emacs-mode uses control keys for the most basic editing functions. If you aren’t familiar with emacs, you can think of these as extensions of the rudimentary “erase” character (usually BACKSPACE or DEL) that UNIX provides through its interface to users’ terminals. For the sake of consistency, we’ll assume your erase character is DEL from now on; if it is CTRL-H or something else, you will need to make a mental substitution. The most basic control-key commands are shown in Table 2-1. (Important: remember that typing CTRL-D when your command line is empty may log you off!) The basic keyboard habits of emacs-mode are easy to learn, but they do require that you assimilate a couple of concepts that are peculiar to the emacs editor.

The first of these is the use of CTRL-B and CTRL-F for backward and forward cursor motion. These keys have the advantage of being obvious mnemonics. You can also use the left and right cursor motion keys (“arrow” keys), but for the rest of this discussion we will use the control keys, as they work on all keyboards. In emacs-mode, the point (sometimes also called dot) is an imaginary place just to the left of the character the cursor is on. In the command descriptions in Table 2-1, some say “forward” while others say “backward.” Think of forward as “to the right of point” and backward as “to the left of point.”

For example, let’s say you type in a line and, instead of typing RETURN, you type CTRL-B and hold it down so that it repeats. The cursor will move to the left until it is over the first character on the line, like this:

$ [f]grep -l Duchess < ~cam/book/alice_in_wonderland

Now the cursor is on the f, and point is at the beginning of the line, just before the f. If you type DEL, nothing will happen because there are no characters to the left of point. However, if you press CTRL-D (the “delete character forward” command) you will delete the first letter:

$ [g]rep -l Duchess < ~cam/book/alice_in_wonderland

Point is still at the beginning of the line. If this were the desired command, you could hit RETURN now and run it; you don’t need to move the cursor back to the end of the line. However, you could type CTRL-F repeatedly to get there:

$ grep -l Duchess < ~cam/book/alice_in_wonderland[]

At this point, typing CTRL-D wouldn’t do anything, but hitting DEL would erase the final d.

The basic commands are really all you need to get around a command line, but a set of more advanced commands lets you do it with fewer keystrokes. These commands operate on words rather than single characters; emacs-mode defines a word as a sequence of one or more alphanumeric characters.

The word commands are shown in Table 2-2. The basic commands are all single characters, whereas these consist of two keystrokes, ESC followed by a letter. You will notice that the command ESC X, where X is any letter, often does for a word what CTRL-X does for a single character. “Kill” is another word for “delete”; it is the standard term used in the readline library documentation for an “undoable” deletion.

To return to our example: if we type ESC-B, point will move back a word. Since the underscore (_) is not an alphanumeric character, emacs-mode will stop there:

$ grep -l Duchess < ~cam/book/alice_in_[w]onderland

The cursor is on the w in wonderland, and point is between the _ and the w. Now let’s say we want to change the -l option of this command from Duchess to Cheshire. We need to move back on the command line, so we type ESC-B four more times. This gets us here:

$ grep -l Duchess < ~[c]am/book/alice_in_wonderland

If we type ESC-B again, we end up at the beginning of Duchess:

$ grep -l [D]uchess < ~cam/book/alice_in_wonderland

Why? Remember that a word is defined as a sequence of alphanumeric characters only. Therefore < is not a word; the next word in the backward direction is Duchess. We are now in position to delete Duchess, so we type ESC-D and get:

$ grep -l []< ~cam/book/alice_in_wonderland

Now we can type in the desired argument:

$ grep -l Cheshire[]< ~cam/book/alice_in_wonderland

If you want Duchess back again you can use the CTRL-Y command. The CTRL-Y “yank” command will undelete a word if the word was the last thing deleted. In this case, CTRL-Y would insert Duchess at the point.

There are still more efficient ways of moving around a command line in emacs-mode. A few commands deal with the entire line; they are shown in Table 2-3.

