This section covers the conventions used in this book.

Emacs commands consist of a modifier, such as Ctrl or Meta, followed by one or two characters. Commands shown in this book abbreviate Ctrl to C and Meta to M:

C-g

Hold down the Ctrl key and press g.

M-x

Hold down the Meta key and press x.

Sometimes Meta is followed by a literal hyphen character. In these cases, we spell out Meta:

Meta -

Hold down the Meta key and press -.

To complete a command you may need to press Enter. (This key may be labeled Return.)

Enter

Press the Enter key.

Esc

Can be used as an alternative to Meta. Press Esc, release it, then press the next key.

To find a group of commands quickly, look for tables in each section that summarize commands. These tables are formatted like this:

Throughout the book, you'll find keystrokes to type, followed by a screenshot showing the results.

This book uses the following font conventions:

boldface

Indicates operating system commands, Emacs keystrokes, command names, and variables.

italic

Indicates filenames, URLs, and new terms when first introduced.

constant width

Indicates buffer names, Lisp code, C code, Emacs messages, and other excerpts from programs.

constant width italic

Indicates dummy parameters that you replace with an actual value. May also be shown sometimes in angle brackets (<filename>).

When you enter Emacs, you see a large workspace near the top of the window where you do your editing. (See Figure 1-1.)

Figure�1-1.�Understanding the Emacs display

A cursor marks your position. The cursor is also called point, particularly among people who are more familiar with Emacs and in the online help system; therefore, it's useful to remember this term.

You don't have to do anything special before you start typing. As long as you type alphanumeric characters and punctuation, Emacs inserts them into your buffer. The cursor indicates where Emacs inserts the new characters; it moves as you type. Unlike many editors (particularly vi), Emacs does not have separate modes for inserting text and giving commands. Try typing something right now, and you'll begin to see how easy Emacs is to use. (If you get stuck for any reason, just press C-g.)

The toolbar is a new feature in Emacs 21. Its basic icons and their functions are listed in Table 1-3. Note that the toolbar is context sensitive; in some modes, such as the Info mode for reading the Emacs manual, the toolbar changes to provide browsing help. We'll discuss those icons when we cover the relevant modes.

The menu bar menu lists the options File, Edit, Options, Buffers, Tools, and Help; you can explore them to see what options are available.

In addition to navigating the menus using the mouse, Emacs now offers pop-up menus. In the Emacs window, hold down Ctrl and click the right mouse button to pop up the Edit menu.[6]

You can access menus without a mouse using the keyboard. In this case, using keyboard commands is much more efficient than menus, but for completeness, we'll show you how to use the text-based menus. (If you prefer to use the mouse with Emacs but have access only to a text interface, see Chapter 13 to learn how to download and install a version of Emacs that runs graphically on Unix, Linux, Mac OS X, or Windows.)

If your mouse does not work with the menus, press F10 or M-` (a back quote, the single open quotation mark, located above the Tab key in the upper-left corner of many keyboards) to access them.

Just above the bottom of the window (on the second-to-last line), Emacs prints a lot of information about what it's doing. This line is called the mode line. At the beginning of the mode line, you may see some information about the coding system that Emacs is using for the file; usually you'll see just --:, indicating that there is no unusual encoding scheme in place. Near the left edge of the mode line, you may see two asterisks (**). These asterisks indicate that you've modified whatever you're editing. If you haven't made any changes, the asterisks won't be there. Next, Emacs prints the name of the buffer you are editing (*scratch*). Following this, Emacs shows where you are in the buffer�your position relative to the rest of the file and what line you are on (L5 for line 5 in Figure 1-1). If you're at the beginning of the file, Emacs prints the word Top; if you're at the end, it prints Bot; if you're in the middle, it shows you a percentage (for example, 50% means you're looking at the midpoint); and if the entire file is visible, Emacs prints the word All. In parentheses following this is the editing mode or modes you are in, in this case Lisp Interaction is the major mode (no minor modes are active). The scrollbar on the side of the window also indicates your position in the file.[7]

You will often work with several buffers simultaneously. In this case, each buffer has its own mode line, and when you switch buffers, the mode line reflects the state of the current buffer. Don't worry about this for now; just remember that every buffer has a mode line to describe it.

Below the mode line is the minibuffer. This is the area where Emacs echoes the commands you enter and where you specify filenames for Emacs to find, values for search and replace, and so on. It is also where Emacs displays error messages. If you find yourself stuck in the minibuffer, press C-g to get out again.

You can open a file by specifying the filename when you start Emacs from the command line or by typing C-x C-f (the long command name is find-file).

The paper icon on the toolbar also runs this command. In some applications, a similar icon simply creates a new, unnamed file (e.g., Document1 in Word). Emacs expects you to provide a filename, as we'll see in a moment.

If you happen to read the wrong file, an easy way to get the right file is by typing C-x C-v (for find-alternate-file). This command means "Read a different file instead of the one I just read." After typing C-x C-v, Emacs puts the name of the current file in the minibuffer; you can then correct a typo or the path, the most common reasons for finding the wrong file. Make the correction and press Enter. Emacs replaces the buffer's contents with the alternate file.

Emacs has a very helpful feature known as completion. If you want an existing file, you need only type the first few letters of the name, enough to uniquely identify the filename. Press Tab, and Emacs completes the filename for you. For example, suppose you are trying to find a file called dickens.

If you want to insert one file into another, you simply move to the appropriate location in the file and type C-x i. (Yes, we know, we haven't told you how to move around in a file yet. Use the arrow keys for now and we'll teach you the "real" Emacs cursor movement commands in Chapter 2.) To append a file, move to the end of the file (M->) and type C-x i. As with C-x C-f, Emacs prompts you for the filename in the minibuffer.

When you use any command that asks for a filename (such as C-x C-f), Emacs displays a default directory in the minibuffer and asks you to type the rest of the filename. How does Emacs choose the default directory? The default directory is taken from the buffer that the cursor is currently in. If you are editing a file in your home directory when you type C-x C-f, Emacs assumes you want to edit another file in your home directory. If you are editing the file /sources/macros/html.macs then Emacs makes the default directory /sources/macros. If you want to find a file in another directory, edit the default directory that Emacs displays.

Emacs has extensive online help, which is discussed further in Chapter 14. You can enter help through the lifesaver icon on the toolbar or through the Help menu. Either method will show you a help menu, described later in this section. To enter help using the keyboard, press C-h. Pressing C-h ? gives you a list of options. Pressing C-h t starts a tutorial that is an excellent introduction to Emacs.

To get information about the meaning of a keystroke combination, press C-h k for describe-key. For example, if you type C-h k C-x i, Emacs displays a description of the insert-file command, which is bound to C-x i. Pressing C-h f (for describe-function) asks Emacs to describe a function (really just a command name, such as find-file). Essentially, C-h k and C-h f give you the same information; the difference is that with C-h k, you press a key whereas with C-h f, you type a command name.

Assume you want to find out about what C-x i does.

You can also use the Help menu to access help commands quickly, and you can get there either through the menu or through the lifesaver on the toolbar. On this menu, you find options we've discussed here: Emacs Tutorial, Describe → Describe Key, and Describe → Describe Function. It includes a host of interesting options, including access to the Emacs frequently asked questions (FAQ) file, a new search feature, and even an Emacs psychiatrist (you might tell it something like "Emacs is driving me over the edge today"). There's an interface to Info, Emacs's online documentation. Simply choose Read the Emacs Manual to start Info.

In this section, we've given a very brief introduction to a few of the paths you can take in the help system. There are many more help facilities; they are described thoroughly in Chapter 14. The help features we've described here should be enough to get you started; if you want to learn more, jump ahead to Chapter 14.

Now you know the basic commands for starting and stopping Emacs and for working with files. Chapter 2 builds on these commands to give you the skills you need for editing with Emacs. Table 1-4 summarizes the commands we covered in this chapter.

��Emacs doesn't do what this book says or look like our screenshots. Make sure that you have GNU Emacs 21.3.5 or later running by typing M-x version Enter or selecting Help → About Emacs. Read the section "Making Emacs Work the Way You Want" in Chapter 2. You may need to install a graphical version of Emacs if you are running in a terminal window; see Chapter 13 for details.

��The toolbar icons are completely different. The icons changed between Emacs 21.3.1 and Emacs 21.3.5. The older icons do the same thing; the newer ones are substantially better looking and more intuitive. Upgrade Emacs using instructions in Chapter 13.

��You can't access menus using the mouse. Use the text-based menus instead by pressing F10 or M-`. Better yet, install a graphical version of Emacs using the instructions in Chapter 13.

��PgUp doesn't work properly when using text-based menus. PgUp is probably bound to some application-specific function, such as scrolling in the Mac OS X Terminal application. Press Shift-PgUp, F10, or M-` to access the menus.

��You can't see a mode line or minibuffer. Your Emacs window is bigger than your display. See Chapter 10 for information on how to get Emacs to start with a reasonable window size. As a temporary workaround, resize the window. (On some Windows systems, maximizing the window ironically makes it smaller, solving the problem.)

The easiest way to move the cursor is to click the left button on your mouse or to press the arrow keys. However, it's a hassle to reach for a mouse all the time. Learn to use keyboard commands to move around so that you will ultimately achieve blinding speed and maximum productivity in Emacs.

To use Emacs commands to move the cursor forward one space, type C-f (f for "forward"). As you might guess, C-b moves the cursor backward. To move up, type C-p (for previous-line), and to move down, type C-n (for next-line). It's easier to memorize commands if you remember what the letters stand for.

Figure 2-2 illustrates how to move up, down, left, and right using Emacs commands.

Figure�2-2.�Basic cursor motion

If you're at the end of a line, C-f moves to the first character on the next line. Likewise, if you're at the beginning of a line, C-b moves to the last character of the previous line. If there's no place to go, Emacs beeps and displays the message Beginning of buffer or End of buffer.

Now we'll learn some more advanced ways to move the cursor. One common way is moving forward and backward by word: M-f moves forward a word; M-b moves backward a word. You can also move to the beginning or end of the line. C-a moves you to the beginning of the line (just like a is the beginning of the alphabet). C-e moves you to the end of the line. To move backward one sentence, type M-a; to move forward one sentence, type M-e. To move forward a whole paragraph at a time, type M-}; to move backward a paragraph, type M-{. If you're in the middle of a sentence or paragraph, moving back a sentence or paragraph actually takes you to the beginning of the current sentence or paragraph.

Figure 2-3 uses a few paragraphs of Victor Hugo's Les Mis�rables to show how you can move the cursor more than one character at a time.

Figure�2-3.�Moving the cursor more than one character at a time

You may have picked up on a pattern here. Notice the difference between commands starting with Ctrl and those starting with Meta. Ctrl commands generally move in smaller units than their associated Meta commands. For example, C-b moves the cursor backward one character, whereas M-b moves the cursor back one word. Likewise, C-a moves to the beginning of the line, whereas M-a moves to the beginning of a sentence.

