This document describes the GNU Readline Library, a utility which aids in the consistency of user interface across discrete programs that need to provide a command line interface.
Published by the Free Software Foundation
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Copyright (C) 1989, 1991 Free Software Foundation, Inc.
This chapter describes the basic features of the GNU command line editing interface.
The following paragraphs describe the notation used to represent keystrokes.
The text C-k is read as `Control-K' and describes the character produced when the k key is pressed while the Control key is depressed.
The text M-k is read as `Meta-K' and describes the character produced when the meta key (if you have one) is depressed, and the k key is pressed. If you do not have a meta key, the identical keystroke can be generated by typing ESC first, and then typing k. Either process is known as metafying the k key.
The text M-C-k is read as `Meta-Control-k' and describes the character produced by metafying C-k.
In addition, several keys have their own names. Specifically, DEL, ESC, LFD, SPC, RET, and TAB all stand for themselves when seen in this text, or in an init file (@xref{Readline Init File}).
Often during an interactive session you type in a long line of text, only to notice that the first word on the line is misspelled. The Readline library gives you a set of commands for manipulating the text as you type it in, allowing you to just fix your typo, and not forcing you to retype the majority of the line. Using these editing commands, you move the cursor to the place that needs correction, and delete or insert the text of the corrections. Then, when you are satisfied with the line, you simply press RETURN. You do not have to be at the end of the line to press RETURN; the entire line is accepted regardless of the location of the cursor within the line.
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 (see section Conditional Init Constructs). Other lines denote variable settings and key bindings.
set
command within the init file. Here is how you
would specify that you wish to use vi
line editing commands:
set editing-mode viRight now, there are only a few variables which can be set; so few, in fact, that we just list them here:
bell-style
comment-begin
insert-comment
command is executed. The default value
is "#"
.
completion-query-items
100
.
convert-meta
disable-completion
self-insert
. The default is `off'.
editing-mode
editing-mode
variable controls which editing mode you are
using. By default, Readline starts up in Emacs editing mode, where
the keystrokes are most similar to Emacs. This variable can be
set to either `emacs' or `vi'.
enable-keypad
expand-tilde
horizontal-scroll-mode
keymap
keymap
names are
emacs
,
emacs-standard
,
emacs-meta
,
emacs-ctlx
,
vi
,
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 the editing-mode
variable also affects the
default keymap.
mark-directories
mark-modified-lines
input-meta
meta-flag
is a
synonym for this variable.
output-meta
show-all-if-ambiguous
visible-stats
Control-u: universal-argument Meta-Rubout: backward-kill-word Control-o: "> output"In the above example, `C-u' is bound to the function
universal-argument
, 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).
"\C-u": universal-argument "\C-x\C-r": re-read-init-file "\e[11~": "Function Key 1"In the above example, `C-u' is bound to the function
universal-argument
(just as it was in the first example),
`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 following escape sequences are available when specifying key
sequences:
\C-
\M-
\e
\\
\"
\'
"\C-x\\": "\\"
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 three parser directives used.
$if
$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
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
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
$if Bash # Quote the current or previous word "\C-xq": "\eb\"\ef\"" $endif
$endif
$if
command.
$else
$if
directive are executed if
the test fails.
Here is an example of an inputrc file. This illustrates key binding, variable assignment, and conditional syntax.
# This file controls the behaviour of line input editing for # programs that use the Gnu Readline library. Existing programs # include FTP, Bash, and Gdb. # # You can re-read the inputrc file with C-x C-r. # Lines beginning with '#' are comments. # # Set various bindings for emacs mode. set editing-mode emacs $if mode=emacs Meta-Control-h: backward-kill-word Text after the function name is ignored # # Arrow keys in keypad mode # #"\M-OD": backward-char #"\M-OC": forward-char #"\M-OA": previous-history #"\M-OB": next-history # # Arrow keys in ANSI mode # "\M-[D": backward-char "\M-[C": forward-char "\M-[A": previous-history "\M-[B": next-history # # Arrow keys in 8 bit keypad mode # #"\M-\C-OD": backward-char #"\M-\C-OC": forward-char #"\M-\C-OA": previous-history #"\M-\C-OB": next-history # # Arrow keys in 8 bit ANSI mode # #"\M-\C-[D": backward-char #"\M-\C-[C": forward-char #"\M-\C-[A": previous-history #"\M-\C-[B": next-history C-q: quoted-insert $endif # An old-style binding. This happens to be the default. TAB: complete # Macros that are convenient for shell interaction $if Bash # edit the path "\C-xp": "PATH=${PATH}\e\C-e\C-a\ef\C-f" # prepare to type a quoted word -- insert open and close double quotes # and move to just after the open quote "\C-x\"": "\"\"\C-b" # insert a backslash (testing backslash escapes in sequences and macros) "\C-x\\": "\\" # Quote the current or previous word "\C-xq": "\eb\"\ef\"" # Add a binding to refresh the line, which is unbound "\C-xr": redraw-current-line # Edit variable on current line. "\M-\C-v": "\C-a\C-k$\C-y\M-\C-e\C-a\C-y=" $endif # use a visible bell if one is available set bell-style visible # don't strip characters to 7 bits when reading set input-meta on # allow iso-latin1 characters to be inserted rather than converted to # prefix-meta sequences set convert-meta off # display characters with the eighth bit set directly rather than # as meta-prefixed characters set output-meta on # if there are more than 150 possible completions for a word, ask the # user if he wants to see all of them set completion-query-items 150 # For FTP $if Ftp "\C-xg": "get \M-?" "\C-xt": "put \M-?" "\M-.": yank-last-arg $endif
This section describes Readline commands that may be bound to key sequences.
