Introduction to
EMACS and XEMACS
CMSC 121 Introduction to UNIX
Much of the material in these slides was taken from
Dan Hood’s CMSC 121 Lecture Notes.
Emacs Background
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Emacs is a powerful and extensible text editor.
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Emacs originally was an acronym for Editor MACroS.
The first Emacs was a set of macros written in 1976 at MIT by Richard M
Stallman.
Emacs has become a standard editor used by programmers worldwide.
There are several varieties of Emacs, by typing emacs at the
command prompt, you are throw into one of two modes:
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The terminal-mode (from an ssh connection or without X Window):
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This mode has no toolbars, and all commands are given via keyboard.
Do not think that this is a useless mode, as sometimes the only connection that
you may have to a machine is remote.
The graphical-mode (requires X Window):
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It looks similar to the terminal-mode, but with some added features for X.
There is a toolbar across the top of the window, from which many common
tasks can be accessed.
You may wish to type emacs& (note the &), as this will free up the shell for
other tasks (such as compiling).
XEmacs
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This version of Emacs that has many
enhancements specifically for X Window and
should be launched locally.
There is a graphical toolbar (like MS Word) for
basic options as well as a text driven toolbar for
other options.
To invoke XEmacs just type xemacs. If you do
not want to tie up the shell, use xemacs&.
Creating and Opening Files
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To create a file, type the name of the file that
you wish to create after the emacs command.
Example: emacs foo.c & or xemacs foo.c &
(& optional).
To open a file, type the name after the
command, just as above.
Tutorial and References
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Emacs comes with a built in tutorial.
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To access it type F1 then T.
The tutorial covers many of the basic tasks, such as cursor
movement to more advanced skills such as searching and
replacing text.
References - from basic commands to the full manual
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A BASIC EMACS Reference Card
A much more EXTENSIVE EMACS Reference Card
The Complete Manual Online - at GNU.org
XEmacs
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XEmacs is a graphical variant of Emacs.
It too is freely available for download
(http://www.xemacs.org/) and is also licensed under
the GPL license
(http://www.gnu.org/licenses/licenses.html#GPL).
XEmacs for Windows
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For those of you who use Windows, that there are MS
Windows ports of XEmacs.
XEmacs Commands
Mostly all of the Emacs commands are available to you
under XEmacs
One useful XEmacs command:
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Alt-G - Goto Line number
.emacs Configuration File
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When Emacs (or XEmacs) begins, it looks for and
reads a file named .emacs in your home directory to
obtain configuration information.
Save this .emacs file (note the leading "dot") in your
UNIX home directory to get the following features
(you will need to restart emacs to invoke these options):
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Automatic formatting - in accordance with coding style
standards of many CMSC classes - (ALWAYS check with your
instructor as to specific standards)
A working backspace key - backspace will now delete to
the left of the cursor instead of invoking "help".
A more logical help key - It remaps CTRL-X? to be the
new "help" key.
Customizing Emacs
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The .emacs file contains user specific information and
customizations to the XEmacs/Emacs editors. You can
set up this file to do all sorts of customizations from
building additional menu bars, to highlighting, to utility
functionality.
There are 2 ways of going about customizing
XEmacs/Emacs:
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Manually edit this configuration file - this requires some
knowledge of the language used to configure the editor and
requires the user to manually edit the ".emacs" file.
Save configuration changes from within the editor - or
you can save the changes from within the editor itself, and it
writes out settings automatically to the ".emacs" file.
I find that I tend to use a mixture of both manual and
automatic editing of the ".emacs" file.
Sample CMSC 201 .emacs File
(custom-set-faces)
(global-set-key "\C-h" 'delete-backward-char)
(global-set-key "\C-x?" 'help-command)
;; set style to "Ellemtel" for C++
(add-hook 'c++-mode-hook
'(lambda () (c-set-style "ellemtel")))
;; set style to "Ellemtel" for C
(add-hook 'c-mode-hook
'(lambda () (c-set-style "ellemtel")))
;; special effects for 'C‘
(add-hook 'c-mode-hook 'turn-on-font-lock)
Another .emacs File
;; no tabs please
(setq-default indent-tabs-mode nil)
(setq default-tab-width 4)
;; line & col nums
(setq line-number-mode t)
(setq column-number-mode t)
;; font coloring
(setq font-lock-auto-fontify t)
(setq font-lock-mode-maximum-decoration
t)
(require 'font-lock)
;; my email
(custom-set-variables
'(user-mail-address
"your_username_here@umbc.edu" t)
'(query-user-mail-address nil))
;; some key bindings
(global-set-key [(f1)] (lambda () (interactive)
(manual-entry (current-word))))
(global-set-key [f2] 'ispell-word)
;; map that mouse wheel
(global-set-key [button4] 'scroll-down)
(global-set-key [button5] 'scroll-up)
;; automatic indentation upon return
(global-set-key [(return)] 'newline-andindent)
;; stop beeping
(setq visible-bell 1)
;; make sure that every file has a newline
(setq require-final-newline t)
Emacs Modes
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C Mode: Emacs supports C programming with a
variety of options in C mode.
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C -> Comment Out Region
C -> Uncomment Region
C -> Indent Line or Region
C -> Foreword Statement
C -> Backward Statement
C++ Mode: C++ mode also supports the same
functions as under C mode, but under the C++ menu.
HTML Mode
Lisp Mode
Compiling in XEmacs
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One of the nice features of XEmacs is the ability to compile source code
from within it.
Do the following to compile code from within XEmacs:
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Click on the Compile button
Edit the prompt in the window that appears that shows you what the current
command is to compile.
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The Compilation Output – this is where XEmacs is really useful.
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By default XEmacs suggests the command "make -k".
This may or may not be what you want.
If you do not have a makefile (or don't know what one is) then you can change the
command to something like "gcc -Wall -ansi *.c" by clicking on "Edit command".
If you have errors, gcc (for example) will report file and line numbers that the
errors occurred on.
XEmacs goes a step further and hyperlinks that error containing the file and line
number.
So when you click on it, it will open that file in the current buffer and jump to that
line number.
XEmacs will also make sure that you saved all open files, to avoid compiling
the sources without compiling them first.