READLINE (3)
get a line from a user with editing
SYNOPSIS
B
#include <readline.h>
#include <history.h>
B
char *readline (prompt)
char *prompt;
COPYRIGHT
n Readline is Copyright (C) 1989, 1991, 1993, 1995, 1996 by the Free Software Foundation, Inc.
t Readline is Copyright \(co 1989, 1991, 1993, 1995, 1996 by the Free Software Foundation, Inc.
DESCRIPTION
readline
will read a line from the terminal
and return it, using
prompt
as a prompt. If
prompt
is null, no prompt is issued. The line returned is allocated with
malloc (3),
so the caller must free it when finished. The line returned
has the final newline removed, so only the text of the line
remains.
readline
offers editing capabilities while the user is entering the
line.
By default, the line editing commands
are similar to those of emacs.
A vi-style line editing interface is also available.
RETURN VALUE
readline
returns the text of the line read. A blank line
returns the empty string. If
EOF
is encountered while reading a line, and the line is empty,
NULL
is returned. If an
EOF
is read with a non-empty line, it is
treated as a newline.
NOTATION
An emacs-style notation is used to denote
keystrokes. Control keys are denoted by C-key, e.g., C-n
means Control-N. Similarly,
meta
keys are denoted by M-key, so M-x means Meta-X. (On keyboards
without a
meta
key, M-x means ESC x, i.e., press the Escape key
then the
x
key. This makes ESC the meta prefix.
The combination M-C-x means ESC-Control-x,
or press the Escape key
then hold the Control key while pressing the
x
key.)
Readline commands may be given numeric
arguments ,
which normally act as a repeat count. Sometimes, however, it is the
sign of the argument that is significant. Passing a negative argument
to a command that acts in the forward direction (e.g., kill-line)
causes that command to act in a backward direction. Commands whose
behavior with arguments deviates from this are noted.
When a command is described as killing text, the text
deleted is saved for possible future retrieval
(yanking). The killed text is saved in a
kill ring. Consecutive kills cause the text to be
accumulated into one unit, which can be yanked all at once.
Commands which do not kill text separate the chunks of text
on the kill ring.
INITIALIZATION FILE
Readline is customized by putting commands in an initialization
file (the inputrc file).
The name of this file is taken from the value of the
INPUTRC
environment variable. 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 and variables are set.
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.
Other lines denote key bindings and variable settings.
Each program using this library may add its own commands
and bindings.
For example, placing
or
C-Meta-u: universal-argument
into the
inputrc
would make M-C-u execute the readline command
universal-argument .
The following symbolic character names are recognized while
processing key bindings:
RUBOUT ,
DEL ,
ESC ,
LFD ,
NEWLINE ,
RET ,
RETURN ,
SPC ,
SPACE ,
and
TAB .
In addition to command names, readline allows keys to be bound
to a string that is inserted when the key is pressed (a macro).
The syntax for controlling key bindings in the
inputrc
file is simple. All that is required is the name of the
command or the text of a macro and a key sequence to which
it should be bound. The name may be specified in one of two ways:
as a symbolic key name, possibly with Meta- or Control-
prefixes, or as a key sequence.
When using the form keyname:\^function-name or macro,
keyname
is the name of a key spelled out in English. For example:
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 ,
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).
In the second form, "keyseq":\^function-name or macro,
keyseq
differs from
keyname
above in that strings denoting
an entire key sequence may be specified by placing the sequence
within double quotes. Some GNU Emacs style key escapes can be
used, as in the following example.
"\eC-u": universal-argument
"\eC-x\eC-r": re-read-init-file
"\ee[11~": "Function Key 1"
In this example,
C-u
is again bound to the function
universal-argument .
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 .
The full set of GNU Emacs style escape sequences is
\eC-
\eM-
\ee
\e\e
\e"
\e'
In addition to the GNU Emacs style escape sequences, a second
set of backslash escapes is available:
\ea
\eb
\ed
\ef
\en
\er
\et
\ev
\e\fInnn\fP
the character whose ASCII code is the octal value nnn
(one to three digits)
\ex\fInnn\fP
the character whose ASCII code is the hexadecimal value nnn
(one to three digits)
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.
