Introduction to Emacs

Andy Harris

(originally appeared in Install, Configure, and Customize Slackware Linux

–Prima Tech 2000. Reprinted with Permission.)

In this chapter, we willyou examine Emacs, a powerful and popular text editor. We willYou look at many of the features available in Emacs, and explore how you can use it to enhance your text development efforts whether you are working on simple text documents, managing a web server, or writing complex programs.

Why a tText eEditor?

For those raised on GUI interfaces, it might seem strange to even need a text editor. After all, Star Office and some of the other commercial materials available can do all that a text editor can and much more. Modern word processors can handle text with formatting, graphics, and a host of special features. All these things would factors make a program which simply edits text seem to be out of date, or even a little quaint.

Text editing was originally a very large part of computing, and it has never really gone away. Most computer programs still ultimately start out as text files, no matter how elaborate they will beare when compiled. WeYou might use fancy editors for writing code or for designing web pages, but eventually it all comes back to text editing. Computer users find themselves constantly needing to edit text files.

Text editors really come into their own when you find yourself needing to access your computer remotely, or when you do not have access to all the graphical features of your editor. This is especially common when you are using your computer as a web server or when you are doing some kind of programming.

Why cChoose Emacs?

Emacs is not the only choice of text editor in the linuxLinux world. A number of other editors are usually included with linuxLinux or unixUnix installs. These other editors, especially vi (Visual Editor) are also extremely popular. Linux people are prone to have 'religious wars' about which editor they prefer, but it probably makes sense to know more than one. Golfers have a lot of clubs in their bag, because every shot is a little bit different. If you do a lot of text editing, you should know a number of editors, because some jobs require a very powerful editor such as Emacs, and some don't. If you think you are going to be needing some high-powered text editing, it makes a lot of sense to add Emacs to your list of skills.

Emacs is especially useful if you will find yourself writing HTML pages or programs in languages likesuch as C, Java, or Perl. We willIn this chapter, you learn examine how it can help you to efficiently write, test, and debug programs. We willYou also look at some of its exceptionally powerful features, including facilities for searching and replacing text, features that aid in writing, editing and running macros, modes that let you interact with the linuxLinux environment without leaving your editor, and customization features that let you configure Emacs however you wish.

It is not my goal to turn you into an Emacs fanatic, feeling somehow superior to those unfortunate souls doomed to an eternity with vi or (shudder) pico. I simply want to introduce you to a program that can radically change the way you do certain jobs. Emacs is not a simple application. It has a learning curve, and it will requires some effort to master. If you are willing to spend some time with it, you will probably find that it profoundly improves the way you do some of your work.

Understanding Emacs cConventions

It will make my job a lot easier if I startI’ll begin by describing some of the assumptions and conventions about Emacs. Emacs assumes the same things about its users that linuxLinux does in general: Emacs users are smart, they don't mind learning things, but they want excellent performance, solid reliability, and oh, yeah, they want it to be free. In all these ways, Emacs is very much in the same spirit as Linux itself. Although Emacs is available in many forms, including some with GUIs, it is at its heart a text-based program. The assumption is that the user might want to use menus occaisonallyoccasionally for obscure commands, but will usually uses keyboard commands.

We willDo not assume any particular graphics shell, because they are largely irrelevant when you are doing text editing. In fact, one of the primary reasons you may be interested in Emacs is because it gives you such tremendous power in text mode. This can be very handy if you are using your computer remotely through telnet. If your computer will be functioning as a web server, many of your clients will never see your graphic shell, but will only have access through telnet, which is a text-only interface. Emacs is quite often run from a remote computer, or even from a dumb terminal. For this reason, we cannot make any assumptions about how the user is connected, how the keyboard is mapped, or even what kinds of keys the user has on the keyboard. This would seem to be a huge barrier, but Emacs has some clever solutions to this issue, as you will see soon.

This is shows how Emacs looks when run from a Telnet session. Notice that it is text-only.

Here is the same file being edited under a graphical shell.

Emacs is heavily reliant on keyboard commands for control. Keyboard commands can be difficult to memorize, but this tends to not be as big a barrier as you might think. First of all, most of the common commands have reasonably easy mnemonics, such as 'control-f' for 'forward a character' and 'control-b' for 'back a character'. Secondly, Emacs has a menu system, which you can use when you cannot remember a control sequence. Thirdly, you will find that using keyboard commands can be self-reinforcing, because they are so much quicker than using a mouse or a menu. If you are a touch typist, your hands will never need to leave the keyboard, even when you are sending complex commands to your editor. Finally, you will find that you won't really ever need to make yourself a set of 'Emacs flash cards' to learn your command sequences, because the ones you use frequently will just etch themselves into your brain and your fingers. After you've had enough practice, you won't even have to think about a particular sequence, because it will just be automatic.

Caution

Before we get much farther here, there are a few is an important keystrokes you should know in case you get into trouble. Emacs has a habit of opening windows on you, and occasionally giving you a strange window or prompt that you don’t know what to do with. When you find yourself stuck, try ‘control-g’. This is the ‘get me out of here’ command. It is used much like the escape key is often used in other programs.

Control cCombinations

Many of the Emacs commands utilize the 'control' key. As I mentioned before, Emacs is designed to work on a variety of different keyboards. Fortunately, almost every keyboard made has a control key. (Even my ancient 'first love', the TRS-80 model I, had a control key. I was the envy of my neighborhood with that awesome 16K of memory!! Sigh....). In any case, it is reasonable to assume a control key. In Emacs documentation, a control sequence is marked with a capital C followed by a dash, so Control + g would look like this: C-g

It is not surprising that all the most common commands are control commands. The commands that are used for cursor movement, cutting and pasting, and all the other things that you do the most often are all simple control combinations. Of course, with a standard keyboard, you still have a limited number of control combinations. Emacs has a lot of commands, more than can be called with the control key and a single character, so Emacs uses a number of other tricks for controlling the program. In addition to the normal control sequences, there are special multi-key sequences. For example, all the file management commands start with C-x. Finding (opening) a file is C-x C-f, and saving a file is C-x C-s.

Meta Combinations

Even these multi-key sequences are not enough to control the many commands that Emacs supports. In addition to the control sequences, Emacs supports a second control key, called the 'meta' key. Here's where things get just a little strange. Most keyboards have a secondary control key, but they aren't all called the same thing. The keyboards in the Intel tradition have an 'Alt' key, Macintoshes have a 'Flower' key, and Sun workstations have a 'Diamond' key. All of these keys have a common purpose, to invoke another set of control sequences. The problem is that Emacs cannot always recognize these keys. If, for example, the user is running Emacs from a windows-based telnet program, the alt key is mapped to the local telnet client, and will not be sent across the telnet connection. To avoid this kind of problem, Emacs has multiple ways of reading the meta key. In a linuxLinux install, you will probably be able to use the 'alt' key as your meta key. If that does not work, you can use the escape key instead.

