Friday, 24 October 2008

Emacs Help


Emacs is perhaps world's most powerful text can do lot's of stuff using emacs in a very powerful way.I will just try to list out few tasks that you can accomplish with help of emacs:

  • Editing text files
  • Programming
  • Searching and replacing patterns in a text file
  • Checking mail
  • Reading news
  • Listening to Songs
  • Executing commands
  • Can also work as a file manager

When you start emacs(using command emacs &) can see a menu bar on the top of the emacs window,a tool bar just below the menu bar.And then most of the remaining space is occupied by the editing buffer(where actual editing is performed).You can see a scroll bar in the left side of window.

Another thing that you will observe that at the end of editing buffer there exists some sort of seperator..and below it exists another small area.

Well this area is very important..
Seperator is called ---> Modeline
Area below is called ---> Message Area
Commands typed by you will be echoed in the message area, as well as response from emacs and messages from emacs will be also shown there.

Commands Conventions

All of the emacs commands are basically in the form of some special key bindings.These key bindings may initially appear a bit daunting but are very convenient. Usually all of the emacs commands start with either with control or alt key.Rest of the printable characters are sent to the editing buffer and are not considered as command.

For Example:
To open a new file:
To undo changes:
To browse through info pages:
Press x and f key respectively while ctrl key is> ctrl-x,u:
Press x while ctrl key is pressed and now leave ctrl key(as well as x)and press> alt-x-info:
press x while alt key is pressed and now leave alt(as well as x) and type info manually in the message> -:
One impotant thing is all the hyphen's are used for illustration purpose only. They are not to be included in commands.


Here i will try to give all the essential commands with help of which you can easily work with emacs. One thing you should keep in mind is that you need not to remember all the commands. You can work with emacs very easily using a limited list of commands. The method to enter the command has been explained in the earlier section.

To open a new/existing file.when you press this command you can see a message ">

To write the file to disk(or in other words to save the file.)

To quit emacs.If you have any running processes(let us say shell) or any unsaved buffer it will ask you either to save the changes or discard them and then quit emacs.

Go to the beginning of line.

Go to the end of line.

Go to previous line.

Go to next line.

Go to the beginning of buffer.

Go to the end of buffer.

Kill line. This command will kill one line starting from current cursor position.

Move one character forward.

Move one char backward.

To write the existing buffer with a different file name.

To delete one word to the right of cursor.

To move one word forward.

to move one word backward.

To move one sentence backward. But in this case cursor doesn't stop at the blank lines.

To move one sentence forward.

To start shell from emacs.

To switch to buffer. This command ask the name of the buffer you want to switch.

List all the existing buffers.

This command Will ask for what command you want to see manual pages. Thus a message related to it will appear in the message area.

To browse through info pages.

To check mail

To start play mp3 songs from emacs. This packages doesn't come by default on the Red Hat releases, so you have to download a package called mpg123.el.

By pressing this command you can see the list of available commands in emacs.

To start spell checking from emacs.

To undo your last set of changes.

To change the background color of emacs buffer.

Now many of the commands has been described below and a description of how to bind keys with these commands is also given below.


You can check spelling of a buffer using the command `alt-x-ispell-buffer`. You can use 'r' to enter a mis-spelled word for yourself.
'a': emacs will accept the word as correct for present session.
'A': emacs will accept the word as correct for all session.
spacebar: ignore the error.
ctrl-r: enter in to recursive editing.


Can be also used for spelling checking..thus in this mode the spelling of the word will be checked on the fly and highlighted if there is an error. So either you can edit the word yourself or else left click on the word and let emacs suggest options.

Completing The Text From Another Part of the Buffer

Let's say you are editing a text file and you are typing several words lot's of times then you can use this thing. We can use keystroke "alt-/" to auto complete a word that you have typed before.

Some Very Important Keystrokes for Moving Around

alt-e: to end of the paragraph.
alt-a: to the beginning of the paragraph.
alt-}: to move forward one paragraph
alt-{: backward one paragraph.
alt-<: go to the beginning of buffer alt->: go to the end of buffer

Customization of Emacs

Emacs can be very easily customized this is one of the reasons it is such a powerful editor.If you try command "alt-set-background-color" then you will find that you can change the background color of the current face. But the settings won't be saved thus next time you will start emacs your changes will be lost. Emacs reads a file called $HOME_DIR/.emacs(~/.emacs) on startup. By editing this file you can customize emacs very easily and your changes will saved. Here i am giving contents of my .emacs file. By looking at the comments itself you can guess what is the function of that line. Even of you don't, relax and simply use it for the time being. Just simply copy following lines and paste it to a file called .emacs(if something is already there in that file then you make sure it should be deleted).

