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Using EMACS on OITUNIX
Appendix B: Useful Emacs Commands
Handout: 108bMay 1997
Operating System: OITUNIX
Description: EMACS commands
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useful EMACS commands
alphabetized list of EMACS commands with keybindings (if any) and
descriptions
discussion
ARG: the "universal argument" -- C-u #
numeric arguments -- M #
more on the command line -- M-x
marking a region -- C-@ or C-2
marking a rectangle
buffers and windows
kill vs. delete and the yank buffer
modes and filename extensions
string matching and regular expressions
special characters in regular expressions
Below are two lists of useful EMACS commands. Neither list is complete. For complete documentation refer to the GNU EMACS Manual, which is available in Acadmeic Computing reference areas. The first list is grouped according to functions. The next list is alphabetized by the names of the commands.
EMACS key ProComm for DOS key EMACS key ProComm for DOS key
M Alt-4 C-\ Alt-1
EMACS commands -- by functions
getting help
C-h help-command
C-h a help-apropos
C-h t help-with-tutorial
C-h b describe-bindings
C-h ? help-for-help
C-h C-h help-for-help
leaving EMACS
C-x C-c save-buffers-kill emacs
C-z suspend-emacs
error recovery
C-g cancel-command
C-x u undo-last-command
C-l redraw-garbage-screen
cursor motion
C-a beginning-of-line
C-b backward-character
C-e end-of-line
C-f forward-character
C-n next-line
C-p previous-line
C-o open-line
M-f forward-word
M-b backward-word
scrolling
C-v scroll-up
C-l center-current-line-in window
C-x < scroll-left
C-x > scroll-right
M- < beginning-of-buffer or-file
M- > end-of-buffer-or-file
M-v scroll-down
marking commands
C-@ set-mark-command
or C-2
C-x C-x exchange-point-and-mark
killing and deleting
<X| delete-backward-character (VT320)
C-d delete-character
C-k kill-line
C-w kill-region
C-y yank
C-x k kill-buffer
M-d kill-word
M-k kill-sentence
M-w copy-region-as-kill
M-y yank-pop
incremental search
C-\ incremental-search-forward (OIT only)
C-r incremental-search-backward
[return] exit-incremental-search
replacing text
M-% query-replace
rectangle commands
C-x r o open-rectangle
C-c k kill-rectangle
(no key) yank-rectangle
C-x r copy-rectangle-to-register
window commands
C-x 2 split-window vertically (1 above other)
C-x 3 split-window horizontally
C-x 0 delete-current-window
C-x 1 delete-other-window
C-x o other-window
C-x ^ enlarge-window-vertically
C-x } enlarge-window-horizontally
file & buffer commands
C-x C-f find-file
C-x C-w write-file (prompts for name)
C-x i insert-file
M-s save-buffer-with-same-name
C-x C-b list-buffers
C-x b switch-to-buffer
utilities
C-u universal-argument
C-c w what-line
C-c v overwrite-mode toggle
C-x = what-cursor-position
M-! shell-command
M-g goto-line
M-= count-lines-in-region
alphabetized list of EMACS commands
with keybindings (if any) and descriptions
See the discussion of ARG and other mysterious phrases in the following list. If there is no keybinding, you enter M-x to move to the command line and enter the command.
keys commands descriptions
append-to-file append contents of region to end
of a file. Prompts for filename.
C-b backward-char Move cursor left ARG characters
(right if ARG is negative).
M- < beginning-of-buffer Move cursor to the beginning of
the buffer; leave mark at
previous position.
C-a beginning-of-line Move cursor to the beginning
of the current line
C-h a command-apropo Prompts for a string, and lists
all EMACS commands that contain
that string, with brief
description.
copy-file Copy FILE to new name. Prompts
for old file name and new file
name.
C-x r copy-rectangle-to-register Copy rectangular area into a
register. Prompts for register
name which must be one character.
M- w copy-region-as-kill Save the region as if killed, but
don't kill it.
M- = count-lines-region Display number of lines in
the region.
count-matches Display number of matches for a
string (REGEXP) following cursor.
C-d delete-char Delete the following ARG
characters (previous with
negative ARG)
delete-file Delete specified file. Prompts
for a file name.