There's one caveat about moving by sentence or paragraph. Emacs defines a sentence pretty strictly. You need two spaces after the final punctuation mark, unless you're at the end of the line. If there's only one space, Emacs won't recognize it. Similarly, moving backward and forward by paragraph involves understanding the Emacs definition of a paragraph. To Emacs (and to most of us), paragraphs are either indented with a tab or at least one space or have blank lines between them (block style). You can change these definitions, but first you have to understand how to use regular expressions, which are discussed briefly in Chapter 3 and in more depth in Chapter 11. Chapter 10 discusses how to change variables.

If your file has page breaks in it, you can move to the next page or previous page by typing C-x ] (forward-page) or C-x [ (backward-page). Similar to paragraph and sentence movement, moving by page involves the Emacs definition of what a page is. A variable called page-delimiter defines what constitutes a page break. If there are no Emacs-recognized page breaks in the file, Emacs regards the buffer as one very long page. In this case, the forward-page command takes you to the end of the buffer, and the backward-page command takes you to the beginning of the buffer.

In text mode, a page break is a formfeed character that tells the printer to move to the next page (to feed the next form or page through the printer, hence the term formfeed) before continuing to print. If you are in text mode and you want to insert page breaks in your file, type C-q C-l (the lowercase letter L). C-q is the quoted-insert command. It tells Emacs to put a C-l control character in your file, rather than interpreting C-l as the recenter command. A C-l character looks like two characters (^L), but it's really only one. (Try to erase one using Del and see what we mean.)

Like other graphical applications, you can use the scrollbar to move around in Emacs. Like most things in Emacs, in addition to using the mouse or scrollbar to move around, you should learn Emacs's own keyboard commands to maximize your productivity.

If you want to page through a file one screen at a time, use the PgDown key or type C-v. Emacs displays the next full screen from your file. It leaves a couple of lines from the previous screen at the top to give you a sense of context. Likewise, pressing M-v (or the PgUp key) shows you the previous screen. Together, M-v and C-v provide a convenient way to scroll through a file quickly.

Scrolling happens automatically if you type any motion command that takes you beyond the limits of the text currently displayed. For example, if you are on the last line of the screen and press C-n, Emacs scrolls forward. Similarly, if you are at the top of the screen and press C-p, Emacs scrolls backward.

You often want to move all the way to the beginning or the end of a file. Type M-> or press End to go to the end of a buffer. To go to the beginning, type M-< or press Home. It may help you to remember that > points to the end of the buffer, and < points to the beginning of the buffer.

There are two more ways to move around that may come in handy. M-x goto-line EnternEnter moves the cursor to line n of the file. Of course, Emacs starts counting lines from the beginning of the file. Likewise, M-x goto-char EnternEnter goes to the nth character of the file, counting from the beginning. In both cases, n is a number.

For programmers, these commands are useful because many compilers give error messages like Syntax error on line 356. By using these commands, you can move easily to the location of your error. There are some more sophisticated ways to link Emacs with error reports from compilers and other programs. In addition, several other cursor motion commands are applicable only when you are editing programs (see Chapter 9 for details).

Now let's learn some efficiency tricks. Emacs lets you repeat any command as many times as you want to. First, you can repeat a command any number of times by pressing M-n before the command, where n is the number of times you want to repeat it. This command is called the digit-argument command.

You can give M-n a large argument if you want it to repeat the command many times. For example, let's say you are editing a large file of 1000 lines. If you typed M-500 C-n, the cursor would move down 500 lines, to the halfway point in the file. If you give M-n a larger argument than it can execute, it repeats the command as many times as possible and then stops.

There's another multiplier command you can use, too: C-u (the universal-argument command). You can give C-u an argument just like you do M-n. Typing either M-5 or C-u 5 repeats the command that follows five times. But unlike M-n, C-u doesn't need an argument to repeat commands. With no argument, C-u executes the next command four times. If you type C-u C-u, it executes the command 16 times. In this way, you can stack up C-u's to make commands execute many times: 16, 64, 256, and so on.[11]

C-l, the recenter command, puts the current line in the center of the window vertically. This feature is useful if you're typing at the bottom or the top of the display. Typing C-l quickly moves the material that you care about to the middle of the display, where it is easier to see the full context.

C-l also redraws the display, if for any reason it appears obscured or contains random characters. This doesn't happen as often as it used to when we used terminals, but it can be a handy thing to know about, especially if you find yourself using Emacs remotely in a terminal interface.

Table 2-2 lists cursor movement commands. If the command is mnemonic, the word to remember is given in italics.

You can access many Emacs commands by pressing standard keys on your keyboard, such as PageDown (to scroll down one screen) or Home (to go to the beginning of a buffer). Figure 2-4 shows a sample keyboard layout and what the keys do. Your keys may be in a slightly different place, but if you have a key with the same or a similar name, it should work. We say "should" because there are situations in which the keys won't work�for example, if you use Emacs on a remote machine. We recommend that you also learn the standard Emacs commands; they work on any keyboard, and they are often easier to reach once you learn them.

Figure�2-4.�Emacs commands and your keyboard

Before you start practicing deletion commands, you might want to know the undo command, which is discussed fully later in this chapter. Typing C-_ or C-x u undoes your last edit; typing undo again undoes the edit before that one, and so on.

Emacs provides many ways to delete text. The simplest way to delete text is to press the Del key, which deletes the character immediately to the left of the cursor. See Figure 2-4 for possible locations of the Del key on your keyboard. It is sometimes referred to as the Backspace key. Del is easiest to define by what it does: it deletes the previous character. If you're typing and you decide to erase the last character you typed, what key do you reach for? That's the key Emacs refers to as Del.

Emacs provides a number of other deletion commands�perhaps too many for your taste, although you'll eventually find a reason to use most of them. For example, C-d (for delete-character) deletes the character under the cursor. The command for deleting the next word is M-d (for kill-word). Once again, note how the Meta key augments the command: C-d operates on a character, and M-d operates on a word.

Emacs has commands to delete the next or previous word, sentence, and paragraph. By their names, you can guess what they do when you're between words, sentences, or paragraphs. If you're in the middle of an entity, however, they do something a little surprising: they delete a portion of the current word, sentence, or paragraph, backward or forward depending on whether the command deletes previous or next. For example, here's how M-d acts differently depending on where the cursor is.

By now you may have noticed that some deletion commands in Emacs are called kill commands, such as kill-region, kill-word, and the like. In Emacs, killing is not fatal, but in fact, quite the opposite. Text that has been killed is not gone forever but is hidden in an area called the kill ring. The kill ring, though it sounds somewhat like a violent gang, is an internal storage area where Emacs puts things you've copied or deleted. Do not confuse the kill ring with the system clipboard, which allows for copying and pasting between applications. We'll cover how Emacs relates to the system clipboard later in this chapter.

You can get back what you've deleted by typing C-y (for yank).[12] Conveniently, if you kill several lines in succession, Emacs collects them into a single item and places the whole unit into the kill ring; a single C-y command will bring everything back. In the following example, we'll use C-k four times to delete the first two lines of A Tale of Two Cities. (Remember: the first C-k deletes the text; the second C-k deletes the remaining blank line.) Then we'll use a single C-y to bring everything back.

What if the text you want to delete is just a phrase? Or half a paragraph? Or several paragraphs? In Emacs, you select text by defining an area called a region. You can mark regions with the mouse or by using the keyboard. What happens with the mouse is a bit complicated, so we describe it later in this chapter, following our discussion of the system clipboard.

To define a region using the keyboard, you use a secondary pointer called a mark. Some versions of Emacs display the mark on the screen; unfortunately, in GNU Emacs, the mark is invisible.

You set the mark at one end of the region by pressing C-Space or C-@, then move the cursor to the other end of the region. (The cursor is sometimes also referred to as point. There is one minor but important difference between the cursor and the point, however. The cursor is on top of a character; in Emacs, the point is actually in between the character the cursor is on and the previous character. As we said, this difference is minor, but it helps you to visualize where the cursor should be when you mark a region.) Figure 2-5 illustrates point, mark, and region.

Figure�2-5.�Point, mark, and region

Let's mark a sample region. In this example, we remove the phrase "it was the worst of times." First, we find the beginning of the phrase. Then we set the mark, move forward to the end of the phrase, and cut.

Move to the beginning of "it" and press C-Space.

Set the mark; Mark set appears in the minibuffer.

Move to the "i" in "it was the age of wisdom." Because the point is really just before the "i," this placement will be just right.

Move to the "i" in "it was the age of wisdom"

The point is at the end of the region to be marked.

Now the region is marked. If the region is not highlighted, you'll want to make sure it is marked correctly before giving the delete command. Press C-x C-x (for exchange-point-and-mark); this command swaps the locations of the mark and the point. If the cursor moves to where you thought the mark was, the region is marked correctly. Especially because you can't see the mark, it's a good habit to check its location using C-x C-x before deleting a region. People who have used Emacs for years still forget to set the mark and then make a deletion without knowing what they've just deleted. (The undo command, bound to C-_ and C-x u, comes in handy in such a case.)

To cut the region, press C-w (for kill-region). (The scissors icon on the toolbar also works.)

Press: C-w

C-w cuts the region.

If you're not sure of what you deleted, just press C-_ to undo it. The text is still marked, and you can delete it again with C-w if you want to. To move text, mark it, press C-w to cut the region, then move the cursor to the place you want to insert the text, and press C-y. If you yank the text back into the wrong location, just type C-_ to undo it, then move to the place you really wanted to put the text, and press C-y again.

When you're defining a region, you normally set the mark at one end and then move the cursor to the other end of the region. A few shortcuts are helpful in some of the most common situations. To mark a paragraph, press M-h. This sets the mark at the end of the paragraph and places the cursor at the beginning automatically. Similarly, C-x h (for mark-whole-buffer) marks the entire buffer; the cursor goes to the beginning, and the mark is placed at the end. Finally, C-x C-p marks the current page, with pages being defined by the C-l character if you are in text mode. Of course, marking a paragraph, page, or buffer is usually only the prelude to some other operation, like killing (C-w).

To copy text, mark a region, then press M-w (for kill-ring-save; the toolbar icon with two pieces of paper also runs this command). Move the cursor to the place where you want to insert the copied text and press C-y. Copying text is exactly the same as killing it, except that Emacs doesn't delete anything. The text you have copied is placed in the kill ring, so you can use C-y to access it as often as you like.

One advantage to M-w is that it works on read-only files and buffers. For example, if you wanted to create a file of Emacs hints, you could use M-w to copy some text from online help into one of your buffers.

Here are the steps for some common deletion tasks.

To mark a region:

1.�Move the cursor to the beginning of the area you want to delete.

2.�Press C-Space. Emacs displays the message Mark set.

3.�Move the cursor to the end of the region you want to delete.

To delete a region:

1.�Mark the region to be deleted.

2.�Press C-w to delete the region.

To move text:

1.�Delete the text you want to move using the procedures for marking and deleting a region.

2.�Move the cursor where you want to insert the text.

