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+@comment %**start of header (This is for running Texinfo on a region.)
+@setfilename rltech.info
+@comment %**end of header (This is for running Texinfo on a region.)
+@setchapternewpage odd
+
+@ifinfo
+This document describes the GNU Readline Library, a utility for aiding
+in the consitency of user interface across discrete programs that need
+to provide a command line interface.
+
+Copyright (C) 1988, 1994, 1996 Free Software Foundation, Inc.
+
+Permission is granted to make and distribute verbatim copies of
+this manual provided the copyright notice and this permission notice
+pare preserved on all copies.
+
+@ignore
+Permission is granted to process this file through TeX and print the
+results, provided the printed document carries copying permission
+notice identical to this one except for the removal of this paragraph
+(this paragraph not being relevant to the printed manual).
+@end ignore
+
+Permission is granted to copy and distribute modified versions of this
+manual under the conditions for verbatim copying, provided that the entire
+resulting derived work is distributed under the terms of a permission
+notice identical to this one.
+
+Permission is granted to copy and distribute translations of this manual
+into another language, under the above conditions for modified versions,
+except that this permission notice may be stated in a translation approved
+by the Foundation.
+@end ifinfo
+
+@node Programming with GNU Readline
+@chapter Programming with GNU Readline
+
+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.
+
+@menu
+* Basic Behavior:: Using the default behavior of Readline.
+* Custom Functions:: Adding your own functions to Readline.
+* Readline Variables:: Variables accessible to custom
+ functions.
+* Readline Convenience Functions:: Functions which Readline supplies to
+ aid in writing your own
+* Custom Completers:: Supplanting or supplementing Readline's
+ completion functions.
+@end menu
+
+@node Basic Behavior
+@section Basic Behavior
+
+Many programs provide a command line interface, such as @code{mail},
+@code{ftp}, and @code{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
+@code{gets()} or @code{fgets ()}.
+
+@findex readline
+@cindex readline, function
+The function @code{readline ()} prints a prompt and then reads and returns
+a single line of text from the user. The line @code{readline}
+returns is allocated with @code{malloc ()}; you should @code{free ()}
+the line when you are done with it. The declaration for @code{readline}
+in ANSI C is
+
+@example
+@code{char *readline (char *@var{prompt});}
+@end example
+
+@noindent
+So, one might say
+@example
+@code{char *line = readline ("Enter a line: ");}
+@end example
+@noindent
+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 @code{readline} encounters an @code{EOF} while reading the line, and the
+line is empty at that point, then @code{(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
+@key{C-p} for example), you must call @code{add_history ()} to save the
+line away in a @dfn{history} list of such lines.
+
+@example
+@code{add_history (line)};
+@end example
+
+@noindent
+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 @code{gets ()} library
+function, and has the advantage of no static buffer to overflow:
+
+@example
+/* 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);
+@}
+@end example
+
+This function gives the user the default behaviour of @key{TAB}
+completion: completion on file names. If you do not want Readline to
+complete on filenames, you can change the binding of the @key{TAB} key
+with @code{rl_bind_key ()}.
+
+@example
+@code{int rl_bind_key (int @var{key}, int (*@var{function})());}
+@end example
+
+@code{rl_bind_key ()} takes two arguments: @var{key} is the character that
+you want to bind, and @var{function} is the address of the function to
+call when @var{key} is pressed. Binding @key{TAB} to @code{rl_insert ()}
+makes @key{TAB} insert itself.
+@code{rl_bind_key ()} returns non-zero if @var{key} is not a valid
+ASCII character code (between 0 and 255).
+
+Thus, to disable the default @key{TAB} behavior, the following suffices:
+@example
+@code{rl_bind_key ('\t', rl_insert);}
+@end example
+
+This code should be executed once at the start of your program; you
+might write a function called @code{initialize_readline ()} which
+performs this and other desired initializations, such as installing
+custom completers (@pxref{Custom Completers}).
+
+@node Custom Functions
+@section Custom Functions
+
+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.
+
+@menu
+* The Function Type:: C declarations to make code readable.
+* Function Writing:: Variables and calling conventions.
