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1 *diff.txt* For Vim version 7.2. Last change: 2009 Feb 11
4 VIM REFERENCE MANUAL by Bram Moolenaar
7 *diff* *vimdiff* *gvimdiff* *diff-mode*
8 This file describes the +diff feature: Showing differences between two,
9 three or four versions of the same file.
11 The basics are explained in section |08.7| of the user manual.
13 1. Starting diff mode |vimdiff|
14 2. Viewing diffs |view-diffs|
15 3. Jumping to diffs |jumpto-diffs|
16 4. Copying diffs |copy-diffs|
17 5. Diff options |diff-options|
19 {not in Vi}
21 ==============================================================================
22 1. Starting diff mode
24 The easiest way to start editing in diff mode is with the "vimdiff" command.
25 This starts Vim as usual, and additionally sets up for viewing the differences
26 between the arguments. >
28 vimdiff file1 file2 [file3 [file4]]
30 This is equivalent to: >
32 vim -d file1 file2 [file3 [file4]]
34 You may also use "gvimdiff" or "vim -d -g". The GUI is started then.
35 You may also use "viewdiff" or "gviewdiff". Vim starts in readonly mode then.
36 "r" may be prepended for restricted mode (see |-Z|).
38 The second and following arguments may also be a directory name. Vim will
39 then append the file name of the first argument to the directory name to find
40 the file.
42 This only works when a standard "diff" command is available. See 'diffexpr'.
44 Diffs are local to the current tab page |tab-page|. You can't see diffs with
45 a window in another tab page. This does make it possible to have several
46 diffs at the same time, each in their own tab page.
48 What happens is that Vim opens a window for each of the files. This is like
49 using the |-O| argument. This uses vertical splits. If you prefer horizontal
50 splits add the |-o| argument: >
52 vimdiff -o file1 file2 [file3 [file4]]
54 If you always prefer horizontal splits include "horizontal" in 'diffopt'.
56 In each of the edited files these options are set:
58 'diff' on
59 'scrollbind' on
60 'scrollopt' includes "hor"
61 'wrap' off
62 'foldmethod' "diff"
63 'foldcolumn' value from 'diffopt', default is 2
65 These options are set local to the window. When editing another file they are
66 reset to the global value.
67 The options can still be overruled from a modeline when re-editing the file.
68 However, 'foldmethod' and 'wrap' won't be set from a modeline when 'diff' is
69 set.
71 The differences shown are actually the differences in the buffer. Thus if you
72 make changes after loading a file, these will be included in the displayed
73 diffs. You might have to do ":diffupdate" now and then, not all changes are
74 immediately taken into account.
76 In your .vimrc file you could do something special when Vim was started in
77 diff mode. You could use a construct like this: >
79 if &diff
80 setup for diff mode
81 else
82 setup for non-diff mode
83 endif
85 While already in Vim you can start diff mode in three ways.
87 *E98*
88 :diffsplit {filename} *:diffs* *:diffsplit*
89 Open a new window on the file {filename}. The options are set
90 as for "vimdiff" for the current and the newly opened window.
91 Also see 'diffexpr'.
93 *:difft* *:diffthis*
94 :diffthis Make the current window part of the diff windows. This sets
95 the options like for "vimdiff".
97 :diffpatch {patchfile} *:diffp* *:diffpatch*
98 Use the current buffer, patch it with the diff found in
99 {patchfile} and open a buffer on the result. The options are
100 set as for "vimdiff".
101 {patchfile} can be in any format that the "patch" program
102 understands or 'patchexpr' can handle.
103 Note that {patchfile} should only contain a diff for one file,
104 the current file. If {patchfile} contains diffs for other
105 files as well, the results are unpredictable. Vim changes
106 directory to /tmp to avoid files in the current directory
107 accidentally being patched. But it may still result in
108 various ".rej" files to be created. And when absolute path
109 names are present these files may get patched anyway.
111 To make these commands use a vertical split, prepend |:vertical|. Examples: >
113 :vert diffsplit main.c~
114 :vert diffpatch /tmp/diff
116 If you always prefer a vertical split include "vertical" in 'diffopt'.
118 *E96*
119 There can be up to four buffers with 'diff' set.
121 Since the option values are remembered with the buffer, you can edit another
122 file for a moment and come back to the same file and be in diff mode again.
124 *:diffo* *:diffoff*
125 :diffoff Switch off diff mode for the current window.
127 :diffoff! Switch off diff mode for all windows in the current tab page.
129 The ":diffoff" command resets the relevant options to their default value.
130 This may be different from what the values were before diff mode was started,
131 the old values are not remembered.
133 'diff' off
134 'scrollbind' off
135 'scrollopt' without "hor"
136 'wrap' on
137 'foldmethod' "manual"
138 'foldcolumn' 0
140 ==============================================================================
141 2. Viewing diffs *view-diffs*
143 The effect is that the diff windows show the same text, with the differences
144 highlighted. When scrolling the text, the 'scrollbind' option will make the
145 text in other windows to be scrolled as well. With vertical splits the text
146 should be aligned properly.
