readline - get a line from a user with editing
readline (const char *prompt);
Readline is Copyright (C) 1989-2002 by the Free Software Foundation,
readline will read a line from the terminal and return it, using prompt
as a prompt. If prompt is NULL or the empty string, no prompt is
issued. The line returned is allocated with malloc(3); 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.
This manual page describes only the most basic use of readline. Much
more functionality is available; see The GNU Readline Library and The
GNU History Library for additional information.
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.
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
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.
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
into the inputrc would make M-C-u execute the readline command univer-
The following symbolic character names are recognized while processing
key bindings: DEL, ESC, ESCAPE, LFD, NEWLINE, RET, RETURN, RUBOUT,
SPACE, SPC, 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).
Key Bindings [Toc] [Back]
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-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, but
the symbolic character names are not recognized.
"\e[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 available when specifying
key sequences is
\C- control prefix
\M- meta prefix
\e an escape character
\" literal ", a double quote
\' literal ', a single quote
In addition to the GNU Emacs style escape sequences, a second set of
backslash escapes is available:
\a alert (bell)
\f form feed
\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 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.
Variables [Toc] [Back]
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
set variable-name value
Except where noted, readline variables can take the values On or Off
(without regard to case). The variables and their default values are:
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.
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.
If set to On, readline performs filename matching and completion
in a case-insensitive fashion.
This determines when the user is queried about viewing the number
of possible completions generated by the possible-comple-
tions 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.
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 it with an escape character (in effect, using escape
as the meta prefix).
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.
Controls whether readline begins with a set of key bindings similar
to emacs or vi. editing-mode can be set to either emacs or
When set to On, readline will try to enable the application keypad
when it is called. Some systems need this to enable the
If set to on, tilde expansion is performed when readline
attempts word completion.
If set to on, the history code attempts to place point at the
same location on each history line retrived with previous-his-
tory or next-history.
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
If set to On, readline will enable eight-bit input (that is, it
will not clear the eighth bit in the characters it reads),
regardless of what the terminal claims it can support. The name
meta-flag is a synonym for this variable.
isearch-terminators (``C-[ C-J'')
The string of characters that should terminate an incremental
search without subsequently executing the character as a command.
If this variable has not been given a value, the characters
ESC and C-J will terminate an incremental search.
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
If set to On, completed directory names have a slash appended.
If set to On, history lines that have been modified are displayed
with a preceding asterisk (*).
If set to On, completed names which are symbolic links to directories
have a slash appended (subject to the value of
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.
If set to On, readline will display characters with the eighth
bit set directly rather than as a meta-prefixed escape sequence.
If set to On, readline uses an internal more-like pager to display
a screenful of possible completions at a time.
If set to On, readline will display completions with matches
sorted horizontally in alphabetical order, rather than down the
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
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.
Conditional Constructs [Toc] [Back]
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
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 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
The application construct is used to include applicationspecific
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
# Quote the current or previous word
$endif This command, as seen in the previous example, terminates an $if
$else Commands in this branch of the $if directive are executed if the
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:
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. To search backward in the
history for a particular string, type C-r. Typing C-s searches forward
through the history. The characters present in the value of the
isearch-terminators variable are used to terminate an incremental
search. If that variable has not been assigned a value the Escape and
C-J characters will terminate an incremental search. C-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
To find other matching entries in the history list, type C-s or C-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. A movement command will terminate the search, make the last line
found the current line, and begin editing.
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.
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.
In the following descriptions, point refers to the current cursor position,
and mark refers to a cursor position saved by the set-mark command.
The text between the point and mark is referred to as the
Commands for Moving [Toc] [Back]
Move to the start of the current line.
Move to the end of the line.
Move forward a character.
Move back a character.
Move forward to the end of the next word. Words are composed of
alphanumeric characters (letters and digits).
Move back to the start of the current or previous word. Words
are composed of alphanumeric characters (letters and digits).
Clear the screen leaving the current line at the top of the
screen. With an argument, refresh the current line without
clearing the screen.
Refresh the current line.
Commands for Manipulating the History [Toc] [Back]
accept-line (Newline, Return)
Accept the line regardless of where the cursor is. If this line
is non-empty, it may be added to the history list for future
recall with add_history(). If the line is a modified history
line, the history line is restored to its original state.
Fetch the previous command from the history list, moving back in
Fetch the next command from the history list, moving forward in
Move to the first line in the history.
