rluser.texinfo

linux下bash的源码

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This file documents the end user interface to the GNU command line
editing features.  It is to be an appendix to manuals for programs which
use these features.  There is a document entitled "readline.texinfo"
which contains both end-user and programmer documentation for the GNU
Readline Library.

Copyright (C) 1988 Free Software Foundation, Inc.

Authored by Brian Fox and Chet Ramey.

Permission is granted to process this file through Tex and print the
results, provided the printed document carries copying permission notice
identical to this one except for the removal of this paragraph (this
paragraph not being relevant to the printed manual).

Permission is granted to make and distribute verbatim copies of this manual
provided the copyright notice and this permission notice are preserved on
all copies.

Permission is granted to copy and distribute modified versions of this
manual under the conditions for verbatim copying, provided also that the
GNU Copyright statement is available to the distributee, and provided that
the entire resulting derived work is distributed under the terms of a
permission notice identical to this one.

Permission is granted to copy and distribute translations of this manual
into another language, under the above conditions for modified versions.
@end ignore

@comment If you are including this manual as an appendix, then set the
@comment variable readline-appendix.

@node Command Line Editing
@chapter Command Line Editing

This chapter describes the basic features of the GNU
command line editing interface.

@menu
* Introduction and Notation::	Notation used in this text.
* Readline Interaction::	The minimum set of commands for editing a line.
* Readline Init File::		Customizing Readline from a user's view.
* Bindable Readline Commands::	A description of most of the Readline commands
				available for binding
* Readline vi Mode::		A short description of how to make Readline
				behave like the vi editor.
@end menu

@node Introduction and Notation
@section Introduction to Line Editing

The following paragraphs describe the notation used to represent
keystrokes.

The text @key{C-k} is read as `Control-K' and describes the character
produced when the Control key is depressed and the @key{k} key is struck.

The text @key{M-k} is read as `Meta-K' and describes the character
produced when the meta key (if you have one) is depressed, and the @key{k}
key is struck.  If you do not have a meta key, the identical keystroke
can be generated by typing @key{ESC} @i{first}, and then typing @key{k}.
Either process is known as @dfn{metafying} the @key{k} key.

The text @key{M-C-k} is read as `Meta-Control-k' and describes the
character produced by @dfn{metafying} @key{C-k}.

In addition, several keys have their own names.  Specifically,
@key{DEL}, @key{ESC}, @key{LFD}, @key{SPC}, @key{RET}, and @key{TAB} all
stand for themselves when seen in this text, or in an init file
(@pxref{Readline Init File}, for more info).

@node Readline Interaction
@section Readline Interaction
@cindex interaction, readline

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 @key{RETURN}.  You do not have to be at the
end of the line to press @key{RETURN}; the entire line is accepted
regardless of the location of the cursor within the line.

@menu
* Readline Bare Essentials::	The least you need to know about Readline.
* Readline Movement Commands::	Moving about the input line.
* Readline Killing Commands::	How to delete text, and how to get it back!
* Readline Arguments::		Giving numeric arguments to commands.
@end menu

@node Readline Bare Essentials
@subsection Readline Bare Essentials

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 @key{C-b} to move the cursor to the left, and then
correct your mistake.  Afterwards, you can move the cursor to the right
with @key{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.

@table @asis
@item @key{C-b}
Move back one character.
@item @key{C-f}
Move forward one character.
@item @key{DEL}
Delete the character to the left of the cursor.
@item @key{C-d}
Delete the character underneath the cursor.
@item @w{Printing characters}
Insert the character into the line at the cursor.
@item @key{C-_}
Undo the last thing that you did.  You can undo all the way back to an
empty line.
@end table

@node Readline Movement Commands
@subsection Readline Movement Commands


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 @key{C-b}, @key{C-f},
@key{C-d}, and @key{DEL}.  Here are some commands for moving more rapidly
about the line.

@table @key
@item C-a
Move to the start of the line.
@item C-e
Move to the end of the line.
@item M-f
Move forward a word.
@item M-b
Move backward a word.
@item C-l
Clear the screen, reprinting the current line at the top.
@end table

Notice how @key{C-f} moves forward a character, while @key{M-f} moves
forward a word.  It is a loose convention that control keystrokes
operate on characters while meta keystrokes operate on words.

@node Readline Killing Commands
@subsection Readline Killing Commands

@cindex Killing text
@cindex Yanking text

@dfn{Killing} text means to delete the text from the line, but to save
it away for later use, usually by @dfn{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 @dfn{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.
@cindex Kill ring

Here is the list of commands for killing text.

@table @key
@item C-k
Kill the text from the current cursor position to the end of the line.

@item M-d
Kill from the cursor to the end of the current word, or if between
words, to the end of the next word.

@item M-DEL
Kill from the cursor the start of the previous word, or if between
words, to the start of the previous word.

@item C-w
Kill from the cursor to the previous whitespace.  This is different than
@key{M-DEL} because the word boundaries differ.

@end table

And, here is how to @dfn{yank} the text back into the line.  Yanking
means to copy the most-recently-killed text from the kill buffer.

@table @key
@item C-y
Yank the most recently killed text back into the buffer at the cursor.

@item M-y
Rotate the kill-ring, and yank the new top.  You can only do this if
the prior command is @key{C-y} or @key{M-y}.
@end table

@node Readline Arguments
@subsection Readline Arguments

You can pass numeric arguments to Readline commands.  Sometimes the
argument acts as a repeat count, other times it is the @i{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 @key{M--} @key{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 (@key{-}), 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 @key{C-d} command an argument of 10, you could type @key{M-1 0 C-d}.