148 The alignment of text will go wrong when:
149 - 'wrap' is on, some lines will be wrapped and occupy two or more screen
150 lines
151 - folds are open in one window but not another
152 - 'scrollbind' is off
153 - changes have been made to the text
154 - "filler" is not present in 'diffopt', deleted/inserted lines makes the
155 alignment go wrong
157 All the buffers edited in a window where the 'diff' option is set will join in
158 the diff. This is also possible for hidden buffers. They must have been
159 edited in a window first for this to be possible.
161 *:DiffOrig* *diff-original-file*
162 Since 'diff' is a window-local option, it's possible to view the same buffer
163 in diff mode in one window and "normal" in another window. It is also
164 possible to view the changes you have made to a buffer since the file was
165 loaded. Since Vim doesn't allow having two buffers for the same file, you
166 need another buffer. This command is useful: >
167 command DiffOrig vert new | set bt=nofile | r # | 0d_ | diffthis
168 \ | wincmd p | diffthis
169 (this is in |vimrc_example.vim|). Use ":DiffOrig" to see the differences
170 between the current buffer and the file it was loaded from.
172 A buffer that is unloaded cannot be used for the diff. But it does work for
173 hidden buffers. You can use ":hide" to close a window without unloading the
174 buffer. If you don't want a buffer to remain used for the diff do ":set
175 nodiff" before hiding it.
177 *:diffu* *:diffupdate*
178 :diffu[pdate] Update the diff highlighting and folds.
180 Vim attempts to keep the differences updated when you make changes to the
181 text. This mostly takes care of inserted and deleted lines. Changes within a
182 line and more complicated changes do not cause the differences to be updated.
183 To force the differences to be updated use: >
185 :diffupdate
188 Vim will show filler lines for lines that are missing in one window but are
189 present in another. These lines were inserted in another file or deleted in
190 this file. Removing "filler" from the 'diffopt' option will make Vim not
191 display these filler lines.
194 Folds are used to hide the text that wasn't changed. See |folding| for all
195 the commands that can be used with folds.
197 The context of lines above a difference that are not included in the fold can
198 be set with the 'diffopt' option. For example, to set the context to three
199 lines: >
201 :set diffopt=filler,context:3
204 The diffs are highlighted with these groups:
206 |hl-DiffAdd| DiffAdd Added (inserted) lines. These lines exist in
207 this buffer but not in another.
208 |hl-DiffChange| DiffChange Changed lines.
209 |hl-DiffText| DiffText Changed text inside a Changed line. Vim
210 finds the first character that is different,
211 and the last character that is different
212 (searching from the end of the line). The
213 text in between is highlighted. This means
214 that parts in the middle that are still the
215 same are highlighted anyway. Only "iwhite" of
216 'diffopt' is used here.
217 |hl-DiffDelete| DiffDelete Deleted lines. Also called filler lines,
218 because they don't really exist in this
219 buffer.
221 ==============================================================================
222 3. Jumping to diffs *jumpto-diffs*
224 Two commands can be used to jump to diffs:
225 *[c*
226 [c Jump backwards to the previous start of a change.
227 When a count is used, do it that many times.
228 *]c*
229 ]c Jump forwards to the next start of a change.
230 When a count is used, do it that many times.
232 It is an error if there is no change for the cursor to move to.
234 ==============================================================================
235 4. Diff copying *copy-diffs* *E99* *E100* *E101* *E102* *E103*
236 *merge*
237 There are two commands to copy text from one buffer to another. The result is
238 that the buffers will be equal within the specified range.
240 *:diffg* *:diffget*
241 :[range]diffg[et] [bufspec]
242 Modify the current buffer to undo difference with another
243 buffer. If [bufspec] is given, that buffer is used. If
244 [bufspec] refers to the current buffer then nothing happens.
245 Otherwise this only works if there is one other buffer in diff
246 mode.
247 See below for [range].
249 *:diffpu* *:diffput* *E793*
250 :[range]diffpu[t] [bufspec]
251 Modify another buffer to undo difference with the current
252 buffer. Just like ":diffget" but the other buffer is modified
253 instead of the current one.
254 When [bufspec] is omitted and there is more than one other
255 buffer in diff mode where 'modifiable' is set this fails.
256 See below for [range].
258 *do*
259 do Same as ":diffget" without argument or range. The "o" stands
260 for "obtain" ("dg" can't be used, it could be the start of
261 "dgg"!).
263 *dp*
264 dp Same as ":diffput" without argument or range.
266 When no [range] is given, the diff at the cursor position or just above it is
267 affected. When [range] is used, Vim tries to only put or get the specified
268 lines. When there are deleted lines, this may not always be possible.
270 There can be deleted lines below the last line of the buffer. When the cursor
271 is on the last line in the buffer and there is no diff above this line, the
272 ":diffget" and "do" commands will obtain lines from the other buffer.