3.�Press C-y. Emacs inserts the text you deleted.

To copy text:

1.�Mark the region you want to copy.

2.�Press M-w to copy the text.

3.�Move the cursor where you want to insert the copied text and press C-y. Emacs inserts the text you copied.

Earlier we mentioned the kill ring, a temporary storage area in which Emacs saves the stuff you delete. So far, we've assumed that you're interested in resurrecting what you've most recently killed. However, the kill ring does a lot more. It actually stores your last 30 deletions. We've seen that C-y restores the text you deleted most recently. Typing M-y deletes the text you just yanked and gets the next most recent text from the kill ring.

Here's how it works. In Table 2-4, assume that you've just killed the words "most recent." C-y retrieves these words from the kill ring. When you press M-y, Emacs gets rid of "most recent" and gets the next entry from the kill ring ("second-last").

Using the menus, you can access text from the kill ring in a more straightforward way: by choosing Edit → Select and Paste. A menu showing deletions appears, with the most recent ones on top. To show you as many deletions as possible, each line in the window represents a separate deletion. So if you've killed a large region, say 500 lines, you see only the beginning of the first line of that deletion, ellipses, and the end of the deletion. Your selection is pasted into the buffer at the cursor position.

Table 2-5 summarizes commands for working with regions.

Emacs 21 plays well with the clipboard, though it still may not do what you want it to in some cases. Let's dig into this in a little more detail.

By default, text that you cut or copy using icons on the toolbar or options on the Edit menu is placed on the clipboard and is accessible to other applications.

Unfortunately, Emacs diverges by platform on this issue. Normally we save platform-specific issues for Chapter 13, but cutting and pasting is such a vital operation that we must describe the differences here.

On Windows and Mac OS X (but not on Linux) any text you cut or copy using C-w or M-w is also copied to the clipboard.

On Windows and Mac OS X, simply selecting text with the mouse places it on the clipboard. (This doesn't work on Linux.). Most applications require you to highlight text, then issue a copy command. Emacs doesn't. Table 2-6 shows how this works on various platforms.

As we mentioned, in other applications, you typically cut and paste by selecting text, then issuing a copy command. How do you then paste that text into Emacs?

Not surprisingly, the paste icon on the toolbar and the associated option on the Edit menu do this in most cases (see Table 2-7; Emacs on Mac OS X disables both the icon and the option inappropriately; the associated command name clipboard-yank works, however). C-y inserts text from the clipboard too. Additionally, an easy mouse gesture works on most platforms: simply click the middle mouse button or mouse wheel in the Emacs window to paste from the clipboard. The caveat here is that you must have a mouse with a middle button.

Now that you've learned the basics of editing�moving the cursor to the right position, deleting, copying, and moving text�you can learn some tricks that make editing easier.

The most common typo involves the transposition of two letters, and most typos are noticed immediately after you make them. Pressing C-t transposes two letters, to put them in the right order:

Mistakes in capitalization are also common and annoying typing errors. Emacs has some special commands for fixing capitalization. To capitalize the first letter of any word, put the cursor on the first letter and press M-c. To put a word in lowercase, press M-l. To put a word in uppercase, press M-u. The key bindings here are mnemonic: Meta followed by c for capitalize, l for lowercase, and u for uppercase. Note that if the cursor is in the middle of a word, Emacs takes action only from the character under the cursor to the end of the word. You can easily use M-l to lowercase the second half of a word, and so on.

If you notice that the word you just typed is incorrect, you can use the same commands prefaced by Meta- (press and hold Meta followed by a hyphen). This corrects the previous word without moving the cursor. If the cursor is positioned in the middle of a word, using Meta- before a command causes it to work on the first part of the word (the part preceding the cursor), rather than the part following the cursor.

For example, starting with abcdefghij:

You may be used to typing over old text rather than having to delete it. There is a certain satisfaction in destroying some really bad text in this way. You can do this in Emacs, too, by entering a minor mode called overwrite mode. When you're in overwrite mode, any new text you type wipes out the text that's underneath. When you're not in overwrite mode (i.e., in normal Emacs), any new text you type is inserted at the cursor position and any subsequent text is pushed to the right. (Other software may refer to this as insert mode; because it is the way GNU Emacs normally behaves, it doesn't have a name here.)

To enter overwrite mode, press the Insert key.[15]Ovwrt should appear on the mode line. If this doesn't work (or if you don't have an Insert key), type M-x overwrite-mode Enter. You can turn off overwrite mode by typing M-x overwrite-mode Enter again. Using Emacs's command completion, simply type M-x ov and press Enter. This is enough of a unique string to tell Emacs you want to toggle overwrite mode. Completion, one of the best shortcuts in Emacs, is discussed further in Chapter 14.

Sometimes you start a command by accident or change your mind about it. Don't worry: with Emacs, you can quit in the middle or undo it.

When you want to cancel any command that's in progress, press C-g. The word Quit appears in the command area. This command is helpful when you are stuck in the minibuffer and didn't really mean to go there. Depending on what you were doing, you may have to press C-g a few times.

What happens if you make a mistake while you're editing? You can undo your changes by pressing C-_ or C-x u (for undo; conveniently, the toolbar also has an undo icon, a curved left arrow). By typing undo repeatedly, you can gradually work your way back to a point before your mistake.[16] Although the undo command is very powerful, saving your file frequently, if not compulsively, is nevertheless a good idea. We usually save a file whenever we stop typing�even if only for a few seconds. Train your fingers to press C-x C-s whenever you pause; it's a good habit to form.

If you're used to typing C-z to undo, you can easily change Emacs's behavior to match your habits. See "Making Emacs Work the Way You Want" at the end of this chapter for information on CUA mode.

What if you'd like to redo a command after you type undo? There is no formal redo command, but you can use undo in the following way. Just move the cursor in any direction, and type C-_ or C-x u again. Emacs redoes the last command you undid. You can repeat it to redo previous undos.

Although undo is an important command, it can be slow if you want to undo a large number of changes. Table 2-11 summarizes three methods for undoing changes and circumstances in which you might want to use them.

If the undo command isn't useful, there's another way to restore a file to an earlier state. If you want to get the file back to the state that is stored on disk, type M-x revert-buffer Enter. Emacs asks the following question:

Revert buffer from file filename? (yes or no)

The filename is the name of your original file. Type yes if you want to restore the file, or no if you've changed your mind. Emacs copies the file stored on disk into the buffer, conveniently forgetting everything that happened since the last time you saved the file. Although this command is called revert-buffer, note that it can revert only buffers associated with files.

The first time you save a file during an editing session, Emacs creates a backup file. If something disastrous happens, and the other techniques for undoing changes won't help you, you can always return to the backup file. The name of the backup file is the same as the name of the file you're editing, with a tilde (~) added. For example, if you are editing the file text, the backup file is text~.

Emacs doesn't provide any special commands for restoring a buffer from the backup copy. The easiest way to do this is to edit the backup copy and then save it as the real file. For example, if you were working with a file called text, you could: exit Emacs by typing C-x C-c, then start Emacs again by typing emacstext~. After the backup file is displayed, save it as the real file by typing C-x C-wtextEnter. As a safeguard, Emacs asks you before it writes over the original file:

File text exists; overwrite? (y or n)

Type y to overwrite the original file with the backup file.

GNU Emacs also has a numbered backup facility. If you turn on numbered backups, Emacs creates a backup file (with the suffix ~n~) every time you save your file. n increments with each successive save. If you are nervous about deleting older versions, it might be worth using: you can keep all of your old versions forever, if you want to. However, numbered backups can also waste disk space; a happy medium may be to tell Emacs to keep the last n versions, where n is the number of versions you want to keep. The variables that control numbered backups are described in Appendix A. If you are interested in full-blown version control, check out VC mode, discussed in Chapter 12. Table 2-12 summarizes the commands for stopping commands and undoing changes.

We've just discussed how to eliminate changes you don't want to keep; getting back changes you've lost is a different kind of problem. You might lose changes if the power goes out momentarily or if the computer you're working on suddenly freezes or is turned off accidentally. You might also lose changes if you exit Emacs abnormally. Luckily, Emacs, being the watchful editor that it is, saves your file for you every so often in auto-save files. If you watch carefully, you'll see the message Auto saving in the minibuffer from time to time. Using auto-save files, you can get back most, if not all, of your changes. The name of an auto-save file is the same as the name of the file you are editing, with a sharp (#) added to the beginning and the end. For example, if you are editing the file text, its auto-save file is #text#.

To recover text from an auto-save file, type M-x recover-file Enter. Emacs opens a window that lists both the file and its associated auto-save file so that you can compare the time at which they were created, their size, and so forth. Emacs asks you the following question:

Recover auto-save file #text#? (yes or no)

Type yes to confirm that you want to copy the contents of the auto-save file into the current file or no if you change your mind. (If you are unsure, you might want to use C-x C-f to read the auto-save file #text# into a buffer first and look it over carefully before using the recover-file command. If you really want to compare the differences between the two versions, see "Comparing Files Between Windows" in Chapter 4.)

When does Emacs create auto-save files? Emacs creates an auto-save file every few hundred keystrokes or if Emacs is terminated abnormally.[18] You can change the frequency with which Emacs creates auto-save files by changing the variable auto-save-interval. By default, Emacs creates an auto-save file every 300 keystrokes. For more information on changing variable values, see Chapter 10.

There's one more important fact to know about Emacs and auto-save files. If you delete a large portion of a file, Emacs stops auto-saving the file and displays a message telling you so. To make Emacs start auto-saving again, save the file with C-x C-s or type M-1 M-x auto-save Enter (that's the number 1).

Now you've learned enough commands for most of the editing you'll do with Emacs. At this point, you may want to learn how to make Emacs turn on certain features like auto-fill mode automatically, so you don't have to turn them on every time you enter Emacs. The next section provides a brief introduction to customization; this topic is covered in much greater detail in Chapter 10.

If you've been reading straight through this book, you may have started a list of things you'd like to change about Emacs, such as

��Hiding the toolbar

��Changing Emacs cut and paste commands to C-x, C-c, and C-v

��Turning on text mode and a fill mode so Emacs does word wrap

��Changing the way some of the keys work

We're going to tell you how to give Emacs the to-do list, a list of options to turn on each time you enter Emacs. These options are defined in an initialization file called .emacs. Initialization files run automatically. Some run when you start up your computer. Others, like .emacs, run when you start up an associated software program. So .emacs runs automatically when you start Emacs and turns on whatever options the file defines. Emacs doesn't need this file to run; its only purpose is to make Emacs work the way you want it to.

The .emacs file consists of Lisp statements. If you're not a Lisp programmer, you can think of each line as an incantation that follows a certain pattern; you need to type it exactly.

Emacs now has another way to handle customization: an interactive interface called Custom that writes Lisp for you and automatically inserts it in your .emacs file. The Custom interface is discussed in Chapter 10, but we'll show you an even faster method for common options.

When you want to add a line to your .emacs file directly, take these steps:

1.�Enter Emacs (if you're not already there).