Move to the end of the input history, i.e., the line currently
Search backward starting at the current line and moving `up'
through the history as necessary. This is an incremental
Search forward starting at the current line and moving `down'
through the history as necessary. This is an incremental
Search backward through the history starting at the current line
using a non-incremental search for a string supplied by the
Search forward through the history using a non-incremental
search for a string supplied by the user.
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.
Search backward through the history for the string of characters
between the start of the current line and the point. This is a
Insert the first argument to the previous command (usually the
second word on the previous line) at point. 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.
Commands for Changing Text [Toc] [Back]
Delete the character at point. 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 delete-char, then return EOF.
Delete the character behind the cursor. When given a numeric
argument, save the deleted text on the kill ring.
Delete the character under the cursor, unless the cursor is at
the end of the line, in which case the character behind the cursor
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.
Insert a tab character.
self-insert (a, b, A, 1, !, ...)
Insert the character typed.
Drag the character before point forward over the character at
point, moving point forward as well. If point is at the end of
the line, then this transposes the two characters before point.
Negative arguments have no effect.
Drag the word before point past the word after point, moving
point over that word as well. If point is at the end of the
line, this transposes the last two words on the line.
Uppercase the current (or following) word. With a negative
argument, uppercase the previous word, but do not move point.
Lowercase the current (or following) word. With a negative
argument, lowercase the previous word, but do not move point.
Capitalize the current (or following) word. With a negative
argument, capitalize the previous word, but do not move point.
Toggle overwrite mode. With an explicit positive numeric argument,
switches to overwrite mode. With an explicit non-positive
numeric argument, switches to insert mode. This command affects
only emacs mode; vi mode does overwrite differently. Each call
to readline() starts in insert mode. In overwrite mode, characters
bound to self-insert replace the text at point rather than
pushing the text to the right. Characters bound to back-
ward-delete-char replace the character before point with a
space. By default, this command is unbound.
Killing and Yanking [Toc] [Back]
Kill the text from point to the end of the line.
backward-kill-line (C-x Rubout)
Kill backward to the beginning of the line.
Kill backward from point to the beginning of the line. The
killed text is saved on the kill-ring.
Kill all characters on the current line, no matter where point
Kill from point the end of the current word, or if between
words, to the end of the next word. Word boundaries are the
same as those used by forward-word.
Kill the word behind point. Word boundaries are the same as
those used by backward-word.
Kill the word behind point, using white space as a word boundary.
The killed text is saved on the kill-ring.
Delete all spaces and tabs around point.
Kill the text between the point and mark (saved cursor position).
This text is referred to as the region.
Copy the text in the region to the kill buffer.
Copy the word before point to the kill buffer. The word boundaries
are the same as backward-word.
Copy the word following point to the kill buffer. The word
boundaries are the same as forward-word.
Yank the top of the kill ring into the buffer at point.
Rotate the kill ring, and yank the new top. Only works following
yank or yank-pop.
Numeric Arguments [Toc] [Back]
digit-argument (M-0, M-1, ..., M--)
Add this digit to the argument already accumulating, or start a
new argument. M-- starts a negative argument.
This is another way to specify an argument. If this command is
followed by one or more digits, optionally with a leading minus
sign, those digits define the argument. If the command is followed
by digits, executing universal-argument again ends the
numeric argument, but is otherwise ignored. As a special case,
if this command is immediately followed by a character that is
neither a digit or minus sign, the argument count for the next
command is multiplied by four. The argument count is initially
one, so executing this function the first time makes the argument
count four, a second time makes the argument count sixteen,
and so on.
Completing [Toc] [Back]
Attempt to perform completion on the text before point. The
actual completion performed is application-specific. Bash, for
instance, attempts completion treating the text as a variable
(if the text begins with $), username (if the text begins with
~), hostname (if the text begins with @), or command (including
aliases and functions) in turn. If none of these produces a
match, filename completion is attempted. Gdb, on the other
hand, allows completion of program functions and variables, and
only attempts filename completion under certain circumstances.
List the possible completions of the text before point.
Insert all completions of the text before point that would have
been generated by possible-completions.
Similar to complete, but replaces the word to be completed with
a single match from the list of possible completions. Repeated
execution of menu-complete steps through the list of possible
completions, inserting each match in turn. At the end of the
list of completions, the bell is rung (subject to the setting of
0 and the original text is restored. An argument of n moves n
positions forward in the list of matches; a negative argument
may be used to move backward through the list. This command is
intended to be bound to TAB, but is unbound by default.
