readline - get a line from a user with editing
readline (const char *prompt);
Readline is Copyright (C) 1989-2002 by the Free Software
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
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
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.
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
The following symbolic character names are recognized
while processing key bindings: DEL, ESC, ESCAPE, LFD, NEW-
LINE, 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
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, key-
name is the name of a key spelled out in English. For
Control-o: "> output"
In the above example, C-u is bound to the function univer-
sal-argument, M-DEL is bound to the function back-
ward-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, key-
seq 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.
"\[11~": "Function Key 1"
In this example, C-u is again bound to the function uni-
versal-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
- control prefix
M- meta prefix
e an escape character
t horizontal tab
nnn the eight-bit character whose value is the
octal value nnn (one to three digits)
HH 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 form
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 audi-
ble, 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
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-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
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
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 vi.
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.
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-history 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 new line.
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
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 mark-directories).
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 metaprefixed
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 screen.
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.
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
$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 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 applica-
tion 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 command.
$else 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
Readline provides commands for searching through the command
history for lines containing a specified string.
There are two search modes: incremental and non-incremen-
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 current line.
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 region.
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
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
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 the list.
Fetch the next command from the history list, moving
forward in the list.
Move to the first line in the history.
Move to the end of the input history, i.e., the
line currently being entered.
Search backward starting at the current line and
moving `up' through the history as necessary. This
is an incremental search.
Search forward starting at the current line and
moving `down' through the history as necessary.
This is an incremental search.
Search backward through the history starting at the
current line using a non-incremental search for a
string supplied by the user.
Search forward through the history using a nonincremental
search for a string supplied by the
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 non-incremental search.
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
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
Delete the character under the cursor, unless the
cursor is at the end of the line, in which case the
character behind the cursor is deleted.
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 is.
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 for-
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
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
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
Rotate the kill ring, and yank the new top. Only
works following yank or yank-pop.
digit-argument (M-0, M-1, ..., M--)
Add this digit to the argument already accumulating,
or start a new argument. M-- starts a negative
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
List the possible completions of the text before
Insert all completions of the text before point
that would have been generated by possible-comple-
Similar to complete, but replaces the word to be
completed with a single match from the list of possible
completions. Repeated execution of menu-com-
plete 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 Bbell-style) and the original
text is restored. An argument of n moves n posi-
tions 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
Keyboard Macros [Toc] [Back]
start-kbd-macro (C-x ()
Begin saving the characters typed into the current
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
Abort the current editing command and ring the terminal's
bell (subject to the setting of
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
Metafy the next character typed. ESC f is equivalent
undo (C-_, C-x C-u)
Incremental undo, separately remembered for each
Undo all changes made to this line. This is like
executing the undo command enough times to return
the line to its initial state.
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 occurrences.
Without a numeric argument, the value of the readline
comment-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 inputrc file.
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 inputrc
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 inputrc
When in vi command mode, this causes a switch to
emacs editing mode.
When in emacs editing mode, this causes a switch to
vi editing mode.
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 email@example.com. If you have a fix,
you are welcome to mail that as well! Suggestions and
`philosophical' bug reports may be mailed to bug-read-
firstname.lastname@example.org or posted to the Usenet newsgroup
Comments and bug reports concerning this manual page
should be directed to chet@ins.CWRU.Edu.
It's too big and too slow.
GNU Readline 4.3 2002 January 22 19 [ Back ]