C-x 1 delete-other-windows Make current window fill the
screen
delete-rectangle Delete (don't save) text in
rectangle with cursor and mark
as corners.
C-x 0 delete-window Remove current window from the
display.
C-h b describe-bindings Show a list of all defined
keys, and their definitions.
C-h k describe-key Display documentation of the
function which KEY invokes.
M-> end-of-buffer Move cursor to the end of the
buffer; leave mark at previous
position.
C-e end of line Move cursor to end of current
line.
C-x^ enlarge-window-vertically Make current window ARG lines
bigger.
C-x} enlarge-window-horizontally Make current window ARG columns
wider.
C-x C-x exchange-point-and-mark Put the mark where cursor is now,
and cursor where mark is now.
M-x execute-extended-command Prefix for typing any
command from the command line.
C-x C-f find-file Edit file FILENAME.
C-f forward-character Move cursor right ARG charaters
(left if ARG is negative).
M-g goto-line Go to line ARG, counting from
line 1 at beginning of buffer;
prompts for line number.
C-h help-command
C-h? help-for-help You have typed C-h, the help
character. Type a Help option,
or c-h for a description of the
options.
C-h t help-with-tutorial Select the EMACS learn by
doing tutorial.
C-x i insert-file Insert contents of a file into
buffer after cursor.
C-x g insert-register Insert contents of a register.
Prompts for a name of register
(one character).
C-\ isearch-forward Do incremental search forward.
OIT version of EMACS only; cannot
be used with ProComm for DOS.
C-r isearch-backward Do incremental search backward.
keep-lines Delete all lines except those
containing a given string
(REGEXP)
C-g keyboard-quit Restart a sequence of command
keys.
C-x k kill-buffer Get rid of the specified buffer.
Prompts for name of buffer.
C-k kill-line Kill the rest of the current
line. If ARG is given, kills next
ARG lines.
C-w kill-region Kill between cursor and mark.
C-c k kill-rectangle Remove rectangle with corners
at cursor and mark; (save in yank
buffer).
C-x C-b list-buffers Display a list of names of
existing buffers.
C-x C-d list-directory Display a list of files in
a directory, as with ls.
list-matching-lines or occur Show all lines following cursor
containing a match for a given
string (REGEXP).
C-n next-line Move cursor verticaly down ARG
lines.
occur Show all lines that follow
current line that contain a match
for a given string (REGEXP).
occur-mode-goto-occurrence Goes to line in buffer where
occurrence was found. Must be
entered from the window that
shows the occurrences.
C-c o open-rectangle Blank out rectangle with corners
at cursor mark, shifting text
right.
C-x o other-window Select the ARG'th different
window.
C-c v overwrite-mode Toggle overwrite mode.
C-p previous-line Move cursor vertically up ARG
lines.
M- % query-replace Replace some occurrences of
FROM-STRING with TO-STRING.
possible responses for Query-
replace are:
(SPC =yes; Del =no; ! =replace
all; M means quit)
C-^ quoted-insert Read next input character and
insert it.
C- l redraw-display Clear the screen and display
again what is supposed to appear
on it.
replace-string Replace all occurrences of
FROM-STRING with TO-STRING.
M- s save-buffer Save current buffer in file
(if modified).
C-x C-c save-buffers-kill-emacs Offer to save each buffer, then
quit EMACS.
M- v scroll-down Scroll text of current window
downward (backwards). ARG lines
or full screen if no ARG is
given.
C-x < scroll-left Scroll display ARG columns left,
or full screen if no ARG is
given.
C-x > scroll-right Scroll display ARG columns right,
or full screen if no ARG is
given.
C-v scroll-up Scroll text of current window
upward (forward) ARG lines; or
full screen if no ARG.
C-@ or C-2
set-mark-command Set mark at current cursor
location.
set-variable Set the value of a VARIABLE;
prompts for variable name and
value.
shell Start a "shell" for running unix
commands without leaving EMACS.
M- ! shell-command Execute a unix command from
inside EMACS
shrink-window Make current window ARG lines
smaller.
C-x 3 split-window-horizontally Split current window into two
windows side by side.