Using CTRL-A, CTRL-E, and CTRL-K should be straightforward. Remember that CTRL-Y will always undelete the last thing deleted; if you use CTRL-K, that could be quite a few characters.

Now we know how to get around the command line efficiently and make changes. But that doesn’t address the original issue of recalling previous commands by accessing the history list. emacs-mode has several commands for doing this, summarized in Table 2-4.

CTRL-P and CTRL-N move you through the command history. If you have cursor motion keys (arrow keys) you can use them instead. The up-arrow is the same as CTRL-P and the down-arrow is the same as CTRL-N. For the rest of this discussion, we’ll stick to using the control keys because they can be used on all keyboards.

CTRL-P is by far the one you will use most often—it’s the “I made a mistake, let me go back and fix it” key. You can use it as many times as you wish to scroll back through the history list. If you want to get back to the last command you entered, you can hold down CTRL-N until bash beeps at you, or just type ESC->. As an example, you hit RETURN to run the command above, but you get an error message telling you that your option letter was incorrect. You want to change it without retyping the whole thing.

First, you would type CTRL-P to recall the bad command. You get it back with point at the end:

$ grep -l Duchess < ~cam/book/alice_in_wonderland[]

After CTRL-A, ESC-F, two CTRL-Fs, and CTRL-D, you have:

$ grep -[]Duchess < ~cam/book/alice_in_wonderland

You decide to try -s instead of -l, so you type s and hit RETURN. You get the same error message, so you give up and look it up in the manual. You find out that the command you want is fgrep—not grep—after all.

You sigh heavily and go back and find the fgrep command you typed in an hour ago. To do this, you type CTRL-R; whatever was on the line will disappear and be replaced by (reverse-i-search)`':. Then type fgrep, and you will see this:

$ (reverse-i-search)`fgrep': fgrep -l Duchess <~cam/book/ 
   alice_in_wonderland[]

The shell dynamically searches back through the command history each time you type a letter, looking for the current substring in the previous commands. In this example, when you typed f the shell would have printed the most recent command in the history with that letter in it. As you typed more letters, the shell narrowed the search until you ended up with the line displayed above. Of course, this may not have been the particular line you wanted. Typing CTRL-R again makes the shell search further back in the history list for a line with “fgrep” in it. If the shell doesn’t find the substring again, it will beep.

If you try the fgrep command by hitting RETURN, two things will happen. First, of course, the command will run. Second, this line will be entered into the history list at the end, and your “current line” will be at the end as well. You will no longer be somewhere else in the command history.

Another handy trick to save typing if you have already done a search is to type CTRL-R twice in a row. This recalls the previous search string you typed in.^[3]

CTRL-P, CTRL-N, and CTRL-R are clearly the most important emacs-mode commands that deal with the command history. The others are less useful but are included for compatibility with the full emacs editor.

One of the most powerful (and typically underused) features of emacs-mode is its textual completion facility, inspired by similar features in the full emacs editor, the C shell, and (originally) the old DEC TOPS-20 operating system.

The premise behind textual completion is simple: you should have to type only as much of a filename, user name, function, etc., to identify it unambiguously. This is an excellent feature; there is an analogous one in vi-mode. We recommend that you take the time to learn it, since it will save you quite a bit of typing.

There are three commands in emacs-mode that relate to textual completion. The most important is TAB.^[4] When you type in a word of text followed by TAB, bash will attempt to complete the name. Then one of four things can happen:

For example, assume you have a directory with the files tweedledee.c and tweedledum.c. You want to compile the first of these by typing cc tweedledee.c. You type cc twee followed by TAB. This is not an unambiguous prefix, since the prefix “twee” is common to both filenames, so the shell only completes out to cc tweedled. You need to type more letters to distinguish between them, so you type e and hit TAB again. Then the shell completes out to "cc tweedledee.c“, leaving the extra space for you to type in other filenames or options.

