9.2.1. Firing It Up

GNU Emacs is simply invoked as:

$ emacs options

$ xemacs options

In Emacs lingo, C-x means Ctrl-X, and M-p is equivalent to Alt-P. As you might guess, C-M-p means Ctrl-Alt-P.

Using these conventions, press C-x followed by C-f to read in a file or create a new one. The keystrokes display a prompt at the bottom of your screen showing your current working directory. You can create a buffer now to hold what will end up to be the content of a new file; let's call the file wibble.txt. We now see the following:

  


-----Emacs: wibble.txt           (Fundamental)----All-------------------

To the right of the buffer type is the word All, which means that you are currently looking at the entire file (which is empty). Typically, you will see a percentage, which represents how far into the file you are.

Find file: /home/loomer/mdw/.bash

Possible completions are: 
.bash_profile                      .bashrc 


--**-Emacs: *Completions*     (Fundamental)----All----------------------

After you complete the filename, the *Completions* buffer goes away and the new file is displayed for editing. This is one example of how Emacs uses temporary buffers to present information.

You can switch to another buffer using the C-x b command, which asks you for the name of the buffer (usually the name of the file within the buffer). For example, pressing C-x b presents the prompt:

Switch to buffer: (default wibble.txt)

 MR Buffer        Size   Mode        File 
 -- ------        ----   ----        ---- 
.   wibble.txt     44    Fundamental /home/loomer/mdw/wibble.txt 
    .bashrc        1763  Fundamental /home/loomer/mdw/.bashrc 
    *scratch*      0     Lisp Interaction 
 *  *Buffer List*  265   Buffer Menu

Popping up the buffer menu splits the Emacs screen into two "windows," which you can switch between using C-x o. More than two concurrent windows are possible as well. In order to view just one window at a time, switch to the appropriate one and press C-x 1. This hides all of the other windows, but you can switch to them later using the C-x b command just described. Using C-x k actually deletes a buffer from Emacs's memory.

9.2.3. Tutorial and Online Help

Using the C-h command gives you a list of help options on the last line of the display. Pressing C-h again describes what they are. In particular, C-h followed by t drops you into the Emacs tutorial. It should be self-explanatory, and an interactive tutorial about Emacs tells you more about the system than we can hope to cover here.

As you see, text is presented along with a menu to other "nodes." Pressing m and then entering a node name from the menu will allow you to read that note. You can read nodes sequentially by pressing the space bar, which jumps to the next node in the document (indicated by the information line at the top of the buffer). Here, the next node is Instructions, which is the first node in the menu.

Each node also has a link to the parent node (Up), which here is (dir), meaning the Info page directory. Pressing u takes you to the parent node. In addition, each node has a link to the previous node, if it exists (in this case, it does not). The p command moves to the previous node. The l command returns you to the node most recently visited.

Within the Info reader, pressing ? gives you a list of commands and pressing h presents you with a short tutorial on using the system. Since you're running Info within Emacs, you can use Emacs commands as well (such as C-x b to switch to another buffer).

If you think that the Info system is arcane and obsolete, please keep in my mind that it was designed to work on all kinds of systems, including those lacking graphics or powerful processing capabilities.

Other online help is available within Emacs. Pressing C-h C-h gives you a list of help options. One of these is C-h k, after which you press a key, and documentation about the function that is bound to that key appears.

9.2.4. Deleting, Copying, and Moving Text

The mark can be set using the key C-@ (or C-Space on most systems). Moving the cursor to a location and pressing C-@ sets the mark at that position. You can now move the cursor to another location within the document, and the region is defined as the text between mark and point.

For example, type the following text into an Emacs buffer:

The rain falls on the main plains in Spain. 
Here is a line that we wish to move. 
She sells Bourne shells by the sea shore.
 


--**-Emacs: wibble.txt           (Fundamental)----All-------------------

Now, move the cursor to the beginning of the second line ("Here is a line…"), and set the mark with C-@. Move to the end of the line (with C-e), and delete the region, using C-w. The buffer should now look like the following:

The rain falls on the main plains in Spain. 
 
She sells Bourne shells by the sea shore.


--**-Emacs: wibble.txt           (Fundamental)----All-------------------

In order to yank the text just deleted, move the cursor to the end of the buffer, and press C-y. The line should be pasted at the new location:

The rain falls on the main plains in Spain. 

She sells Bourne shells by the sea shore.
Here is a line that we wish to move.  


--**-Emacs: wibble.txt           (Fundamental)----All-------------------

Pressing C-y repeatedly will insert the text multiple times.

Text that is deleted using other kill commands, such as C-k, is also added to the kill ring. This means that you don't need to set the mark and use C-w to move a block of text; any deletion command will do.

In order to recover previously deleted blocks of text (which are saved on the kill ring), use the command M-y after yanking with C-y. M-y replaces the yanked text with the previous block from the kill ring. Pressing M-y repeatedly cycles through the contents of the kill ring. This feature is useful if you wish to move or copy multiple blocks of text.

Emacs also provides a more general register mechanism, similar to that found in vi. Among other things, you can use this feature to save text you want to paste in later. A register has a one-character name; let's use a for this example:

1. At the beginning of the text you want to save, set the mark by pressing the Control key and space bar together (or if that doesn't work, press C-@).

