a test if the diff output looks alright. If it doesn't, you will

get an error message. Possible causes:

- The "diff" program cannot be executed.

- The "diff" program doesn't produce normal "ed" style diffs (see above).

- The 'shell' and associated options are not set correctly. Try if filtering

works with a command like ":!sort".

- You are using 'diffexpr' and it doesn't work.

If it's not clear what the problem is set the 'verbose' option to one or more

to see more messages.

The self-installing Vim for MS-Windows includes a diff program. If you don't

have it you might want to download a diff.exe. For example from


USING PATCHES diff-patchexprLINK

The 'patchexpr' option can be set to use something else than the standard

"patch" program.

When 'patchexpr' is empty, Vim will call the "patch" program like this:

patch -o outfile origfile < patchfile

This should work fine with most versions of the "patch" program. Note that a

CR in the middle of a line may cause problems, it is seen as a line break.

If the default doesn't work for you, set the 'patchexpr' to an expression that

will have the same effect. These variables are set to the file names used:

v:fname_in original file

v:fname_diff patch file

v:fname_out resulting patched file

Example (this does the same as 'patchexpr' being empty):

set patchexpr=MyPatch()

function MyPatch()

:call system("patch -o " . v:fname_out . " " . v:fname_in .

\ " < " . v:fname_diff)


Make sure that using the "patch" program doesn't have unwanted side effects.

For example, watch out for additionally generated files, which should be

deleted. It should just patch the file and nothing else.

Vim will change directory to "/tmp" or another temp directory before

evaluating 'patchexpr'. This hopefully avoids that files in the current

directory are accidentally patched. Vim will also delete files starting with

v:fname_in and ending in ".rej" and ".orig".