readline - get a line from a user with editing
readline (const char *prompt);
Readline is Copyright (C) 1989-2002 by the Free Software Foundation, Inc.
will read a line from the terminal and return it, using
as a prompt. If prompt
or the empty
string, no prompt is issued. The line returned is allocated with
(3); the caller must free it when finished. The line returned has
the final newline removed, so only the text of the line remains.
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
for additional information.
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
denoted by M- key
, so M-x means Meta-X. (On keyboards without a
key, M- x
means ESC x
, i.e., press the Escape key
then the x
key. This makes ESC the meta prefix
. The combination
, 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
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
. 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
file). The name of this file is taken from the value of the
environment variable. If that variable is unset, the default is
. 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
For example, placing
into the inputrc
would make M-C-u execute the readline command
The following symbolic character names are recognized while processing key
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-
prefixes, or as a key sequence.
When using the form 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
is bound to the function
, and C-o
is bound to run the macro expressed
on the right hand side (that is, to insert the text ``> output'' into the
In the second form, "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
. C-x C-r
is bound to the function
, 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
- control prefix
- meta prefix
- 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:
- alert (bell)
- form feed
- carriage return
- horizontal tab
- vertical tab
- the eight-bit character whose value is the octal value
nnn (one to three digits)
- 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 "
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
command. Other programs using this library provide similar mechanisms. The
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
(without regard to case). The variables and their default values
- 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
- 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
- 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 prefixing it with an escape character (in effect, using escape as the
- 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
- expand-tilde (Off)
- 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.
- 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
- input-meta (Off)
- 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.
- 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, completed directory names have a slash
- mark-modified-lines (Off)
- If set to On, history lines that have been modified
are displayed with a preceding asterisk ( *).
- mark-symlinked-directories (Off)
- If set to On, completed names which are symbolic
links to directories have a slash appended (subject to the value of
- match-hidden-files (On)
- 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.
- output-meta (Off)
- If set to On, readline will display characters with
the eighth bit set directly rather than as a meta-prefixed escape
- page-completions (On)
- If set to On, readline uses an internal
more-like pager to display a screenful of possible completions at a
- print-completions-horizontally (Off)
- If set to On, readline will display completions with
matches sorted horizontally in alphabetical order, rather than down the
- 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
- 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
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:
# Quote the current or previous word
- 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:
Readline provides commands for searching through the command history for lines
containing a specified string. There are two search modes: 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
. Typing C-s
searches forward through the history. The
characters present in the value of the isearch-terminators
used to terminate an incremental search. If that variable has not been
assigned a value the Escape
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
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
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
command. The text between the point and mark is referred to as
- 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)
- Move back a character.
- 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 the current or 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
- Refresh the current line.
- 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.
- 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
- 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
- non-incremental-forward-search-history (M-n)
- 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
- yank-nth-arg (M-C-y)
- 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
- delete-char (C-d)
- 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.
- backward-delete-char (Rubout)
- 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 is
- 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)
- Insert a tab character.
(a, b, A, 1, !, ...)
- Insert the character typed.
- transpose-chars (C-t)
- 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.
- transpose-words (M-t)
- 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.
- 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.
- 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 backward-delete-char
replace the character before point with a space. By default, this command
- kill-line (C-k)
- 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.
- unix-line-discard (C-u)
- 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
- kill-word (M-d)
- 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.
- backward-kill-word (M-Rubout)
- Kill the word behind point. Word boundaries are the same as
those used by backward-word.
- unix-word-rubout (C-w)
- Kill the word behind point, using white space as a word
boundary. The killed text is saved on the kill-ring.
- delete-horizontal-space (M-\)
- 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 (C-y)
- Yank the top of the kill ring into the buffer at
- yank-pop (M-y)
- 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 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.
- complete (TAB)
- 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.
- possible-completions (M-?)
- List the possible completions of the text before
- insert-completions (M-*)
- 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.
- 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.
- 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 (C-g)
- 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.
- prefix-meta (ESC)
- 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.
- revert-line (M-r)
- Undo all changes made to this line. This is like executing
the undo command enough times to return the line to its initial
- tilde-expand (M-&)
- 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
- character-search (C-])
- A character is read and point is moved to the next
occurrence of that character. A negative count searches for previous
- character-search-backward (M-C-])
- A character is read and point is moved to the previous
occurrence of that character. A negative count searches for subsequent
- insert-comment (M-#)
- 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
- 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
- emacs-editing-mode (C-e)
- When in vi command mode, this causes a switch to
emacs editing mode.
- vi-editing-mode (M-C-j)
- 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
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
. Characters assigned to signal generation by stty
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
Emacs Standard bindings
" " to "/" self-insert
"0" to "9" self-insert
":" to "~" self-insert
Emacs Meta bindings
Emacs Control-X bindings
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
- The Gnu History Library, Brian Fox and Chet
- 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
. If you have a fix, you are welcome to
mail that as well! Suggestions and `philosophical' bug reports may be mailed
or posted to the Usenet newsgroup
Comments and bug reports concerning this manual page should be directed to
It's too big and too slow.