ediff: Quick Help Commands
3.1 Quick Help Commands
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‘?’
Toggles the Ediff Quick Help window ON and OFF.
‘G’
Prepares a mail buffer for sending a praise or a curse to the Ediff
maintainer.
‘E’
Brings up the top node of this manual, where you can find further
information on the various Ediff functions and advanced issues,
such as customization, session groups, etc.
‘v’
Scrolls up buffers A and B (and buffer C where appropriate) in a
coordinated fashion.
‘V’
Scrolls the buffers down.
‘<’
Scrolls the buffers to the left simultaneously.
‘>’
Scrolls buffers to the right.
‘wd’
Saves the output from the diff utility, for further reference.
With prefix argument, saves the plain output from ‘diff’ (see
‘ediff-diff-program’ and ‘ediff-diff-options’). Without the
argument, it saves customized ‘diff’ output (see
‘ediff-custom-diff-program’ and ‘ediff-custom-diff-options’), if it
is available.
‘wa’
Saves buffer A, if it was modified.
‘wb’
Saves buffer B, if it was modified.
‘wc’
Saves buffer C, if it was modified (if you are in a session that
compares three files simultaneously).
‘a’
_In comparison sessions:_ Copies the current difference region (or
the region specified as the prefix to this command) from buffer A
to buffer B. Ediff saves the old contents of buffer B’s region; it
can be restored via the command ‘rb’, which see.
_In merge sessions:_ Copies the current difference region (or the
region specified as the prefix to this command) from buffer A to
the merge buffer. The old contents of this region in buffer C can
be restored via the command ‘r’.
‘b’
Works similarly, but copies the current difference region from
buffer B to buffer A (in _comparison sessions_) or the merge buffer
(in _merge sessions_).
Ediff saves the old contents of the difference region copied over;
it can be reinstated via the command ‘ra’ in comparison sessions
and ‘r’ in merge sessions.
‘ab’
Copies the current difference region (or the region specified as
the prefix to this command) from buffer A to buffer B. This (and
the next five) command is enabled only in sessions that compare
three files simultaneously. The old region in buffer B is saved
and can be restored via the command ‘rb’.
‘ac’
Copies the difference region from buffer A to buffer C. The old
region in buffer C is saved and can be restored via the command
‘rc’.
‘ba’
Copies the difference region from buffer B to buffer A. The old
region in buffer A is saved and can be restored via the command
‘ra’.
‘bc’
Copies the difference region from buffer B to buffer C. The
command ‘rc’ undoes this.
‘ca’
Copies the difference region from buffer C to buffer A. The
command ‘ra’ undoes this.
‘cb’
Copies the difference region from buffer C to buffer B. The
command ‘rb’ undoes this.
‘p’
‘DEL’
Makes the previous difference region current.
‘n’
‘SPC’
Makes the next difference region current.
‘j’
‘-j’
‘Nj’
Makes the very first difference region current.
‘-j’ makes the last region current. Typing a number, N, and then
‘j’ makes the difference region N current. Typing −N (a negative
number) then ‘j’ makes current the region Last − N.
‘ga’
Makes current the difference region closest to the position of the
point in buffer A.
However, with a prefix argument, Ediff would position all variants
around the area indicated by the current point in buffer A: if the
point is inside a difference region, then the variants will be
positioned at this difference region. If the point is not in any
difference region, then it is in an area where all variants agree
with each other. In this case, the variants will be positioned so
that each would display this area (of agreement).
‘gb’
Makes current the difference region closest to the position of the
point in buffer B.
With a prefix argument, behaves like ‘ga’, but with respect to
buffer B.
‘gc’
_In merge sessions:_ makes current the difference region closest to
the point in the merge buffer.
_In 3-file comparison sessions:_ makes current the region closest
to the point in buffer C.
With a prefix argument, behaves like ‘ga’, but with respect to
buffer C.
‘!’
Recomputes the difference regions, bringing them up to date. This
is often needed because it is common to do all sorts of editing
during Ediff sessions, so after a while, the highlighted difference
regions may no longer reflect the actual differences among the
buffers.
‘*’
Forces refinement of the current difference region, which
highlights the exact words of disagreement among the buffers. With
a negative prefix argument, unhighlights the current region.
Forceful refinement may be needed if Ediff encounters a difference
region that is larger than ‘ediff-auto-refine-limit’. In this
situation, Ediff doesn’t do automatic refinement in order to
improve response time. (Ediff doesn’t auto-refine on dumb
terminals as well, but ‘*’ still works there. However, the only
useful piece of information it can tell you is whether or not the
difference regions disagree only in the amount of white space.)
This command is also useful when the highlighted fine differences
are no longer current, due to user editing.
‘m’
Displays the current Ediff session in a frame as wide as the
physical display. This is useful when comparing files
side-by-side. Typing ‘m’ again restores the original size of the
frame.
‘|’
Toggles the horizontal/vertical split of the Ediff display.