2.�Type C-x C-f ~/.emacs Enter.

3.�Type the line to be added exactly as shown in this book and press Enter.

4.�Press C-x C-s to save the .emacs file.

5.�Press C-x C-c to exit Emacs.

6.�Restart Emacs to have the line take effect.

If you make a minor typing mistake (such as forgetting a single quotation mark or a parenthesis), you are likely to get an error message that says Error in init file when you restart Emacs. Simply edit the .emacs file again, checking the line you added against the place you got it from, whether from this book or another user's .emacs file. Usually, you can find the error if you look hard enough; if not, find someone who has a .emacs file (and preferably understands Lisp) and ask for help. Make the changes, save the file, and restart Emacs.

What if you make a change that essentially keeps Emacs from being able to start? You can still exit Emacs, rename the file, edit it, then save it as .emacs and try again.

New users may find the toolbar helpful. Others may not. It's easy to hide it by selecting Options → Show/Hide → Toolbar, and then Options → Save Options.

When Emacs sets options for you through Custom (and this is what it is doing even when you use the Options menu), it writes your .emacs file. If you already have a .emacs file, it appends to it. Custom essentially groups all of its settings in one part of the file, and it is commented to indicate that you should not change it manually. Here's the .emacs file that we created by selecting this option:

(custom-set-variables

�;; custom-set-variables was added by Custom.

�;; If you edit it by hand, you could mess it up, so be careful.

�;; Your init file should contain only one such instance.

�;; If there is more than one, they won't work right.

'(tool-bar-mode nil nil (tool-bar)))

(custom-set-faces

�;; custom-set-faces was added by Custom.

�;; If you edit it by hand, you could mess it up, so be careful.

�;; Your init file should contain only one such instance.

�;; If there is more than one, they won't work right.

)

This may seem a bit bulky, but as we'll see in the next section, Emacs adds this section only once and then augments it when you set more options either through the options menu or directly through the Custom interface. Also note that this auto-generated Lisp is certainly less clean than Lisp statements you'll typically see in .emacs files. That's another reason not to edit Custom's work directly.

If you're new to Emacs, you might be used to the Common User Access (CUA) conventions for cutting, copying, and pasting, C-x, C-c, and C-v respectively. You might reach for C-z for undo. CUA mode was once an add-on mode that you had to install separately, but it became so popular that it is now part of Emacs. It's coded in a clever way that doesn't interfere with Emacs keystrokes that are prefixed with C-x and C-c. Details on CUA mode can be found in Chapter 13.

You can turn this feature on through the Options menu to try it out. Simply choose Options → C-x/C-c/C-v cut and paste (CUA). After you select this option, a check mark appears next to it on the Options menu. To keep it for subsequent sections, select Save Options from the Options menu. Emacs writes your .emacs file for you. If you turned off the toolbar and then set this option, your .emacs file would look like this (note that the line relating to CUA mode is bold so you can see the difference from the previous example):

(custom-set-variables

��;; custom-set-variables was added by Custom.

��;; If you edit it by hand, you could mess it up, so be careful.

��;; Your init file should contain only one such instance.

��;; If there is more than one, they won't work right.

�'(cua-mode t nil (cua-base))

�'(tool-bar-mode nil nil (tool-bar)))

(custom-set-faces

��;; custom-set-faces was added by Custom.

��;; If you edit it by hand, you could mess it up, so be careful.

��;; Your init file should contain only one such instance.

��;; If there is more than one, they won't work right.

)

Interestingly, Emacs happily writes the .emacs file even if it is open at the time. You can watch Emacs change the file if you have it open when you choose Save Options.

To make text mode the default major mode and start auto-fill mode automatically each time you enter Emacs, add these lines to your .emacs file:

(setq default-major-mode 'text-mode)

(add-hook 'text-mode-hook 'turn-on-auto-fill)

The first line tells Emacs to make text mode the default major mode; in other words, "Turn on text mode unless I tell you otherwise." The second line turns on auto-fill mode whenever you are in text mode. Alternatively, selecting Options→ Word Wrap in Text Modes, and then Options→ Save Options adds auto-fill mode to your .emacs file directly. It doesn't make text mode the default major mode, however.

If you prefer refill mode, replace the second line of code with this line:

(add-hook 'text-mode-hook (lambda ( ) (refill-mode 1)))

Another major use of the .emacs file is to redefine things about Emacs that irritate you. You may have ergonomic concerns about Emacs; more than one person has aggravated carpal tunnel syndrome using the default bindings. You may simply be used to reaching for certain keys for certain functions and would rather change Emacs than your habits. Whatever the case, this section gives a brief introduction to key remapping; for more details, see Chapter 10.

If you use the default bindings (rather than CUA mode), you may use C-x u for undo.[19] (Undo is such a common command that it's easy to type C-x C-u by mistake when you undo repeatedly. Unfortunately, C-x C-u is a disabled command for upcase-region. If you type C-x C-u, an annoying message about enabling the command pops up.

If you don't anticipate a big need for upcasing regions, you can redefine C-x C-u so that it also runs undo. To do so, add this line to your .emacs file:

(define-key global-map "\C-x\C-u" 'undo)

After making this change, typing C-x C-u runs undo, just as C-x u does.

Emacs customization is extremely powerful, and you can make Emacs work just the way you want it to. A far more extensive treatment of customization is found in Chapter 10. This brief introduction is meant to whet your appetite and to make it possible for you to add lines to your .emacs file as we mention potential customizations throughout the book.

The next chapter covers topics such as the many searches offered by Emacs, including query-replace, as well as spell checking and word abbreviation mode (often used to correct typos automatically). If you want to learn about these features, go on to the next chapter. From here on, you can take a selective approach to reading this book, picking and choosing whatever you want to learn about; you don't need to read the rest of the book sequentially.

��You get an error message when you start Emacs after changing the.emacsfile. The message appears only briefly; press M-p to view it again. Edit your .emacs file, checking the lines you added carefully against their source for minor typographical errors. Something as simple as a missing hyphen or apostrophe can cause this error. Fix the error, save the file, exit Emacs, and reenter. In extreme cases (the .emacs file is so messed up that Emacs won't even let you edit it), exit Emacs, rename the .emacs file, and then start Emacs and edit it again to fix it. Rename it back to .emacs and start again.

��Paragraphs are not reformatted properly. This seems to relate to window size. Try resizing the window horizontally until paragraphs format properly.

While you're editing, you frequently want to find something you've already typed. Rather than hunt through the file trying to find what you're looking for, virtually all editors provide some kind of search feature that lets you look for a particular text string. Emacs is no exception to the rule. It supplies a search command�in fact, it provides a dizzying array of search commands. Here's a quick summary of the different kinds of searches that are available:

Incremental search starts to work from the moment you type the first character of the search string. Many users like the efficiency of incremental searches, and they like the highlighting as well. Emacs highlights all occurrences of the search string in aqua blue (if your display supports it) and uses purple to highlight the string at the cursor position (the current match).

Emacs also offers a simple, or nonincremental, search. To use a more straightforward search, type C-s Enter. Type the search string, press Enter, and Emacs begins the search. Simply press C-s again to repeat the search. To start a nonincremental search backwards through the file, press C-r Enter. Again, you type the search string and press Enter to begin the search.

The search icon on the toolbar (a magnifying glass over paper) and the Edit → Search → String Forward option run the same kind of a search. The prompt is slightly different. C-s Enter prompts you with Search: in the minibuffer while the toolbar icon and the menu option prompt with Search for string:. This is a minor difference; the searches are virtually identical otherwise.

Table 3-2 summarizes the simple search commands.

If you're searching for a phrase and you know it's in the file but you can't find it with incremental search, try word search. (You probably can't find your phrase with incremental search because the phrase has a line break in it.) Word search is a nonincremental search that ignores line breaks, spaces, and punctuation. It also requires that your search string match entire words in the file.

To do a word search, type C-s Enter C-w (for word-search-forward). The prompt Word search appears in the minibuffer. (Don't be put off by the prompts that appear along the way: you'll see an I-search prompt after typing C-s and a Search prompt after pressing Enter. Ignore these.) Type the search string and press Enter. Emacs searches for the given string. To do a word search backwards, type C-r Enter C-w instead. For example, assume that you have the following text, with the cursor at the beginning:

He said, "All good elephants are wise, aren't they?"

She answered, "Some are smarter than others, but we

think this is socially conditioned."

The command C-s Enter C-w they she Enter positions the cursor after the word She. This command looks complicated, but it's really nothing more than a word search (C-s Enter C-w) for the word they, followed by the word she. It ignores the punctuation (?") and the newline between they and she.

Assume that you're looking for the word the. You don't want to bother with thence, there, theater, thesis, blithe, or any other word that happens to contain the letters the. In this situation, neither an incremental search nor a simple search is very useful�you need a word search. If you're writing a paper, word search is often exactly what you need. It is the only one of the three basic search commands that allows you to find what you want even if the phrase is split between two lines.

Now that you've seen the three most commonly used searches, you might want to experiment and see which you find most useful.

Search and replace definitely go together, like coffee and cream. Let's say you're working on a new software application and at the last possible moment, the Marketing Department decides to change the product's name.

There's a press release for Whirligig, an email service that periodically reminds you to make healthy lifestyle changes like exercising, drinking water, and taking vitamins. The level of harassment or, as the marketing department says, encouragement, can be set by the user. Whirligig isn't really the most descriptive name, so at the last minute the Marketing Department changes it to HealthBug.

Assume you're in the situation we just described. You want to replace every occurrence of one string with another. You know that Whirligig is never correct, and there is absolutely no ambiguity about how you want to replace it. When you want to replace every instance of a given string, you can use a simple command that tells Emacs to do just that. Type M-x replace-string Enter, then type the search string and press Enter. Now type the replacement string and press Enter again. Emacs replaces all occurrences in the file from the cursor position onward. If you want to search and replace throughout the file, press M-< to go to the beginning of the file before typing this command. Here's a quick example of using replace-string.

Few search and replace situations are as straightforward as those we've described. Often you're not sure that you want to replace every appearance of your search string: a global replacement can be reckless. If you want to decide whether to replace the string on a case-by-case basis, use a query-replace, which allows you to change a string conditionally throughout a file. After Emacs finds an occurrence of the search string, it asks whether it should replace it, and you respond accordingly.

To use query-replace, go to the beginning of the buffer using M-< and then type M-%. The prompt Query replace: appears in the minibuffer. Type the search string and press Enter. Now this appears:

Query replace searchstring with:

Type the replacement string and press Enter. So far, this procedure is almost identical to a replace-string operation; only the prompts are different.

Emacs now searches for the first occurrence of the search string. When it finds one, a new prompt appears:

Query replacing searchstring with newstring

Before performing the replacement, Emacs waits for a response to tell it what to do. Table 3-3 lists the possible responses and their results.