beginning-of-line (C-a)
end-of-line (C-e)
forward-char (C-f)
backward-char (C-b)
forward-word (M-f)
backward-word (M-b)
clear-screen (C-l)
redraw-current-line ()
accept-line (Newline, Return)
previous-history (C-p)
next-history (C-n)
beginning-of-history (M-<)
end-of-history (M->)
reverse-search-history (C-r)
forward-search-history (C-s)
non-incremental-reverse-search-history (M-p)
non-incremental-forward-search-history (M-n)
history-search-forward ()
history-search-backward ()
yank-nth-arg (M-C-y)
yank-last-arg (M-., M-_)
yank-nth-arg
.
delete-char (C-d)
EOF
.
backward-delete-char (Rubout)
quoted-insert (C-q, C-v)
tab-insert (M-TAB)
self-insert (a, b, A, 1, !, ...)
transpose-chars (C-t)
transpose-words (M-t)
upcase-word (M-u)
downcase-word (M-l)
capitalize-word (M-c)
kill-line (C-k)
backward-kill-line (C-x Rubout)
unix-line-discard (C-u)
kill-whole-line ()
kill-word (M-d)
forward-word
.
backward-kill-word (M-DEL)
backward-word
.
unix-word-rubout (C-w)
delete-horizontal-space ()
kill-region ()
copy-region-as-kill ()
copy-backward-word ()
copy-forward-word ()
yank (C-y)
yank-pop (M-y)
digit-argument (M-0, M-1, ... M--)
universal-argument ()
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.
By default, this is not bound to a key.
complete (TAB)
possible-completions (M-?)
insert-completions (M-*)
possible-completions
.
start-kbd-macro (C-x ()
end-kbd-macro (C-x ))
call-last-kbd-macro (C-x e)
re-read-init-file (C-x C-r)
abort (C-g)
bell-style
).
do-uppercase-version (M-a, M-b, M-x, ...)
prefix-meta (ESC)
undo (C-_, C-x C-u)
revert-line (M-r)
undo
command enough times to get back to the beginning.
tilde-expand (M-~)
set-mark (C-@)
exchange-point-and-mark (C-x C-x)
character-search (C-])
character-search-backward (M-C-])
insert-comment (M-#)
comment-begin
variable is inserted at the beginning of the current line,
and the line is accepted as if a newline had been typed.
dump-functions ()
dump-variables ()
dump-macros ()
While the Readline library does not have a full set of vi
editing functions, it does contain enough to allow simple editing
of the line. The Readline vi
mode behaves as specified in
the POSIX 1003.2 standard.
In order to switch interactively between emacs
and vi
editing modes, use the command M-C-j (toggle-editing-mode).
The Readline default is emacs
mode.
When you enter a line in vi
mode, you are already placed in
`insertion' mode, as if you had typed an `i'. Pressing ESC
switches you into `command' mode, where you can edit the text of the
line with the standard vi
movement keys, move to previous
history lines with `k' and subsequent lines with `j', and
so forth.
This chapter describes the interface between the GNU Readline Library and other programs. If you are a programmer, and you wish to include the features found in GNU Readline such as completion, line editing, and interactive history manipulation in your own programs, this section is for you.
Many programs provide a command line interface, such as mail
,
ftp
, and sh
. For such programs, the default behaviour of
Readline is sufficient. This section describes how to use Readline in
the simplest way possible, perhaps to replace calls in your code to
gets()
or fgets ()
.
The function readline ()
prints a prompt and then reads and returns
a single line of text from the user. The line readline
returns is allocated with malloc ()
; you should free ()
the line when you are done with it. The declaration for readline
in ANSI C is
char *readline (char *prompt);
So, one might say
char *line = readline ("Enter a line: ");
in order to read a line of text from the user. The line returned has the final newline removed, so only the text remains.
If readline
encounters an EOF
while reading the line, and the
line is empty at that point, then (char *)NULL
is returned.
Otherwise, the line is ended just as if a newline had been typed.
If you want the user to be able to get at the line later, (with
C-p for example), you must call add_history ()
to save the
line away in a history list of such lines.
add_history (line)
;
For full details on the GNU History Library, see the associated manual.
It is preferable to avoid saving empty lines on the history list, since
users rarely have a burning need to reuse a blank line. Here is
a function which usefully replaces the standard gets ()
library
function, and has the advantage of no static buffer to overflow:
/* A static variable for holding the line. */ static char *line_read = (char *)NULL; /* Read a string, and return a pointer to it. Returns NULL on EOF. */ char * rl_gets () { /* If the buffer has already been allocated, return the memory to the free pool. */ if (line_read) { free (line_read); line_read = (char *)NULL; } /* Get a line from the user. */ line_read = readline (""); /* If the line has any text in it, save it on the history. */ if (line_read && *line_read) add_history (line_read); return (line_read); }
This function gives the user the default behaviour of TAB
completion: completion on file names. If you do not want Readline to
complete on filenames, you can change the binding of the TAB key
with rl_bind_key ()
.
int rl_bind_key (int key, int (*function)());
rl_bind_key ()
takes two arguments: key is the character that
you want to bind, and function is the address of the function to
call when key is pressed. Binding TAB to rl_insert ()
makes TAB insert itself.
rl_bind_key ()
returns non-zero if key is not a valid
ASCII character code (between 0 and 255).