+@end menu
+
+@node The Function Type
+@subsection The Function Type
+
+For readabilty, we declare a new type of object, called
+@dfn{Function}. A @code{Function} is a C function which
+returns an @code{int}. The type declaration for @code{Function} is:
+
+@noindent
+@code{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 @var{func} which was a pointer to a function. Instead of the
+classic C declaration
+
+@code{int (*)()func;}
+
+@noindent
+we may write
+
+@code{Function *func;}
+
+@noindent
+Similarly, there are
+
+@example
+typedef void VFunction ();
+typedef char *CPFunction (); @r{and}
+typedef char **CPPFunction ();
+@end example
+
+@noindent
+for functions returning no value, @code{pointer to char}, and
+@code{pointer to pointer to char}, respectively.
+
+@node Function Writing
+@subsection Writing a New Function
+
+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 @code{foo} looks like
+
+@example
+@code{foo (int count, int key)}
+@end example
+
+@noindent
+where @var{count} is the numeric argument (or 1 if defaulted) and
+@var{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.
+
+@node Readline Variables
+@section Readline Variables
+
+These variables are available to function writers.
+
+@deftypevar {char *} rl_line_buffer
+This is the line gathered so far. You are welcome to modify the
+contents of the line, but see @ref{Allowing Undoing}.
+@end deftypevar
+
+@deftypevar int rl_point
+The offset of the current cursor position in @code{rl_line_buffer}
+(the @emph{point}).
+@end deftypevar
+
+@deftypevar int rl_end
+The number of characters present in @code{rl_line_buffer}. When
+@code{rl_point} is at the end of the line, @code{rl_point} and
+@code{rl_end} are equal.
+@end deftypevar
+
+@deftypevar int rl_mark
+The mark (saved position) in the current line. If set, the mark
+and point define a @emph{region}.
+@end deftypevar
+
+@deftypevar int rl_done
+Setting this to a non-zero value causes Readline to return the current
+line immediately.
+@end deftypevar
+
+@deftypevar 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.
+@end deftypevar
+
+@deftypevar {char *} rl_prompt
+The prompt Readline uses. This is set from the argument to
+@code{readline ()}, and should not be assigned to directly.
+@end deftypevar
+
+@deftypevar {char *} rl_library_version
+The version number of this revision of the library.
+@end deftypevar
+
+@deftypevar {char *} rl_terminal_name
+The terminal type, used for initialization.
+@end deftypevar
+
+@deftypevar {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
+(@pxref{Conditional Init Constructs}).
+@end deftypevar
+
+@deftypevar {FILE *} rl_instream
+The stdio stream from which Readline reads input.
+@end deftypevar
+
+@deftypevar {FILE *} rl_outstream
+The stdio stream to which Readline performs output.
+@end deftypevar
+
+@deftypevar {Function *} rl_startup_hook
+If non-zero, this is the address of a function to call just
+before @code{readline} prints the first prompt.
+@end deftypevar
+
+@deftypevar {Function *} rl_event_hook
+If non-zero, this is the address of a function to call periodically
+when readline is waiting for terminal input.
+@end deftypevar
+
+@deftypevar {Function *} rl_getc_function
+If non-zero, @code{readline} will call indirectly through this pointer
+to get a character from the input stream. By default, it is set to
+@code{rl_getc}, the default @code{readline} character input function
+(@pxref{Utility Functions}).
+@end deftypevar
+
+@deftypevar {Function *} rl_redisplay_function
+If non-zero, @code{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 @code{rl_redisplay}, the default @code{readline}
+redisplay function (@pxref{Redisplay}).
+@end deftypevar
+
+@deftypevar {Keymap} rl_executing_keymap
+This variable is set to the keymap (@pxref{Keymaps}) in which the
+currently executing readline function was found.
+@end deftypevar
+
+@deftypevar {Keymap} rl_binding_keymap
+This variable is set to the keymap (@pxref{Keymaps}) in which the
+last key binding occurred.
+@end deftypevar
+
+@node Readline Convenience Functions
+@section Readline Convenience Functions
+
+@menu
+* Function Naming:: How to give a function you write a name.
+* Keymaps:: Making keymaps.