Now that you've learned the basics of query-replace, let's talk about a shortcut that applies not only in query-replace but anywhere in Emacs: repeating complex commands, with slight modifications. We often exit a query-replace by mistake or decide that the replacement we really wanted was just slightly different. Do we have to type it all again? No. Simply go the beginning of the file and press C-x Esc Esc. The last complex command you typed appears. If it's not the one you want, type M-p to see the previous command (do this as many times as necessary; M-n goes to the next command). For example, let's go to the beginning of the file and repeat the query-replace we just carried out.

When you do a query-replace, you inevitably see something else you want to change in the file. Try it a few times�you'll see what we mean! We typically try to remember the problem until we're done, then get frustrated when we forget exactly what and where the problem was.

Fortunately, Emacs provides an easier way. It allows you to start a recursive edit while you're in the middle of a query-replace. By starting a recursive edit, you effectively put query-replace on hold while you make any other desired edits. When you exit the recursive edit, the query-replace resumes where you left off.

To start a recursive edit while in query-replace, press C-r. (Note that like many other key bindings, C-r has a different meaning in query-replace than it does in standard Emacs.) When you start a recursive edit, square brackets ([ ]) appear on the mode line. Let's go back, one more time, to our public relations piece. You've used query-replace to find the first Bug to change to Bot, and you are about to press Space to fix it, when you remember that the lawyers said that the "64 ounces of water" statement was too specific and could be construed as giving medical advice. A quick recursive edit saves the day.

By default, Emacs searches are not case-sensitive. Look at the Options menu and you'll see that the option Case-Insensitive Search is the only option that is checked by default.

What does this mean in practical terms? If you search for the word random, the search finds random, Random, and RANDOM, as well as oddities like RanDoM and rANdOM. When doing replacements, Emacs pays attention to the form of the word being replaced and replaces it with the same case. If you replaced random with tandem, Random would be replaced with Tandem, and RANDOM would be replaced with TANDEM. If you mix capitalization, the replacement string appears just as you type it. healthbug would be replaced with HealthBug if that was the case in the replacement string. In other words, the default search and replacement operations usually do what you want: they find a search string regardless of its case and adjust the replacement appropriately for its context. However, sometimes you need finer control.

The variable case-fold-search determines whether searches are case-sensitive. It applies to all searches: incremental searches, word searches, searches within search-and-replace operations, and so on. By default, case-fold-search is set to t, which means "ignore case unless the user types in mixed or uppercase." This sensible default is usually just what you want. But if you need case-sensitive searches, the Case-Insensitive Search option on the Options menu provides an easy way to experiment with this variable.

Likewise, if you don't want Emacs to adjust the case of your replacement strings, you can set the variable case-replace. Again, its value is t (for "true") by default, which means "adjust the case of a replacement string to match the original text"�that is, capitalize the replacement if the original word was capitalized and so on. Setting this variable to nil means "never adjust the case of the replacement string; always put it in exactly as I typed it." To change the value of case-replace, type M-x set-variable Enter case-replace Enter nil Enter (there's no menu option for this variable).

Both the menu option and the set-variable command change the behavior of Emacs only temporarily. If you start a new editing session, you'll be back to the default behavior. This is probably what you want, because searching separately for capitalized and lowercase words is inconvenient.

You can set the value for the Case-Insensitive Search option permanently by selecting Save Options from the Options menu or by adding this line to your .emacs file:

(setq-default case-fold-search nil)��; require exact matches

To set case-replace permanently, add the following line to your .emacs file. You'll need to restart Emacs to have the change take effect.

(setq-default case-replace nil)������; never change case when replacing

You could change these variables through Emacs's interactive customization facility, Custom, instead (see Chapter 10).

Sometimes none of the simpler searches described in this chapter are adequate. Regular expressions allow you to build searches with strings that contain various wildcards.

Table 3-4 shows some of the characters you can use in creating a regular expression.

Emacs includes two spell-checking interfaces: to the Unix spell checker, spell, and to Ispell, which many people, including us, prefer. We say "interfaces" because Emacs does not include the executables for either of these spell-checkers. Because Ispell is superior and runs on a variety of platforms, we'll cover only Ispell here. If you attempt to run Ispell and it is not available, you'll have to install it. Chapter 13 provides details on installing Ispell on Windows and on Mac OS X.

A further enhancement to Ispell is Flyspell, a command that highlights misspelled words on the fly. If you have Ispell installed, you'll have Flyspell support as well.

Ispell includes options to check a buffer, a region, the comments in a program, or a single word. After you type the command telling Ispell what area you want to check, it works the same way for all these options. We'll describe ispell-buffer here. If all the words are spelled correctly, Ispell displays the message, Spell-checking done. If Ispell finds a misspelled word, a screen like the following appears. Let's spell-check a hastily typed passage from Homer's Odyssey.

Sometimes when you are typing, you'll say, "That doesn't look right." To check the word the cursor is on, type M-$ (for ispell-word). Ispell checks the spelling of the word and displays word : ok if the word is spelled correctly. If the word is incorrect, Ispell displays a window with the options discussed earlier.

You might start typing a word and then wonder, "How is that spelled?" This is where ispell-complete-word comes in. You're typing a word and you get stuck. Type M-Tab (for ispell-complete-word) and you get a list of choices. After typing occur, you use this command to find out the answer.

Flyspell highlights misspelled words as you type. You can also use it to check existing text. The commands for doing this are different.

To check text as you type, enter Flyspell mode by typing M-x flyspell-mode Enter. Fly appears on the mode line. If you set up Emacs to enter Flyspell mode automatically, your text is always spell-checked "on the fly." An alternative to Flyspell mode is Flyspell prog mode. In this mode, designed for programmers, Emacs highlights misspellings only in comments or strings. To enter it, type M-x flyspell-prog-mode Enter.

To check existing text, you run M-x flyspell-buffer Enter. This command is like ispell-buffer; it spell-checks the entire buffer. Flyspell's interface is different; it underlines all the words it suspects are misspelled and gives you a pop-up menu of alternatives.

The best way to check out Flyspell mode is to turn it on and type some misspelled text to see it in action. No matter whether you enter Flyspell mode or run flyspell-buffer, you correct errors in the same way. We'll demonstrate flyspell-buffer on our misspelled odyssey file. Because it's an existing file (not a new file we're typing), we need to issue the flyspell-buffer command.

Word abbreviation mode and dynamic abbreviations are two features that lazy typists will love. The authors proudly include themselves in that category, so you'll be in good company if you choose to explore these features. Dynamic abbreviations are less complex, so we'll discuss them first.

Let's say that you are a scientist writing a paper on invertebrates. You're likely to have many long technical words in your paper, and if you're like us, you get tired of typing long words.

Dynamic abbreviations come to the rescue. After you've typed a long word once, you can simply type a few letters and give the command M-/ (for dabbrev-expand). Emacs inserts the nearest word that starts with that string.

��You search for a string you can see on the screen, and Emacs can't find it. The most probable explanation is that Emacs is taking into account line breaks and punctuation, and you're not including these in the search string. Use word search, which ignores any line breaks or punctuation, to find the string.

��You get a message that says, Searching for program: No such file or directory ispell. You don't have Ispell installed. Ispell is external to Emacs; see Chapter 13 for details on installing Ispell on Mac OS X and Windows.

��You can't see the pop-up menu in Flyspell. You activate this pop-up menu by pointing the mouse at a given word and pressing the middle mouse button. Essentially, you need a three-button mouse to run Flyspell.

Conceptually, Emacs is different from most applications in two important ways. First, its window terminology is different. Second, Emacs buffers are not tied to windows or frames, unlike most applications.

Let's get our terms straight first. GUI windows are not Emacs windows. Emacs calls GUI windows frames. In part, this terminology is necessary because Emacs predates GUIs and is still often used on terminals without GUI windows. Emacs windows are split screens. We've seen them already; for example, when you ask for keyboard help, you see it displayed in a *Help* buffer at the bottom of your screen. Figures Figure 4-1 and Figure 4-2 show Emacs frames and Emacs windows. In Figure 4-1, we see our dickens and odyssey buffers in two separate frames. Figure 4-2 shows a single frame displaying two Emacs windows, one on top of the other, showing these two files.

Figure�4-1.�Editing dickens and odyssey in Emacs frames

Figure�4-2.�Editing dickens and odyssey in Emacs windows

From now on, when we say frame, we mean a separate GUI window. When we say window, we mean a portion of the current Emacs display. And from a practical standpoint, we emphasize that this is not an either-or proposition. Even if you prefer multiple frames, you will still use Emacs-style windows sometimes. Emacs itself will see to that.

Now what about buffers? Essentially, both windows and frames are ways to display a buffer, which, as defined in Chapter 1, may contain a copy of a file or not. Buffers may contain files. They may be Emacs-generated buffers, like *Messages*, *scratch*, or *Help*. Or they may be buffers that you create but haven't written to a file.

Most GUI applications tie certain files to certain GUI windows or, in Emacspeak, frames. Emacs's detachment of buffers from their display (whether a split display or a separate frame) is more powerful and flexible. To be honest, most of the time we prefer using a single Emacs frame and switching between buffers using C-x b. It's much easier than mousing between frames or dealing with a split screen, though each has its advantages in some situations.

How do you know how many buffers are active in Emacs and what they are? There are three ways: the buffer list (which appears in a window when you type C-x C-b), the Buffers menu (which lists active buffers and commands for navigating them), and the Buffer pop-up menu (accessed by holding down Ctrl and clicking the left mouse button, which lists buffers by mode).

Emacs creates its own specialized buffers. The names for these internal buffers generally have the format *buffer name*. *Help*, *scratch*, and *Buffer List* are just a few of the buffers that Emacs creates.

When you start Emacs, it generates two buffers:

*Messages*

*scratch*

*Messages* is a buffer where Emacs accumulates messages from its startup and from the minibuffer. *scratch* is just what it sounds like: a temporary scratchpad where you can type. It won't be saved unless you explicitly write it to a file using C-x C-w.

Of course, typically you edit files with Emacs. These files are then copied into buffers of the same name. If you ask for help, you'll also have a *Help* buffer.

The number of buffers you can have really has no limit. Most of the time, only one or two buffers are displayed, but even if you can't see them, all the buffers you create in an Emacs session are still active. You can think of them as a stack of pages, with the one being displayed as the top page. At any time, you can turn to another page (another buffer), or you can create a new page.

Each buffer has an associated major mode that determines much about how Emacs behaves in that buffer. For example, text mode, designed for writing text, behaves differently from Lisp mode, which is designed for writing Lisp programs.

You can display multiple buffers in separate windows or frames or both. The important thing to remember is that all the buffers you create are active even if they are not currently displayed.

If you want to create a buffer that contains a file, simply type C-x C-f to find the file. Emacs automatically creates a second buffer and moves you there. If you already have a copy of the file in a buffer, C-x C-f just moves you to the existing buffer. This move is sensible and probably really what you want anyhow; if C-x C-f read the file from disk every time, you could end up with many versions of the same file that were each slightly different. If the filename you give C-x C-f doesn't exist, Emacs assumes you want to create a new file by that name and moves you to a blank buffer.