Thus, to disable the default TAB behavior, the following suffices:
rl_bind_key ('\t', rl_insert);
This code should be executed once at the start of your program; you
might write a function called initialize_readline ()
which
performs this and other desired initializations, such as installing
custom completers (see section Custom Completers).
Readline provides many functions for manipulating the text of the line, but it isn't possible to anticipate the needs of all programs. This section describes the various functions and variables defined within the Readline library which allow a user program to add customized functionality to Readline.
For readabilty, we declare a new type of object, called
Function. A Function
is a C function which
returns an int
. The type declaration for Function
is:
typedef int Function ();
The reason for declaring this new type is to make it easier to write code describing pointers to C functions. Let us say we had a variable called func which was a pointer to a function. Instead of the classic C declaration
int (*)()func;
we may write
Function *func;
Similarly, there are
typedef void VFunction (); typedef char *CPFunction (); and typedef char **CPPFunction ();
for functions returning no value, pointer to char
, and
pointer to pointer to char
, respectively.
In order to write new functions for Readline, you need to know the calling conventions for keyboard-invoked functions, and the names of the variables that describe the current state of the line read so far.
The calling sequence for a command foo
looks like
foo (int count, int key)
where count is the numeric argument (or 1 if defaulted) and key is the key that invoked this function.
It is completely up to the function as to what should be done with the numeric argument. Some functions use it as a repeat count, some as a flag, and others to choose alternate behavior (refreshing the current line as opposed to refreshing the screen, for example). Some choose to ignore it. In general, if a function uses the numeric argument as a repeat count, it should be able to do something useful with both negative and positive arguments. At the very least, it should be aware that it can be passed a negative argument.
These variables are available to function writers.
Variable: char * rl_line_buffer
This is the line gathered so far. You are welcome to modify the contents of the line, but see section Allowing Undoing.
Variable: int rl_point
The offset of the current cursor position in rl_line_buffer
(the point).
Variable: int rl_end
The number of characters present in rl_line_buffer
. When
rl_point
is at the end of the line, rl_point
and
rl_end
are equal.
Variable: int rl_mark
The mark (saved position) in the current line. If set, the mark and point define a region.
Variable: int rl_done
Setting this to a non-zero value causes Readline to return the current line immediately.
Variable: int rl_pending_input
Setting this to a value makes it the next keystroke read. This is a way to stuff a single character into the input stream.
Variable: char * rl_prompt
The prompt Readline uses. This is set from the argument to
readline ()
, and should not be assigned to directly.
Variable: char * rl_library_version
The version number of this revision of the library.
Variable: char * rl_terminal_name
The terminal type, used for initialization.
Variable: char * rl_readline_name
This variable is set to a unique name by each application using Readline. The value allows conditional parsing of the inputrc file (see section Conditional Init Constructs).
Variable: FILE * rl_instream
The stdio stream from which Readline reads input.
Variable: FILE * rl_outstream
The stdio stream to which Readline performs output.
Variable: Function * rl_startup_hook
If non-zero, this is the address of a function to call just
before readline
prints the first prompt.
Variable: Function * rl_event_hook
If non-zero, this is the address of a function to call periodically when readline is waiting for terminal input.
Variable: Function * rl_getc_function
If non-zero, readline
will call indirectly through this pointer
to get a character from the input stream. By default, it is set to
rl_getc
, the default readline
character input function
(see section Utility Functions).
Variable: VFunction * rl_redisplay_function
If non-zero, readline
will call indirectly through this pointer
to update the display with the current contents of the editing buffer.
By default, it is set to rl_redisplay
, the default readline
redisplay function (see section Redisplay).
Variable: Keymap rl_executing_keymap
This variable is set to the keymap (see section Selecting a Keymap) in which the currently executing readline function was found.
Variable: Keymap rl_binding_keymap
This variable is set to the keymap (see section Selecting a Keymap) in which the last key binding occurred.
The user can dynamically change the bindings of keys while using Readline. This is done by representing the function with a descriptive name. The user is able to type the descriptive name when referring to the function. Thus, in an init file, one might find
Meta-Rubout: backward-kill-word
This binds the keystroke Meta-Rubout to the function
descriptively named backward-kill-word
. You, as the
programmer, should bind the functions you write to descriptive names as
well. Readline provides a function for doing that:
Function: int rl_add_defun (char *name, Function *function, int key)
Add name to the list of named functions. Make function be
the function that gets called. If key is not -1, then bind it to
function using rl_bind_key ()
.
Using this function alone is sufficient for most applications. It is the recommended way to add a few functions to the default functions that Readline has built in. If you need to do something other than adding a function to Readline, you may need to use the underlying functions described below.
Key bindings take place on a keymap. The keymap is the association between the keys that the user types and the functions that get run. You can make your own keymaps, copy existing keymaps, and tell Readline which keymap to use.
Function: Keymap rl_make_bare_keymap ()
Returns a new, empty keymap. The space for the keymap is allocated with
malloc ()
; you should free ()
it when you are done.
Function: Keymap rl_copy_keymap (Keymap map)
Return a new keymap which is a copy of map.
Function: Keymap rl_make_keymap ()
Return a new keymap with the printing characters bound to rl_insert, the lowercase Meta characters bound to run their equivalents, and the Meta digits bound to produce numeric arguments.
Function: void rl_discard_keymap (Keymap keymap)
Free the storage associated with keymap.
Readline has several internal keymaps. These functions allow you to change which keymap is active.
Function: Keymap rl_get_keymap ()
Returns the currently active keymap.
Function: void rl_set_keymap (Keymap keymap)
Makes keymap the currently active keymap.
Function: Keymap rl_get_keymap_by_name (char *name)
Return the keymap matching name. name is one which would
be supplied in a set keymap
inputrc line (@xref{Readline Init File}).
Function: char * rl_get_keymap_name (Keymap keymap)
Return the name matching keymap. name is one which would
be supplied in a set keymap
inputrc line (@xref{Readline Init File}).
You associate keys with functions through the keymap. Readline has
several internal keymaps: emacs_standard_keymap
,
emacs_meta_keymap
, emacs_ctlx_keymap
,
vi_movement_keymap
, and vi_insertion_keymap
.
emacs_standard_keymap
is the default, and the examples in
this manual assume that.
These functions manage key bindings.
Function: int rl_bind_key (int key, Function *function)
Binds key to function in the currently active keymap. Returns non-zero in the case of an invalid key.
Function: int rl_bind_key_in_map (int key, Function *function, Keymap map)
Bind key to function in map. Returns non-zero in the case of an invalid key.
Function: int rl_unbind_key (int key)
Bind key to the null function in the currently active keymap. Returns non-zero in case of error.
Function: int rl_unbind_key_in_map (int key, Keymap map)
Bind key to the null function in map. Returns non-zero in case of error.
Function: int rl_generic_bind (int type, char *keyseq, char *data, Keymap map)
Bind the key sequence represented by the string keyseq to the arbitrary
pointer data. type says what kind of data is pointed to by
data; this can be a function (ISFUNC
), a macro
(ISMACR
), or a keymap (ISKMAP
). This makes new keymaps as
necessary. The initial keymap in which to do bindings is map.
Function: int rl_parse_and_bind (char *line)
Parse line as if it had been read from the inputrc
file and
perform any key bindings and variable assignments found
(@xref{Readline Init File}).
Function: int rl_read_init_file (char *filename)
Read keybindings and variable assignments from filename (@xref{Readline Init File}).
These functions allow you to find out what keys invoke named functions and the functions invoked by a particular key sequence.
Function: Function * rl_named_function (char *name)
Return the function with name name.
Function: Function * rl_function_of_keyseq (char *keyseq, Keymap map, int *type)
Return the function invoked by keyseq in keymap map.
If map is NULL, the current keymap is used. If type is
not NULL, the type of the object is returned in it (one of ISFUNC
,
ISKMAP
, or ISMACR
).
Function: char ** rl_invoking_keyseqs (Function *function)
Return an array of strings representing the key sequences used to invoke function in the current keymap.
Function: char ** rl_invoking_keyseqs_in_map (Function *function, Keymap map)
Return an array of strings representing the key sequences used to invoke function in the keymap map.
Function: void rl_function_dumper (int readable)
Print the readline function names and the key sequences currently
bound to them to rl_outstream
. If readable is non-zero,
the list is formatted in such a way that it can be made part of an
inputrc
file and re-read.
Function: void rl_list_funmap_names ()
Print the names of all bindable Readline functions to rl_outstream
.
Supporting the undo command is a painless thing, and makes your functions much more useful. It is certainly easy to try something if you know you can undo it. I could use an undo function for the stock market.
If your function simply inserts text once, or deletes text once, and
uses rl_insert_text ()
or rl_delete_text ()
to do it, then
undoing is already done for you automatically.
If you do multiple insertions or multiple deletions, or any combination
of these operations, you should group them together into one operation.
This is done with rl_begin_undo_group ()
and
rl_end_undo_group ()
.
The types of events that can be undone are:
enum undo_code { UNDO_DELETE, UNDO_INSERT, UNDO_BEGIN, UNDO_END };
Notice that UNDO_DELETE
means to insert some text, and
UNDO_INSERT
means to delete some text. That is, the undo code
tells undo what to undo, not how to undo it. UNDO_BEGIN
and
UNDO_END
are tags added by rl_begin_undo_group ()
and
rl_end_undo_group ()
.
Function: int rl_begin_undo_group ()
Begins saving undo information in a group construct. The undo
information usually comes from calls to rl_insert_text ()
and
rl_delete_text ()
, but could be the result of calls to
rl_add_undo ()
.
Function: int rl_end_undo_group ()
Closes the current undo group started with rl_begin_undo_group
()
. There should be one call to rl_end_undo_group ()
for each call to rl_begin_undo_group ()
.
Function: void rl_add_undo (enum undo_code what, int start, int end, char *text)
Remember how to undo an event (according to what). The affected text runs from start to end, and encompasses text.
Function: void free_undo_list ()
Function: int rl_do_undo ()
Undo the first thing on the undo list. Returns 0
if there was
nothing to undo, non-zero if something was undone.
Finally, if you neither insert nor delete text, but directly modify the
existing text (e.g., change its case), call rl_modifying ()
once, just before you modify the text. You must supply the indices of
the text range that you are going to modify.
Function: int rl_modifying (int start, int end)
Tell Readline to save the text between start and end as a single undo unit. It is assumed that you will subsequently modify that text.
Function: void rl_redisplay ()
Change what's displayed on the screen to reflect the current contents
of rl_line_buffer
.
Function: int rl_forced_update_display ()
Force the line to be updated and redisplayed, whether or not Readline thinks the screen display is correct.
Function: int rl_on_new_line ()
Tell the update routines that we have moved onto a new (empty) line, usually after ouputting a newline.
Function: int rl_reset_line_state ()
Reset the display state to a clean state and redisplay the current line starting on a new line.
Function: int rl_message (va_alist)
The arguments are a string as would be supplied to printf
. The
resulting string is displayed in the echo area. The echo area
is also used to display numeric arguments and search strings.
Function: int rl_clear_message ()
Clear the message in the echo area.
Function: int rl_insert_text (char *text)
Insert text into the line at the current cursor position.
Function: int rl_delete_text (int start, int end)
Delete the text between start and end in the current line.
Function: char * rl_copy_text (int start, int end)
Return a copy of the text between start and end in the current line.
Function: int rl_kill_text (int start, int end)
Copy the text between start and end in the current line to the kill ring, appending or prepending to the last kill if the last command was a kill command. The text is deleted. If start is less than end, the text is appended, otherwise prepended. If the last command was not a kill, a new kill ring slot is used.
Function: int rl_read_key ()
Return the next character available. This handles input inserted into
the input stream via pending input (see section Readline Variables)
and rl_stuff_char ()
, macros, and characters read from the keyboard.
Function: int rl_getc (FILE *)
Return the next character available from the keyboard.
Function: int rl_stuff_char (int c)
Insert c into the Readline input stream. It will be "read"
before Readline attempts to read characters from the terminal with
rl_read_key ()
.
Function: rl_extend_line_buffer (int len)
Ensure that rl_line_buffer
has enough space to hold len
characters, possibly reallocating it if necessary.
Function: int rl_initialize ()
Initialize or re-initialize Readline's internal state.
Function: int rl_reset_terminal (char *terminal_name)
Reinitialize Readline's idea of the terminal settings using
terminal_name as the terminal type (e.g., vt100
).
Function: int alphabetic (int c)
Return 1 if c is an alphabetic character.
Function: int numeric (int c)
Return 1 if c is a numeric character.
Function: int ding ()
Ring the terminal bell, obeying the setting of bell-style
.
The following are implemented as macros, defined in chartypes.h
.
Function: int uppercase_p (int c)
Return 1 if c is an uppercase alphabetic character.
Function: int lowercase_p (int c)
Return 1 if c is a lowercase alphabetic character.
Function: int digit_p (int c)
Return 1 if c is a numeric character.
Function: int to_upper (int c)
If c is a lowercase alphabetic character, return the corresponding uppercase character.
Function: int to_lower (int c)
If c is an uppercase alphabetic character, return the corresponding lowercase character.
Function: int digit_value (int c)
If c is a number, return the value it represents.
An alternate interface is available to plain readline()
. Some
applications need to interleave keyboard I/O with file, device, or
window system I/O, typically by using a main loop to select()
on various file descriptors. To accomodate this need, readline can
also be invoked as a `callback' function from an event loop. There
are functions available to make this easy.
Function: void rl_callback_handler_install (char *prompt, Vfunction *lhandler)
Set up the terminal for readline I/O and display the initial expanded value of prompt. Save the value of lhandler to use as a callback when a complete line of input has been entered.
Function: void rl_callback_read_char ()
Whenever an application determines that keyboard input is available, it
should call rl_callback_read_char()
, which will read the next
character from the current input source. If that character completes the
line, rl_callback_read_char
will invoke the lhandler
function saved by rl_callback_handler_install
to process the
line. EOF
is indicated by calling lhandler with a
NULL
line.
Function: void rl_callback_handler_remove ()
Restore the terminal to its initial state and remove the line handler. This may be called from within a callback as well as independently.
Here is a function which changes lowercase characters to their uppercase equivalents, and uppercase characters to lowercase. If this function was bound to `M-c', then typing `M-c' would change the case of the character under point. Typing `M-1 0 M-c' would change the case of the following 10 characters, leaving the cursor on the last character changed.
/* Invert the case of the COUNT following characters. */ int invert_case_line (count, key) int count, key; { register int start, end, i; start = rl_point; if (rl_point >= rl_end) return (0); if (count < 0) { direction = -1; count = -count; } else direction = 1; /* Find the end of the range to modify. */ end = start + (count * direction); /* Force it to be within range. */ if (end > rl_end) end = rl_end; else if (end < 0) end = 0; if (start == end) return (0); if (start > end) { int temp = start; start = end; end = temp; } /* Tell readline that we are modifying the line, so it will save the undo information. */ rl_modifying (start, end); for (i = start; i != end; i++) { if (uppercase_p (rl_line_buffer[i])) rl_line_buffer[i] = to_lower (rl_line_buffer[i]); else if (lowercase_p (rl_line_buffer[i])) rl_line_buffer[i] = to_upper (rl_line_buffer[i]); } /* Move point to on top of the last character changed. */ rl_point = (direction == 1) ? end - 1 : start; return (0); }
Typically, a program that reads commands from the user has a way of disambiguating commands and data. If your program is one of these, then it can provide completion for commands, data, or both. The following sections describe how your program and Readline cooperate to provide this service.
In order to complete some text, the full list of possible completions must be available. That is, it is not possible to accurately expand a partial word without knowing all of the possible words which make sense in that context. The Readline library provides the user interface to completion, and two of the most common completion functions: filename and username. For completing other types of text, you must write your own completion function. This section describes exactly what such functions must do, and provides an example.
There are three major functions used to perform completion:
rl_complete ()
. This function is
called with the same arguments as other Readline
functions intended for interactive use: count and
invoking_key. It isolates the word to be completed and calls
completion_matches ()
to generate a list of possible completions.
