Although the Readline library comes with a set of Emacs-like
keybindings installed by default, it is possible to use a different set
of keybindings.
Any user can customize programs that use Readline by putting
commands in an inputrc file, conventionally in his home directory.
The name of this
file is taken from the value of the environment variable INPUTRC. If
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.
29.3.1. Readline Init File Syntax
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 (refer to Section 29.3.2 Conditional Init Constructs). Other lines
denote variable settings and key bindings.
Variable Settings
You can modify the run-time behavior of Readline by
altering the values of variables in Readline
using the set command within the init file.
The syntax is simple:
set variablevalue
Here, for example, is how to
change from the default Emacs-like key binding to use
vi line editing commands:
set editing-mode vi
Variable names and values, where appropriate, are recognized without regard
to case.
A great deal of run-time behavior is changeable with the following
variables.
bell-style
Controls what happens when Readline wants to ring the terminal bell.
If set to 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.
comment-begin
The string to insert at the beginning of the line when the
insert-comment command is executed. The default value
is "#".
completion-ignore-case
If set to on, Readline performs filename matching and completion
in a case-insensitive fashion.
The default value is off.
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.
This variable must be set to an integer value greater than or equal to 0.
The default limit is 100.
convert-meta
If set to on, Readline will convert characters with the
eighth bit set to an ascii key sequence by stripping the eighth
bit and prefixing an [ESC] character, converting them to a
meta-prefixed key sequence. The default value is on.
disable-completion
If set to On, Readline will inhibit word completion.
Completion characters will be inserted into the line as if they had
been mapped to self-insert. The default is off.
editing-mode
The editing-mode variable controls which default set of
key bindings is used. By default, Readline starts up in Emacs editing
mode, where the keystrokes are most similar to Emacs. This variable can be
set to either emacs or vi.
enable-keypad
When set to on, Readline will try to enable the application
keypad when it is called. Some systems need this to enable the
arrow keys. The default is off.
expand-tilde
If set to on, tilde expansion is performed when Readline
attempts word completion. The default is off.
If set to on, the history code attempts to place point at the
same location on each history line retrived with previous-history
or next-history.
horizontal-scroll-mode
This variable can be set to either on or off. Setting it
to on means that the text of the lines being edited 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 off.
input-meta
If set to on, Readline will enable eight-bit input (it
will not clear the eighth bit in the characters it reads),
regardless of what the terminal claims it can support. The
default value is off. The name meta-flag is a
synonym for this variable.
isearch-terminators
The string of characters that should terminate an incremental search without
subsequently executing the character as a command (refer to Section 29.2.5 Searching for Commands in the History).
If this variable has not been given a value, the characters [ESC] and
C-J will terminate an incremental search.
keymap
Sets Readline's idea of the current keymap for key binding commands.
Acceptable keymap names are
emacs,
emacs-standard,
emacs-meta,
emacs-ctlx,
vi,
vi-move,
vi-command, and
vi-insert.
vi is equivalent to vi-command; emacs is
equivalent to emacs-standard. The default value is emacs.
The value of the editing-mode variable also affects the
default keymap.
mark-directories
If set to on, completed directory names have a slash
appended. The default is on.
mark-modified-lines
This variable, when set to on, causes Readline to display an
asterisk (*) at the start of history lines which have been modified.
This variable is off by default.
mark-symlinked-directories
If set to on, completed names which are symbolic links
to directories have a slash appended (subject to the value of
mark-directories).
The default is off.
match-hidden-files
This variable, when set to on, causes Readline to match files whose
names begin with a . (hidden files) when performing filename
completion, unless the leading . is
supplied by the user in the filename to be completed.
This variable is on by default.
output-meta
If set to on, Readline will display characters with the
eighth bit set directly rather than as a meta-prefixed escape
sequence. The default is off.
page-completions
If set to on, Readline uses an internal more-like pager
to display a screenful of possible completions at a time.
This variable is on by default.
print-completions-horizontally
If set to on, Readline will display completions with matches
sorted horizontally in alphabetical order, rather than down the screen.
The default is off.
show-all-if-ambiguous
This alters the default behavior of the completion functions. If
set to 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 off.
visible-stats
If set to on, a character denoting a file's type
is appended to the filename when listing possible
completions. The default is off.
Key Bindings
The syntax for controlling key bindings in the init file is
simple. First you need to find the name of the command that you
want to change. The following sections contain tables of the command
name, the default keybinding, if any, and a short description of what
the command does.
Once you know the name of the command, simply place on a line
in the init file the name of the key
you wish to bind the command to, a colon, and then the name of the
command. The name of the key
can be expressed in different ways, depending on what you find most
comfortable.
In addition to command names, readline allows keys to be bound
to a string that is inserted when the key is pressed (a macro).
keyname: function-name or macro
keyname is the name of a key spelled out in English. For example:
In the above example, C-u is bound to the function
universal-argument,
M-DEL is bound to the function backward-kill-word, 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).
A number of symbolic character names are recognized while
processing this key binding syntax:
DEL,
ESC,
ESCAPE,
LFD,
NEWLINE,
RET,
RETURN,
RUBOUT,
SPACE,
SPC,
and
TAB.