+* Binding Keys:: Changing Keymaps.
+* Associating Function Names and Bindings:: Translate function names to
+ key sequences.
+* Allowing Undoing:: How to make your functions undoable.
+* Redisplay:: Functions to control line display.
+* Modifying Text:: Functions to modify @code{rl_line_buffer}.
+* Utility Functions:: Generally useful functions and hooks.
+* Alternate Interface:: Using Readline in a `callback' fashion.
+@end menu
+
+@node Function Naming
+@subsection Naming a Function
+
+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
+
+@example
+Meta-Rubout: backward-kill-word
+@end example
+
+This binds the keystroke @key{Meta-Rubout} to the function
+@emph{descriptively} named @code{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:
+
+@deftypefun int rl_add_defun (char *name, Function *function, int key)
+Add @var{name} to the list of named functions. Make @var{function} be
+the function that gets called. If @var{key} is not -1, then bind it to
+@var{function} using @code{rl_bind_key ()}.
+@end deftypefun
+
+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.
+
+@node Keymaps
+@subsection Selecting a Keymap
+
+Key bindings take place on a @dfn{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.
+
+@deftypefun Keymap rl_make_bare_keymap ()
+Returns a new, empty keymap. The space for the keymap is allocated with
+@code{malloc ()}; you should @code{free ()} it when you are done.
+@end deftypefun
+
+@deftypefun Keymap rl_copy_keymap (Keymap map)
+Return a new keymap which is a copy of @var{map}.
+@end deftypefun
+
+@deftypefun 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.
+@end deftypefun
+
+@deftypefun void rl_discard_keymap (Keymap keymap)
+Free the storage associated with @var{keymap}.
+@end deftypefun
+
+Readline has several internal keymaps. These functions allow you to
+change which keymap is active.
+
+@deftypefun Keymap rl_get_keymap ()
+Returns the currently active keymap.
+@end deftypefun
+
+@deftypefun void rl_set_keymap (Keymap keymap)
+Makes @var{keymap} the currently active keymap.
+@end deftypefun
+
+@deftypefun Keymap rl_get_keymap_by_name (char *name)
+Return the keymap matching @var{name}. @var{name} is one which would
+be supplied in a @code{set keymap} inputrc line (@pxref{Readline Init File}).
+@end deftypefun
+
+@node Binding Keys
+@subsection Binding Keys
+
+You associate keys with functions through the keymap. Readline has
+several internal keymaps: @code{emacs_standard_keymap},
+@code{emacs_meta_keymap}, @code{emacs_ctlx_keymap},
+@code{vi_movement_keymap}, and @code{vi_insertion_keymap}.
+@code{emacs_standard_keymap} is the default, and the examples in
+this manual assume that.
+
+These functions manage key bindings.
+
+@deftypefun int rl_bind_key (int key, Function *function)
+Binds @var{key} to @var{function} in the currently active keymap.
+Returns non-zero in the case of an invalid @var{key}.
+@end deftypefun
+
+@deftypefun int rl_bind_key_in_map (int key, Function *function, Keymap map)
+Bind @var{key} to @var{function} in @var{map}. Returns non-zero in the case
+of an invalid @var{key}.
+@end deftypefun
+
+@deftypefun int rl_unbind_key (int key)
+Bind @var{key} to the null function in the currently active keymap.
+Returns non-zero in case of error.
+@end deftypefun
+
+@deftypefun int rl_unbind_key_in_map (int key, Keymap map)
+Bind @var{key} to the null function in @var{map}.
+Returns non-zero in case of error.
+@end deftypefun
+
+@deftypefun int rl_generic_bind (int type, char *keyseq, char *data, Keymap map)
+Bind the key sequence represented by the string @var{keyseq} to the arbitrary
+pointer @var{data}. @var{type} says what kind of data is pointed to by
+@var{data}; this can be a function (@code{ISFUNC}), a macro
+(@code{ISMACR}), or a keymap (@code{ISKMAP}). This makes new keymaps as
+necessary. The initial keymap in which to do bindings is @var{map}.