Caution

One important thing about using the escape key as a meta key: It does not act exactly like the control key. When you activate a control sequence, you press the control key down and hold it down as you press another key. If you are using 'alt' as your meta key, you can do pretty much the same thing. If you are using the escape key, it must be pressed and released before you press the next key.

In any case, the meta key is used for a lot of commands, and in the Emacs documentation, it often looks like this:

M-b

stands for

Meta key and b

One very interesting characteristic of meta sequences is that they tend to amplify control sequences. For example, C-f means 'go forward one character', and M-f means 'go forward one word.' Likewise, C-y means to yank (or paste) whatever was last cut. M-y means to pull an earlier cut and paste it. I'll explain these commands later, but the main point here is that control commands and meta commands are often related, and the meta command is usually a more powerful version of the control command.

M-x cCommands

There's a couple of other ways to get to commands in the Emacs environment. One of the most powerful is by knowing a command's name. For example, I can never remember what the command sequence for 'interactively spell the current buffer' is. For me, it is easier to remember the name of the command, ispell-buffer. When you can remember the name of a command, you can invoke it directly, with M-x. So, to start the spell checker, I type 'M-x ispell-buffer.' This will work even for commands that do not have a keystroke combination bound to them.

Using the mMenus

In addition to all these techniques, Emacs has a set of menus, which contain all the most useful commands. In the GUI world, online menus are not anything shocking, but they are very unusual in text-based programs in the unixUnix tradition. Most unixUnix editors do not have them.

Here is how the menus might look under a graphical shell.

If you are running Emacs in some kind of graphical shell, you can use your mouse to access the menus in the normal way. If you are in a text mode, the mouse may not work correctly. In most setups, you can use the F10 key to invoke the online menus. If that doesn't work, you can try M-` (Note that ` is the backtick, not the apostrophe. It is often on the same key as the ~ tilde character). If that doesn't work, you can always call up a crude form of menus with this command:

M-x tmm-menubar.

In any case, you should see a set of menu items pop up. In text mode, the menus will look unusual, because they will be at the bottom of the screen, but after you play around, you will see that they act pretty typically.

In figure 13-04, you will see Emacs run with a text mode menu active. Note that the menu is on the bottom, but all the same commands are available (Compare with figure 13-03). You can access this kind of menu even when you are on a system without a GUI interface.

Example of text mode menu

Here is the text-mode menu. Note that the menu is on the bottom, but all the same commands are available. You can access this kind of menu even with non-graphical systems or connections.

The oOnline hHelp sSystems

Emacs is also unusual in the amount of online help it provides. Unix-style programs are not generally known for excellent help systems, but Emacs has many kinds of help, some of which are pretty useful. All the help commands can be accessed by C-h, and the first one to learn is C-h ?, which will bring up a list of other help options. There are a number of choices here, but we'll go through the most useful for beginners.

C-h t is a tutorial. This brings up a window with a text file in it. The text file is instructions in how to get around in Emacs. If you haven't already done so, you should take a break from reading, and run this tutorial. It will get you up and running quickly. You can't hurt anything, so just play around with it to get the basic ideas. The rest of this chapter will make a lot more sense when you've done a little playing on your own. You will find that the tutorial takes you through many of the same topics as this chapter, and touches on a few other interesting things.

Getting aApropos hHelp

If you want help on some particular topic, you can invoke the apropos help feature with

C-h a

This will ask you for a particular keyword, and will search for any command name that contains that word. It is kind of like an index system in a more traditional help system. Like those indices, the results can sometimes be exactly what you are looking for, or they can be overwhelming and useless.

Finding all the cCurrent kKeystrokes

As you have already seen, Emacs has a bewildering number of commands. You can use the C-h b command to describe the current key bindings. This will open up a little window that will contain a list of all the keystroke commands Emacs recognizes, and what commands will be invoked by that sequence.

Getting mMore dDetailed hHelp

C-h i invokes info mode, which is a full-fledged, hypertext help system. It has a lot of information. It can be overwhelming, but it is as good a help system as you will find in the unixUnix editor world.

help commands

Key	command	what it does
C-h ?	help-for-help	shows a list of the help commands
C-h t	help-with-tutorial	runs the online tutorial
C-h a	command-apropos	allows user to search for a command containing a word
C-h m	describe-mode	describes anything special about the current setup
C-h b	describe-bindings	gives a list of the current key commands
C-h i	info	runs the special info help system
M-` (F10)	tmm-menubar	opens the menu in text mode

Basic eEditing

Well, the point of all this was to edit some text, so let's get going. As complicated as Emacs can be, editing text is very easy. You just type it in, and it goes on the screen.

Cursor mMovement

You will usually want to be able to move around in your document, and Emacs gives you a number of ways to do that. You can probably use your arrow keys in the normal way, but you might want to learn some other techniques as well. These other techniques can be used without your hands ever leaving the main keyboard, and they allow for some more flexible options.

Character mMovement

The easiest kind of movement is a character at a time. Use the arrows to go left, right, up, and down. You can also use control characters, because the arrow commands are not available on every terminal. C-f is forward, C-b is back, C-p is previous line, and C-n is next line.

If it's easier for you, remember that p is the last letter in 'up' and n is the last letter in 'down.'

Word and lLine mMovement

If you want to move more quickly through a file, you can move a word at a time. To go forward a word, you can use M-f, and M-b goes back a word at a time. Notice the relationship between the control combination and the meta combination.

To go to the beginning of the current line, use C-a. C-e goes to the end of the current line.

Semantic mMovement

Emacs has the ability to move in even more powerful ways. You can go forward or back in increments of a sentence, a paragraph, or a

screen. The following summarizes the various movement commands.

Adding an aArgument to a cCommand

You can also modify the movement commands by adding an argument to the command. Precede the command with C-u and a number to make the command execute that number of times. For example,

C-u 8 C-f

moves forward eight characters

C-u 4 M-b

moves back four words.

Movement commands

Key	command	what it does
C-f (right arrow)	forward-char	move forward one character
C-b (left arrow)	backward-char	move backwards one character
C-p (up arrow)	previous-line	move up one line
C-n (down arrow)	next-line	move down one line
M-f	forward-word	move forward one word
M-b	backward-word	move backwards one word
C-v	scroll-up	move cursor DOWN one screen in the document
M-v	scroll-down	move cursor UP one screen in the document
M-<	beginning-of-buffer	Go to the beginning of the document
M->	end-of-buffer	Go to the end of the document
C-a	beginning-of-line	go to beginning of line. (surprise.)
C-e	end-of-line	go to the end of the line

Deleting Stuff

It is surprising how often the destructive commands come in play when creating text files. Fortunately, Emacs provides a number of ways to delete text.