"keyseq": function-name or macro
keyseq differs from 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.
In the above example, C-u is again bound to the function
universal-argument (just as it was in the first example),
C-xC-r is bound to the function re-read-init-file,
and [ESC][[][1][1][~] is bound to insert
the text Function Key 1.
The following gnu Emacs style escape sequences are available when
specifying key sequences:
\C-
control prefix
\M-
meta prefix
\e
an escape character
\\
backslash
\"
["], a double quotation mark
\'
['], a single quote or apostrophe
In addition to the gnu Emacs style escape sequences, a second
set of backslash escapes is available:
\a
alert (bell)
\b
backspace
\d
delete
\f
form feed
\n
newline
\r
carriage return
\t
horizontal tab
\v
vertical tab
\nnn
the eight-bit character whose value is the octal value nnn
(one to three digits)
\xHH
the eight-bit character whose value is the hexadecimal value HH
(one or two hex digits)
When entering the text of a macro, single or double quotes must
be used to indicate a macro definition.
Unquoted text is assumed to be a function name.
In the macro body, the backslash escapes described above are expanded.
Backslash will quote any other character in the macro text,
including " and '.
For example, the following binding will make C-x \
insert a single \ into the line:
"\C-x\\": "\\"
29.3.2. Conditional Init Constructs
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 four parser directives used.
$if
The $if construct 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
The mode= form of the $if directive is used to test
whether Readline is in emacs or vi mode.
This may be used in conjunction
with the set keymap command, for instance, to set bindings in
the emacs-standard and emacs-ctlx keymaps only if
Readline is starting out in emacs mode.
term
The 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 both 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.
application
The application construct is used to include
application-specific settings. Each program using the Readline
library sets the application name, and you can test for
a particular value.
This could be used to bind key sequences to functions useful for
a specific program. For instance, the following command adds a
key sequence that quotes the current or previous word in Bash:
$if Bash
# Quote the current or previous word
"\C-xq": "\eb\"\ef\""
$endif
$endif
This command, as seen in the previous example, terminates an
$if command.
$else
Commands in this branch of the $if directive are executed if
the test fails.
$include
This directive takes a single filename as an argument and reads commands
and bindings from that file.
For example, the following directive reads from /etc/inputrc:
$include /etc/inputrc
29.3.3. Sample Init File
Here is an example of an inputrc file. This illustrates key
binding, variable assignment, and conditional syntax.
# This file controls the behaviour of line input editing for
# programs that use the GNU Readline library. Existing
# programs include FTP, Bash, and GDB.
#
# You can re-read the inputrc file with C-x C-r.
# Lines beginning with '#' are comments.
#
# First, include any systemwide bindings and variable
# assignments from /etc/Inputrc
$include /etc/Inputrc
#
# Set various bindings for emacs mode.
set editing-mode emacs
$if mode=emacs
Meta-Control-h: backward-kill-word Text after the function name is ignored
#
# Arrow keys in keypad mode
#
#"\M-OD": backward-char
#"\M-OC": forward-char
#"\M-OA": previous-history
#"\M-OB": next-history
#
# Arrow keys in ANSI mode
#
"\M-[D": backward-char
"\M-[C": forward-char
"\M-[A": previous-history
"\M-[B": next-history
#
# Arrow keys in 8 bit keypad mode
#
#"\M-\C-OD": backward-char
#"\M-\C-OC": forward-char
#"\M-\C-OA": previous-history
#"\M-\C-OB": next-history
#
# Arrow keys in 8 bit ANSI mode
#
#"\M-\C-[D": backward-char
#"\M-\C-[C": forward-char
#"\M-\C-[A": previous-history
#"\M-\C-[B": next-history
C-q: quoted-insert
$endif
# An old-style binding. This happens to be the default.
TAB: complete
# Macros that are convenient for shell interaction
$if Bash
# edit the path
"\C-xp": "PATH=${PATH}\e\C-e\C-a\ef\C-f"
# prepare to type a quoted word --
# insert open and close double quotes
# and move to just after the open quote
"\C-x\"": "\"\"\C-b"
# insert a backslash (testing backslash escapes
# in sequences and macros)
"\C-x\\": "\\"
# Quote the current or previous word
"\C-xq": "\eb\"\ef\""
# Add a binding to refresh the line, which is unbound
"\C-xr": redraw-current-line
# Edit variable on current line.
"\M-\C-v": "\C-a\C-k$\C-y\M-\C-e\C-a\C-y="
$endif
# use a visible bell if one is available
set bell-style visible
# don't strip characters to 7 bits when reading
set input-meta on
# allow iso-latin1 characters to be inserted rather
# than converted to prefix-meta sequences
set convert-meta off
# display characters with the eighth bit set directly
# rather than as meta-prefixed characters
set output-meta on
# if there are more than 150 possible completions for
# a word, ask the user if he wants to see all of them
set completion-query-items 150
# For FTP
$if Ftp
"\C-xg": "get \M-?"
"\C-xt": "put \M-?"
"\M-.": yank-last-arg
$endif