+@end deftypefun
+
+@deftypefun int rl_parse_and_bind (char *line)
+Parse @var{line} as if it had been read from the @code{inputrc} file and
+perform any key bindings and variable assignments found
+(@pxref{Readline Init File}).
+@end deftypefun
+
+@deftypefun int rl_read_init_file (char *filename)
+Read keybindings and variable assignments from @var{filename}
+(@pxref{Readline Init File}).
+@end deftypefun
+
+@node Associating Function Names and Bindings
+@subsection Associating Function Names and Bindings
+
+These functions allow you to find out what keys invoke named functions
+and the functions invoked by a particular key sequence.
+
+@deftypefun {Function *} rl_named_function (char *name)
+Return the function with name @var{name}.
+@end deftypefun
+
+@deftypefun {Function *} rl_function_of_keyseq (char *keyseq, Keymap map, int *type)
+Return the function invoked by @var{keyseq} in keymap @var{map}.
+If @var{map} is NULL, the current keymap is used. If @var{type} is
+not NULL, the type of the object is returned in it (one of @code{ISFUNC},
+@code{ISKMAP}, or @code{ISMACR}).
+@end deftypefun
+
+@deftypefun {char **} rl_invoking_keyseqs (Function *function)
+Return an array of strings representing the key sequences used to
+invoke @var{function} in the current keymap.
+@end deftypefun
+
+@deftypefun {char **} rl_invoking_keyseqs_in_map (Function *function, Keymap map)
+Return an array of strings representing the key sequences used to
+invoke @var{function} in the keymap @var{map}.
+@end deftypefun
+
+@deftypefun void rl_function_dumper (int readable)
+Print the readline function names and the key sequences currently
+bound to them to @code{rl_outstream}. If @var{readable} is non-zero,
+the list is formatted in such a way that it can be made part of an
+@code{inputrc} file and re-read.
+@end deftypefun
+
+@deftypefun void rl_list_funmap_names ()
+Print the names of all bindable Readline functions to @code{rl_outstream}.
+@end deftypefun
+
+@node Allowing Undoing
+@subsection Allowing Undoing
+
+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 @code{rl_insert_text ()} or @code{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 @code{rl_begin_undo_group ()} and
+@code{rl_end_undo_group ()}.
+
+The types of events that can be undone are:
+
+@example
+enum undo_code @{ UNDO_DELETE, UNDO_INSERT, UNDO_BEGIN, UNDO_END @};
+@end example
+
+Notice that @code{UNDO_DELETE} means to insert some text, and
+@code{UNDO_INSERT} means to delete some text. That is, the undo code
+tells undo what to undo, not how to undo it. @code{UNDO_BEGIN} and
+@code{UNDO_END} are tags added by @code{rl_begin_undo_group ()} and
+@code{rl_end_undo_group ()}.
+
+@deftypefun int rl_begin_undo_group ()
+Begins saving undo information in a group construct. The undo
+information usually comes from calls to @code{rl_insert_text ()} and
+@code{rl_delete_text ()}, but could be the result of calls to
+@code{rl_add_undo ()}.
+@end deftypefun
+
+@deftypefun int rl_end_undo_group ()
+Closes the current undo group started with @code{rl_begin_undo_group
+()}. There should be one call to @code{rl_end_undo_group ()}
+for each call to @code{rl_begin_undo_group ()}.
+@end deftypefun
+
+@deftypefun void rl_add_undo (enum undo_code what, int start, int end, char *text)
+Remember how to undo an event (according to @var{what}). The affected
+text runs from @var{start} to @var{end}, and encompasses @var{text}.
+@end deftypefun
+
+@deftypefun void free_undo_list ()
+Free the existing undo list.
+@end deftypefun
+
+@deftypefun int rl_do_undo ()
+Undo the first thing on the undo list. Returns @code{0} if there was
+nothing to undo, non-zero if something was undone.
+@end deftypefun
+
+Finally, if you neither insert nor delete text, but directly modify the
+existing text (e.g., change its case), call @code{rl_modifying ()}
+once, just before you modify the text. You must supply the indices of
+the text range that you are going to modify.
+
+@deftypefun int rl_modifying (int start, int end)
+Tell Readline to save the text between @var{start} and @var{end} as a
+single undo unit. It is assumed that you will subsequently modify
+that text.