If you didn’t know what options were available after trying to complete cc twee, you could press TAB again. bash prints out the possible completions for you and presents your input line again:

$ cc tweedled
tweedledee.c  tweedledum.c
$ cc tweedled

A related command is ESC-?, which expands the prefix to all possible choices, listing them to standard output. Be aware that the completion mechanism doesn’t necessarily expand to a filename. If there are functions and commands that satisfy the string you provide, the shell expands those first and ignores any files in the current directory. As we’ll see, you can force completion to a particular type.

It is also possible to complete other environment entities. If the text being completed is preceded by a dollar sign ($), the shell attempts to expand the name to that of a shell variable (see Chapter 3, for a discussion of shell variables). If the text is preceded by a tilde (~), completion to a username is attempted; if preceded by an at sign (@), a hostname is attempted.

For example, suppose there was a username cameron on the system. If you wanted to change to this user’s home directory, you could just use tilde notation and type the first few letters of the name, followed by a TAB:

$ cd ~ca

which would expand to:

$ cd ~cameron/

You can force the shell to complete to specific things. Table 2-5 lists the standard keys for these.

If you find that you are interested only in completing long filenames, you are probably better off using ESC-/ rather than TAB. This ensures that the result will be a filename and not a function or command name.

Several miscellaneous commands complete emacs editing mode; they are shown in Table 2-6.

BSD-derived systems use CTRL-V and CTRL-W as default settings for the “quote next character” and “word erase” terminal interface functions, respectively.

A few of these miscellaneous commands are worth discussing, even though they may not be among the most useful emacs-mode commands.

CTRL-O is useful for repeating a sequence of commands you have already entered. Just go back to the first command in the sequence and press CTRL-O instead of RETURN. This will execute the command and bring up the next command in the history list. Press CTRL-O again to enter this command and bring up the next one. Repeat this until you see the last command in the sequence; then just hit RETURN.

Of the case-changing commands, ESC-L is useful when you hit the CAPS LOCK key by accident and don’t notice it immediately. Since all-caps words aren’t used too often in the UNIX world, you probably won’t use ESC-U very often.

CTRL-V will cause the next character you type to appear in the command line as is; i.e., if it is an editing command (or an otherwise special character like CTRL-D), it will be stripped of its special meaning.

If it seems like there are too many synonyms for RETURN, bear in mind that CTRL-M is actually the same (ASCII) character as RETURN, and that CTRL-J is actually the same as LINEFEED, which UNIX usually accepts in lieu of RETURN anyway.

ESC-. and ESC-_ are useful if you want to run several commands on a given file. The usual UNIX convention is that a filename is the last argument to a command. Therefore you can save typing by just entering each command followed by SPACE and then typing ESC-. or ESC-_. For example, say you want to examine a file using more, so you type:

$ more myfilewithaverylongname

Then you decide you want to print it, so you type the print command lp. You can avoid typing the very long name by typing lp followed by a space and then ESC-. or ESC-_; bash will insert myfilewithaverylongname for you.

A full range of vi editing commands are available to you in control mode. The simplest of these move you around the command line and are summarized in Table 2-8. vi-mode contains two “word” concepts. The simplest is any sequence of non-blank characters; we’ll call this a non-blank word. The other is any sequence of only alphanumeric characters (letters and digits) plus the underscore (_), or any sequence of only non-alphanumeric characters; we’ll just call this a word.^[6]

All of these commands except the last three can be preceded by a number that acts as a repeat count. Whenever you type a number for the repeat count, the number replaces the command prompt for the duration of the repeat command. If your keyboard has cursor motion keys (“arrow” keys), you can use the left and right arrows to move between characters instead of the h and l keys. Repeat counts will work with the cursor keys as well.

The last two will be familiar to users of UNIX utilities (such as grep) that use regular expressions, as well as to vi users.

Time for a few examples. Let’s say you type in this line and, before you hit RETURN, decide you want to change it:

$ fgrep -l Duchess < ~cam/book/alice_in_wonderland[]

As shown, your cursor is beyond the last character of the line. First, type ESC to enter control mode; your cursor will move back one space so that it is on the d. Then if you type h, your cursor will move back to the n. If you type 3h from the n, you will end up at the r.

Now we will see the difference between the two “word” concepts. Go back to the end of the line by typing $. If you type b, the word in question is alice_in_wonderland, and the cursor will end up on the a:

$ fgrep -l Duchess < ~cam/book/[a]lice_in_wonderland

If you type b again, the next word is the slash (it’s a “sequence” of non-alphanumeric characters), so the cursor ends up over it:

$ fgrep -l Duchess < ~cam/book[/]alice_in_wonderland

However, if you typed B instead of b, the non-blank word would be the entire pathname, and the cursor would end up at the beginning of it—over the tilde:

$ fgrep -l Duchess < [~]cam/book/alice_in_wonderland

You would have had to type b four times—or just 4b—to get the same effect, since there are four “words” in the part of the pathname to the left of /alice_in_wonderland: book, slash, cam, and the leading tilde.

At this point, w and W do the opposite: typing w gets you over the c, since the tilde is a “word,” while typing W brings you to the end of the line. But whereas w and W take you to the beginning of the next word, e and E take you to the end of the current word. Thus, if you type w with the cursor on the tilde, you get to:

$ fgrep -l Duchess < ~[c]am/book/alice_in_wonderland

Then typing e gets you to:

$ fgrep -l Duchess < ~ca[m]/book/alice_in_wonderland

And typing an additional w gets you to:

$ fgrep -l Duchess < ~cam[/]book/alice_in_wonderland

On the other hand, E gets you to the end of the current non-blank word—in this case, the end of the line. (If you find these commands non-mnemonic, you’re right. The only way to assimilate them is through lots of practice.)

Now that you know how to enter control mode and move around on the command line, you need to know how to get back into input mode so you can make changes and type in additional commands. A number of commands take you from control mode into input mode; they are listed in Table 2-9. All of them enter input mode a bit differently.

Most likely, you will use either i or a consistently, and you may use R occasionally. I and A are abbreviations for 0i and $a respectively. To illustrate the difference between i, a, and R, say we start out with our example line:

$ fgrep -l Duchess < ~cam/book[/]alice_in_wonderland

If you type i followed by end, you will get:

$ fgrep -l Duchess < ~cam/bookend[/]alice_in_wonderland

That is, the cursor will always appear to be under the / before alice_in_wonderland. But if you type a instead of i, you will notice the cursor move one space to the right. Then if you type miss_, you will get:

$ fgrep -l Duchess < ~cam/book/miss_[a]lice_in_wonderland

That is, the cursor will always be just after the last character you typed, until you type ESC to end your input. Finally, if you go back to the first a in alice_in_wonderland, type R instead, and then type through_the_looking_glass, you will see:

$ fgrep -l Duchess < ~cam/book/through_the_looking_glas[s]

In other words, you will be replacing (hence R) instead of inserting text.

Why capital R instead of lowercase r? The latter is a slightly different command, which replaces only one character and does not enter input mode. With r, the next single character overwrites the character under the cursor. So if we start with the original command line and type r followed by a semicolon, we get:

$ fgrep -l Duchess < ~cam/book[;]alice_in_wonderland

If you precede r with a number N, it will allow you to replace the next N existing characters on the line—but still not enter input mode. Lowercase r is effective for fixing erroneous option letters, I/O redirection characters, punctuation, and so on.

Now that you know how to enter commands and move around the line, you need to know how to delete. The basic deletion command in vi-mode is d followed by one other letter. This letter determines what the unit and direction of deletion is, and it corresponds to a motion command, as listed previously in Table 2-8.

Table 2-10 shows some commonly used examples.

These commands have a few variations and abbreviations. If you use a c instead of d, you will enter input mode after it does the deletion. You can supply a numeric repeat count either before or after the d (or c). Table 2-11 lists the available abbreviations.

Most people tend to use D to delete to end of line, dd to delete an entire line, and x (as “backspace”) to delete single characters. If you aren’t a hardcore vi user, you may find it difficult to make sure the more esoteric deletion commands are at your fingertips.

Every good editor provides “un-delete” commands as well as delete commands, and vi-mode is no exception. vi-mode maintains a delete buffer that stores all of the modifications to text on the current line only (note that this is different from the full vi editor). The command u undoes previous text modifications. If you type u, it will undo the last change. Typing it again will undo the change before that. When there are no more undo’s, bash will beep. A related command is . (dot), which repeats the last text modification command.

There is also a way to save text in the delete buffer without having to delete it in the first place: just type in a delete command but use y (“yank”) instead of d. This does not modify anything, but it allows you to retrieve the yanked text as many times as you like later on. The commands to retrieve yanked text are p, which inserts the text on the current line to the right of the cursor, and P, which inserts it to the left of the cursor. The y, p, and P commands are powerful but far better suited to “real vi" tasks like making global changes to documents or programs than to shell commands, so we doubt you’ll use them very often.

The next group of vi control mode commands we cover allows you to move around in and search your command history. This is the all-important functionality that lets you go back and fix an erroneous command without retyping the entire line. These commands are summarized in Table 2-12.

The first two can also be accomplished with the up and down cursor movement keys if your keyboard has them. The first three can be preceded by repeat counts (e.g., 3k or 3- moves back three lines in the command history).

If you aren’t familiar with vi and its cultural history, you may be wondering at the wisdom of choosing such seemingly poor mnemonics as h, j, k, and l for backward character, forward line, backward line, and forward character, respectively. Well, there actually is a rationale for the choices—other than that they are all together on the standard keyboard. Bill Joy originally developed vi to run on Lear-Siegler ADM-3a terminals, which were the first popular models with addressable cursors (meaning that a program could send an ADM-3a command to move the cursor to a specified location on the screen). The ADM-3a’s h, j, k, and l keys had little arrows on them, so Joy decided to use those keys for appropriate commands in vi. Another (partial) rationale for the command choices is that CTRL-H is the traditional backspace key, and CTRL-J denotes linefeed.

Perhaps + and - are better mnemonics than j and k, but the latter have the advantage of being more easily accessible to touch typists. In either case, these are the most basic commands for moving around the history list. To see how they work, let’s use the same examples from the emacs-mode section earlier.

You enter the example command (RETURN works in both input and control modes, as does LINEFEED or CTRL-J):

$ fgrep -l Duchess < ~cam/book/alice_in_wonderland

but you get an error message saying that your option letter was wrong. You want to change it to -s without having to retype the entire command. Assuming you are in control mode (you may have to type ESC to put yourself in control mode), you type k or - to get the command back. Your cursor will be at the beginning of the line:

$ [f]grep -l Duchess < ~cam/book/alice_in_wonderland

Type w to get to the -, then l to get to the l. Now you can replace it by typing rs; press RETURN to run the command.

Now let’s say you get another error message, and you finally decide to look at the manual page for the fgrep command. You remember having done this a while ago today, so rather than typing in the entire man command, you search for the last one you used. To do this, type ESC to enter control mode (if you are already in control mode, this will have no effect), then type / followed by man or ma. To be on the safe side, you can also type ^ma; the ^ means match only lines that begin with ma.^[7]

But typing /^ma doesn’t give you what you want: instead, the shell gives you:

$ make myprogram

To search for “man” again, you can type n, which does another backward search using the last search string. Typing / again without an argument and hitting RETURN will accomplish the same thing.

The G command retrieves the command whose number is the same as the numeric prefix argument you supply. G depends on the command numbering scheme described in Chapter 3 Section 3.4.2.3. Without a prefix argument, it goes to command number 1. This may be useful to former C shell users who still want to use command numbers.

There are some additional motion commands in vi-mode, although they are less useful than the ones we saw earlier in the chapter. These commands allow you to move to the position of a particular character in the line. They are summarized in Table 2-13, in which x denotes any character.

All of these commands can be preceded by a repeat count.

Starting with the previous example: let’s say you want to change Duchess to Duckess. Make sure that you’re at the end of the line (or, in any case, to the left of the h in Duchess); then, if you type Fh, your cursor will move to the h:

$ fgrep -l Duc[h]ess < ~cam/book/alice_in_wonderland

At this point, you could type r to replace the h with k. But let’s say you wanted to change Duchess to Dutchess. You would need to move one space to the right of the u. Of course, you could just type l. But, given that you’re somewhere to the right of Duchess, the fastest way to move to the c would be to type Tu instead of Fu followed by l.

As an example of how the repeat count can be used with character-finding commands, let’s say you want to change the filename from alice_in_wonderland to alice. In this case, assuming your cursor is still on the D, you need to get to one character beyond the second slash. To do this, you can type 2fa. Your cursor will then be on the a in alice_in_wonderland.

The character-finding commands also have associated delete commands. Read the command definitions in the previous table and mentally substitute “delete” for move. You’ll get what happens when you precede the given character-finding command with a d. The deletion includes the character given as argument. For example, assume that your cursor is under the a in alice_in_wonderland:

$ fgrep -l Duchess < ~cam/book/[a]lice_in_wonderland

If you want to change alice_in_wonderland to natalie_in_wonderland, one possibility is to type dfc. This means “delete right to next occurrence of c,” i.e., delete “alic”. Then you can type i (to enter input mode) and then “natali” to complete the change.

One final command rounds out the vi control mode commands for getting around on the current line: you can use the pipe character (|) to move to a specific column, whose number is given by a numeric prefix argument. Column counts start at 1; count only your input, not the space taken up by the prompt string. The default repeat count is 1, of course, which means that typing | by itself is equivalent to 0 (see Table 2-8).

Although the character-finding commands and | are not particularly useful, vi-mode provides one additional feature that we think you will use quite often: textual completion. This feature is not part of the real vi editor, and it was undoubtedly inspired by similar features in emacs and, originally, in the TOPS-20 operating system for DEC mainframes.

The rationale behind textual completion is simple: you should have to type only as much of a filename, user name, function, etc. as is necessary. Backslash () is the command that tells bash to do completion in vi-mode. If you type in a word, hit ESC to enter control mode, and then type , one of four things will happen; they are the same as for TAB in emacs-mode:

A related command is *. It behaves similarly to ESC-, but if there is more than one completion possibility (number four in the previous list), it lists all of them and allows you to type further. Thus, it resembles the * shell wildcard character.

Less useful is the command =, which does the same kind of expansion as *, but in a different way. Instead of expanding the names onto the command line, it prints them, then gives you your shell prompt back and retypes whatever was on your command line before you typed =. For example, if the files in your directory include tweedledee.c and tweedledum.c, and you type tweedl followed by ESC and then =, you will see this:

$ cc tweedl
tweedledee.c tweedledum.c

It is also possible to expand other environment entities, as we saw in emacs-mode. If the text being expanded is preceded by a dollar sign ($), the shell will attempt to expand the name to that of a shell variable. If the text is preceded by a tilde (~), expansion to a username is attempted; if preceded by an at sign (@), a hostname.

Several miscellaneous commands round out vi-mode; some of them are quite esoteric. They are listed in Table 2-14.

The first of these can be preceded by a repeat count. A repeat count of n preceding the ~ changes the case of the next n characters. The cursor will advance accordingly.

A repeat count preceding _ causes the nth word in the previous command to be inserted in the current line; without the count, the last word is used. Omitting the repeat count is useful because a filename is usually the last thing on a UNIX command line, and because users often run several commands in a row on the same file. With this feature, you can type all of the commands (except the first) followed by ESC-_, and the shell will insert the filename.

The default startup file is called .inputrc and must exist in your home directory if you wish to customize readline. You can change the default filename by setting the environment variable INPUTRC (see Chapter 3 for further information on environment variables).

