Learning GNU Emacs, 3rd Edition

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:

Simple search

You give Emacs a search string, and it finds the next occurrence. You will find this search in almost any editor.

Incremental search

With incremental search, Emacs starts to search the file as soon as you type the first character of a search string. It continues to search as you type more characters.

Word search

A word search is like a simple search, except that Emacs searches only for full words and phrases. For example, if you are searching for the word hat, you don't have to worry about finding the word that. A word search is also useful when you need to find a phrase that is spread across two lines.

Regular expression search

To search for patterns, you can use a regular expression search. For example, if you wanted to find all instances of B1 and B2, you could search for them using the regular expression B[12]. However, regular expressions can be extremely complex. We'll give a brief introduction to this topic here; it is discussed more fully in Chapter 11.

Incremental regular expression search

This search procedure is a combination of an incremental search and a regular expression search.

You can search forward or backward. Searches can be either case-sensitive, meaning that Emacs considers upper- and lowercase letters to be different (i.e., the words This and this are different) or case-insensitive, in which upper- and lowercase are not differentiated (i.e., This and this are equivalent). By default, searches are case-insensitive, with upper- and lowercase letters considered to be the same. One exception: if you type any uppercase letters, Emacs makes the whole search string case-sensitive; it assumes you are looking for something precise since you've made the extra effort to type some letters in uppercase.

Replacement operations are closely related to searches. As with searches, Emacs offers you several different flavors:

Simple search and replace

In this procedure, Emacs replaces all occurrences of one string with another. Usually, this is too radical a solution and can have unintended results. Try query-replace instead.

Query-replace

With query-replace, Emacs conditionally replaces a string throughout a file. Emacs finds all occurrences of the search string, and for each one it asks you whether or not to perform the replacement. This type of replacement is useful if you need to change some, but not all, instances of a word or phrase throughout a file.

Regular expression replace

Regular expression replacement uses the powerful pattern matching facility of the same name to find strings and replace them.

So now you know what you'll be looking at. Don't be intimidated by the wealth of searches that are available. In practice, you'll probably settle on one search command and one replace command and use these for 99 percent of your work. For example, we use incremental search and query-replace most of the time. If you're a writer, you may use word search all the time; if you're a programmer, you might want a regular expression search. If you're just beginning, you may want to learn incremental search and read the rest of this chapter later. However, if you know what's available, you'll be able to make use of the other search commands when they become useful.

3.1.1 Incremental Search

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).

Type: C-s m

Emacs highlights all the words that start with m.

To start an incremental search, type C-s and then type the text you want to find. Emacs temporarily enters Isearch mode. Notice how this search works: Emacs looks for each character as soon as you type it. For example, if you are searching for the word meter, in an incremental search Emacs finds the next m as soon as you type the m; it finds the next me as soon as you type the e; it finds the met as soon as you type the t; and so on. Sooner or later, you either find what you want, or Emacs is unable to find anything. If you find what you want, press Enter; doing so stops the search at the current place in the file. If Emacs can't find anything that matches your search string, it prints the message

Search failed

Here's what happens when we search for the word meter; the numbers show how the cursor moves with each new letter in the search string.

Type: C-s meter

Emacs moves the cursor from one position to another as you type the letters of the search string.

In this incremental search, Emacs moves the cursor from position 1 to 2, to 3, and so on, as you type the search string meter. Also, note that

Isearch

What happens if you find the string you're looking for but not the right occurrence of the string? Let's say you're searching for the word eschatology and you find the word, but you're still not in the right place. Simply press C-s again to find the next occurrence of the current search string. Emacs uses the same search string; you don't have to retype it.

Remember to press Enter when you've found the text you want. Forgetting to stop the search (by pressing Enter or with any other cursor movement command) is a common mistake: you type a few things, and suddenly Emacs is off looking at some completely different part of the file. What has happened? Emacs thinks you're still searching, and it has just added the characters you've typed to the search string.

If you type a letter in your search string incorrectly, press Del: Emacs moves back to the first instance of the reduced string in the file. If you keep pressing Del to delete characters from the search string, you'll see Emacs cycle back through the file to previous matches.

To cancel a search (that is, to give up searching), type C-g. This command brings you back to the place where the search began.

To search backward through a file, use C-r, which works exactly like C-s except that it searches in the opposite direction. It puts the cursor at the beginning of the text you find. Just as you can do when repeating C-s, you can press C-r to make the search go in the other direction without retyping the search string.