C-x C-f is always followed by a filename. The command for moving between buffers, C-x b, is followed by a buffer name. Did you realize that the mode line doesn't display filenames but only buffer names? Some versions of Emacs show both, but GNU Emacs shows only the buffer name. The buffer name and the filename, if any, are the same unless you change them (see the section "Renaming Buffers," later in this chapter).

To move between the buffers, type C-x b. Emacs shows you a default buffer name. Press Enter if that's the buffer you want, or type the first few characters of the correct buffer name and press Tab. Emacs fills in the rest of the name. Now press Enter to move to the buffer.

You can do the following with C-x b:

It's easy to create buffers, and just as easy to delete them when you want to. You may want to delete buffers if you feel your Emacs session is getting cluttered with too many buffers. Perhaps you started out working on a set of five buffers and now want to do something with another five. Getting rid of the first set of buffers makes it a bit easier to keep things straight. Deleting a buffer can also be a useful emergency escape. For example, some replacement operation may have had disastrous results. You can kill the buffer and choose not to save the changes, then read the file again.

Deleting a buffer doesn't delete the underlying file nor is it the same as not displaying a buffer. Buffers that are not displayed are still active whereas deleted buffers are no longer part of your Emacs session. Using the analogy of a stack of pages, deleting a buffer is like taking a page out of the current stack of buffers you are editing and filing it away.

Deleting buffers doesn't put you at risk of losing changes, either. If you've changed the buffer (and the buffer is associated with a file), Emacs asks if you want to save your changes before the buffer is deleted. You will lose changes to any buffers that aren't connected to files, but you probably don't care about these buffers.

Deleting a buffer is such a basic operation that it is on the Emacs toolbar, the X symbol. Now let's learn how to do it from the keyboard to increase your fluency in Emacs.

To delete a buffer, type C-x k (for kill-buffer). Emacs shows the name of the buffer currently displayed; press Enter to delete it or type another buffer name if the one being displayed is not the one you want to delete, then press Enter. If you've made changes that you haven't yet saved, Emacs displays the following message:

Buffer buffer name modified. Kill anyway? (yes or no).

To ditch your changes, type yes, and Emacs kills the buffer. To stop the buffer deletion process, type no. You can then type C-x C-s to save the buffer, followed by C-x k to kill it.

You can also have Emacs ask you about deleting each buffer, and you can decide whether to kill each one individually. Type M-x kill-some-buffers to weed out unneeded buffers this way. Emacs displays the name of each buffer and whether or not it was modified, then asks whether you want to kill it. Emacs offers to kill each and every buffer, including the buffers it creates automatically, like *scratch* and *Messages*. If you kill all the buffers in your session, Emacs creates a new *scratch* buffer; after all, something has to display on the screen!

Windows are areas on the screen in which Emacs displays the buffers that you are editing. You can have multiple windows on the screen at one time, each displaying a different buffer or different parts of the same buffer. Granted, the more windows you have, the smaller each one is; unlike GUI windows, Emacs windows can't overlap, so as you add more windows, the older ones shrink. The screen is like a pie; you can cut it into many pieces, but the more pieces you cut, the smaller they have to be. You can place windows side-by-side, one on top of the other, or mix them. Each window has its own mode line that identifies the buffer name, the modes you're running, and your position in the buffer. To make it clear where one window begins and another ends, mode lines are usually shaded.

As we've said, windows are not buffers. In fact, you can have more than one window on the same buffer. Doing so is often helpful if you want to look at different parts of a large file simultaneously. You can even have the same part of the buffer displayed in two windows, and any change you make in one window is reflected in the other.

The difference between buffers and windows becomes important when you think about marking, cutting, and pasting text. Marks are associated with buffers, not with windows, and each buffer can have only one mark. If you go to another window on the same buffer and set the mark, Emacs moves the mark to the new location, forgetting the place you set it last.

As for cursors, you have only one cursor, and the cursor's location determines the active window. However, although there is only one cursor at a time, each window does keep track of your current editing location separately�that is, you can move the cursor from one window to another, do some editing, jump back to the first window, and be in the same place. A window's notion of your current position (whether or not the cursor is in the window) is called the point. Each window has its own point. It's easy to use the terms point and cursor interchangeably�but we'll try to be specific.

You can create horizontal windows or vertical windows or both, but personally we place vertical windows with the more advanced esoterica near the end of the chapter. Here we'll discuss creating horizontal windows, finding a file in a new window, and deleting windows.

The most commonly used window command is C-x 2 (for split-window-vertically). This command splits the current window into two, horizontally oriented windows. You can repeat this command to split the screen into more horizontal windows.

To move from one window to another, type C-x o (o stands for other in this command). If you have more than two windows displayed, Emacs moves from one to the next. There's no way to specify which window to move to, so you may have to type C-x o a few times to get to the one you want if you have more than two windows displayed. (You can also click your mouse in a window if you're using the GUI version.)

Now that you can create windows and can move between them, what else can you do? Practically anything. With our two windows on dickens open, one on top of the other. Initially, both of these windows are looking at the same file.

Deleting a window only means that it isn't displayed anymore; it doesn't delete any of the information or any of your unsaved changes. The underlying buffer is still there, and you can switch to it using C-x b. To delete the window you're in, type C-x 0 (zero). If you want to delete all windows but the one you're working on, type C-x 1 (one), meaning "make this my one and only window." As you'd expect, the remaining window "grows" to fill up the rest of the space. You can also delete all windows on a certain buffer by typing: M-x delete-windows-on EnterbuffernameEnter.

By now you know that Emacs calls GUI windows "frames." In this section, we'll cover how to create frames, navigate between frames, and delete frames.

To open a new frame, type C-x 5 2 (for make-frame). Emacs makes a new frame containing the current buffer and puts it on top of the current frame.

If your new frame completely overlaps your current frame, you may need to size the new frame to tell them apart. For a more convenient solution, add these lines to your .emacs file:

(setq initial-frame-alist '((top . 10) (left . 30)

����������������������������(width . 90) (height . 50)))

(setq default-frame-alist '((width . 80) (height . 45)))

These lines set up sizes for the width and height of Emacs frames. The first frame is the size set in initial-frame-alist (in this example, 90 characters wide by 50 lines high with top and left defining an inset), and subsequent frames, specified by default-frame-alist, will be 80 characters wide and 45 lines high. Depending on your display, you can make these numbers smaller or larger.

Here we edit a bit of Henry James.

You can move between frames in several ways. You can use the mouse to select a frame or press C-x 5 o to go to another frame. To see a list of current frames, select Frames from the Buffers menu. (If you have only one frame, the Frames option does not appear on this menu.)

To get rid of a frame, press C-x 5 0. Emacs deletes the frame you are in. Deleting a frame, like deleting a window, affects only the display. The underlying buffer is still active, and you can move to it by typing C-x b.

If you try to use C-x 5 0 to delete the only frame that is left, Emacs won't do it. To exit Emacs, type C-x C-c or close the frame as you would any other GUI window using the mouse.

To minimize a frame, either minimize it in the usual way or press C-z. Table 4-1 summarizes the frame commands.

In this section, we'll learn about saving multiple buffers, renaming buffers, read-only buffers, and operations you can do with the buffer list�not only a useful tool but a good introduction to the principles you'll encounter in the directory editor, Dired, covered in Chapter 5.

You know about saving buffers individually by typing C-x C-s. Once you're using multiple buffers, you should also know that you can save them all at once by typing C-x s (for save-some-buffers). Emacs asks you if you want to save each buffer that is connected with a file (it doesn't offer to save new buffers you've created but have not associated with a file and, of course, it doesn't save its own internal buffers). For each buffer, you can answer y to save it or n not to. You can also type ! to save all the buffers without asking. If you want to save this buffer and no more, type a period (.). If you want to cancel the command and not save the current buffer, press q (of course, any buffers you saved before pressing q are already saved; q does not undo those). You may want to look at the buffer before deciding whether to save it; if so, type C-r. Emacs enters view mode, allowing you to look at the buffer but not make changes. Press q to exit view mode and continue saving buffers.

When you are editing a file, the buffer takes on the name of the file. If you have long filenames, you may find it convenient to rename buffers to shorter names (this renaming doesn't affect the filename, just the buffer name). This feature is mostly useful on versions of Emacs that don't offer good completion capabilities; in GNU Emacs, whenever you have to type a buffer name, you just type the first few unique letters and press Tab to have Emacs complete the name for you. In some circumstances, you may want to rename buffers.

To rename a buffer, type M-x rename-buffer. Emacs asks for the new name; type it and press Enter. The new name is displayed on the mode line. Renaming buffers comes in particularly handy in shell mode, described in Chapter 5. You start one command shell, and then rename the buffer and start another, in this way running as many shells as you have use for simultaneously.

As mentioned earlier, in GNU Emacs only the buffer name is displayed on the mode line, rather than the buffer name and the filename. Even if you rename a buffer that contains a file, Emacs remembers the connection between buffer and file, which you can see if you save the file (C-x C-s) or display the buffer list (described later in the chapter).

What if you have two buffers with the same name? Let's say you are editing a file called outline from your home directory and another file called outline from one of your subdirectories. Both buffers are called outline, but Emacs differentiates them by appending <2> to the name of the second buffer. (You can tell which is which by looking at the buffer list, discussed later in this chapter.) Emacs offers an option that adds a directory to buffers in this situation: select Use Directory in Buffer Names from the Options menu. Let's say you've turned on this option and are editing a file called .localized; Emacs will call this buffer simply .localized. Now you find a second file of the same name from a subdirectory. Instead of calling this buffer .localized<2>, Emacs names the buffer directory/.localized, making it easy for you to tell the buffers apart at a glance. This option has some limitations. It shows only the parent directory, not the full path, and it shows directory names only if multiple buffers have the same name. We wish it would go a bit further and provide the option of including the directory on the mode line for all buffers.

One word of advice: if you have a lot of buffers with names like proposal, proposal<2>, and proposal<3> around, you're probably forgetting to edit the directory when you ask for a file. If you try to find a file but get the directory wrong, Emacs assumes you want to start a new file. For example, let's say you want to edit the file ~/work/proposal, but instead ask for the file ~/novel/proposal. Since ~/novel/proposal doesn't exist, Emacs creates a new, empty buffer named proposal. If you correct your mistake (C-x C-f ~/work/proposal), Emacs renames your buffers accordingly: your empty buffer proposal is associated with ~/novel/proposal; the buffer you want is named proposal<2>.

Here's a hint for dealing with the very common mistake of finding the wrong file. If you notice that you've found the wrong file with C-x C-f, use C-x C-v to replace it with the one you want. C-x C-v finds a file, but instead of making a new buffer, it replaces the file in the current buffer. It means "get me the file I really meant to find instead of this one." Using this command circumvents the problem of having unnecessary numbered buffers (i.e., proposal, proposal<2>, and so on) lying around.

