Introduction to EMACS and XEMACS

1
Introduction to EMACS and XEMACS

• CMSC 121 Introduction to UNIX
• Much of the material in these slides was taken
  from
• Dan Hoods CMSC 121 Lecture Notes.

2
Emacs Background

• Emacs is a powerful and extensible text editor.
• 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
• The terminal-mode (from an ssh connection or
  without X Window)
• 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)
• 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).

3
XEmacs

• 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.

4
Creating and Opening Files

• 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.

5
Tutorial and References

• Emacs comes with a built in tutorial.
• 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
• A BASIC EMACS Reference Card
• A much more EXTENSIVE EMACS Reference Card
• The Complete Manual Online - at GNU.org

6
XEmacs

• 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.htmlGPL).
• XEmacs for Windows
• 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
• Alt-G - Goto Line number

7
.emacs Configuration File

• 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)
• 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.

8
Customizing Emacs

• 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
• 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.

9
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)

10
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_at_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-and-indent)
• stop beeping
• (setq visible-bell 1)
• make sure that every file has a newline
• (setq require-final-newline t)

11
Emacs Modes

• C Mode Emacs supports C programming with a
  variety of options in C mode.
• C -gt Comment Out Region
• C -gt Uncomment Region
• C -gt Indent Line or Region
• C -gt Foreword Statement
• C -gt Backward Statement
• C Mode C mode also supports the same
  functions as under C mode, but under the C
  menu.
• HTML Mode
• Lisp Mode

12
Compiling in XEmacs

• 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
• Click on the Compile button
• Edit the prompt in the window that appears that
  shows you what the current command is to compile.
• 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".
• The Compilation Output this is where XEmacs is
  really useful.
• 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.