Horizontal split is convenient when it is possible to compare files
side-by-side. If the frame in which files are displayed is too
narrow and lines are cut off, typing ‘m’ may help some.
‘@’
Toggles auto-refinement of difference regions (i.e., automatic
highlighting of the exact words that differ among the variants).
Auto-refinement is turned off on devices where Emacs doesn’t
support highlighting.
On slow machines, it may be advantageous to turn auto-refinement
off. The user can always forcefully refine specific difference
regions by typing ‘*’.
‘h’
Cycles between full highlighting, the mode where fine differences
are not highlighted (but computed), and the mode where highlighting
is done with ASCII strings. The latter is not really recommended,
unless on a dumb TTY.
‘r’
Restores the old contents of the region in the merge buffer. (If
you copied a difference region from buffer A or B into the merge
buffer using the commands ‘a’ or ‘b’, Ediff saves the old contents
of the region in case you change your mind.)
This command is enabled in merge sessions only.
‘ra’
Restores the old contents of the current difference region in
buffer A, which was previously saved when the user invoked one of
these commands: ‘b’, ‘ba’, ‘ca’, which see. This command is
enabled in comparison sessions only.
‘rb’
Restores the old contents of the current difference region in
buffer B, which was previously saved when the user invoked one of
these commands: ‘a’, ‘ab’, ‘cb’, which see. This command is
enabled in comparison sessions only.
‘rc’
Restores the old contents of the current difference region in
buffer C, which was previously saved when the user invoked one of
these commands: ‘ac’, ‘bc’, which see. This command is enabled in
3-file comparison sessions only.
‘##’
Tell Ediff to skip over regions that disagree among themselves only
in the amount of white space and line breaks.
Even though such regions will be skipped over, you can still jump
to any one of them by typing the region number and then ‘j’.
Typing ‘##’ again puts Ediff back in the original state.
‘#c’
Toggle case sensitivity in the diff program. All diffs are
recomputed. Case sensitivity is controlled by the variables
‘ediff-ignore-case-option’, ‘ediff-ignore-case-option3’, and
‘ediff-ignore-case’, which are explained elsewhere.
‘#h’
‘#f’
Ediff works hard to ameliorate the effects of boredom in the
workplace...
Quite often differences are due to identical replacements (e.g.,
the word “foo” is replaced with the word “bar” everywhere). If the
number of regions with such boring differences exceeds your
tolerance threshold, you may be tempted to tell Ediff to skip these
regions altogether (you will still be able to jump to them via the
command ‘j’). The above commands, ‘#h’ and ‘#f’, may well save
your day!
‘#h’ prompts you to specify regular expressions for each variant.
Difference regions where each variant’s region matches the
corresponding regular expression will be skipped from then on.
(You can also tell Ediff to skip regions where at least one variant
matches its regular expression.)
‘#f’ does dual job: it focuses on regions that match the
corresponding regular expressions. All other regions will be
skipped over. 
Selective Browsing, for more.
‘A’
Toggles the read-only property in buffer A. If file A is under
version control and is checked in, it is checked out (with your
permission).
‘B’
Toggles the read-only property in buffer B. If file B is under
version control and is checked in, it is checked out.
‘C’
Toggles the read-only property in buffer C (in 3-file comparison
sessions). If file C is under version control and is checked in,
it is checked out.
‘~’
Swaps the windows where buffers A and B are displayed. If you are
comparing three buffers at once, then this command would rotate the
windows among buffers A, B, and C.
‘i’
Displays all kinds of useful data about the current Ediff session.
‘D’
Runs ‘ediff-custom-diff-program’ on the variants and displays the
buffer containing the output. This is useful when you must send
the output to your Mom.
With a prefix argument, displays the plain ‘diff’ output.
Patch and Diff Programs, for details.
‘R’
Displays a list of currently active Ediff sessions—the Ediff
Registry. You can then restart any of these sessions by either
clicking on a session record or by putting the cursor over it and
then typing the return key.
(Some poor souls leave so many active Ediff sessions around that
they lose track of them completely... The ‘R’ command is designed
to save these people from the recently discovered Ediff Proficiency
Syndrome.)
Typing ‘R’ brings up Ediff Registry only if it is typed into an
Ediff Control Panel. If you don’t have a control panel handy, type
this in the minibuffer: ‘M-x eregistry’. Registry of Ediff
Sessions.
‘M’
Shows the session group buffer that invoked the current Ediff
session. Session Groups, for more information on session
groups.
‘z’
Suspends the current Ediff session. (If you develop a condition
known as Repetitive Ediff Injury—a serious but curable illness—you
must change your current activity. This command tries hard to hide
all Ediff-related buffers.)
The easiest way to resume a suspended Ediff session is through the
registry of active sessions. Registry of Ediff Sessions,
for details.
‘q’
Terminates this Ediff session. With a prefix argument (e.g.,‘1q’),
asks if you also want to delete the buffers of the variants.
Modified files and the results of merges are never deleted.