While you're working, you may need to read some file that you don't want to change: you just want to browse through it and look at its contents. Of course, it is easy to touch the keyboard accidentally and make spurious modifications. We've discussed several ways to restore the original file, but it would be better to prevent this from happening at all. How?

You can make any buffer read-only by pressing C-x C-q. Try this on a practice buffer and you'll notice that two percent signs (%%) appear on the left side of the mode line, in the same place where asterisks (**) appear if you've changed a buffer. The percent signs indicate that the buffer is read-only.[22] If you try to type in a read-only buffer, Emacs just beeps at you and displays an error message (Buffer is read-only) in the minibuffer. What happens when you change your mind and want to start editing the read-only buffer again? Just type C-x C-q again. This command toggles the buffer's read-only status�that is, typing C-x C-q repeatedly makes the buffer alternate between read-only and read-write.

Of course, toggling read-only status doesn't change the permissions on a file. If you are editing a buffer containing someone else's file, C-x C-q does not change the read-only status. One way to edit someone else's file is to make a copy of your own using the write-file command, and then make changes. Let's say you want to change a proposal that is owned by someone else. Read the file, write the file as one you own using C-x C-w, then change it from read-only to writable status by pressing C-x C-q. None of this, of course, modifies the original file; it just gives you a copy to work with. If you want to move a minor amount of text from a read-only file to another, you can mark the text then press M-w to copy it. Move to the place you want to put the text and press C-y to paste it.

You can open a file as read-only in a new window by typing C-x 4 r or in a new frame by typing C-x 5 r. This is one of a number of commands in which 4 means window and 5 means frame.

Because you can create an unlimited number of buffers in an Emacs session, you can have so many buffers going that you can't remember them all. At any point, you can get a list of your buffers (yes, we know you know how to do that by holding down Ctrl and clicking the left mouse button, but this is a little different). This list provides you with important information�for example, whether you've changed the buffer since you last saved it.

If you press C-x C-b, Emacs lists your buffers. It creates a new *Buffer List* window on the screen, which shows you all the buffers.

Type: C-x C-b

Emacs displays a list of buffers.

You can use this list as an informational display ("these are my buffers") or you can actually work with buffers from this list, as covered in the next section.

Figure 4-3 shows what each of the symbols in the buffer list means.

Figure�4-3.�Understanding the buffer list

The buffer list is more than a display. From the buffer list, you can display, delete, and save buffers. To move to the buffer list window, type C-x o. Emacs puts the cursor in the first column. For a particular buffer, press n or C-n to move down a line or p or C-p to move up a line. You can also press Space to move down to the next line and Del to move up. (The up and down arrow keys work, too.) This array of up and down choices may seem confusing, but multiple bindings are given to make it easy to move up and down without consulting a book like this one.

You use a set of one-character commands to work with the buffers that are listed. To delete a buffer, go to the line for the buffer you want to delete and type d or k. The letter D appears in the first column. You can mark as many buffers for deletion as you want to. The buffers aren't deleted immediately; when you're finished marking buffers, press x (which stands for "execute") to delete them. If any of the buffers you want to delete are connected with files, Emacs asks if you want to save the changes before doing anything. (Note that it does not ask you about buffers that aren't connected with files, so be sure to save any that you want before deleting them.)

If you change your mind about deleting a buffer before typing x, you can unmark the buffer by going to the appropriate line and typing u. As a convenience, the Del key also unmarks the previous buffer in the list. Why would you do this? Simple: d automatically moves you down one line. If you mark a file for deletion and immediately change your mind, you can press a single Del rather than moving to the previous line and typing u for unmark).

To save a buffer, go to the line for the buffer you want to save and press s. The letter S appears in the first column. Press x when you really want to save the buffer. Therefore, you can look at the buffer list, choose which buffers you want to delete and which you want to save, and then type x to do everything at once. Again, you can press u or Del to cancel saves if you change your mind.

One command that affects a buffer immediately when you type it is tilde (~). Typing ~ marks a buffer as unmodified. In effect, this symbol tells Emacs not to save changes automatically (since the buffer is unmodified, Emacs has no reason to save changes with its auto-save feature). Of course, if you have made changes, the changes are still in the buffer; it's just that you're in essence "lying" to Emacs to say that no changes have been made. Also, if you change the buffer again after marking it unmodified, Emacs once again knows it has been modified and saves it automatically in a backup file. The backup filename (not coincidentally) has the format filename~.

You can change a buffer's status from read-write to read-only and back again by pressing %. Pressing % changes the buffer's status immediately. Percentage signs appear on the mode line when a buffer is read-only. When you are editing, you can toggle a buffer between read-write and read-only by pressing C-x C-q, as we discussed earlier.

You can also use the buffer list to display multiple buffers in windows. To display one of the buffers in a full screen, move the cursor into the buffer list's window; use C-n and C-p to move to the line for the buffer that you want, and press 1 (the number one). Emacs displays the buffer in a full-screen window.

If you want to display one of the buffers in place of the buffer list, you can press f. To put a buffer in another window (i.e., one not occupied by the buffer list), type o. Emacs displays the buffer in the other window and puts the cursor there. Pressing C-o has a slightly different result; Emacs displays the buffer in another window but doesn't put the cursor there.

One final buffer display command remains. You can ask Emacs to display multiple buffers and have Emacs create windows for them dynamically. To select buffers to be displayed in windows, press m (for mark) next to the buffers you want. Emacs displays a > next to the buffers you mark with m. To tell Emacs to display the buffers you've marked, press v. Emacs makes horizontal windows to display the buffers you've chosen.

To get rid of the *Buffer List* window, type C-x 0 if you are in the buffer list window or C-x 1 (the number one) if you are in another window. Table 4-2 shows a summary of buffer manipulation commands.

Depending on your requirements, you may want to work with side-by-side windows in addition to or instead of horizontal windows. For finer control, you may want to know how to size windows (and because they're not GUI windows, you can't do that with the mouse).[23] You may also want to know how to compare files between windows, a good feature for basic file comparison.

To split the window vertically into two side-by-side windows, type C-x 3. You can execute this step repeatedly to create more side-by-side windows.

How do you move between windows? As we mentioned earlier, C-x o moves you to the "next" window. But how does Emacs determine what that is?

The best way to express it is to say that Emacs moves through the windows in natural reading order, from left to right, then down, and again from left to right. In Figure 4-4, buffer names are numbered to show you how Emacs moves from one window to the next.

Figure�4-4.�Moving between windows (Mac OS X)

Alternatively, you can simply select the window you want using the mouse.

Emacs always splits windows into two equal parts. Such a split is often good enough, but sometimes it's not, particularly if you become a window aficionado. When you have four or five or six windows on your screen at once, controlling each window's size becomes important. Otherwise, the windows you are most interested in will eventually become too small, and useful editing is almost impossible when you can see only five or six lines from a file. If you want to make the window you're working on taller, type C-x ^. Emacs lengthens the current window and makes the one below it smaller, accordingly. To make the current window wider, type C-x }. Emacs makes this window wider, at the expense of the one to the right of it.

To make windows smaller, you can shrink them. To shrink a window vertically, type M-x shrink-window. Emacs shrinks the current window by one line and the other windows on the screen grow accordingly. To shrink a window horizontally, type C-x {. This command makes the window one column narrower and enlarges the other windows on the screen horizontally.

Usually you want to work in larger increments than one line or one column at a time, however. When you type C-u preceding any of these commands, the command works in increments of four lines or columns at a time. For example, with two horizontal windows on the screen, let's use C-u C-x ^ to enlarge the james window.

Windows in Emacs can be as big as your screen. There's a limit to how small windows can be, however, and this limit is specified by the variables window-min-height (whose default is four lines) and window-min-width (whose default is ten characters). If you enlarge other windows to the point that their counterparts become less than ten characters wide or four lines high, Emacs deletes the smaller windows. You can set these variables to other values if you want to; more information on setting variables is found in Chapter 10.

Especially if you're looking for minute differences between large files, the compare-windows command comes in handy. To use compare-windows, you must first have the buffers you want to compare in two windows, either side by side or horizontally. Go to the beginning of each buffer, then type M-x compare-windows. Emacs scrolls each buffer to the place where the discrepancy is. It places the point in each buffer at the place of the discrepancy, so using C-x o to move the cursor between buffers will show you exactly where the files differ.[24]

Of course, this maneuver finds only the first difference between the two buffers. Finding the second, third, and so on, is a bit tricky. The compare-windows command works only if the point in both buffers is in exactly the same place. Therefore, you need to move past the discrepancy in both buffers before you can type M-x compare-windows again. The Unix diff command provides a more comprehensive (although somewhat awkward looking) way to find the differences between two files. Emacs also provides an interface to Ediff, with options on the Compare menu (a submenu of the Tools menu). Ediff is far more comprehensive; see Chapter 12 for details.

Table 4-4 summarizes the window commands discussed in this chapter.

Once you start working with multiple files, remembering just where you were in each one becomes harder. Bookmarks provide a convenient way of marking your place in a file, a place you can easily return to. You might, for example, be working with a file that has a long pathname. Rather than retype the pathname each time you start Emacs, you could just jump to a bookmark you've named current project by having Emacs find the file and put the cursor wherever you set the bookmark.

Bookmarks make the process of finding your place in any file easier. Particularly if you are working on a project several directories down from your home directory or in a totally different filesystem, putting bookmarks in the file makes it easy to get back there.

When you create a bookmark, Emacs creates a bookmark file in your home directory, called .emacs.bmk. It saves any new bookmarks in this file automatically when you exit Emacs.

Bookmarks are stored by user. If you and others access the same online documentation set, you can hold your place with your bookmark and they can hold their places with theirs, never interfering with each other's reading.

From the Edit menu, you can access the Bookmarks menu, which lists all the bookmark commands you'll probably ever need. We feel the menu interface for bookmarks is particularly well developed; even if you don't normally use menus, you might want to make an exception in this case. (At least until you learn the commands. Bookmarks are addictive, and when you use them frequently, the commands are easier to type than to reach by menu.)

To place a bookmark at the cursor position, type C-x r m (for bookmark-set). Emacs asks for a bookmark name, which can be virtually any length (practically speaking, as long as the width of your display) and can include spaces (so current project or Moore proposal's greatest flaw or Othello Act 2 Scene 4 would all be fine). Emacs also puts a default bookmark in parentheses, suggesting the filename if you haven't used a bookmark during this session (in which case it uses the bookmark name). Either press Enter to accept the default or type a bookmark name and then press Enter. You now have a bookmark you can jump to at any time, in any Emacs session.

One subtlety: if you give a new bookmark the same name as an old one, Emacs assumes you just want to move the bookmark, even if it was formerly in another file. So remember to make bookmark names unique unless you are really trying to move them.

To move to a bookmark, press C-x r b (for bookmark-jump). Type the bookmark's name, or type the first few letters and press Tab. Emacs either finishes the bookmark's name or gives you a window of possible choices. Press Enter after the bookmark's name appears. Emacs retrieves the file and places the cursor at the bookmark location; the file is retrieved no matter how complicated its path is.