C-x 2 split-window-vertically Split current window into two
windows; one above the other.
C-z suspend-emacs Stop EMACS and return to superior
process. You can resume EMACS at
the same place using %emacs.
C-x b switch-to-buffer Select a different buffer in the
current window. Prompts for
buffer name.
C-x C-u upcase-region Convert the region to upper case.
In programs, wants two arguments.
C-x u undo Undo some previous changes.
C-u universal-argument Enter a numeric argument for the
following command.
view-register Display what is contained in a
register. Prompts for 1 character
register name.
C-x = what-cursor-position Display information on Cursor
Position (on screen and within
Buffer).
C-c w what-line Display the line number (within
the buffer) of the cursor.
C-x C-w write-file Write current buffer to a file.
write-region Write current region to a file.
C-y yank Reinsert the last stretch of
killed text.
M- y yank-pop Replace just-yanked stretch of
killed-text with previously
killed text.
yank-rectangle Insert the last killed rectangle
with upper left corner at cursor.
ARG: the "universal argument" -- C-u #
The "universal argument" is used to enter a numeric argument or repeat factor for an EMACS command. In the descriptions of EMACS commands, the word ARG is used to refer to the universal argument. The universal argument may also be negative (to cause the command to move or act backwards through the buffer).
The universal argument must precede the command to which it is to be applied.
Examples:
a) C-d deletes the character the cursor is on. If
you need to delete 10 characters, starting at the
cursor, you could press C-d 10 times, or you could use
the universal argument, and type C-u 10 C-d.
b) Without numeric argument, C-v scrolls up (forward) a screen. Using universal argument, you can scroll forward a specific number of lines: C-u 50 C-v scrolls forward 50 lines of text.
c) to insert 33 asterisks into your file at the current cursor location, type: C-u 33 *
If you do not precede one of these commands by the universal argument, a default number will be used: a screenful for the scrolling commands; 1 for most other commands.
The numeric argument is similar to the "universal argument": any EMACS command may be given a numeric argument that indicates how many times the command should execute. Numeric arguments may also be negative (to cause the command to move or act backwards through the buffer).
Examples:
a) M5 C-d deletes the character the cursor is on
plus the next 4 characters.
b) M10 C-v scrolls up (forward) 10 lines.
M-10 C-v scrolls down (backward) 10 lines.
more on the command line --
M-x
Some commands do not have a key binding. These commands must be entered on the command line (also referred to as the mini- buffer). For commands that you don't use very often, you may find it easier to remember the name of the command than its binding. Press M-x, then you can type any EMACS command.
Examples:
The command "replace-string" does not have a key binding. To use it, press M-x then type replace-string.
The "copy-region-as-kill" command has the key binding M-w. If you want to use this command, but don't remember the binding press M-x and type copy-region.
When you are typing commands on the command line, you only need to type enough of the command to make each word unique; EMACS will fill in the rest. For example to enter "replace string", you can just type repl and press the space bar. EMACS completes the first word, replace-, and waits for you to type the second word. For the second word, it's enough to type st and press <return>. If you do not type enough to make a word unique, EMACS will show you a list of all possibilities. You must then enter additional letters until your choice is clear. In the previous example, if you had only typed rep [for replace] and pressed space, EMACS would show you a list of commands beginning with the words repeat and replace. When you add the "l", it completes the first word.
marking a region -- C-@ or
C-2
Many EMACS commands operate on only a selected part of your file. For example you might want to copy, move, or delete a section of text. To select the part you want to do something with, you need to put a "mark" at the beginning of the chosen section, and the cursor at the end (or the cursor at the beginning of the section, and a "mark" at the end.)
The "mark" is invisible. You set it by typing C-@ or C-2 at the place you want marked. Once the mark is set, it remains in the same place until you set it somewhere else. In addition to the C-2 command, the beginning-of-buffer (M-<) and end-of-buffer (M->) commands also reset the mark.