It then either lists the possible completions, inserts the possible
completions, or actually performs the
completion, depending on which behavior is desired.
completion_matches ()
uses your
generator function to generate the list of possible matches, and
then returns the array of these matches. You should place the address
of your generator function in rl_completion_entry_function
.
completion_matches ()
, returning a string each time. The
arguments to the generator function are text and state.
text is the partial word to be completed. state is zero the
first time the function is called, allowing the generator to perform
any necessary initialization, and a positive non-zero integer for
each subsequent call. When the generator function returns
(char *)NULL
this signals completion_matches ()
that there are
no more possibilities left. Usually the generator function computes the
list of possible completions when state is zero, and returns them
one at a time on subsequent calls. Each string the generator function
returns as a match must be allocated with malloc()
; Readline
frees the strings when it has finished with them.
Function: int rl_complete (int ignore, int invoking_key)
Complete the word at or before point. You have supplied the function
that does the initial simple matching selection algorithm (see
completion_matches ()
). The default is to do filename completion.
Variable: Function * rl_completion_entry_function
This is a pointer to the generator function for completion_matches
()
. If the value of rl_completion_entry_function
is
(Function *)NULL
then the default filename generator function,
filename_completion_function ()
, is used.
Here is the complete list of callable completion functions present in Readline.
Function: int rl_complete_internal (int what_to_do)
Complete the word at or before point. what_to_do says what to do with the completion. A value of `?' means list the possible completions. `TAB' means do standard completion. `*' means insert all of the possible completions. `!' means to display all of the possible completions, if there is more than one, as well as performing partial completion.
Function: int rl_complete (int ignore, int invoking_key)
Complete the word at or before point. You have supplied the function
that does the initial simple matching selection algorithm (see
completion_matches ()
and rl_completion_entry_function
).
The default is to do filename
completion. This calls rl_complete_internal ()
with an
argument depending on invoking_key.
Function: int rl_possible_completions (int count, int invoking_key))
List the possible completions. See description of rl_complete
()
. This calls rl_complete_internal ()
with an argument of
`?'.
Function: int rl_insert_completions (int count, int invoking_key))
Insert the list of possible completions into the line, deleting the
partially-completed word. See description of rl_complete ()
.
This calls rl_complete_internal ()
with an argument of `*'.
Function: char ** completion_matches (char *text, CPFunction *entry_func)
Returns an array of (char *)
which is a list of completions for
text. If there are no completions, returns (char **)NULL
.
The first entry in the returned array is the substitution for text.
The remaining entries are the possible completions. The array is
terminated with a NULL
pointer.
entry_func is a function of two args, and returns a
(char *)
. The first argument is text. The second is a
state argument; it is zero on the first call, and non-zero on subsequent
calls. entry_func returns a NULL
pointer to the caller
when there are no more matches.
Function: char * filename_completion_function (char *text, int state)
A generator function for filename completion in the general case. Note that completion in Bash is a little different because of all the pathnames that must be followed when looking up completions for a command. The Bash source is a useful reference for writing custom completion functions.
Function: char * username_completion_function (char *text, int state)
A completion generator for usernames. text contains a partial username preceded by a random character (usually `~'). As with all completion generators, state is zero on the first call and non-zero for subsequent calls.
Variable: Function * rl_completion_entry_function
A pointer to the generator function for completion_matches ()
.
NULL
means to use filename_entry_function ()
, the default
filename completer.
Variable: CPPFunction * rl_attempted_completion_function
A pointer to an alternative function to create matches.
The function is called with text, start, and end.
start and end are indices in rl_line_buffer
saying
what the boundaries of text are. If this function exists and
returns NULL
, or if this variable is set to NULL
, then
rl_complete ()
will call the value of
rl_completion_entry_function
to generate matches, otherwise the
array of strings returned will be used.
Variable: CPFunction * rl_filename_quoting_function
A pointer to a function that will quote a filename in an application-
specific fashion. This is called if filename completion is being
attempted and one of the characters in rl_filename_quote_characters
appears in a completed filename. The function is called with
text, match_type, and quote_pointer. The text
is the filename to be quoted. The match_type is either
SINGLE_MATCH
, if there is only one completion match, or
MULT_MATCH
. Some functions use this to decide whether or not to
insert a closing quote character. The quote_pointer is a pointer
to any opening quote character the user typed. Some functions choose
to reset this character.
Variable: CPFunction * rl_filename_dequoting_function
A pointer to a function that will remove application-specific quoting characters from a filename before completion is attempted, so those characters do not interfere with matching the text against names in the filesystem. It is called with text, the text of the word to be dequoted, and quote_char, which is the quoting character that delimits the filename (usually `'' or `"'). If quote_char is zero, the filename was not in an embedded string.
Variable: Function * rl_char_is_quoted_p
A pointer to a function to call that determines whether or not a specific
character in the line buffer is quoted, according to whatever quoting
mechanism the program calling readline uses. The function is called with
two arguments: text, the text of the line, and index, the
index of the character in the line. It is used to decide whether a
character found in rl_completer_word_break_characters
should be
used to break words for the completer.
Variable: int rl_completion_query_items
Up to this many items will be displayed in response to a possible-completions call. After that, we ask the user if she is sure she wants to see them all. The default value is 100.
Variable: char * rl_basic_word_break_characters
The basic list of characters that signal a break between words for the
completer routine. The default value of this variable is the characters
which break words for completion in Bash, i.e.,
" \t\n\"\\'`@$><=;|&{("
.
Variable: char * rl_basic_quote_characters
List of quote characters which can cause a word break.
Variable: char * rl_completer_word_break_characters
The list of characters that signal a break between words for
rl_complete_internal ()
. The default list is the value of
rl_basic_word_break_characters
.
Variable: char * rl_completer_quote_characters
List of characters which can be used to quote a substring of the line.
Completion occurs on the entire substring, and within the substring
rl_completer_word_break_characters
are treated as any other character,
unless they also appear within this list.
Variable: char * rl_filename_quote_characters
A list of characters that cause a filename to be quoted by the completer when they appear in a completed filename. The default is empty.
Variable: char * rl_special_prefixes
The list of characters that are word break characters, but should be left in text when it is passed to the completion function. Programs can use this to help determine what kind of completing to do. For instance, Bash sets this variable to "$@" so that it can complete shell variables and hostnames.
Variable: int rl_completion_append_character
When a single completion alternative matches at the end of the command line, this character is appended to the inserted completion text. The default is a space character (` '). Setting this to the null character (`\0') prevents anything being appended automatically. This can be changed in custom completion functions to provide the "most sensible word separator character" according to an application-specific command line syntax specification.
Variable: int rl_ignore_completion_duplicates
If non-zero, then disallow duplicates in the matches. Default is 1.
Variable: int rl_filename_completion_desired
Non-zero means that the results of the matches are to be treated as filenames. This is always zero on entry, and can only be changed within a completion entry generator function. If it is set to a non-zero value, directory names have a slash appended and Readline attempts to quote completed filenames if they contain any embedded word break characters.
Variable: int rl_filename_quoting_desired
Non-zero means that the results of the matches are to be quoted using
double quotes (or an application-specific quoting mechanism) if the
completed filename contains any characters in
rl_filename_quote_chars
. This is always non-zero
on entry, and can only be changed within a completion entry generator
function. The quoting is effected via a call to the function pointed to
by rl_filename_quoting_function
.
Variable: int rl_inhibit_completion
If this variable is non-zero, completion is inhibit<ed. The completion
character will be inserted as any other bound to self-insert
.
Variable: Function * rl_ignore_some_completions_function
This function, if defined, is called by the completer when real filename
completion is done, after all the matching names have been generated.
It is passed a NULL
terminated array of matches.
The first element (matches[0]
) is the
maximal substring common to all matches. This function can
re-arrange the list of matches as required, but each element deleted
from the array must be freed.
Variable: Function * rl_directory_completion_hook
This function, if defined, is allowed to modify the directory portion of filenames Readline completes. It is called with the address of a string (the current directory name) as an argument. It could be used to expand symbolic links or shell variables in pathnames.
Here is a small application demonstrating the use of the GNU Readline
library. It is called fileman
, and the source code resides in
`examples/fileman.c'. This sample application provides
completion of command names, line editing features, and access to the
history list.
/* fileman.c -- A tiny application which demonstrates how to use the GNU Readline library. This application interactively allows users to manipulate files and their modes. */ #include <stdio.h> #include <sys/types.h> #include <sys/file.h> #include <sys/stat.h> #include <sys/errno.h> #include <readline/readline.h> #include <readline/history.h> extern char *getwd (); extern char *xmalloc (); /* The names of functions that actually do the manipulation. */ int com_list (), com_view (), com_rename (), com_stat (), com_pwd (); int com_delete (), com_help (), com_cd (), com_quit (); /* A structure which contains information on the commands this program can understand. */ typedef struct { char *name; /* User printable name of the function. */ Function *func; /* Function to call to do the job. */ char *doc; /* Documentation for this function. */ } COMMAND; COMMAND commands[] = { { "cd", com_cd, "Change to directory DIR" }, { "delete", com_delete, "Delete FILE" }, { "help", com_help, "Display this text" }, { "?", com_help, "Synonym for `help'" }, { "list", com_list, "List files in DIR" }, { "ls", com_list, "Synonym for `list'" }, { "pwd", com_pwd, "Print the current working directory" }, { "quit", com_quit, "Quit using Fileman" }, { "rename", com_rename, "Rename FILE to NEWNAME" }, { "stat", com_stat, "Print out statistics on FILE" }, { "view", com_view, "View the contents of FILE" }, { (char *)NULL, (Function *)NULL, (char *)NULL } }; /* Forward declarations. */ char *stripwhite (); COMMAND *find_command (); /* The name of this program, as taken from argv[0]. */ char *progname; /* When non-zero, this global means the user is done using this program. */ int done; char * dupstr (s) int s; { char *r; r = xmalloc (strlen (s) + 1); strcpy (r, s); return (r); } main (argc, argv) int argc; char **argv; { char *line, *s; progname = argv[0]; initialize_readline (); /* Bind our completer. */ /* Loop reading and executing lines until the user quits. */ for ( ; done == 0; ) { line = readline ("FileMan: "); if (!line) break; /* Remove leading and trailing whitespace from the line. Then, if there is anything left, add it to the history list and execute it. */ s = stripwhite (line); if (*s) { add_history (s); execute_line (s); } free (line); } exit (0); } /* Execute a command line. */ int execute_line (line) char *line; { register int i; COMMAND *command; char *word; /* Isolate the command word. */ i = 0; while (line[i] && whitespace (line[i])) i++; word = line + i; while (line[i] && !whitespace (line[i])) i++; if (line[i]) line[i++] = '\0'; command = find_command (word); if (!command) { fprintf (stderr, "%s: No such command for FileMan.