Characters

For the most part, you can use the normal delete and backspace keys to delete text a character at a time, but these commands will not always work as you suspect when you are accessing Emacs through a telnet session. Sometimes in this case you will need to explicitly set up your telnet program to send delete and backspace characters correctly. In any case, you can always use C-d to delete the current character. C-d acts like the typical delete key. It deletes the character directly under the cursor, moving all following characters one character to the left. The backspace key deletes the character to the left of the cursor. The characters deleted by using the del key, the C-d command, or the backspace key are really gone, and cannot be 'yanked' back (more on the yank command in a few minutes.) They can be retrieved by the undo command (C-x u.)

Deleting wWords, lLines, and sSentences

Often you will be manipulating larger units of text, and you will find yourself wanting to delete words, sentences, lines, or paragraphs at a time. Emacs supports a number of commands for doing exactly this:

***{Begin Table]***

Deletion commands

Key Command What it Does

C-d (Del) delete-character Delete current char

M-d kill-word Delete current word

BackSpace(Del) backward-delete-character Delete previous char

M-Backspace backward-kill-word Delete previous word

C-k kill-line Delete rest of line

M-k kill-sentence Delete rest of sentence

C-x Backspace backward-kill-sentence Delete previous sentence

***{End Table]***

One note about killing a line: A line usually goes until it reaches a carriage return character. In Emacs, if you hit the C-k command, you will delete the entire line, but not the newline character. If you hit C-k again, you will delete the newline character as well.

Marking a rRegion

Sometimes, you will want to delete things that do not exactly fit within the definitions of the above commands. You can also mark an entire region and kill it all in one command. There are a number of Emacs commands that operate on a region, so it is a good skill to have. Unfortunately, Emacs does not display in any obvious way which text is in a region, so it can be a tricky concept to get used to.

Basically, here's how it works. You're used to the cursor, which is visible, and indicates where the next character you type will go. In addition to this visible cursor, Emacs supports another cursor which is not visible. This second cursor is called the mark. To work with a region, you move the visible cursor until it is at the beginning or end of some text you want to work with (for now, we'll just assume we want to delete the text.) Use the C-space or C-@ command to set the mark at the current cursor position. The two commands mean exactly the same thing, but not all keyboards will support C-space. At the bottom of the screen, you will see a 'mark set' message.

Now you can move the cursor to the other end of the text you wish to manipulate, and you can activate a region command, such as C-w kill-region). Everything between the current cursor position and the mark will be deleted.

TIP

Sadly, Emacs does not put a visible cursor where the mark is, but there is a terrific command for figuring out where the mark currently is. It is C-x C-x, which means exchange-point-and-mark. What this command does is move the cursor to wherever the mark was, and move the mark to where the cursor was. Use this command twice in a row to see the beginning and the end of a region. It's a really good idea to do this before you run region commands like kill-region, because some of the other commands might move the mark without you knowing it has happened.

Yanking (pPasting) sStuff bBack

Deleting things can be therapeutic, but often you will not want something simply destroyed, but moved to another place in the document. Most text editors provide some sort of cut, copy, and paste mechanism. Emacs provides this capability, with a few twists.

Essentially, all of the kill commands (the ones with 'kill' in their Emacs name) are cut commands. What this means is if you delete a word, sentence, line, or paragraph, that text is automatically stored in a buffer which you will be able to access later. The only deletion commands that do not have this behavior are the ones that work on only one character at a time. In Emacs, pasting is called 'yanking'. (The authors of Emacs apparently loved mnemonics so much that they often changed the names of commands so they could make a keystroke that matched!) The standard yank command is C-y. This command causes the last element that was cut to be pasted back into the document at the current cursor position.

What makes this interesting is the way that things are added to the kill buffer. Imagine the following line:

one two three four five

If we were to go to the beginning of the line, and hit M-d, we would delete one word (the word 'one') and it would be put in the kill buffer. Now, if we moved somewhere else, and hit the C-y command, the contents of that buffer (the word one) would be pasted. That's not at all surprising, but here's a twist:

What if we started with the same line, put our cursor at the beginning, and hit M-d 3 times? Clearly, the line would now contain the values

four five

but the real question is "what is in the buffer?" When we hit the yank command, we will see

one two three

If you do a series of identical kill commands, Emacs treats them all as one command, and places them together. This is very handy, because most of the time you will want to move a series of words, lines, or sentences.

The kill ring

The kill buffer of Emacs is flexible in another way. In many systems, there is only one buffer for copy and paste. Emacs keeps track of the last thirty deletions! (more or less. The exact number can be changed by the user) To yank back earlier text, start with the C-y command, then hit M-y until you see the specific text you are looking for. If you keep hitting M-y, you will originally come back to the last thing killed. Because of this behavior, the kill buffer in Emacs is more accurately referred to as a kill ring, because it can contain many items, and you can go around the ring to find them.

No doubt one of the reasons for Emacs' popularity is how much it adds to the bizarre vocabulary of techies. It's fun just to be able to mutter things about 'yanking from the kill ring.' Sometimes I love being a nerd...

TIP

Here's an interesting way to take advantage of the kill ring: If you have some kind of text that is difficult to type and that you will be using a lot in a document, you can type it once and kill it. Then, whenever you need that phrase, you can yank it from the kill ring. This way you only have to type it once!

Insertion and deletion commands

Key	command	what it does
C-d (Del)	delete-character	Delete current char
BackSpace(Del)	backward-delete-character	Delete previous char
M-Backspace	backward-kill-word	Delete previous word
C-k	kill-line	Delete rest of line
M-k	kill-sentence	Delete rest of sentence
C-x Backspace	backward-kill-sentence	Delete previous sentence
C-@ (C-SPACE)	set-mark	set a boundary for copying or deleting
M-d	kill-word	remove next word, keep it in buffer
C-w	kill-region	cut from mark to here, keep in buffer
C-k	kill-line	cut from here to end of line, keep in buffer
C-y	yank	paste last thing put in buffer
M-y	yank-pop	paste previous buffer (C-y must happen first)

Files, wWindows, and bBuffers

Basic file management is a critical part of any text editor. Emacs provides all the typical functionality, but adds some special features, such as the ability to work with multiple files at the same time, and the ability to have multiple windows open at once, even in a text-based environment.

Files

Of course, you will rarely write text without it being stored somehow in a file. Emacs provides a number of ways to manipulate files, including features for managing multiple files at the same time.

Opening an eExisting fFile

When you are on the linuxLinux command line, you can open up Emacs with a file by typing 'Emacs filename' If the file already exists, Emacs will start with the file loaded in. If the file does not already exist, you will get a blank screen associated with the filename you chose.