274 To be able to get those lines from another buffer in a [range] it's allowed to
275 use the last line number plus one. This command gets all diffs from the other
276 buffer: >
278 :1,$+1diffget
280 Note that deleted lines are displayed, but not counted as text lines. You
281 can't move the cursor into them. To fill the deleted lines with the lines
282 from another buffer use ":diffget" on the line below them.
283 *E787*
284 When the buffer that is about to be modified is read-only and the autocommand
285 that is triggered by |FileChangedRO| changes buffers the command will fail.
286 The autocommand must not change buffers.
288 The [bufspec] argument above can be a buffer number, a pattern for a buffer
289 name or a part of a buffer name. Examples:
291 :diffget Use the other buffer which is in diff mode
292 :diffget 3 Use buffer 3
293 :diffget v2 Use the buffer which matches "v2" and is in
294 diff mode (e.g., "file.c.v2")
296 ==============================================================================
297 5. Diff options *diff-options*
299 Also see |'diffopt'| and the "diff" item of |'fillchars'|.
302 FINDING THE DIFFERENCES *diff-diffexpr*
304 The 'diffexpr' option can be set to use something else than the standard
305 "diff" program to compare two files and find the differences.
307 When 'diffexpr' is empty, Vim uses this command to find the differences
308 between file1 and file2: >
310 diff file1 file2 > outfile
312 The ">" is replaced with the value of 'shellredir'.
314 The output of "diff" must be a normal "ed" style diff. Do NOT use a context
315 diff. This example explains the format that Vim expects: >
317 1a2
318 > bbb
319 4d4
320 < 111
321 7c7
322 < GGG
323 ---
324 > ggg
326 The "1a2" item appends the line "bbb".
327 The "4d4" item deletes the line "111".
328 The '7c7" item replaces the line "GGG" with "ggg".
330 When 'diffexpr' is not empty, Vim evaluates to obtain a diff file in the
331 format mentioned. These variables are set to the file names used:
333 v:fname_in original file
334 v:fname_new new version of the same file
335 v:fname_out resulting diff file
337 Additionally, 'diffexpr' should take care of "icase" and "iwhite" in the
338 'diffopt' option. 'diffexpr' cannot change the value of 'lines' and
339 'columns'.
341 Example (this does almost the same as 'diffexpr' being empty): >
343 set diffexpr=MyDiff()
344 function MyDiff()
345 let opt = ""
346 if &diffopt =~ "icase"
347 let opt = opt . "-i "
348 endif
349 if &diffopt =~ "iwhite"
350 let opt = opt . "-b "
351 endif
352 silent execute "!diff -a --binary " . opt . v:fname_in . " " . v:fname_new .
353 \ " > " . v:fname_out
354 endfunction
356 The "-a" argument is used to force comparing the files as text, comparing as
357 binaries isn't useful. The "--binary" argument makes the files read in binary
358 mode, so that a CTRL-Z doesn't end the text on DOS.
360 *E810* *E97*
361 Vim will do a test if the diff output looks alright. If it doesn't, you will
362 get an error message. Possible causes:
363 - The "diff" program cannot be executed.
364 - The "diff" program doesn't produce normal "ed" style diffs (see above).
365 - The 'shell' and associated options are not set correctly. Try if filtering
366 works with a command like ":!sort".
367 - You are using 'diffexpr' and it doesn't work.
368 If it's not clear what the problem is set the 'verbose' option to one or more
369 to see more messages.
371 The self-installing Vim includes a diff program. If you don't have it you
372 might want to download a diff.exe. For example from
373 http://jlb.twu.net/code/unixkit.php.
376 USING PATCHES *diff-patchexpr*
378 The 'patchexpr' option can be set to use something else than the standard
379 "patch" program.
381 When 'patchexpr' is empty, Vim will call the "patch" program like this: >
383 patch -o outfile origfile < patchfile
385 This should work fine with most versions of the "patch" program. Note that a
386 CR in the middle of a line may cause problems, it is seen as a line break.
388 If the default doesn't work for you, set the 'patchexpr' to an expression that
389 will have the same effect. These variables are set to the file names used:
391 v:fname_in original file
392 v:fname_diff patch file
393 v:fname_out resulting patched file
395 Example (this does the same as 'patchexpr' being empty): >
397 set patchexpr=MyPatch()
398 function MyPatch()
399 :call system("patch -o " . v:fname_out . " " . v:fname_in .
400 \ " < " . v:fname_diff)
401 endfunction
403 Make sure that using the "patch" program doesn't have unwanted side effects.
404 For example, watch out for additionally generated files, which should be
405 deleted. It should just patch the file and nothing else.
406 Vim will change directory to "/tmp" or another temp directory before
407 evaluating 'patchexpr'. This hopefully avoids that files in the current
408 directory are accidentally patched. Vim will also delete files starting with
409 v:fname_in and ending in ".rej" and ".orig".
411 vim:tw=78:ts=8:ft=help:norl: