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This document describes the GNU Readline Library, a utility which aids in the consistency of user interface across discrete programs that need to provide a command line interface.
Published by the Free Software Foundation
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Copyright (C) 1989, 1991 Free Software Foundation, Inc.
This chapter describes the basic features of the GNU command line editing interface.
The following paragraphs describe the notation used to represent keystrokes.
The text C-k is read as `Control-K' and describes the character produced when the Control key is depressed and the k key is struck.
The text M-k is read as `Meta-K' and describes the character produced when the meta key (if you have one) is depressed, and the k key is struck. If you do not have a meta key, the identical keystroke can be generated by typing ESC first, and then typing k. Either process is known as metafying the k key.
The text M-C-k is read as `Meta-Control-k' and describes the character produced by metafying C-k.
In addition, several keys have their own names. Specifically, DEL, ESC, LFD, SPC, RET, and TAB all stand for themselves when seen in this text, or in an init file (see section Readline Init File, for more info).
Often during an interactive session you type in a long line of text, only to notice that the first word on the line is misspelled. The Readline library gives you a set of commands for manipulating the text as you type it in, allowing you to just fix your typo, and not forcing you to retype the majority of the line. Using these editing commands, you move the cursor to the place that needs correction, and delete or insert the text of the corrections. Then, when you are satisfied with the line, you simply press RETURN. You do not have to be at the end of the line to press RETURN; the entire line is accepted regardless of the location of the cursor within the line.
In order to enter characters into the line, simply type them. The typed character appears where the cursor was, and then the cursor moves one space to the right. If you mistype a character, you can use your erase character to back up and delete the mistyped character.
Sometimes you may miss typing a character that you wanted to type, and not notice your error until you have typed several other characters. In that case, you can type C-b to move the cursor to the left, and then correct your mistake. Afterwards, you can move the cursor to the right with C-f.
When you add text in the middle of a line, you will notice that characters to the right of the cursor are `pushed over' to make room for the text that you have inserted. Likewise, when you delete text behind the cursor, characters to the right of the cursor are `pulled back' to fill in the blank space created by the removal of the text. A list of the basic bare essentials for editing the text of an input line follows.
The above table describes the most basic possible keystrokes that you need in order to do editing of the input line. For your convenience, many other commands have been added in addition to C-b, C-f, C-d, and DEL. Here are some commands for moving more rapidly about the line.
Notice how C-f moves forward a character, while M-f moves forward a word. It is a loose convention that control keystrokes operate on characters while meta keystrokes operate on words.
Killing text means to delete the text from the line, but to save it away for later use, usually by yanking (re-inserting) it back into the line. If the description for a command says that it `kills' text, then you can be sure that you can get the text back in a different (or the same) place later.
When you use a kill command, the text is saved in a kill-ring. Any number of consecutive kills save all of the killed text together, so that when you yank it back, you get it all. The kill ring is not line specific; the text that you killed on a previously typed line is available to be yanked back later, when you are typing another line.
Here is the list of commands for killing text.
And, here is how to yank the text back into the line. Yanking means to copy the most-recently-killed text from the kill buffer.
You can pass numeric arguments to Readline commands. Sometimes the argument acts as a repeat count, other times it is the sign of the argument that is significant. If you pass a negative argument to a command which normally acts in a forward direction, that command will act in a backward direction. For example, to kill text back to the start of the line, you might type M-- C-k.
The general way to pass numeric arguments to a command is to type meta digits before the command. If the first `digit' you type is a minus sign (-), then the sign of the argument will be negative. Once you have typed one meta digit to get the argument started, you can type the remainder of the digits, and then the command. For example, to give the C-d command an argument of 10, you could type M-1 0 C-d.
Although the Readline library comes with a set of Emacs-like
keybindings installed by default,
it is possible that you would like to use a different set
of keybindings. You can customize programs that use Readline by putting
commands in an init file in your home directory. The name of this
file is taken from the value of the environment variable
that variable is unset, the default is `~/.inputrc'.
When a program which uses the Readline library starts up, the init file is read, and the key bindings are set.
In addition, the
C-x C-r command re-reads this init file, thus
incorporating any changes that you might have made to it.