To avoid typing your search string, you can copy text from the buffer into the search string. To copy text from the cursor position through the next space or punctuation mark into the search string, type C-s C-w (it may help to think of C-s C-w as "search a word"). To copy text from the cursor to the end of the line into the search string, type C-s C-y. Notice that the text that is yanked is always converted to lowercase; this conversion ensures that the search will be case-insensitive. You can also copy text from the kill ring to the search string by typing C-s M-y. After you've given this command, you can press M-p to see previous items from the kill ring. M-n takes you to the next item if you've gone back with M-p.

Once you're in an incremental search, certain keys (such as Enter and Del) have different functions than they normally do. This situation may sound confusing, but it's actually fairly easy to get used to. Table 3-1 shows a summary of key functions during incremental search.

Table 3-1. Incremental search commands

3.1.2 Simple Searches

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:

Search for string:

Table 3-2 summarizes the simple search commands.

Table 3-2. Simple search commands

searchstring

searchstring

3.1.3 Word Search

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

I-search

Search

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.

3.2.1 Simple Search and Replace Operations

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.

Initial state:

Whirligig appears four times, but the cursor is positioned after the first instance.

Now we'll do the replacement.

Type: M-x replace-string Enter Whirligig Enter HealthBug Enter

Emacs replaces all instances from the cursor position onward.

The replacement occurs only from the cursor position onward; Whirligig in the first sentence is still incorrect. We'll work with this example again in a moment.

3.2.2 Query-Replace

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:

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.

Table 3-3. Responses during query-replace

searchstring

newstring

This list seems like a lot of keystrokes to remember, but you can get away with knowing two or three. Most of the time you'll respond to the prompt by pressing Space, telling Emacs to perform the replacement and go on to the next instance, or n to skip this replacement and go on to the next instance. If you're not too sure what will happen, enter a comma (,); Emacs makes the replacement but doesn't go on until you press Space. After performing the first few replaces, you may realize that there's no need to inspect every change individually. Typing an exclamation mark (!) tells Emacs to go ahead and finish the job without bothering you anymore. If you remember these keystrokes, you're all set.

How does this work in practice? Let's revisit our previous example, assuming that we want to change Whirligig to HealthBug throughout (and that we didn't save the changes we made with replace-string).

Type: M-< M-% Whirligig Enter HealthBug Enter

You're ready to replace the first occurrence; press Space to go on.

Press: Space

When you press Space, Emacs replaces the first word; the query-replace operation then moves to the second word.

This procedure continues until you reach the end of the file. As we've said, typing ! fixes the rest of the file.

In Table 3-3, you might have noticed that several keys, such as Space, have specialized meanings while the replacement is in progress. In practice, using these keys for a different function is not confusing, though it might sound bad on paper. You might want to try a query-replace on a practice file to get the hang of using the different responses. If you are easily amused, you might enjoy opening the Emacs FAQ, saving it as another file, then replacing Emacs throughout.

3.2.3 Repeating Query-Replaces (and Other Complex Commands)

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.

Type: M-< followed by C-x Esc Esc

Emacs puts the last complex command in the minibuffer; in fact it looks more complex than we remember it.

When we press M-<, we move to the beginning of the file; when we press C-x Esc Esc, the last complex command is displayed. Emacs speaks to itself in dark words, but we can still see that this is the command that we want.

This is the right command, so we don't have to press M-p to see a previous command. If we wanted to, we could change the query-replace strings before pressing Enter. In this case, the Marketing Department has once again changed the product's name from HealthBug (since bug could be construed as pest) to HealthBot (neutral, but a bit less descriptive in our opinion). Our earlier query replace changed Whirligig to HealthBug. We need to modify this command so it replaces Bug with Bot.

In the minibuffer, change Whirligig to Bug and HealthBug to Bot and press Enter.

Pressing Enter executes the command again with the modified search and replacement strings.

As we mentioned, C-x Esc Esc works for any command involving input in the minibuffer, not just query-replace. But we use this feature most frequently in query-replace. It is also good for repeating keyboard macros (see Chapter 6).

3.2.4 Recursive Editing

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 (

[ ]

Type: C-r

Notice the square brackets around

(Text Fill)

Now do any editing you want to; you are in an editing mode just like standard Emacs. Move down to the third line and delete "64 ounces of." When you want to resume the query-replace, press C-M-c. This command tells Emacs to leave the recursive edit and reactivate the query-replace. Emacs moves back to the point where you were when you started the recursive edit. You can then continue making replacements just as if nothing had happened.

Delete "64 ounces of," then type C-M-c

Emacs goes back to query-replace and you press Space to fix the next Bug.