Deletes the character under the cursor if not at the beginning
or end of the line (like delete-char). If at the end of the
line, behaves identically to possible-completions.
Keyboard Macros [Toc] [Back]
start-kbd-macro (C-x ()
Begin saving the characters typed into the current keyboard
end-kbd-macro (C-x ))
Stop saving the characters typed into the current keyboard macro
and store the definition.
call-last-kbd-macro (C-x e)
Re-execute the last keyboard macro defined, by making the characters
in the macro appear as if typed at the keyboard.
Miscellaneous [Toc] [Back]
re-read-init-file (C-x C-r)
Read in the contents of the inputrc file, and incorporate any
bindings or variable assignments found there.
Abort the current editing command and ring the terminal's bell
(subject to the setting of bell-style).
do-uppercase-version (M-a, M-b, M-x, ...)
If the metafied character x is lowercase, run the command that
is bound to the corresponding uppercase character.
Metafy the next character typed. ESC f is equivalent to Meta-f.
undo (C-_, C-x C-u)
Incremental undo, separately remembered for each line.
Undo all changes made to this line. This is like executing the
undo command enough times to return the line to its initial
Perform tilde expansion on the current word.
set-mark (C-@, M-<space>)
Set the mark to the point. If a numeric argument is supplied,
the mark is set to that position.
exchange-point-and-mark (C-x C-x)
Swap the point with the mark. The current cursor position is
set to the saved position, and the old cursor position is saved
as the mark.
A character is read and point is moved to the next occurrence of
that character. A negative count searches for previous occurrences.
A character is read and point is moved to the previous occurrence
of that character. A negative count searches for subsequent
Without a numeric argument, the value of the readline com-
ment-begin variable is inserted at the beginning of the current
line. If a numeric argument is supplied, this command acts as a
toggle: if the characters at the beginning of the line do not
match the value of comment-begin, the value is inserted, otherwise
the characters in comment-begin are deleted from the beginning
of the line. In either case, the line is accepted as if a
newline had been typed. The default value of comment-begin
makes the current line a shell comment. If a numeric argument
causes the comment character to be removed, the line will be
executed by the shell.
Print all of the functions and their key bindings to the readline
output stream. If a numeric argument is supplied, the output
is formatted in such a way that it can be made part of an
Print all of the settable variables and their values to the
readline output stream. If a numeric argument is supplied, the
output is formatted in such a way that it can be made part of an
Print all of the readline key sequences bound to macros and the
strings they ouput. If a numeric argument is supplied, the output
is formatted in such a way that it can be made part of an
When in vi command mode, this causes a switch to emacs editing
When in emacs editing mode, this causes a switch to vi editing
The following is a list of the default emacs and vi bindings. Characters
with the eighth bit set are written as M-<character>, and are
referred to as metafied characters. The printable ASCII characters not
mentioned in the list of emacs standard bindings are bound to the
self-insert function, which just inserts the given character into the
input line. In vi insertion mode, all characters not specifically mentioned
are bound to self-insert. Characters assigned to signal generation
by stty(1) or the terminal driver, such as C-Z or C-C, retain that
function. Upper and lower case metafied characters are bound to the
same function in the emacs mode meta keymap. The remaining characters
are unbound, which causes readline to ring the bell (subject to the
setting of the bell-style variable).
Emacs Mode [Toc] [Back]
Emacs Standard bindings
" " to "/" self-insert
"0" to "9" self-insert
":" to "~" self-insert
Emacs Meta bindings
Emacs Control-X bindings
VI Mode bindings [Toc] [Back]
VI Insert Mode functions
" " to "~" self-insert
VI Command Mode functions
" " forward-char
"1" to "9" vi-arg-digit
The Gnu Readline Library, Brian Fox and Chet Ramey
The Gnu History Library, Brian Fox and Chet Ramey
Individual readline initialization file
Brian Fox, Free Software Foundation
Chet Ramey, Case Western Reserve University
If you find a bug in readline, you should report it. But first, you
should make sure that it really is a bug, and that it appears in the
latest version of the readline library that you have.
Once you have determined that a bug actually exists, mail a bug report
to firstname.lastname@example.org. If you have a fix, you are welcome to mail
that as well! Suggestions and `philosophical' bug reports may be
mailed to email@example.com or posted to the Usenet newsgroup
Comments and bug reports concerning this manual page should be directed
It's too big and too slow.
GNU Readline 4.3 2002 January 22 READLINE(3)
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