With menus, there's an easier way to move to a bookmark. When you select Edit → Bookmarks→ Jump to Bookmark, Emacs displays a window of available bookmarks. Select the bookmark you want, and Emacs displays the file with the cursor in the bookmark's position. This is useful if you have set many bookmarks, but we prefer to stick with the keyboard as much as possible.

You may find that you made the name of your bookmark too generic; current project may be too vague if you are juggling projects and the one in your hand is the current one. To rename a bookmark, type M-x bookmark-rename. If you do the renaming from the keyboard, Emacs prompts Old bookmark name: and you type the old name and press Enter. (If you use the menus, you select the old name from a window instead.) Then Emacs asks, New name: and you type the new name and press Enter, all very straightforwardly. Renaming a bookmark does just that and nothing else: it doesn't change the bookmark's location or its contents; it simply changes its name.

To delete a bookmark, press M-x bookmark-delete. Type the name of the bookmark to delete or select it with the mouse. Deleting a bookmark doesn't in any way affect the file that was marked.

This discussion brings up an interesting question. What happens if you delete text in a file in which you've put a bookmark? Because a bookmark points to a position in a file and not to a piece of text, the bookmark stays in the same place after the text is deleted, just as the cursor remains in the same place after you delete several paragraphs. This fact is more intuitive than it sounds. You don't delete bookmarks by deleting marked text. Let's say you have a file with four lines. You bookmark the third line, then later delete lines two through four. When you jump to that bookmark again, it appears after the first line, the end of the file.

Inserting text works the same way. Bookmarks point to a position in a file, not to text. If you insert a new line before the third line, the bookmark remains at the point in the file where you set it, in this case, the beginning of the new line. If you move text around, the bookmark points to the same location in the file, the line and column where you set it.

What happens if you delete a file that has a bookmark in it? If you delete the whole file or even rename it and then try to access a bookmark attached to the file, Emacs gives you the following error message:

filename nonexistent. Relocate "bookmark name"? (y or n)

If you press y, you can give a new path to the file, which works well if you really just renamed or moved the file but didn't delete it. If you press n, however, Emacs gives you a message, along with some advice:

Bookmark not relocated, consider removing it

In other words, Emacs argues that no one needs bookmarks to nonexistent files, and we're inclined to agree.

Remember the buffer list we discussed earlier in this chapter? Bookmarks have a similar list with one-letter commands that allow you to work with all your bookmarks at once.

To work with a list of bookmarks, type C-x r l (the lowercase letter "L"). The *Bookmark List* buffer appears.

You can add annotations to your bookmarks. These annotations can provide any type of information you want: details about the file in question, what you are doing with it, documentation for someone else on your project to review when looking at your files, or really anything you want.

Annotations are most easily added from the bookmark list itself. Open the bookmark list using C-x r l, then move to the line of the bookmark you want to annotate. Type e, the command to edit an annotation.

In addition to those we've discussed, there are a few more esoteric bookmark commands. These include bookmark-insert, which inserts the text of the bookmarked file at the cursor position; bookmark-write, which prompts for a new filename in which to save bookmarks; and bookmark-load, to load these separate bookmark files. These commands are less useful than the others, but you may think of some clever uses we have not.

Table 4-6 summarizes bookmark commands.

One of the most important features of Emacs is its ability to run a command shell in a buffer. Once you have started a shell buffer, you can do all of your normal command-line work within Emacs. What does this buy you?

��You don't have to leave Emacs to get a command prompt. If you want to print or compile a file that you're editing, you can do it immediately.

��You can use Emacs editing features to write your commands.

��You can use Emacs editing features to "back up" through your command list, copy an old command, modify it, and execute it again.

��You can save your shell buffer, keeping a transcript of your editing session�which automatically includes the output from every command that you ran. For debugging or remembering commands you run infrequently, this can be invaluable.

��You can copy output from commands into a file or into another command.

��You can save complex commands in a file and insert the file at the prompt, rather than retyping the command.

As you get used to working within Emacs, you will undoubtedly discover more and more ways to put shell mode to use.

In this section, we discuss shell mode. Later in this chapter, we discuss directory editing, printing, and calendar and diary features for doing simple time management in Emacs. Right now, we'll start with a simple variation on shell mode, a feature that lets you execute commands one at a time.

To run a command while you're in an Emacs session, type M-!. Emacs asks for the command you want to run. Type the command and press Enter. Emacs then opens a window called *Shell Command Output* where it displays the results of your command.

Dired is one of the most interesting features of Emacs. With Dired, you can look at a listing of all the files in a directory, delete them, rename them, copy them, and perform almost all basic file operations. More important, Dired can make you more productive. For example, you can work with groups of files, deleting, moving, compressing, or even query-replacing strings in them.

There are several ways to start directory editing. If you're not in Emacs, invoke Emacs with a directory name as an argument, for example:

% emacs literature

Emacs starts up editing the directory literature: you'll see a single window that contains a listing of the literature directory. You can also start the directory editor by using C-x C-f (or any other command for visiting a file) and naming a directory, rather than a file. For example, typing C-x C-f literature gets you ready to edit the literature directory. Typing C-x d (for dired) or selecting the folder icon on the toolbar also starts Dired; you then specify a directory name. Finally, dragging a folder onto the Emacs window also starts Dired.[26]

No matter how you start the editor, the result is the same.

When you look at a directory listing, you may want to get a quick look at the files. Dired's v command does just this: put the cursor on the file you want to view and press v (for dired-view-file). Emacs displays the file in view mode.[27] This is a read-only mode, so you can't modify the file. Press C-c or q to return to the directory listing. While you're viewing the file, you can use s to start an incremental search, or press Enter to scroll the display down one line. Typing = tells you what line the cursor is on. There are a number of shortcuts for other Emacs commands (like marking text), but frankly, the regular commands work correctly. There's no reason to remember a special set of commands when the ones you already know work.

If you want to edit a file from the Dired buffer, move to the line the file is on and press Enter (a variety of other keystrokes work as well, such as f for find or e for edit). Emacs finds the file and you can edit it. This is a completely normal editing buffer: you can make any changes you want, save them, visit other files, and so on. Typing C-x b followed by the name of the directory you were working in moves you back to the Dired buffer. Or you can use the buffer menu (C-x C-b) to find and display the Dired buffer.

Viewing and editing files is nice, but you already know how to do that�right? You're waiting for the interesting stuff: how to delete files.

As we've said, file deletion is almost identical to buffer deletion with the buffer list. If you learned how to delete buffers, you know the basics of deleting files with Dired. First, you flag a file for deletion by moving to the file's name and typing d. Doing this places a D on the left margin and moves the cursor to the next file in the list. You can flag as many files as you want. You can change your mind at this point and type u to undelete the file. At some later time, you type x to delete the files (more on this in a minute). The following screen shows what the Dired buffer looks like when you flag a few files for deletion.

Compressing files saves disk space, and Dired provides an easy way to do it. Put the cursor on the line of the file you want to compress and press Z (for dired-do-compress). Emacs asks the following:

Compress or uncompress filename? (y or n)

Emacs compresses the file if it's not compressed and uncompresses it if it is.[28] Press y to compress or uncompress the current file. Compression happens immediately, so you can watch both the extension and file size change as Emacs compresses the file.

What about editing compressed files? Although it's not on by default, Emacs has an automatic compression/decompression mode called auto-compress mode. To enter it for this session, type M-x auto-compress-mode Enter, which turns automatic compression on. To enable auto-compression automatically, add this line to your .emacs file:

(auto-compression-mode�����������1)

In Chapter 4, we discussed comparing files in two windows. Emacs provides a way to do this using the diff command in Dired. Set the mark on the file you want diff to compare, put the cursor on the other file, then type =. Emacs compares the two files and opens a window with a *diff* buffer containing the output from the command.

Emacs has a separate option for comparing a file to its backup file. Put the cursor on the file you want to compare with its backup and type M-=. Emacs displays a *diff* buffer showing the differences between the two files.

If you are serious about version control, you may want to check out Chapter 12, which discusses version control as well as the GNU tool ediff.

While Dired's implementation of diff is useful (and there are implementations of chmod, grep, and find as well), in a more general sense, you can perform any command on a file by pressing an exclamation point (!). For example, let's alphabetize the phone list file using the sort command.

Often when you are cleaning up directories, you're moving files between them, organizing subdirectories, and the like. This naturally involves a lot of moving among directories.

To move to the parent directory of the one you're in, press ^. To move to the next directory in the buffer, press >; pressing <, not surprisingly, moves you to the previous directory in the buffer.

Sometimes it's more convenient to edit a directory and its subdirectories in the same buffer. To insert a subdirectory in the current Dired buffer, move to it and press i. Emacs inserts the subdirectory at the end of the buffer. If you insert more subdirectories in this fashion, they will appear in alphabetical order at the end of the buffer.

As you can see, much of your file maintenance and cleanup can be done easily from within Dired. Table 5-2 summarizes Dired commands, some of which we haven't fully discussed. There's more to learn about Dired,[29] but now that you know the basics, you can experiment on your own.

Emacs is a natural place to organize all your work. It won't replace your Palm or other handheld, but ongoing work in this area may help you sync your favorite device with your Emacs-based schedule. Here we cover the main features that Emacs itself offers�the calendar and the diary.

��In shell mode on Mac OS X, Emacs says, "Warning: no access to tty (Bad file descriptor). Thus no job control in this shell." This happens with the graphical version of Emacs, not with the version run from the Mac OS X Terminal application. If you change to a different shell using the instructions under "Which shell?" earlier in this chapter, the error goes away.

��Some commands don't work on Mac OS X. The graphical version of Mac OS X fails to find some operating system commands, especially when invoking them through M-! (for shell-command). Change to a different shell; see "Which shell?" earlier in this chapter for details. Another problem is that some Unix commands are not available by default on Mac OS X. Try them in the Mac Terminal application to see if they work at all before trying them in shell mode. To increase Mac OS X's Unix functionality, use Fink (http://fink.sourceforge.net) to download a wide variety of Unix commands and software for Mac OS X.

��Some commands don't work on Windows. This chapter describes many commands that have no Windows equivalent. The Windows port of Emacs works well for most Dired functions, the calendar, and the diary. To get Unix command functionality under Windows, install Cygwin (http://cygwin.com).

��Printing does not work from Windows on USB printers. Many USB printers do not support printing from the command line. This problem is not specific to Emacs.

So far, we've covered the basics of writing, executing, and saving keyboard macros. Now let's discuss a couple of more advanced features Emacs lets you add to your macros: pausing a macro for keyboard input and inserting a query in a macro.

Tabs provide an easy way to do some simple formatting. While we were revising this book, we found that the way Emacs handles tabs has changed a great deal. This section describes first how Emacs works by default and then discusses what you can do to change the default behavior to meet your needs.

If you open a new file in text mode, tabs are set every eight spaces by default. (Programming modes have their own indentation behavior; see Chapter 9 for details.)