‘%’
Toggles narrowing in Ediff buffers. Ediff buffers may be narrowed
if you are comparing only parts of these buffers via the commands
‘ediff-windows-*’ and ‘ediff-regions-*’, which see.
‘C-l’
Restores the usual Ediff window setup. This is the quickest way to
resume an Ediff session, but it works only if the control panel of
that session is visible.
‘$$’
While merging with an ancestor file, Ediff is determined to reduce
user’s wear and tear by saving him and her much of unproductive,
repetitive typing. If it notices that, say, file A’s difference
region is identical to the same difference region in the ancestor
file, then the merge buffer will automatically get the difference
region taken from buffer B. The rationale is that this difference
region in buffer A is as old as that in the ancestor buffer, so the
contents of that region in buffer B represents real change.
You may want to ignore such “obvious” merges and concentrate on
difference regions where both files “clash” with the ancestor,
since this means that two different people have been changing this
region independently and they had different ideas on how to do
this.
The above command does this for you by skipping the regions where
only one of the variants clashes with the ancestor but the other
variant agrees with it. Typing ‘$$’ again undoes this setting.
‘$*’
When merging files with large number of differences, it is
sometimes convenient to be able to skip the difference regions for
which you already decided which variant is most appropriate.
Typing ‘$*’ will accomplish precisely this.
To be more precise, this toggles the check for whether the current
merge is identical to its default setting, as originally decided by
Ediff. For instance, if Ediff is merging according to the
“combined” policy, then the merge region is skipped over if it is
different from the combination of the regions in buffers A and B.
(Warning: swapping buffers A and B will confuse things in this
respect.) If the merge region is marked as “prefer-A” then this
region will be skipped if it differs from the current difference
region in buffer A, etc.
‘/’
Displays the ancestor file during merges.
‘&’
In some situations, such as when one of the files agrees with the
ancestor file on a difference region and the other doesn’t, Ediff
knows what to do: it copies the current difference region from the
second buffer into the merge buffer.
In other cases, the right course of action is not that clearcut,
and Ediff would use a default action. The above command changes
the default action. The default action can be ‘default-A’ (choose
the region from buffer A), ‘default-B’ (choose the region from
buffer B), or ‘combined’ (combine the regions from the two
buffers). Merging and diff3, for further details.
The command ‘&’ also affects the regions in the merge buffers that
have ‘default-A’, ‘default-B’, or ‘combined’ status, provided they
weren’t changed with respect to the original. For instance, if
such a region has the status ‘default-A’ then changing the default
action to ‘default-B’ will also replace this merge-buffer’s region
with the corresponding region from buffer B.
‘s’
Causes the merge window shrink to its minimum size, thereby
exposing as much of the variant buffers as possible. Typing ‘s’
again restores the original size of that window.
With a positive prefix argument, this command enlarges the merge
window. E.g., ‘4s’ increases the size of the window by about 4
lines, if possible. With a negative numeric argument, the size of
the merge window shrinks by that many lines, if possible. Thus,
‘-s’ shrinks the window by about 1 line and ‘-3s’ by about 3 lines.
This command is intended only for temporary viewing; therefore,
Ediff restores window C to its original size whenever it makes any
other change in the window configuration. However, redisplaying
(‘C-l’) or jumping to another difference does not affect window C’s
size.
The split between the merge window and the variant windows is
controlled by the variable ‘ediff-merge-window-share’, which see.
‘+’
Combines the difference regions from buffers A and B and copies the
result into the merge buffer. Merging and diff3, and the
variables ‘ediff-combine-diffs’ and ‘ediff-combination-pattern’.
‘=’
You may run into situations when a large chunk of text in one file
has been edited and then moved to a different place in another
file. In such a case, these two chunks of text are unlikely to
belong to the same difference region, so the refinement feature of
Ediff will not be able to tell you what exactly differs inside
these chunks. Since eyeballing large pieces of text is contrary to
human nature, Ediff has a special command to help reduce the risk
of developing a cataract.
In other situations, the currently highlighted region might be big
and you might want to reconcile of them interactively.
All of this can be done with the above command, ‘=’, which compares
regions within Ediff buffers. Typing ‘=’ creates a child Ediff
session for comparing regions in buffers A, B, or C as follows.
First, you will be asked whether you want to compare the fine
differences between the currently highlighted buffers on a
word-by-word basis. If you accept, a child Ediff session will
start using the currently highlighted regions. Ediff will let you
step over the differences word-wise.
If you reject the offer, you will be asked to select regions of
your choice.
_If you are comparing 2 files or buffers:_ Ediff will ask you to
select regions in buffers A and B.
_If you are comparing 3 files or buffers simultaneously:_ Ediff
will ask you to choose buffers and then select regions inside those
buffers.
_If you are merging files or buffers (with or without ancestor):_
Ediff will ask you to choose which buffer (A or B) to compare with
the merge buffer and then select regions in those buffers.
Info Catalog
ediff: Session Commands
ediff: Other Session Commands