@node Readline Init File
@section Readline Init File

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 @dfn{init} file in your home directory.  The name of this
@ifset BashFeatures
file is taken from the value of the shell variable @code{INPUTRC}.  If
@end ifset
@ifclear BashFeatures
file is taken from the value of the environment variable @code{INPUTRC}.  If
@end ifclear
that variable is unset, the default is @file{~/.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 @code{C-x C-r} command re-reads this init file, thus
incorporating any changes that you might have made to it.

@menu
* Readline Init Syntax::	Syntax for the commands in the inputrc file.
* Conditional Init Constructs::	Conditional key bindings in the inputrc file.
@end menu

@node Readline Init Syntax
@subsection Readline Init Syntax

There are only a few basic constructs allowed in the
Readline init file.  Blank lines are ignored.
Lines beginning with a @key{#} are comments.
Lines beginning with a @key{$} indicate conditional
constructs (@pxref{Conditional Init Constructs}).  Other lines
denote variable settings and key bindings.

@table @asis
@item Variable Settings
You can change the state of a few variables in Readline by
using the @code{set} command within the init file.  Here is how you
would specify that you wish to use @code{vi} line editing commands:

@example
set editing-mode vi
@end example

Right now, there are only a few variables which can be set;
so few, in fact, that we just list them here:

@table @code

@item editing-mode
@vindex editing-mode
The @code{editing-mode} variable 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 @code{emacs} or @code{vi}.

@item horizontal-scroll-mode
@vindex horizontal-scroll-mode
This variable can be set to either @code{On} or @code{Off}.  Setting it
to @code{On} means 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 @code{Off}.

@item mark-modified-lines
@vindex mark-modified-lines
This variable, when set to @code{On}, says to display an asterisk
(@samp{*}) at the start of history lines which have been modified.
This variable is @code{off} by default.

@item bell-style
@vindex bell-style
Controls what happens when Readline wants to ring the terminal bell.
If set to @code{none}, Readline never rings the bell.  If set to
@code{visible}, Readline uses a visible bell if one is available.
If set to @code{audible} (the default), Readline attempts to ring
the terminal's bell.

@item comment-begin
@vindex comment-begin
The string to insert at the beginning of the line when the
@code{vi-comment} command is executed.  The default value
is @code{"#"}.

@item meta-flag
@vindex meta-flag
If set to @code{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 @code{off}.

@item convert-meta
@vindex convert-meta
If set to @code{on}, Readline will convert characters with the
eigth bit set to an ASCII key sequence by stripping the eigth
bit and prepending an @key{ESC} character, converting them to a
meta-prefixed key sequence.  The default value is @code{on}.

@item output-meta
@vindex output-meta
If set to @code{on}, Readline will display characters with the
eighth bit set directly rather than as a meta-prefixed escape
sequence.  The default is @code{off}.

@item completion-query-items
@vindex completion-query-items
The number of possible completions that determines when the user is
asked whether he wants to see the list of possibilities.  If the
number of possible completions is greater than this value,
Readline will ask the user whether or not he wishes to view
them; otherwise, they are simply listed.  The default limit is
@code{100}.

@item keymap
@vindex keymap
Sets Readline's idea of the current keymap for key binding commands.
Acceptable @code{keymap} names are
@code{emacs},
@code{emacs-standard},
@code{emacs-meta},
@code{emacs-ctlx},
@code{vi},
@code{vi-move},
@code{vi-command}, and
@code{vi-insert}.
@code{vi} is equivalent to @code{vi-command}; @code{emacs} is
equivalent to @code{emacs-standard}.  The default value is @code{emacs}.
The value of the @code{editing-mode} variable also affects the
default keymap.

@item show-all-if-ambiguous
@vindex show-all-if-ambiguous
This alters the default behavior of the completion functions.  If
set to @code{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 @code{off}.

@item expand-tilde
@vindex expand-tilde
If set to @code{on}, tilde expansion is performed when Readline
attempts word completion.  The default is @code{off}.

@end table

@item Key Bindings
The syntax for controlling key bindings in the init file is
simple.  First you have to know the name of the command that you
want to change.  The following pages contain tables of the command name,
the default keybinding, and a short description of what the command
does.

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.

@table @asis
@item @w{@var{keyname}: @var{function-name} or @var{macro}}
@var{keyname} is the name of a key spelled out in English.  For example:
@example
Control-u: universal-argument
Meta-Rubout: backward-kill-word
Control-o: ">&output"
@end example

In the above example, @samp{C-u} is bound to the function
@code{universal-argument}, and @samp{C-o} is bound to run the macro
expressed on the right hand side (that is, to insert the text
@samp{>&output} into the line).

@item @w{"@var{keyseq}": @var{function-name} or @var{macro}}
@var{keyseq} differs from @var{keyname} above in that strings
denoting an entire key sequence can be specified, by placing
the key sequence in double quotes.  Some GNU Emacs style key
escapes can be used, as in the following example, but the
special character names are not recognized.

@example
"\C-u": universal-argument
"\C-x\C-r": re-read-init-file
"\e[11~": "Function Key 1"
@end example

In the above example, @samp{C-u} is bound to the function
@code{universal-argument} (just as it was in the first example),
@samp{C-x C-r} is bound to the function @code{re-read-init-file}, and
@samp{ESC [ 1 1 ~} is bound to insert the text @samp{Function Key 1}.
The following escape sequences are available when specifying key
sequences:

@table @code
@item @kbd{\C-}
control prefix
@item @kbd{\M-}
meta prefix
@item @kbd{\e}
an escape character
@item @kbd{\\}
backslash