If you are already in Emacs, and you want to load in a file, you can use the 'find-file' command C-x f.

You will be prompted for a file name. Enter the name of the file, and it will be loaded if it exists, or you will get a blank screen to write in if the file does not yet exist. If you want to import a file into your current document, you can use C-x i to insert the file. The contents of the file will be inserted wherever the cursor currently is.

Saving a fFile

Saving a file is very simple. The main way to do this is through the save-file command, C-x s. This command will save the file using whatever name you have assigned. Note that in Emacs, your files will always have a name, even if you have never saved them before. If you want to save the file to another name (like a save as command in Windows) you can use C-x w, which stands for 'write-file'.

Editing Modes

By now you might have noticed that Emacs sometimes changes its behavior. For example, if you use Emacs to edit an HTML file, you will see an HTML menu appear. If you use Emacs to edit a java or perl program, Emacs might put all the comment characters in one color, and the keywords in another. Also, if you are in a programming language, you might notice that Emacs automatically indents the code whenever you press a semicolon (the end-of-line character for many programming languages). Emacs is capable of changing its behavior to manage special forms of editing. This is one of the things that makes it so endearing to high-end users. It keeps much of the same general characteristics, but it customizes itself to be useful in many contexts. This is done through a technique called 'modes.' Emacs has two kinds of modes, major and minor modes.

Major mModes

The major modes are generally related to kinds of editing. There is a major mode for writing plain text (... and it's called ... text mode!!!) There are also major modes for html, c language programming, typesetting with the Tex and LaTex languages, and even modes for reading email and playing games! We will generally stick to text mode in this chapter, although it is certainly worth exploring the other modes. You will probably find some very entertaining and useful modes in your implementation of Emacs. To find out which modes are installed in your version of Emacs, use C-h p. You will see a list of packages. If you select a package, you will see the modes in that package. In my version, I found 34 packages, most with at least a couple of modes. That should keep you busy on a rainy day. Most of the time, though, people only use a few standard modes. Most of the modes are related to very specific programming languages or other kinds of specialized editing.

Once you are in a particular mode, you will see its name on the bottom line of the editor. You can get more information about that mode by typing C-h m (describe-mode). This will give you an overview of the mode you are in and any special key bindings that might be a part of this mode.

There are two major ways to get into a specific mode. The first way is to simply open up a file. Emacs recognizes a large number of file extensions and automatically opens up the correct mode most of the time. Occasionally, you will need to help Emacs along, so you can go directly to a mode by typing it's name.

If you want to experiment with an interesting mode, you can play around with something called 'picture mode.' Invoke it with M-x picture-mode and use C-h m to see how picture mode works. I won't spoil it for you, but you'll see that it gives you an interesting way to do ASCII art!

Text

The text mode is actually a pretty boring mode. It adds the ability to use the tab key, and very little else. Surprisingly, text mode does not automatically involve word wrap. This is controlled by a minor mode, as we will see shortly. However, the sparseness of text mode is a feature, not a bug. The whole point of working in plain text is to not have any surprises. Text mode is a very clean, very basic mode.

Programming mModes

If you are going to be doing any programming, Emacs is your editor. Programming is a very demanding form of editing, and it has a number of very peculiar needs. We do not have time in this chapter to go through all the programming modes, but it is still worthwhile to note what they have in common. The programming modes feature automatic indentation, which can help make it easier to find logic errors in your program. They also have syntax coloring, which is a feature that changes the color of text elements based on their meaning. With this feature, your code becomes much easier to read and repair. The programming modes have special features for checking to see that special characters such as parentheses and brackets are matched up correctly. If you've ever done any programming in a language such as C, you know how useful that can be. The programming modes also have a compile command, so you can test and run your program without leaving the editor. If you have an error in your program, there are features which help you find the line number where the mistake is reported to be. If you do some programming, Emacs can make your life a whole lot easier.

HTML mMode

Many people use linuxLinux because it is such an ideal operating system for running web servers. Of course, a web server is pretty boring without some web pages on it. The HTML mode turns Emacs into a reasonably powerful HTML editor. It will not give you WYSIWYG results, but it can considerably speed up 'hand-coding' of HTML. For example, if you want to add a hyperlink to an HTML document, and you are in HTML mode, you can just type C-c C-c h, and the following will be inserted into your document:

<a href="http:"></a>

The cursor will be positioned right after the colon, so you can just start entering the url. Similar commands are available for all the most common HTML tags. Use of the HTML mode can considerably speed up the creation and modification of HTML documents.

Minor mModes

In addition to the major modes, Emacs also supports a number of minor modes. These are a little bit different than their big brothers. A document can only be in one major mode at a time, but it could have a number of minor modes activated. While major modes can radically change the behavior of Emacs, minor modes generally are more subtle, and just change a feature or two.

auto-fill

Perhaps the most commonly used minor mode is the auto-fill mode. When you are writing plain text, such as a readme file or an email message or something, you usually want word wrap of some sort to occur. Emacs does not do this as part of its default behavior. The way Emacs is originally set up, when you get to the end of a line, Emacs will generally let you keep on typing, but will put a / at the end of the line, and put the next character on the next line. In this default mode, Emacs does not put any carriage returns in the file, unless you press the 'enter' key. This is important, because in certain kinds of editing, especially programming, a carriage return in the wrong place could be a disaster.

TIP

Why I don't let my students use pico

The system we use in our classes has another editor called pico installed. Pico was meant only for email. It does not have modes, and it is not intended as a programmer's editor. It is very simple, and the students get up and running in no time. I once got a call from a frantic instructor who told me the entire system was down. I asked him what was wrong, and he told me that he'd told his students to load up a certain program in the editor, and to change only one line in the file, then to save it and run it. Although the change was not significant, none of the programs ran, even when they changed the file back to the original value. The problem was, the students were using pico. Pico saw some long lines which would not have looked good in an email message, and put carriage returns in them. When the students tried to run the program, it crashed because the programs no longer were following the stringent requirements of the programming language. While it is possible to turn off the automatic carriage returns in pico, I think programmers should learn some editor designed to help them with the job. My personal preference is (surprise) Emacs, but vi is another terrific choice.

The lesson here is in a text editor that might be used for programming, you will want to be able to turn automatic word wrap on or off at will. That is the purpose of a minor mode. Emacs calls word wrap 'fill' (I have no idea why) so you can turn word wrap on with M-x auto-fill-mode. Incidentally, if you find a paragraph's justification has gotten all messed up, you can invoke the fill-paragraph command (M-q) to clean it up.