When bash starts up, it reads the startup file (if there is one) and any settings there come into effect. The startup file is just a sequence of lines that bind a keyname to a macro or readline function name. You can also place comments in the file by preceding any line with a #.

You can use either an English name or a key escape sequence for the keyname. For example, to bind CTRL-T to the movement command for moving to the end of the current line, you could place Control-t: end-of-line in your .inputrc. If you wanted to use a key escape sequence you could have put "C-t<">: end-of-line. The C- is the escape sequence prefix for Control. The advantage of the key sequence is that you can specify a sequence of keys for an action. In our example, once readline has read this line, typing a CTRL-T will cause the cursor to move to the end of the line.

The end-of-line in the previous example is a readline function. There are over 60 functions that allow you to control everything from cursor motions to changing text and command completion (for a complete list, see the bash manual page). All of the emacs and vi editing mode commands that we looked at in this chapter have associated functions. This allows you to customize the default modes or make up completely new ones using your own key sequences.

Besides the readline functions, you can also bind a macro to a key sequence. A macro is simply a sequence of keystrokes inside single or double quotes. Typing the key sequence causes the keys in the macro to be entered as though you had typed them. For example, we could bind some text to CTRL-T; "C-t<">: <">Curiouser and curiouser!<">. Hitting CTRL-T would cause the phrase Curiouser and curiouser! to appear on the command line.

If you want to use single or double quotes in your macros or key sequence, you can escape them by using a backslash (). Table 2-18 lists the common escape sequences.

readline also allows simple conditionals in the .inputrc. There are three directives: $if, $else, and $endif. The conditional of the $if can be an editing mode, a terminal type, or an application-specific condition.

To test for an editing mode, you can use the form mode= and test for either vi or emacs. For instance, to set up readline so that setting CTRL-T will take place only in emacs mode, you could put the following in your .inputrc:

$if mode=emacs
"C-t": "Curiouser and curiouser!"
$endif

Likewise, to test for a terminal type, you can use the form term=. You must provide the full terminal name on the right-hand side of the test. This is useful when you need a terminal-specific key binding. You may, for instance, want to bind the function keys of a particular terminal type to key sequences.

If you have other applications that use readline, you might like to keep your bash-specific bindings separate. You can do this with the last of the conditionals. Each application that uses readline sets its own variable, which you can test for. To test for bash specifics, you could put $if bash into your .inputrc.

If you want to try out key bindings or you want to see what the current settings are, you can do it from the bash command line by using the bind command. The binding syntax is the same as that of the .inputrc file, but you have to surround each binding in quotes so that it is taken as one argument.

To bind a string to CTRL-T, we could type bind `"C-t<">: <">Curiouser and curiouser!"'. This would bind the given string to CTRL-T just as in the .inputrc, except that the binding will apply only to the current shell and will cease once you log out.

bind also allows you to print out the bindings currently in effect by typing bind -P.^[11] If you do so, you’ll see things like:

               abort can be found on "C-g", "C-xC-g", "eC-g".
               accept-line can be found on "C-j", "C-m".
               alias-expand-line is not bound to any keys
               arrow-key-prefix is not bound to any keys
               backward-char can be found on "C-b", "eOD", "e[D".
               ...

If you just want to see the names of the readline functions, you can use bind -l.

You can also unbind a function by using bind -u along with the name of the function; all keys for that function will then be unbound. Unbinding a key sequence can be done with bind -r followed by the sequence.

bind -x is useful if you want to bind a shell command to a key sequence. For example, bind -x `"C-l”:ls' binds CTRL-L to the ls command. Hitting CTRL-L would then give a directory listing.

Another option you might find useful is -p. This prints out the bindings to standard output in a format that can be re-read by bind, or used as a .inputrc file. So, to create a complete .inputrc file that you can then edit, you could type bind -p > .inputrc.

To read the file back in again you can use another option, -f. This option takes a filename as its argument and reads the key bindings from that file. You can also use it to update the key bindings if you’ve just modified your .inputrc.