Sample .emacs File

;; Set up the keyboard so the delete key on both the regular keyboard
;; and the keypad delete the character under the cursor and to the right
;; under X, instead of the default, backspace behavior.
(global-set-key [delete] 'delete-char)
(global-set-key [kp-delete] 'delete-char)

;; turn on font-lock mode
(global-font-lock-mode t)

;; enable visual feedback on selections
(setq-default transient-mark-mode t)

;; always end a file with a newline
(setq require-final-newline t)

;; stop at the end of the file, not just add lines
(setq next-line-add-newlines nil)

;;to display time

;;to set the cursor color
(set-cursor-color "red")

;;to set the font
(set-frame-font "-*-fixedsysttf-*-*-*-*-15-*-*-*-*-*-*-*")

;;to set foreground color to white
(set-foreground-color "white")

;;to set background color to black
(set-background-color "black")

;;to manage the geometric size of initial window.
(setq initial-frame-alist '((width . 87) (height . 42)))

;;set the keybinding so that you can use f4 for goto line
(global-set-key [f4] 'goto-line)
;;set the keybinding so that f3 will start the shell
(global-set-key [f3] 'shell)
;;set the keybinding so that f5 will start query replace
(global-set-key [f5] 'query-replace)
(global-set-key [f6] 'switch-to-buffer)
(global-set-key [f7] 'hippie-expand)
(global-set-key [f8] 'ispell)

(setq load-path (cons "/home/hemant/elisp" load-path))

(when window-system
;; enable wheelmouse support by default
;; use extended compound-text coding for X clipboard
(set-selection-coding-system 'compound-text-with-extensions))
(autoload 'mpg123 "mpg123" "A Front-end to mpg123" t)

;; custom-set-variables was added by Custom -- don't edit or cut/paste it!
;; Your init file should contain only one such instance.
'(auto-save-default nil)
'(backup-directory-alist (quote (("." . "/home/hemant/backup"))))
'(default-frame-alist (quote ((tool-bar-lines . 1) (menu-bar-lines . 1) (width . 87) (height . 42)))))
;; custom-set-faces was added by Custom -- don't edit or cut/paste it!
;; Your init file should contain only one such instance.
'(font-lock-comment-face ((((class color) (background dark)) (:foreground "chocolate1" :slant italic :family "-*-lucida-medium-r-*-*-14-*-*-*-*-*-*-*"))))
'(fringe ((((class color) (background dark)) (:background "grey10" :width ultra-condensed))))
'(scroll-bar ((t (:background "Dark slate gray")))))
Miscellaneous Commands

Some keystrokes set by me:
f4: goto line //go to some line
f3: to start shell
f5: to start query replace
f6: switch to buffer //switch to different open buffer
f7: hippie expand //auto completion even from other buffer.
f8: to start spell check

Customizing key bindings in emacs:
Put following lines in to your .emacs file and those keystrokes will work for you as well.

(global-set-key [f4] 'goto-line)
(global-set-key [f3] 'shell)
(global-set-key [f5] 'query-replace)
(global-set-key [f6] 'switch-to-buffer)
(global-set-key [f7] 'hippie-expand)
(global-set-key [f8] 'ispell)

Commands Helpfull During Programming jump to newline automatically after termination of an statement:
ctrl-c,ctrl-a: enables addition of newline.


My .emacs file assumes you have fixedsys and lucida fonts installed.(though lucida comes with any standard installation of GNU/Linux..fixedsys won't be installed on your system.Also i have created a directory called ~/elisp where additional elisp packages are stored ,so you must have a directory of that name.Now if you don't have fixedsys and any packages that has to be stored in ~/elisp better remove those lines).Another important default emacs creates backup of files while editing and saves it in current directory with prefix ~.But i have customized emacs so that all the backup files will redirected to ~/backup directory.So you should also create a directory called ~/backup.

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