Getting a lLine nNumber

Another feature that is sometimes very important is having line numbers visible. This is especially true in programming when compilers report a problem on a specific line. There should be some easy way of knowing what line you are on, and there should be an easy command to go directly to any given line. Emacs provides a line-number mode (M-x line-number-mode) and a goto line command (M-x goto-line <number>) The goto line command will work regardless of whether you are in line number mode.

There are a number of other minor modes available to you in Emacs. You can learn more about them in the same way you learned about the major modes. Consult the documentation with C-h p to learn the packages, and when you are in a particular mode, use C-h m to learn about its features. You can also find out more detailed information about the specific modes by using the info browser (C-h i) and searching for a particular mode.

Windows

Emacs is primarily a text-based program, but it has some of the behavior of its gui cousins. You have no doubt seen the Emacs screen split into two or more separate areas, with different things in each. These separate areas are called windows. As you have been playing around with Emacs, you have been opening windows all over the place. The help screen opens up a window, as do the text mode menus. One of the most bewildering thing about Emacs for beginners is the dozens of windows that seem to keep popping out of nowhere. Emacs can handle more than one file at a time in memory, and can even have one file open in two different windows. This can be a powerful but bewildering feature.

Opening mMultiple wWindows

First, let's look at how we open multiple windows without worrying about what goes inside them. Most of the windows commands are C-x commands. C-x 2 breaks the current window into two windows stacked on top of each other. C-x 3 breaks the current window into two windows side by side. C-x o (the letter o) moves you to the next window. C-x 0 kills the current window, and C-x 1 makes the current window the only window.

In figure 13-05, the Emacs screen is split into two windows with the C-x 2 command, then the top window was split again with C-x 3. At this point, all three windows are pointing to the same file and buffer, but they can point to different things if we wish.

Example of an Emacs session split into three windows

Here, the Emacs screen is split into two windows with the C-x 2 command, then the top window was split again with C-x 3. At this point, all three windows are pointing to the same file and buffer, but they can point to different things if we wish.

Generally, the side-by-side placement of windows is not very satisfying, because you can't read the text in either window. The top-and-bottom approach is much better if you find you need two windows. You might not want the windows to be the same size, so you can go into a window and invoke C-x ^ to make that window one line taller. Use the argument feature to make it much larger. For example C-u 10 C-x ^ will make the current window 10 lines taller, and will make the other window 10 lines shorter. This might be handy when, for example, you want a window pointing out at the command line shell, or running the directory editor. (We'll learn how to do these things later, I promise)

Buffers

So far, the windows you have been using have all pointed to exactly the same file. While this can be interesting, it has limited utility. Emacs allows you to have more than one file open at a time, and you can have different files in different buffers. If you have help open, or one of the other specialty modes, Emacs may have generated a buffer or two for you. It is possible (even likely) that you will have more buffers than windows.

How wWindows and bBuffers are rRelated

Essentially, the windows are what the user can see, and the buffers are all of the files (and sometimes some other things) that Emacs currently has in memory. Whenever you use C-x f to open a file, you are also opening a buffer. It isn't at all unusual to have 5 or six buffers open at once if you are working on a project that involves multiple text files. The easiest way to work with buffers is to invoke the buffer list through C-x C-b. This will give you a list of the current buffers. You can treat this list like a menu, using the arrow keys to move up and down the list, and the enter key to choose a specific buffer. That buffer will then be shown. If you know the name of the buffer you want to go to (it is often the same as the file name), you can use C-x b to go to the file directly. C-x b will default to the last buffer you used, so it is very handy if you are going back and forth between only two buffers. In addition, the C-x b command will work on the buffer the cursor is currently in, so you can set up a window set, go to each window, and use C-x b to set exactly what buffer you want to show in that window. This can be very handy in certain situations, such as when you are writing shell scripts and you want a unixUnix shell avaiable for testing the scripts.

File, Buffer, and window handling commands

Key	command	what it does
C-x C-f	find-file	open a new or existing file
C-x C-s	save-buffer	save this file with it's existing name
C-x C-c	save-buffers-kill-emacs	exit emacs
C-x o	other-window	move to another window (if more than one is visible)
C-x 1	delete-other-windows	make the current window the only window visible
C-x 2	split-window-vertically	makes another window (full width of the screen)
C-x 3	split-window-horizontally	makes another window (full height of the screen)
M-x shell	shell	make a unixUnix command line in the current window
C-x b	switch to buffer	switch to a buffer (you’ll be prompted for a buffer name
C-x C-b	list-buffers	displays a buffer menu.

More aAdvanced eEditing

You will be able to get by just fine with the editing commands you

already know, but soon you will find yourself interested in some of the more powerful editing tools supplied by Emacs. These concepts take some practice to master, but you will find that the effort will pay off many times in terms of improved efficiency.

Search and rReplace

Editors have had search and replace features from the very beginning, yet people often do not take advantage of them fully. Clever use of search and replace can often save you a great deal of effort when you find yourself working on some difficult editing problem. Emacs gives you a number of ways of searching for text and replacing it.

Searching for tText

C-s is an incremental-search-forward. What this means is you can type in a phrase, and Emacs will look for partial matches as you type. To explain this concept, I experimented on the chapter you are reading now by starting with the cursor at the beginning of the buffer (M-<). I then invoked C-s, and started typing out the word 'relationship' (it occurs on line 288).

When I typed r, the cursor was positioned at the ‘r’ in 'introduction', the first occurrence of 'r' in the document. When I typed 'e', the cursor was moved to 'features', the first location of 're'. As I kept typing letters, the editor found closer and closer words: 'religious', 'related', and finally 'relationship'. The advantage of an incremental search is that you rarely have to type the entire word. You can usually get just the first few letters and it will take you to the word you are looking for.

CAUTION

Although the cursor appears to have moved when you are doing a sequential search, it doesn't move permanently. To tell the computer you're done searching and you want to do something at this point, you need to invoke one of the cursor movement commands. I usually use M-b so I get to the beginning of whatever word I was looking for in the text.

TIP

Incremental searches start from the current cursor position. You can use this to limit searches to a smaller part of the document, but if you intend to search the entire document, precede the search command with a beginning-of-buffer (M-<) command. If you want to find other occurrences of the word, just hit C-s again. C-s will continue looking for the last search attempted.

Searching is a really great way to get around in longer documents. You can use searches on key words, section titles, or other unusual words or phrases to get to a particular part of a long document. If you wish, you can search backwards instead of forward. Just use C-r, for 'interactive'incremental-search-backward', and you will be searching for previous occurrences of the pattern.

Emacs has more traditional (non - incremental) searching techniques as well, but you will probably not need them unless you are writing macros.

Replacing tText

Searching text is very useful, but the ability to replace the text can be even more handy. This can be used to fix certain common spelling errors, or to update a document easily.