+@end deftypefun
+
+@node Redisplay
+@subsection Redisplay
+
+@deftypefun int rl_redisplay ()
+Change what's displayed on the screen to reflect the current contents
+of @code{rl_line_buffer}.
+@end deftypefun
+
+@deftypefun int rl_forced_update_display ()
+Force the line to be updated and redisplayed, whether or not
+Readline thinks the screen display is correct.
+@end deftypefun
+
+@deftypefun int rl_on_new_line ()
+Tell the update routines that we have moved onto a new (empty) line,
+usually after ouputting a newline.
+@end deftypefun
+
+@deftypefun int rl_reset_line_state ()
+Reset the display state to a clean state and redisplay the current line
+starting on a new line.
+@end deftypefun
+
+@deftypefun int rl_message (va_alist)
+The arguments are a string as would be supplied to @code{printf}. The
+resulting string is displayed in the @dfn{echo area}. The echo area
+is also used to display numeric arguments and search strings.
+@end deftypefun
+
+@deftypefun int rl_clear_message ()
+Clear the message in the echo area.
+@end deftypefun
+
+@node Modifying Text
+@subsection Modifying Text
+
+@deftypefun int rl_insert_text (char *text)
+Insert @var{text} into the line at the current cursor position.
+@end deftypefun
+
+@deftypefun int rl_delete_text (int start, int end)
+Delete the text between @var{start} and @var{end} in the current line.
+@end deftypefun
+
+@deftypefun {char *} rl_copy_text (int start, int end)
+Return a copy of the text between @var{start} and @var{end} in
+the current line.
+@end deftypefun
+
+@deftypefun int rl_kill_text (int start, int end)
+Copy the text between @var{start} and @var{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 @var{start} is less than @var{end},
+the text is appended, otherwise prepended. If the last command was
+not a kill, a new kill ring slot is used.
+@end deftypefun
+
+@node Utility Functions
+@subsection Utility Functions
+
+@deftypefun int rl_read_key ()
+Return the next character available. This handles input inserted into
+the input stream via @var{pending input} (@pxref{Readline Variables})
+and @code{rl_stuff_char ()}, macros, and characters read from the keyboard.
+@end deftypefun
+
+@deftypefun int rl_getc (FILE *)
+Return the next character available from the keyboard.
+@end deftypefun
+
+@deftypefun int rl_stuff_char (int c)
+Insert @var{c} into the Readline input stream. It will be "read"
+before Readline attempts to read characters from the terminal with
+@code{rl_read_key ()}.
+@end deftypefun
+
+@deftypefun int rl_initialize ()
+Initialize or re-initialize Readline's internal state.
+@end deftypefun
+
+@deftypefun int rl_reset_terminal (char *terminal_name)
+Reinitialize Readline's idea of the terminal settings using
+@var{terminal_name} as the terminal type (e.g., @code{vt100}).
+@end deftypefun
+
+@deftypefun int alphabetic (int c)
+Return 1 if @var{c} is an alphabetic character.
+@end deftypefun
+
+@deftypefun int numeric (int c)
+Return 1 if @var{c} is a numeric character.
+@end deftypefun
+
+@deftypefun int ding ()
+Ring the terminal bell, obeying the setting of @code{bell-style}.
+@end deftypefun
+
+The following are implemented as macros, defined in @code{chartypes.h}.
+
+@deftypefun int uppercase_p (int c)
+Return 1 if @var{c} is an uppercase alphabetic character.
+@end deftypefun
+
+@deftypefun int lowercase_p (int c)
+Return 1 if @var{c} is a lowercase alphabetic character.
+@end deftypefun
+
+@deftypefun int digit_p (int c)
+Return 1 if @var{c} is a numeric character.
+@end deftypefun
+
+@deftypefun int to_upper (int c)
+If @var{c} is a lowercase alphabetic character, return the corresponding
+uppercase character.
+@end deftypefun
+
+@deftypefun int to_lower (int c)
+If @var{c} is an uppercase alphabetic character, return the corresponding
+lowercase character.
+@end deftypefun
+
+@deftypefun int digit_value (int c)
+If @var{c} is a number, return the value it represents.