\n", word); return (-1); } /* Get argument to command, if any. */ while (whitespace (line[i])) i++; word = line + i; /* Call the function. */ return ((*(command->func)) (word)); } /* Look up NAME as the name of a command, and return a pointer to that command. Return a NULL pointer if NAME isn't a command name. */ COMMAND * find_command (name) char *name; { register int i; for (i = 0; commands[i].name; i++) if (strcmp (name, commands[i].name) == 0) return (&commands[i]); return ((COMMAND *)NULL); } /* Strip whitespace from the start and end of STRING. Return a pointer into STRING. */ char * stripwhite (string) char *string; { register char *s, *t; for (s = string; whitespace (*s); s++) ; if (*s == 0) return (s); t = s + strlen (s) - 1; while (t > s && whitespace (*t)) t--; *++t = '\0'; return s; } /* **************************************************************** */ /* */ /* Interface to Readline Completion */ /* */ /* **************************************************************** */ char *command_generator (); char **fileman_completion (); /* Tell the GNU Readline library how to complete. We want to try to complete on command names if this is the first word in the line, or on filenames if not. */ initialize_readline () { /* Allow conditional parsing of the ~/.inputrc file. */ rl_readline_name = "FileMan"; /* Tell the completer that we want a crack first. */ rl_attempted_completion_function = (CPPFunction *)fileman_completion; } /* Attempt to complete on the contents of TEXT. START and END bound the region of rl_line_buffer that contains the word to complete. TEXT is the word to complete. We can use the entire contents of rl_line_buffer in case we want to do some simple parsing. Return the array of matches, or NULL if there aren't any. */ char ** fileman_completion (text, start, end) char *text; int start, end; { char **matches; matches = (char **)NULL; /* If this word is at the start of the line, then it is a command to complete. Otherwise it is the name of a file in the current directory. */ if (start == 0) matches = completion_matches (text, command_generator); return (matches); } /* Generator function for command completion. STATE lets us know whether to start from scratch; without any state (i.e. STATE == 0), then we start at the top of the list. */ char * command_generator (text, state) char *text; int state; { static int list_index, len; char *name; /* If this is a new word to complete, initialize now. This includes saving the length of TEXT for efficiency, and initializing the index variable to 0. */ if (!state) { list_index = 0; len = strlen (text); } /* Return the next name which partially matches from the command list. */ while (name = commands[list_index].name) { list_index++; if (strncmp (name, text, len) == 0) return (dupstr(name)); } /* If no names matched, then return NULL. */ return ((char *)NULL); } /* **************************************************************** */ /* */ /* FileMan Commands */ /* */ /* **************************************************************** */ /* String to pass to system (). This is for the LIST, VIEW and RENAME commands. */ static char syscom[1024]; /* List the file(s) named in arg. */ com_list (arg) char *arg; { if (!arg) arg = ""; sprintf (syscom, "ls -FClg %s", arg); return (system (syscom)); } com_view (arg) char *arg; { if (!valid_argument ("view", arg)) return 1; sprintf (syscom, "more %s", arg); return (system (syscom)); } com_rename (arg) char *arg; { too_dangerous ("rename"); return (1); } com_stat (arg) char *arg; { struct stat finfo; if (!valid_argument ("stat", arg)) return (1); if (stat (arg, &finfo) == -1) { perror (arg); return (1); } printf ("Statistics for `%s':\n", arg); printf ("%s has %d link%s, and is %d byte%s in length.\n", arg, finfo.st_nlink, (finfo.st_nlink == 1) ? "" : "s", finfo.st_size, (finfo.st_size == 1) ? "" : "s"); printf ("Inode Last Change at: %s", ctime (&finfo.st_ctime)); printf (" Last access at: %s", ctime (&finfo.st_atime)); printf (" Last modified at: %s", ctime (&finfo.st_mtime)); return (0); } com_delete (arg) char *arg; { too_dangerous ("delete"); return (1); } /* Print out help for ARG, or for all of the commands if ARG is not present. */ com_help (arg) char *arg; { register int i; int printed = 0; for (i = 0; commands[i].name; i++) { if (!*arg || (strcmp (arg, commands[i].name) == 0)) { printf ("%s\t\t%s.\n", commands[i].name, commands[i].doc); printed++; } } if (!printed) { printf ("No commands match `%s'. Possibilties are:\n", arg); for (i = 0; commands[i].name; i++) { /* Print in six columns. */ if (printed == 6) { printed = 0; printf ("\n"); } printf ("%s\t", commands[i].name); printed++; } if (printed) printf ("\n"); } return (0); } /* Change to the directory ARG. */ com_cd (arg) char *arg; { if (chdir (arg) == -1) { perror (arg); return 1; } com_pwd (""); return (0); } /* Print out the current working directory. */ com_pwd (ignore) char *ignore; { char dir[1024], *s; s = getwd (dir); if (s == 0) { printf ("Error getting pwd: %s\n", dir); return 1; } printf ("Current directory is %s\n", dir); return 0; } /* The user wishes to quit using this program. Just set DONE non-zero. */ com_quit (arg) char *arg; { done = 1; return (0); } /* Function which tells you that you can't do this. */ too_dangerous (caller) char *caller; { fprintf (stderr, "%s: Too dangerous for me to distribute. Write it yourself.\n", caller); } /* Return non-zero if ARG is a valid argument for CALLER, else print an error message and return zero. */ int valid_argument (caller, arg) char *caller, *arg; { if (!arg || !*arg) { fprintf (stderr, "%s: Argument required.\n", caller); return (0); } return (1); }