***Begin Sidebar***

War story

The unixUnix system I had been teaching on for years was updated, and the server name changed - literally overnight. Suddenly I had hundreds of documents that had reference to a computer that no longer existed! Without search and replace, I would still probably be finding those errors.

***End Sidebar***

Emacs has some variety in the types of replace expressions it gives us. The most common is query-replace-string, invoked by M-%. This command prompts you for a string to search for, and a string to replace it with. It then goes through the document looking for the search string, and whenever it finds it, you are asked whether you want to replace the string, ignore it, or quit. There is a version (M-x replace-string) that does all the replacements without asking, but this is a prescription for trouble, as it is very easy to make mistakes here. For example, if you decide to change all instances of 'he' to 'she', then 'there' could become 'tshere'. Oops! It's generally better to do the query form, so you can catch these problems.

Using rRegular eExpressions

Emacs also has support for regular expressions. These are a special feature that has long been a part of the unixUnix culture. Regular expressions allow you to search for patterns, rather than specific strings. For example, the regular expression ^hello$ would only match on lines containing nothing but hello. \d\d\d-\d\d\d\d would match on any phone number, and so on. Regular expression syntax can be a difficult thing to learn, but if you use it enough, it can be an incredibly powerful tool. If you already know regular expressions from some other unixUnix tools, or from perl programming, you won't have too much trouble figuring out how Emacs uses them. Regular expressions are one of those things that you could survive just fine without, but once you understand them, you'll wonder how you ever got along without them.

Checking sSpelling

Emacs features a spelling checker that works in a couple of different ways. Both of them rely on the external program 'ispell', so if you do not have that installed, the spelling commands will not work. To check the spelling of the current word, just move the cursor to the beginning of that word and hit M-$. If you want to check the spelling of the entire buffer, move to the beginning of the buffer, and hit M-x ispell-buffer. Ispell is an interactive spelling checker, like you have probably used on more formal word processors. When it encounters a word that it cannot find in its dictionary, it gives you a standard set of options, including suggestions for replacement, ignoring the word, or adding it to a custom dictionary.

The undo fFeature

Another really great feature of Emacs is the undo command. This is invoked by C-x u, and it undoes the last command. In fact, it can be called multiple times to undo a number of commands. This can really save you when you have made some kind of mistake in your document.

Transposition

Transposition errors are among the most common errors in text editing. To fix such an error, move the cursor past the two letters that need to be swapped, and hit C-t to transpose them. There are variations of this command for transposing words (M-t) and for transposing lines (C-x C-t). These are most commonly used to quickly move a word or line towards the end of a document.

Case cChanges

Another common editing mistake is capitalization issues. For some reason, If I have a word that starts with a th, and the 't' is supposed to be capitalized, I often end up accidentally capitalizing the 'h' as well. THis is how it usually works.

To fix this, Emacs has some commands to force an entire word to lowercase (M-l), force the word into all uppercase (M-u), or to force capitalization of only the first character (M-c). All of these commands will move the cursor to the end of the word, so they can be used repeatedly to modify a large amount of text quickly.

Additional Editing commands

Key	command	what it does
C-s	isearch-forward	prompts for a phrase, searches for it interactively
C-r	isearch-backward	prompts for a phrase, searches for previous instances interactively
M-%	query-replace	do an interactive search and replace
M-*	query-replace-regexp	do an interactive regular expression search and replace
M-x replace-string	replace-string	replaces string without asking
M-x ispell-buffer	ispell-buffer	run an interactive spell-checker
C-x u	advertised-undo	undo last command
C-t	transpose-chars	transpose the last two characters
M-t	transpose-words	transpose the last two words
C-x C-t	transpose-lines	transpose the last two lines
M-l	downcase-word	convert current word to all lowercase
M-u	upcase-word	convert current word to all uppercase
M-c	capitalize word	convert first character of current word to capital, all other characters to lowercase

Keyboard Macros

Perhaps the single skill that separates those who just use programs from the true power users is the ability to create and use keyboard macros. Emacs contains features designed to make macros reasonably easy to make, use, and modify. If you have never used keyboard macros before, the basic idea is very simple. You turn on some kind of recorder as you do a set of keystrokes, and the keystrokes are stored. At some point, you tell the program that you are finished recording, and then you can play back the macro. This is really great for doing repetitive jobs. If you find yourself hitting the same key sequence over and over again, such as indenting every line two spaces (this one comes up a lot in programming), it's time for a macro.

Defining a mMacro

To define a macro in Emacs, simply invoke the 'define macro' command with C-x (, type in your keystrokes, and finish with C-x ). Use the open parenthesis to start the macro, and the close parenthesis to finish it. If you make a mistake, use the C-g key to get out of macro recording.

Hints for uUseful mMacros

Although Emacs makes it reasonably easy to create a keyboard macro, that doesn't mean it is easy to make a macro that performs the way you want. It's easy to make mistakes that can cause your macros to do strange things, so there are a few cautions worth noting.

uUse sSemantic cCommands

It's a good idea to think about exactly what you want a command to do in very general terms, not just on the first line. If, for example, you wanted to make a macro that would indent a line by two characters. If you do the macro without recording, it might go like this:

Indent two space macro

Command	Meaning
[space][space]	insert two spaces
C-n	down a line
C-b C-b	back two characters

This would work fine on lines that contain at least two characters, but what happens when you try it on a blank line? You should try it yourself and see, but it will not be the behavior you wish. The 'English' version of this macro should be only slightly different, but that difference will improve the macro quite a bit.

Improved Indent two space algorithm

Command	Meaning
	insert two spaces
	down a line
	beginning of current line

When we add the keystrokes, our macro definition will look like this:

Improved Indent two space macro

Command	Meaning
[space][space]	insert two spaces
C-n	down a line
C-a	beginning of current line

Here's why this version is a little bit better than the other one: Most of the time, with our old algorithm, we were two spaces from the beginning of the line, so back two characters was equivalent to going to the beginning of the line. However, we really meant 'go to the beginning of the line, however many characters that is' Emacs supplies a command for this, and that is the command we should use. Sometimes you will use commands in macros that you might not use elsewhere, just to avoid this kind of ambiguity. When you are recording macros, you are much more likely to need those movement commands which dealt with semantic objects, such as words, sentences, and lines.

sStart and eEnd at rRelated pPositions

Macros are most useful when they are repeated. For this reason, it's a very good idea to start a macro at a very recognizable point, and to end the macro with the cursor at a similar point. For example, my indent code was careful to put the cursor at the beginning of the next line. This doesn't matter if I'm only going to use the macro once, but most of the time, I have a whole group of lines I want to indent.