If you decide to exit the recursive edit and cancel the query-replace in one fell swoop, you can type C-] (for abort-recursive-edit) or M-x top-level Enter rather than C-M-c.

In fact, you can start a recursive edit at any time, not just when you're in a query-replace. The command M-x recursive-edit Enter puts you into a recursive edit; C-M-c takes you out of the recursive edit and brings you back to what you were doing before. You can even have recursive edits within recursive edits, although the possibility for confusion increases with each new level.

3.2.5 Are Emacs Searches Case-Sensitive?

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).

3.2.6 Regular Expressions for Search and Replacement Operations

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.

Table 3-4. Characters for creating regular expressions

If you do a regular expression search for ^word$, you would find instances of word on a line by itself. The ^ says that the w must be the first character on the line, the $ says that the d must be the last character.

If you wanted to find all words starting with beg and ending with the letter s, you could use beg[a-z]*s as your regular expression. This would find the words begins, begets, and begonias, in addition to really odd words like shibegrees and altbegaslia. If you don't want these mutants—that is, if you really want words that begin with beg and end with s, use \. The \< is a special sequence that matches the beginning of a word; \> matches the end of a word. If you wanted to find the words beg, big, and bag; but not begonias, and certainly not any strange words with beg on the inside, you would use \ as the regular expression.

To search for a ^, $, ., *, [, ], or any number of other special characters, you obviously can't use the character itself. Put a backslash (\) first—i.e., to search for a period, search for \. For example, to search for the electronic mail address`:

howie@mcds.com

the regular expression would be:

howie@mcds\.com

This is a barebones introduction to regular expressions; see Chapter 11 for more details and Mastering Regular Expressions by Jeffrey Friedl (O'Reilly) for a book-length treatment of this topic.

You can use regular expressions in incremental searches and in query-replace. Table 3-5 lists the commands you use for regular expression searches. Although they are initiated with slightly different commands, the searches are the same as those described earlier in this chapter.

Table 3-5. Regular expression search commands

Emacs includes two spell-checking interfaces: to the Unix spell checker,

spell

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.

3.3.1 Checking a Buffer

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

Type: Esc x ispell-buffer Enter

Ispell finds the first unrecognized word in the buffer.

Ispell moves to the first unrecognized word, in this case a proper name correctly spelled (except for the proper accent marks). At the top of the screen, Ispell opens a small window that displays alternative spellings, numbered starting with 0. The minibuffer says

C-h or ? for more options, SPC to leave unchanged, character to replace word

Press i:

Ispell moves to the next unrecognized word, another proper name.

We insert a few more proper names and move along to the first real misspelling, pwers.

Ispell finds pwers misspelled.

Ispell opens a window at the top of the screen listing choices for a replacement. Usually one of its top few choices is correct.

To select powers, press: 1

Ispell replaces the word and goes on to the next misspelling.

If one of the words that Ispell lists at the top of the screen is correct, you type the number, and Ispell makes the replacement. To replace a word yourself, press r. After you type the corrected word, Ispell replaces it. If you press R instead, Ispell starts a query-replace through which you can correct all cases of the misspelling in this buffer.

Instead of replacing the word, you may simply want Ispell to skip over it. To skip this occurrence of a misspelled word, press Space. To ignore a misspelled word for the rest of the session for all buffers, press a (for accept). Uppercase A has one subtle difference: it tells Ispell to accept the word for this session but only in this buffer.

If you can see that something more complicated is wrong, you can start a recursive edit by typing C-r. Fix the error and type C-M-c to exit the recursive edit and resume Ispell. (You may recall that we discussed recursive editing earlier in this chapter.)

Our passage repeatedly spells would incorrectly and typing the character beside the correct word only replaces a single incidence, so a better choice would be to type R to query-replace the word throughout the buffer.

Type: R

Ispell asks for the correction for wuld.

Change wuld to would and press Enter.

Ispell starts a query-replace.

We want to replace all occurrences of the misspelled word, so we'll type !, which, as you might recall, means "replace them all without asking."

Type ! then y when prompted about saving your personal dictionary.

Emacs moves to the "next" misspelling, crse.

Ispell replaces the words, then goes on to the next misspelling, crse. Note that this misspelling occurs before the second incorrect wuld. Because we already query-replaced wuld with would, Ispell had to move backward to find the next misspelling.

Remember that Ispell, like all spellcheckers, corrects only true misspellings. If a misspelling forms another word, Ispell will leave it alone. It's up to you to change fries to fires in this passage.

Different forms of the same word must be corrected separately. For example, if you misspell receive, receives, and receiving by reversing the i and the e, you must change each misspelled word.