Having marked one end of the section you want, move the cursor to the other end. Everything starting at the mark, up to (but not including) the cursor is called a "region." Any EMACS command with the word region in it will apply to just that portion of your file. Examples:
copy-region will copy the selected text to the yank buffer
kill-region will delete the selected text
write-region will write the selected text to a file
Rectangles are marked in exactly the same way as regions: put the mark in one corner of the rectangle and the cursor in the diagonally opposite corner. Any command that operates on rectangles will affect only the rectangular area demarcated by the mark and cursor. Examples:
open-rectangle will shift everything right, to leave a
blank rectangle
kill-rectangle will delete the marked rectangle
When a mark is set, the area between the mark and cursor
could be used either as a region or a rectangle.
A "buffer" is a temporary holding area. When you edit a file using EMACS, the file is loaded into an EMACS "buffer." The buffer has the same name as the file that is loaded into it. You edit the "buffer" copy of the file but the original is not changed until you save the buffer.
EMACS lets you keep many files open for editing at the same time. Each open file is loaded into a different buffer. Each time you open a file with find-file (C-x C-f), you are opening a new buffer. In addition, you could also have a "shell" buffer, which allows you to execute unix commands without leaving EMACS. However, you don't usually see all your buffers on the screen. The active or current buffer fills the whole screen; the others (if there are any) are "behind" the current buffer, so you can't see them. The name of the current buffer is displayed on the formation line near the bottom of the screen. When you want to work on a different buffer, you use the switch-to-buffer (C-x b) command. If you can't remember the names of the buffers you have opened, use the list-buffers (C-x C-b) command.
"Windows" are partitions of the screen. You can split your screen into 2 or more "windows," either horizontally or vertically, using the split-window commands. Then you can look at a different buffer in each window. The name of the buffer is listed at the bottom of each window.
kill vs. delete and the yank buffer
The delete commands of EMACS remove parts of text and throw them away. The only way to retrieve something you have deleted is with undo (C-x u), which will put it back in the same place.
The kill commands also remove parts of text, but they are saved in the "kill" buffer. You can take text from the kill buffer and insert it anywhere in your file. Furthermore, when you "insert" something from the kill buffer, it is still available in the kill buffer, so you can yank it again. You can use the kill buffer to duplicate a section of text in many different places in your file.
When you use the "yank" (C-y) command, you always get back the most recently killed text. If you need to insert something that was killed earlier, use yank-pop (M-y) following the yank. This will remove the text that was just yanked, and replace it with the next previously killed text. You can use yank-pop several times until you get back to the text you want to insert. See the OIT tutorial section of this handout for examples of kill and yank.
EMACS has special commands for features that are based on the syntax of particular programming languages and certain applications. The indicator to EMACS is the filename extension, if any. The available EMACS modes and their associated extensions include Fortran, Lisp, C, LaTex, etc. For a list of the modes and their extensions, do a help on variable auto-mode-alist:
C-h v
auto-mode-alist
string matching and regular
expressions
The descriptions of many EMACS commands use the words "regular expression," or REGEXP for short. A regular expression is just a string of characters; however, some characters have special meaning which can be used to make searches more general.
For example, the list-matching-line command lists all lines in the current EMACS buffer which contain matches for a regular expression. Suppose you asked EMACS to list- matching-lines for the regular expression "out". It would list all lines in which any of the following words occurred: out, shout, outside, and many others.
special characters in regular
expressions
The period (.) can be used as a "wild card" to replace a single character. In the above example, if you asked to list-matching-lines for the regular expression "o.t" EMACS would list any lines containing words such as loiter and boats, in addition to out, shout, etc. It would not match doubt, however; the period can only replace one character.
Now suppose you are working with a file that contains decimal numbers, and you need to look at those numbers that end with ".5". If you use ".5" as the regular expression in the search, the decimal point will be interpreted as the wildcard, and EMACS will match it with numbers such as 15.0, and 35.2, as well as 10.5. You can use the backslash (\) before any special character to make it lose its meaning as a special character. So the regular expression \.5 will get you what you want- just numbers like 1.5, 33.5, etc.
There are other special characters and regular expressions can get quite complex. Here we will merely mention what the other special characters are so you will not accidentally use them in a search string. The other special characters are: $, ^, *, +, ?, [, and ]. If you need to use a search string that includes one of these characters, be sure to precede that character with a backslash (\) so it will lose its special meaning.
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