Readline is Copyright (C) 1989-2004 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 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.
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
M-Control-u: universal-argument
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:
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
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:
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.
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
\\
backslash
\
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)
\b
backspace
\d
delete
\f
form feed
\n
newline
\r
carriage return
\t
horizontal tab
\v
vertical tab
\nnn
the eight-bit character whose value is the octal value nnn
(one to three digits)
\xHH
the eight-bit character whose value is the hexadecimal value HH
(one or two hex digits)
When entering the text of a macro, single or double quotes 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
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
setvariable-namevalue
Except where noted, readline variables can take the values
On
or
Off
(without regard to case).
Unrecognized variable names are ignored.
When a variable value is read, empty or null values, "on" (case-insensitive),
and "1" are equivalent to On. All other values are equivalent to
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.
bind-tty-special-chars (On)
If set to On, readline attempts to bind the control characters
treated specially by the kernel's terminal driver to their readline
equivalents.
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. A negative value causes readline to never ask.
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 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.
history-preserve-point (Off)
If set to on, the history code attempts to place point at the
same location on each history line retrieved 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 line.
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
appended.
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
mark-directories).
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
sequence.
page-completions (On)
If set to On, readline uses an internal more-like pager
to display a screenful of possible completions at a time.
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.
show-all-if-unmodified (Off)
This alters the default behavior of the completion functions in
a fashion similar to show-all-if-ambiguous.
If set to
on,
words which have more than one possible completion without any
possible partial completion (the possible completions don't share
a common prefix) 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.
Conditional Constructs
Readline implements a facility similar in spirit to the conditional
compilation features of the C preprocessor which allows key
bindings and variable settings to be performed as the result
of tests. There are four parser directives used.
$if
The
$if
construct allows bindings to be made based on the
editing mode, the terminal being used, or the application using
readline. The text of the test extends to the end of the line;
no characters are required to isolate it.
mode
The mode= form of the $if directive is used to test
whether readline is in emacs or vi mode.
This may be used in conjunction
with the set keymap command, for instance, to set bindings in
the emacs-standard and emacs-ctlx keymaps only if
readline is starting out in emacs mode.
term
The term= form may be used to include terminal-specific
key bindings, perhaps to bind the key sequences output by the
terminal's function keys. The word on the right side of the
=
is tested against the full name of the terminal and the portion
of the terminal name before the first -. This allows
sun
to match both
sun
and
sun-cmd,
for instance.
application
The application construct is used to include
application-specific settings. Each program using the readline
library sets the application name, and 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
"\C-xq": "\eb\"\ef\""
$endif
$endif
This command, as seen in the previous example, terminates an
$if command.
$else
Commands in this branch of the $if directive are executed if
the test fails.
$include
This directive takes a single filename as an argument and reads commands
and bindings from that file. For example, the following directive
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.
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.
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.
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
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
screen.
redraw-current-line
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.
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.
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.
Once the argument n is computed, the argument is extracted
as if the "!n" history expansion had been specified.
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.
The history expansion facilities are used to extract the last argument,
as if the "!$" history expansion had been specified.
Commands for Changing Text
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.
forward-backward-delete-char
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.
tab-insert (M-TAB)
Insert a tab character.
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,
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.
overwrite-mode
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 is unbound.
Killing and Yanking
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-whole-line
Kill all characters on the current line, no matter where point is.
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.
unix-filename-rubout
Kill the word behind point, using white space and the slash character
as the word boundaries.
The killed text is saved on the kill-ring.
delete-horizontal-space (M-\)
Delete all spaces and tabs around point.
kill-region
Kill the text between the point and mark (saved cursor position).
This text is referred to as the region.
copy-region-as-kill
Copy the text in the region to the kill buffer.
copy-backward-word
Copy the word before point to the kill buffer.
The word boundaries are the same as backward-word.
copy-forward-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 point.
yank-pop (M-y)
Rotate the kill ring, and yank the new top. Only works following
yank
or
yank-pop.
Numeric Arguments
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.
universal-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
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 point.
insert-completions (M-*)
Insert all completions of the text before point
that would have been generated by
possible-completions.
menu-complete
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 bell-style)
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.
delete-char-or-list
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
start-kbd-macro (C-x ()
Begin saving the characters typed into the current keyboard macro.
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
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.
ESCf
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 state.
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 mark.
character-search (C-])
A character is read and point is moved to the next occurrence of that
character. A negative count searches for previous occurrences.
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 occurrences.
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.
dump-functions
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.
dump-variables
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 file.
dump-macros
Print all of the readline key sequences bound to macros and the
strings they output. If a numeric argument is supplied,
the output is formatted in such a way that it can be made part
of an inputrc file.
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.
DEFAULT KEY BINDINGS
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).
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 bug-readline@gnu.org.
If you have a fix, you are welcome to mail that
as well! Suggestions and `philosophical' bug reports may be mailed
to bug-readline@gnu.org or posted to the Usenet
newsgroup
gnu.bash.bug.
Comments and bug reports concerning
this manual page should be directed to
chet@ins.CWRU.Edu.
BUGS
It's too big and too slow.
The info file is much more up-to-date. This man page conflicts with it in
a few places, but the conflicts will be resolved in a future release of
readline.