It's very common to start and end at the beginning of a line, sentence, or paragraph. The basic rule is, if you want to be able to repeat a macro, you should stop it at the same kind of position you started it. If your macro operates on words, it should start at the beginning of a word, and end at the beginning of the next word. If it operates on lines, it should start at the beginning of a line and end at the beginning of the next, and so on.

tTest bBefore uUsing with a rRepeat pParameter

If your macros are designed to be repeated, it will be very tempting to use a repetition parameter on it. For example, to repeat the last keyboard macro 5 times, you would just type

C-u 5 C-x e

Macros can use this parameter just like any other command, but it's a great idea to save your file first, and to test the macro, or you could get some unexpected consequences.

Running a mMacro

The basic way to run a macro is with C-x e (call-last-kbd-macro). If you want to record more than one macro, record a macro, then invoke

M-x name-last-kbd-macro.

This command will prompt you for a name, and that name will be attached to that macro. For example, look at the following sequence:

TC Creating and naming a macro

Command	Meaning
C-x (	Start recording a macro
[space][space]	Two spaces
C-n	Down a line
C-a	Beginning of line
C-x )	end macro recording
M-x name-last-kbd-macro	Name that macro
indent-2	The new name
C-u 10 M-x indent-2	Indent the next ten lines

This code records a macro, renames it, and runs it 10 times, indenting the next ten lines in the editor. Even if you record another macro, you can invoke your new command simply by calling its name as an M-x command. The command will only stay named as long as this current session is running. If you want to keep it permanently, see the section on customizing Emacs.

Editing a mMacro

Keyboard macros are so darn useful that Emacs now includes a specialized editor just for working with them. After you have recorded a macro, use C-x C-k to call up the macro editor. Then, you can type C-x e to have the editor bring up the last keyboard macro you defined, or type M-x and the macro name if it is a macro you have named. The editor has several interesting features. Here's how it looks:

The macro editor manipulating the ‘delete two spaces’ macro

As you can see, it is typical Emacs. Nothing glamorous here, but it is very functional. You can change the command name by replacing the text after "Command: " and you can change the keyboard binding, so your macro is attached to some specific keystroke. Be careful about this, so you don't end up over-writing some existing command. I usually use C-c C-something, because this will always be available, but it still might over-write something. If you want to check to see if a keystroke is available, use C-h k to determine what command if any is bound to the keystroke in question. Note that keystroke bindings can change when you are in different modes, so you might have to re-assign a macro if you find yourself in an unusual mode.

Because indenting and deleting indentations come up so often in programming, I have predefined the two macros you have seen here as C-c C-i for indent-2 and C-c C-d for del-2. I have also modified my copy of Emacs so these macros always are loaded whenever I start Emacs up, but that's another topic. (See the “customizing Emacs” section later in this document for details)

Keyboard Macro commands

Key	command	what it does
C-x (	start-kbd-macro	begins recording a macro
C-x )	end-kbd-macro	stops recording the macro
C-x e	call-last-kbd-macro	replay the last macro
M-5 C-x e	call-last-kbd-macro	replay the macro 5 (or however many) times
C-x C-k	edit-kbd-macro	prompts for a macro, loads it into an editor screen
M-x rename-kbd-macro	rename-kbd-macro	lets you temporarily assign a new name to a macro
M-x insert-kbd-macro	insert-kbd-macro	used to insert a macro definition into a lisp file

Emacs and the uUnix sShell

Your text editing does not occur in some kind of a vacuum, but in the context of some other sort of work. It is often very handy to be able to communicate with your command line as you are editing. This is particularly handy if you want to change permissions of files you are making, compile or run programs you are writing, or looking around for a particular file to load up or import. Emacs allows a couple of forms of access to the command line.

Managing fFiles and dDirectories with Dired

Emacs has a terrific file management system built in, called Dired (which stands for directory editor). Dired lets you look at a particular directory, search for files using normal Emacs search commands, mark a series of files for batch processing, and has an easy interface to some of the most common commands, such as copying files, renaming them, and changing file permissions.

Starting up dDired

There are two main ways to set up dired. You can invoke the M-x dired command, which is usually bound to C-x d. This will cause dired to open on the current directory. You can also use the C-x f command, but rather than specifying a file name, give it a directory, and Emacs will open a dired window on that directory.

The dired window often looks like this:

The dired window pointing to a typical directory

As you can see, it looks a lot like a normal unixUnix ls command, but there are some important differences. You can use C-n and C-p (and actually n and p, without the control key) to move up and down the list of files. You can search using the C-s command, just like in a document. If you want to load up a file, just move to it and press the enter key. If you have the appropriate permission, the file will be loaded into a buffer for you. To move to a subdirectory, just move the cursor to that directory and press enter, and a new dired will open pointing to that directory.

You can rename a file by putting the cursor on its name and hitting 'R' (it must be capitalized) You will then be prompted for a new name. Likewise, 'C' allows you to copy a file, and 'M' prompts you for a new permission set for the file. One of the nicest things about dired is the ability to mark a series of files. Let's say you wanted to change several files to 644 permission, so they would be visible to the web server. We can look at a directory file by file, and then hit the m key to mark any of the files we will want to change permission on. When a whole series of files is marked, we can then invoke the 'M' change permission command, and set all file permissions to 644 with one command. This is considerably easier than doing it by hand on the command line, especially if there is no easy unixUnix wildcard trick we can use to isolate our set of files. You can also use the d key to mark files. Any file marked with the 'd' key is marked for deletion, but the deletion won't actually happen until you force it with the 'x' key. You can unmark a marked file with the 'u' key if you made a mistake.

Dired provides even more functionality, but this should give you the basic idea. If you want more information, just go into dired and call up the mode-specific help (C-h m) for a list of commands.

Running a uUnix sShell iInside Emacs

Handy as dired can be, it still cannot replace the good old Linux shell for some things. You will still find times that you would like to be able to run a command. Of course, Emacs provides a number of ways you can do this.

Running oOne lLinux cCommand

If you want to just run one command, you can use M-! run shell-command. You will be prompted for a command, and you can enter in whatever command you wish. The command will be executed under your default shell, and the results will pop into a new buffer. For example, if you type M-! fortune(and of course fortune is installed on your system), you might find a new buffer containing this gem of wisdom:

It pays to memorize the collected poems of Edna St Vincent Millay backwards!!

I have no idea what that means.

If you wish, you can also use C-u M-! to automatically put the results in the current buffer.

Running a sShell in a wWindow

If you wish, you can also run a full-blown linuxLinux shell in another window. This is very handy if you know you're going to be going to the shell a lot, like when you are writing a shell script or compiling a java program and running it with appletviewer. Just use M-x shell to generate a shell. You'll get a new window, and a copy of your default linuxLinux shell will be running inside it.