2. Move point (the cursor) to the end of the region you want to save.

3. Press C-x x followed by the name of the register (a in this case).

4. When you want to paste the text somewhere, press C-x g followed by the name of the register, a.

9.2.5. Searching and Replacing

To replace a string, enter M-%. You are prompted for the string that is currently in the buffer, and then the one you want to replace it with. Emacs displays each place in the buffer where the string is and asks you if you want to replace this occurrence. Press the space bar to replace the string, the Delete key to skip this string, or a period to stop the search.

If you know you want to replace all occurrences of a string that follow your current place in the buffer, without being queried for each one, enter M-x string. (The M-x key allows you to enter the name of an Emacs function and execute it, without use of a key binding. Many Emacs functions are available only via M-x, unless you bind them to keys yourself.) A regular expression can be replaced by entering M-x regexp.

9.2.6. Macros

Here's a trivial example you can try on any text file; it capitalizes the first word of each line.

1. Press C-x ( to begin the macro.

2. Press C-a to put point at the beginning of the current line. It's important to know where you are each time a macro executes. By pressing C-a you are making sure the macro will always go to the beginning of the line, which is where you want to be.

3. Press M-c to make the first letter of the first word a capital letter.

4. Press C-a again to return to the beginning of the line and C-n or the down arrow to go to the beginning of the following line. This ensures that the macro will start execution at the right place next time.

5. Press C-x ) to end the macro.

6. Press C-x e repeatedly to capitalize the following lines. Or press C-u several times, followed by C-x e. The repeated uses of C-u are prefix keys, causing the following command to execute many times. If you get to the end of the document while the macro is still executing, no harm is done; Emacs just beeps and stops executing the macro.

9.2.7. Running Commands and Programming Within Emacs

Simply enter your message within this buffer and use C-c C-s to send it. You can also insert text from other buffers, extend the interface with your own Emacs LISP functions, and so on.

When you run RMAIL, Emacs converts messages in your incoming mailbox to a special format it uses to keep track of messages, and mail will be moved to the file RMAIL in your home directory. Therefore, be careful! Your incoming mail file will be converted to RMAIL format, and to convert it back (in case you don't want to use RMAIL as your mail reader), you need to use the M-x unrmail function.

When you start RMAIL, a buffer is created, displaying the first message in your inbox. The n and p commands can be used to display the previous and next messages. (As with all Emacs modes, using C-h m gives you a summary of the available keys.) While you're viewing a message, the r key replies to that message, opening a mail buffer (as described earlier) with the header fields initialized. While in the mail buffer you can use C-c C-y to insert the original message.

Within RMAIL, the h command displays a summary of the messages in your mailbox:

  11  17-Feb                johnsonm@metalab  Re: Which release?
  12  25-Feb                             schar  Vision Group meeting 
  13  26-Feb                 okir@monad.swb.de  Re: Spaces in .ms? 
  14  26-Feb           wirzeniu@cc.helsinki.fi  Re: LDP
--%%-Emacs: RMAIL-summary    (RMAIL Summary)----50%---------------------

Several M-x commands are available in summary mode for sorting the list, and so forth. RMAIL commands such as n, p, and r may be used as well.

Using the arrow keys, you can select a newsgroup to read. Press the space bar to begin reading articles from that group. Two buffers will be displayed, one containing a list of articles and the other displaying the current article. Using n and p moves to the next and previous articles, f and F follows up to the current article (either with or without including the current article), and r and R replies to the article via electronic mail. There are many other GNUS commands; use C-h m for a list. If you're used to a newsreader such as rn, GNUS will be somewhat familiar.

9.2.8. Tailoring Emacs

; Provide quick way to read mail. 
(global-set-key "\C-cr" 'rmail)

You don't always want your key mappings to be global. As you use TeX mode, C mode, and other modes defined by Emacs, you'll find useful things you'd like to do only in a single mode. Here, we define a simple LISP function to insert some characters into C code, and then bind the function to a key for our convenience:

(defun start-if-block() 
  (interactive) 
  (insert "if () {\n}\n") 
  (backward-char 6) 
)

We start the function by declaring it "interactive" so that we can invoke it (otherwise, it would be used only internally by other functions). Then we use the insert function to put the following characters into our C buffer:

if () { 
}

Strings in Emacs can contain standard C escape characters. Here we've used \n for a newline.

Now we have a template for an if block. To put on the ribbon and the bow, our function also moves backward six characters so that point is within the parentheses, and we can immediately start typing an expression.

Our whole goal was to make it easy to insert these characters, so now let's bind our function to a key:

(define-key c-mode-map "\C-ci" 'start-if-block)

If you're interested in writing your own Emacs LISP functions, you should read the Info pages for elisp, which should be available on your system.

So now, both Backspace and C-h will delete. You've lost your help key. Therefore, another good customization would be to bind another key to C-h. Let's use C-\, which isn't used often for anything else. You have to double the backslash when you specify it as a key:

(keyboard-translate ?\C-\\ ?\C-h)

There are other key bindings you may want to use. For example, you may prefer to use the keys C-f and C-b to scroll forward (or backward) a page at a time, as in vi. In your .emacs file you might include the following lines:

(global-set-key "\C-f" 'scroll-up) 
(global-set-key "\C-b" 'scroll-down)

You can create your own prefix keys, if you really want to extend your current mode with lots of new commands. Use something like:

(global-unset-key "\C-d") 
(global-set-key "\C-d\C-f" 'my-function)

(define-key indented-text-mode-map "\C-m" 'newline-and-indent)

(setq text-mode-hook 'turn-on-auto-fill) 
(setq fill-column 72)