This text describes GNU's command line editing interface. It is
relatively old and may not be entirely correct now. Please send a
firstname.lastname@example.org if you find any errors.
See section Reporting Bugs, for more information about how to report bugs.
The following paragraphs describe the notation we use 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 DEL 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 get `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 get `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 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.
Here is the list of commands for killing text.
And, here is how to yank the text back into the line. Yanking is
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 in one clean sweep. 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.
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, 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 `~/.inputrc'.
When a program which uses the Readline library starts up, the `~/.inputrc' file is read, and the keybindings 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 four constructs allowed in the `~/.inputrc' file:
setcommand within the init file. Here is how you would specify that you wish to use Vi line editing commands:
set editing-mode viRight now, there are only a few variables which can be set; so few in fact, that we just iterate them here:
editing-modevariable controls which editing mode you are using. By default, GNU Readline starts up in Emacs editing mode, where the keystrokes are most similar to Emacs. This variable can either be set to
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 larger 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 starts of history lines which have been modified. This variable is off by default.
Onit means to use a visible bell if one is available, rather than simply ringing the terminal bell. By default, the value is
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
re-read-init-file, and ESC [ 1 1 ~ is bound to insert the text `Function Key 1'.
accept-line (Newline, Return)
quoted-insert (C-q, C-v)
self-insert (a, b, A, 1, !, ...)
digit-argument (M-0, M-1, ... M--)
re-read-init-file (C-x C-r)
do-uppercase-version (M-a, M-b, ...)
While the Readline library does not have a full set of Vi editing functions, it does contain enough to allow simple editing of the line.
In order to switch interactively between Emacs and Vi editing modes, use the command M-C-j (toggle-editing-mode).
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 `edit' 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 so forth.
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