There are only a few basic constructs allowed in the Readline init file. Blank lines are ignored. Lines beginning with a # are comments. Lines beginning with a $ indicate conditional constructs (see section Conditional Init Constructs). Other lines denote variable settings and key bindings.
setcommand within the init file. Here is how you would specify that you wish to use
viline editing commands:
set editing-mode vi
Right now, there are only a few variables which can be set; so few, in fact, that we just list them here:
editing-modevariable controls which editing mode you are using. By default, Readline starts up in Emacs editing mode, where the keystrokes are most similar to Emacs. This variable can be set to either
Off. Setting it to
Onmeans that the text of the lines that you edit will scroll horizontally on a single screen line when they are longer than the width of the screen, instead of wrapping onto a new screen line. By default, this variable is set to
On, says to display an asterisk (`*') at the start of history lines which have been modified. This variable is
none, Readline never rings the bell. If set to
visible, Readline uses a visible bell if one is available. If set to
audible(the default), Readline attempts to ring the terminal's bell.
vi-commentcommand is executed. The default value is
on, Readline will enable eight-bit input (it will not strip the eighth bit from the characters it reads), regardless of what the terminal claims it can support. The default value is
on, Readline will convert characters with the eigth bit set to an ASCII key sequence by stripping the eigth bit and prepending an ESC character, converting them to a meta-prefixed key sequence. The default value is
on, Readline will display characters with the eighth bit set directly rather than as a meta-prefixed escape sequence. The default is
viis equivalent to
emacsis equivalent to
emacs-standard. The default value is
emacs. The value of the
editing-modevariable also affects the default keymap.
on, words which have more than one possible completion cause the matches to be listed immediately instead of ringing the bell. The default value is
on, tilde expansion is performed when Readline attempts word completion. The default is
Once you know the name of the command, simply place the name of the key you wish to bind the command to, a colon, and then the name of the command on a line in the init file. The name of the key can be expressed in different ways, depending on which is most comfortable for you.
Control-u: universal-argument Meta-Rubout: backward-kill-word Control-o: ">&output"
In the above example, `C-u' is bound to the function
universal-argument, and `C-o' is bound to run the macro
expressed on the right hand side (that is, to insert the text
`>&output' into the line).
"\C-u": universal-argument "\C-x\C-r": re-read-init-file "\e[11~": "Function Key 1"
In the above example, `C-u' is bound to the function
universal-argument (just as it was in the first example),
`C-x C-r' is bound to the function
`ESC [ 1 1 ~' is bound to insert the text `Function Key 1'.
The following escape sequences are available when specifying key
When entering the text of a macro, single or double quotes should be used to indicate a macro definition. Unquoted text is assumed to be a function name. Backslash will quote any character in the macro text, including " and '. For example, the following binding will make C-x \ insert a single \ into the line:
Readline implements a facility similar in spirit to the conditional compilation features of the C preprocessor which allows key bindings and variable settings to be performed as the result of tests. There are three parser directives used.
$ifconstruct allows bindings to be made based on the editing mode, the terminal being used, or the application using Readline. The text of the test extends to the end of the line; no characters are required to isolate it.
mode=form of the
$ifdirective is used to test whether Readline is in
vimode. This may be used in conjunction with the `set keymap' command, for instance, to set bindings in the
emacs-ctlxkeymaps only if Readline is starting out in
term=form may be used to include terminal-specific key bindings, perhaps to bind the key sequences output by the terminal's function keys. The word on the right side of the `=' is tested against the full name of the terminal and the portion of the terminal name before the first `-'. This allows sun to match both sun and sun-cmd, for instance.
$if bash # Quote the current or previous word "\C-xq": "\eb\"\ef\"" $endif
$ifdirective are executed if the test fails.
accept-line (Newline, Return)
yank-last-arg (M-., M-_)
quoted-insert (C-q, C-v)
self-insert (a, b, A, 1, !, ...)
backward-kill-line (C-x Rubout)
digit-argument (M-0, M-1, ... M--)
possible-completions. By default, this is not bound to a key.
start-kbd-macro (C-x ()
end-kbd-macro (C-x ))
call-last-kbd-macro (C-x e)
re-read-init-file (C-x C-r)
do-uppercase-version (M-a, M-b, ...)
undo (C-_, C-x C-u)
undocommand enough times to get back to the beginning.
While the Readline library does not have a full set of
editing functions, it does contain enough to allow simple editing
of the line. The Readline
vi mode behaves as specified in
the Posix 1003.2 standard.
In order to switch interactively between
editing modes, use the command M-C-j (toggle-editing-mode).
The Readline default is
When you enter a line in
vi mode, you are already placed in
`insertion' mode, as if you had typed an `i'. Pressing ESC
switches you into `command' mode, where you can edit the text of the
line with the standard
vi movement keys, move to previous
history lines with `k', and following lines with `j', and
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