Advantages of uUsing a sShell uUnder Emacs

This new shell isn't exactly like the original shell, though. It has a few features that make it exceptional. First of all, if you invoke a command like ls that has a long output, the output is in an Emacs window you can scroll and search in.

You can invoke M-p and M-n to get at any of the commands you have already typed into the shell. You can also use C-c C-o to clear the output of the previous command. This is a nice way to avoid cluttering up the buffer.

Note that the normal control sequences you might use with a program running in the shell will not work the same. For example, if you are running some program that is taking to long, in a traditional shell you simply type C-c to end it. Likewise, you are sometimes required to use C-d to mark the end of a file, or a C-z to suspend a process.

If you need these commands, just proceed them with C-c. So, to stop a program, use C-c C-c, and to send a C-d, just type C-c C-d.

Figure 13-08 illustrates a typical use of Emacs. I have the editor split in two, and I have created a small Java program in the top window. The bottom window is a command line shell, where I have compiled and run the program.

Running a shell in a window

This is a typical use of Emacs. I have the editor split in two, and I have created a small Java program in the top window. The bottom window is a command line shell, where I have compiled and run the program.

Customizing Emacs

Once you've been using Emacs for a while, you'll undoubtedly feel the need to tweak it a little bit so it works exactly the way you like. There's a lot you can do with Emacs. Some of the customization can be quite involved, but there's a number of very simple things you can do to make your version of Emacs fit your style a little better.

Changing the .Emacs fFile

Emacs provides a special configuration file called .Emacs, which is normally stored in your main directory. This file might start out empty, or it might already have some code in it which customizes your version of Emacs. To modify your version of Emacs, you can add code to this file. Emacs customizations are written in a dialect of lisp, a language only a computer scientist could love. We won't get into lisp programming here, but there are a number of very interesting things you can do here.

CAUTION

Save a backup of your .Emacs file before messing around with it. You can poke your eye out with that thing. For example, you might accidentally overwrite some important keystroke binding, and lose access to an important function. You might also find that setting an Emacs variable causes unexpected side effects. It’s much easier to fix these problems when you have a copy of the original .Emacs file to compare with. This way, you can keep track of exactly which changes you made.

Re-mapping cCharacter cCombinations

You might also find that you want to change some keystrokes around. This is most commonly used when you have a command you use a lot which has an awkward sequence, and one of the easier keystrokes is linked to a command you never use. For example, I love keyboard macros, but the command to play back the last macro C-x e is very awkward to do many times in succession. I almost never use the C-l (recenter) command. So, I added this line to my .Emacs file:

(global-set-key "\C-l" 'call-last-kbd-macro)

Essentially, you can use this as a template to map any particular command to any key. Of course, you need to be careful that you don't overwrite some important command sequence like C-x. Note that I used “\C” to mean control. If you want to map to the meta key, use “\M”.

Permanently sStoring mMacros

If you have a command or two that you really like, you can permanently add them to your Emacs implementation. Just define the macros, make sure they are named correctly, and go to the buffer that contains the .Emacs file (or load it up if necessary.) In that file, hit M-x insert-kbd-macro, then type the name of the macro you wish to add. This macro will now be available by name whenever you start Emacs. If you want to add a keystroke sequence to the command, you can use the global-set-key trick. As an example, here's the code in my .Emacs file which adds the insert and delete two spaces commands:

;;Andy's custom macros

(defalias 'insert-2-spaces

(read-kbd-macro "2*SPC C-n C-a"))

;;map this to C-c C-i when possible

(global-set-key "\C-c\C-i" 'insert-2-spaces)

(defalias 'del-2-spaces

(read-kbd-macro "2*C-d C-n"))

;;map this to C-c C-d when possible

(global-set-key "\C-c\C-d" 'del-2-spaces)

A portion of my .emacs file with the code to add my custom macros.

Again, this is not intended as a tutorial in modifying Emacs, but you can see from this example how much you can do if you're willing to study the code a little bit.

Changing Variables

You may want to temporarily change the behavior of Emacs in a number of ways. You might want to change whether Emacs automatically displays the date and time, or whether it uses normal or inverse video. These and many of Emacs' other behaviors are controlled by variables. You can look at the info documentation (C-h i) to see which variables Emacs supports, and how you can change them. To change a variable, you will need to add a line to your .Emacs file that looks something like this:

(setq display-time-and-date 1 Turns on date display)

or

(setq display-time-and-date nil Turns off date display)

You can get a lot of mileage out of this simple trick, by digging through the online documentation. You can change all kinds of other things by manipulating variables, including whether Emacs makes a bell sound or flashes on an error, whether matching parentheses will blink, whether searches will be case-sensitive, and a lot more.

Example of Emacs lisp pProgramming

Finally, as an example of the things you can do when you decide to go all out and learn Emacs lisp, I'll show you a couple of other things I added to my .Emacs file. These examples use a language called lisp. Lisp is not terribly difficult to learn, but it is a very old language, and it isn't as clean to work with as some of the newer languages. In any case, here's some simple examples:

HTML tTemplate

The following code asks the user for the title of a page, and generates a simple HTML page with the title automatically placed with a centered heading. The page also contains my email and web information so I don't have to add it to every page I write. Notice especially the way you can get input from the user with the read-string command, and how you can print out a multi-line string. This is probably my favorite lisp program. Simple as it is, I use it all the time.

The HTML template lisp program

Link maker

I use this macro to automate in the creation of web pages that show some external file. Since I teach various forms of programming, I frequently want to be able to write an html page that contains a link to a file, and then the source code of that file within pre tags. This little program does that for me.

My .emacs file with two interesting lisp functions visible

More iInteresting tThings to iInvestigate

As you can see, there is plenty to Emacs, and you've barely scratched the surface. As a little bonus for getting this far, I'm going to suggest you try a few other modes in Emacs. I think you'll find some of them a lot of fun. Don't forget to use the C-h m command to find out mode-specific help!!

· M-x calendar

· M-x blackbox

· M-x dissociate

· M-x doctor

· M-x dunnet

· M-x gomoku

· M-x hanoi

· M-x life

· M-x solitaire

Summary

Still pending

As you can see, Emacs provides a lot of power and flexibility. In this chapter, you have looked at the basic manipulation of Emacs and essential text editing. You have also examined some of the more powerful functions of Emacs, including the search and replace functions, editing modes, and use of multiple windows and buffers. You have also looked briefly at how to customize Emacs to suit your own preferences, by writing keyboard macros and by examining some simple Emacs lisp functions. Emacs is a very complex program, and it can take a lot of time to learn everything it can do. However, you might find that once you spend the energy learning this program, it will become one of your most important tools. The humble text editor can actually be one of the most powerful tools in computing. If you take advantage of Emac’s capabilities, it will reward you by helping you maximize your computing skills.