3.3.2 Checking a Single Word

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

3.3.3 Completing a Word

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.

Type: occur M-Tab

Ispell choices appear at the top of the screen.

To select occurrence, type: 2

Ispell completes the word for you.

This feature varies in its helpfulness. In this case the replacement needed was shown. It won't always work that way, but you can always simply spell it wrong and then use ispell-buffer to fix it.

3.3.4 Spellchecking on the Fly with Flyspell

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

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.

Type: Esc x flyspell-buffer Enter

Flyspell highlights misspelled words (Mac OS X).

Flyspell highlights misspelled words in red. Words that are repeatedly misspelled are highlighted in yellow. Note that it doesn't highlight the proper names we inserted in the dictionary earlier using Ispell; Flyspell checks to see whether words are in your personal dictionary before highlighting them as errors.

You move to a misspelled word and press the middle mouse button to display a pop-up menu of possible replacements. (This implies that you have a three-button mouse, and, to be honest, you need one to make Flyspell work properly.) You select a replacement using the mouse.

Move the cursor to crse and press the middle mouse button.

Flyspell displays a pop-up window of alternatives; you choose one with the mouse (Mac OS X).

Choose curse with the mouse.

Emacs inserts the correct replacement (Mac OS X).

Ispell inserts new words in the dictionary. Flyspell takes it a step further, creating word abbreviations for words that you misspell. In essence, a word abbreviation tells Emacs, in this case, that wrd is just an abbreviation for word, and that therefore Emacs should replace it automatically. If you turn on word abbreviation mode, described in the next section, chronic misspellings that Flyspell encounters will be automatically corrected.

How can you tell Flyspell is using word abbreviations? When you exit a session in which you've used Flyspell, you see a prompt that says,

Save abbrevs in ~/.abbrev_defs (y or n)

What do you do if you encounter a word that's spelled correctly but that Flyspell doesn't recognize? You could insert it in your Ispell dictionary if it's a word you use frequently. The Save word option on the Flyspell pop-up menu handles this. For a temporary fix, the options Accept buffer and Accept session tell Flyspell to accept a word for the current buffer or for all buffers in the current Emacs session automatically. Of course, if it's a word you use frequently, you may want to insert it in the Ispell dictionary to keep Flyspell from flagging it each time.

To enter flyspell mode automatically, add this line to your .emacs file:

(setq-default flyspell-mode t)

Table 3-6 summarizes the Ispell and Flyspell commands.

Table 3-6. Spell-checking commands

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.

3.4.1 Dynamic Abbreviations

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.

Type: In M-/

Emacs inserts the last word starting with in, in this case, interesting.

Interesting was not the word we were hoping for; it's invertebrates we wanted. Without moving the cursor, type M-/ again.

Type: M-/

Emacs inserts the word Invertebrates, which is what we wanted.

The word being expanded need not be earlier in the file to be considered nearest. Emacs looks behind and ahead of the cursor position to find words it can expand. If there are eligible words that are equidistant above and below the cursor position both, Emacs selects the word that is above as the expansion.

Earlier we talked about completing a word with Ispell. Dynamic abbreviations are a bit different. When you complete a word, the word probably isn't in the buffer (yet). When you use a dynamic abbreviation, you simply don't want to type a word you typed earlier and you're asking Emacs to do it for you.

Using dynamic abbreviations doesn't require entering a special minor mode, as standard word abbreviations do. They are simply an aid for the tired typist. Word abbreviation mode has some other advantages, though, such as the ability to create an abbreviation for a phrase or a habitual typo, as we will see next.

3.4.2 Word Abbreviation Mode

Abbrev

(setq-default abbrev-mode t)

(read-abbrev-file "~/.abbrev_defs")

(setq save-abbrevs t)

Abbrev

(text-mode-abbrev-table)

(lisp-mode-abbrev-table)

(fundamental-mode-abbrev-table)

(global-abbrev-table)

"iwthout" 1    "without"

"prhase" 1    "phrase"

"teh"   1    "the"

"fo"   1    "of"

"eamcs"  2    "Emacs"

"wrok"  1    "work"

"aslo"  1    "also"

"sotred" 1    "stored"

"inforamtion" 1  "information"

"esc"   6    "Esc"

"taht"  1    "that"

"chatper" 1    "chapter"

"adn"   1    "and"

"iwth"  1    "with"

"chpater" 1    "chapter"

"loaction" 1    "location"

"recieve" 1    "receive"

"wart"  1    "World Association for Replicant Technology"

3.4.3 Problems You May Encounter

• 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 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.