In the macro body, the backslash escapes described above are expanded.
Backslash will quote any other character in the macro text,
including " and '.
Bash
allows the current readline key bindings to be displayed or modified
with the
bind
builtin command. The editing mode may be switched during interactive
use by using the
-o
option to the
set
builtin command. Other programs using this library provide
similar mechanisms. The
inputrc
file may be edited and re-read if a program does not provide
any other means to incorporate new bindings.
Readline has variables that can be used to further customize its
behavior. A variable may be set in the
inputrc
file with a statement of the form
Except where noted, readline variables can take the values
On
or
Off .
The variables and their default values are:
bell-style (audible)
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, readline attempts to ring the terminal's bell.
comment-begin (``#'')
The string that is inserted in vi mode when the
insert-comment
command is executed.
This command is bound to
M-#
in emacs mode and to
#
in vi command mode.
completion-ignore-case (Off)
If set to On, readline performs filename matching and completion
in a case-insensitive fashion.
completion-query-items (100)
This determines when the user is queried about viewing
the number of possible completions
generated by the possible-completions command.
It may be set to any integer value greater than or equal to
zero. If the number of possible completions is greater than
or equal to the value of this variable, the user is asked whether
or not he wishes to view them; otherwise they are simply listed
on the terminal.
convert-meta (On)
If set to On, readline will convert characters with the
eighth bit set to an ASCII key sequence
by stripping the eighth bit and prepending an
escape character (in effect, using escape as the meta prefix).
disable-completion (Off)
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.
editing-mode (emacs)
Controls whether readline begins with a set of key bindings similar
to emacs or vi.
editing-mode
can be set to either
emacs
or
vi .
enable-keypad (Off)
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.
expand-tilde (Off)
If set to on, tilde expansion is performed when readline
attempts word completion.
horizontal-scroll-mode (Off)
When set to On, makes readline use a single line for display,
scrolling the input horizontally on a single screen line when it
becomes longer than the screen width rather than wrapping to a new line.
keymap (emacs)
Set the current readline keymap. The set of legal keymap names is
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
editing-mode
also affects the default keymap.
mark-directories (On)
If set to On, complete<d directory names have a slash
appended.
mark-modified-lines (Off)
If set to On, history lines that have been modified are displayed
with a preceding asterisk (*).
meta-flag (Off)
If set to On, readline will enable eight-bit input (that is,
it will not strip the high bit from the characters it reads),
regardless of what the terminal claims it can support.
output-meta (Off)
If set to On, readline will display characters with the
eighth bit set directly rather than as a meta-prefixed escape
sequence.
print-completions-horizontally (Off)
If set to On, readline will display completions with matches
sorted horizontally in alphabetical order, rather than down the screen.
show-all-if-ambiguous (Off)
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.
visible-stats (Off)
If set to On, a character denoting a file's type as reported
by stat(2) is appended to the filename when listing possible
completions.
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.
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.
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.
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 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.
The application construct is used to include
application-specific settings. Each program using the readline
library sets the application name, and an initialization
file 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
"\eC-xq": "\eeb\e"\eef\e""
$endif
This command, as seen in the previous example, terminates an
$if command.
Commands in this branch of the $if directive are executed if
the test fails.
This directive takes a single filename as an argument and reads commands
and bindings from that file. For example, the following directive
would read /etc/inputrc:
$include \^ /etc/inputrc
SEARCHING
Readline provides commands for searching through the command history
for lines containing a specified string.
There are two search modes:
incremental
and
non-incremental .
Incremental searches begin before the user has finished typing the
search string.
As each character of the search string is typed, readline displays
the next entry from the history matching the string typed so far.
An incremental search requires only as many characters as needed to
find the desired history entry.
The Escape character is used to terminate an incremental search.
Control-J will also terminate the search.
Control-G will abort an incremental search and restore the original
line.
When the search is terminated, the history entry containing the
search string becomes the current line.
To find other matching entries in the history list, type Control-S or
Control-R as appropriate.
This will search backward or forward in the history for the next
line matching the search string typed so far.
Any other key sequence bound to a readline command will terminate
the search and execute that command.
For instance, a newline will terminate the search and accept
the line, thereby executing the command from the history list.
Non-incremental searches read the entire search string before starting
to search for matching history lines. The search string may be
typed by the user or be part of the contents of the current line.
EDITING COMMANDS
The following is a list of the names of the commands and the default
key sequences to which they are bound.
Command names without an accompanying key sequence are unbound by default.
beginning-of-line (C-a)
Move to the start of the current line.
end-of-line (C-e)
Move to the end of the line.
forward-char (C-f)
Move forward a character.
backward-char (C-b)
forward-word (M-f)
Move forward to the end of the next word. Words are composed of
alphanumeric characters (letters and digits).
backward-word (M-b)
Move back to the start of this, or the previous, word. Words are
composed of alphanumeric characters (letters and digits).
clear-screen (C-l)
Clear the screen leaving the current line at the top of the screen.
With an argument, refresh the current line without clearing the
screen.
redraw-current-line
Refresh the current line.
accept-line (Newline, Return)
Accept the line regardless of where the cursor is. If this line is
non-empty, add it to the history list. If the line is a modified
history line, then restore the history line to its original state.
previous-history (C-p)
Fetch the previous command from the history list, moving back in
the list.
next-history (C-n)
Fetch the next command from the history list, moving forward in the
list.
beginning-of-history (M-<)
Move to the first line in the history.
end-of-history (M->)
Move to the end of the input history, i.e., the line currently being
entered.
reverse-search-history (C-r)
Search backward starting at the current line and moving `up' through
the history as necessary. This is an incremental search.
forward-search-history (C-s)
Search forward starting at the current line and moving `down' through
the history as necessary. This is an incremental search.
non-incremental-reverse-search-history (M-p)
Search backward through the history starting at the current line
using a non-incremental search for a string supplied by the user.
non-incremental-forward-search-history (M-n)
Search forward through the history using a non-incremental search
for a string supplied by the user.
history-search-forward
Search forward through the history for the string of characters
between the start of the current line and the current cursor
position (the point).
This is a non-incremental search.
history-search-backward
Search backward through the history for the string of characters
between the start of the current line and the point.
This is a non-incremental search.
yank-nth-arg (M-C-y)
Insert the first argument to the previous command (usually
the second word on the previous line) at point (the current
cursor position). With an argument
n ,
insert the nth word from the previous command (the words
in the previous command begin with word 0). A negative argument
inserts the nth word from the end of the previous command.
yank-last-arg (M-.\^, M-_\^)
Insert the last argument to the previous command (the last word of
the previous history entry). With an argument,
behave exactly like yank-nth-arg.
Successive calls to yank-last-arg move back through the history
list, inserting the last argument of each line in turn.
delete-char (C-d)
Delete the character under the cursor. If point is at the
beginning of the line, there are no characters in the line, and
the last character typed was not bound to Bdelete-char, then return
EOF .
backward-delete-char (Rubout)
Delete the character behind the cursor. When given a numeric argument,
save the deleted text on the kill ring.
quoted-insert (C-q, C-v)
Add the next character that you type to the line verbatim. This is
how to insert characters like C-q, for example.
tab-insert (M-TAB)
self-insert (a,\ b,\ A,\ 1,\ !,\ ...)
Insert the character typed.
transpose-chars (C-t)
Drag the character before point forward over the character at point.
Point moves forward as well. If point is at the end of the line, then
transpose the two characters before point. Negative arguments don't work.
transpose-words (M-t)
Drag the word behind the cursor past the word in front of the cursor
moving the cursor over that word as well.
upcase-word (M-u)
Uppercase the current (or following) word. With a negative argument,
uppercase the previous word, but do not move point.
downcase-word (M-l)
Lowercase the current (or following) word. With a negative argument,
lowercase the previous word, but do not move point.
capitalize-word (M-c)
Capitalize the current (or following) word. With a negative argument,
capitalize the previous word, but do not move point.
kill-line (C-k)
Kill the text from the current cursor position to the end of the line.
backward-kill-line (C-x Rubout)
Kill backward to the beginning of the line.
unix-line-discard (C-u)
Kill backward from point to the beginning of the line.
The killed text is saved on the kill-ring.
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