+@end deftypefun
+
+@node Alternate Interface
+@subsection Alternate Interface
+
+An alternate interface is available to plain @code{readline()}. Some
+applications need to interleave keyboard I/O with file, device, or
+window system I/O, typically by using a main loop to @code{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.
+
+@deftypefun void rl_callback_handler_install (char *prompt, Vfunction *lhandler)
+Set up the terminal for readline I/O and display the initial
+expanded value of @var{prompt}. Save the value of @var{lhandler} to
+use as a callback when a complete line of input has been entered.
+@end deftypefun
+
+@deftypefun void rl_callback_read_char ()
+Whenever an application determines that keyboard input is available, it
+should call @code{rl_callback_read_char()}, which will read the next
+character from the current input source. If that character completes the
+line, @code{rl_callback_read_char} will invoke the @var{lhandler}
+function saved by @code{rl_callback_handler_install} to process the
+line. @code{EOF} is indicated by calling @var{lhandler} with a
+@code{NULL} line.
+@end deftypefun
+
+@deftypefun 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.
+@end deftypefun
+
+@subsection An Example
+
+Here is a function which changes lowercase characters to their uppercase
+equivalents, and uppercase characters to lowercase. If
+this function was bound to @samp{M-c}, then typing @samp{M-c} would
+change the case of the character under point. Typing @samp{M-1 0 M-c}
+would change the case of the following 10 characters, leaving the cursor on
+the last character changed.
+
+@example
+/* 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);
+@}
+@end example
+
+@node Custom Completers
+@section Custom Completers
+
+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.
+
+@menu
+* How Completing Works:: The logic used to do completion.
+* Completion Functions:: Functions provided by Readline.
+* Completion Variables:: Variables which control completion.
+* A Short Completion Example:: An example of writing completer subroutines.
+@end menu
+
+@node How Completing Works
+@subsection How Completing Works
+
+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:
+
+@enumerate
+@item
+The user-interface function @code{rl_complete ()}. This function is
+called with the same arguments as other Readline
+functions intended for interactive use: @var{count} and
+@var{invoking_key}. It isolates the word to be completed and calls
+@code{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.
+
+@item
+The internal function @code{completion_matches ()} uses your
+@dfn{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 @code{rl_completion_entry_function}.
+
+@item
+The generator function is called repeatedly from
+@code{completion_matches ()}, returning a string each time. The
+arguments to the generator function are @var{text} and @var{state}.
+@var{text} is the partial word to be completed. @var{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
+@code{(char *)NULL} this signals @code{completion_matches ()} that there are
+no more possibilities left. Usually the generator function computes the
+list of possible completions when @var{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 @code{malloc()}; Readline
+frees the strings when it has finished with them.
+
+@end enumerate
+
+@deftypefun 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
+@code{completion_matches ()}). The default is to do filename completion.
+@end deftypefun
+
+@deftypevar {Function *} rl_completion_entry_function
+This is a pointer to the generator function for @code{completion_matches
+()}. If the value of @code{rl_completion_entry_function} is
+@code{(Function *)NULL} then the default filename generator function,
+@code{filename_entry_function ()}, is used.
+@end deftypevar
+
+@node Completion Functions
+@subsection Completion Functions
+
+Here is the complete list of callable completion functions present in
+Readline.
+
+@deftypefun int rl_complete_internal (int what_to_do)
+Complete the word at or before point. @var{what_to_do} says what to do
+with the completion. A value of @samp{?} means list the possible
+completions. @samp{TAB} means do standard completion. @samp{*} means
+insert all of the possible completions. @samp{!} means to display
+all of the possible completions, if there is more than one, as well as
+performing partial completion.
+@end deftypefun
+
+@deftypefun 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
+@code{completion_matches ()} and @code{rl_completion_entry_function}).
+The default is to do filename
+completion. This calls @code{rl_complete_internal ()} with an
+argument depending on @var{invoking_key}.
+@end deftypefun
+
+@deftypefun int rl_possible_completions (int count, int invoking_key))
+List the possible completions. See description of @code{rl_complete
+()}. This calls @code{rl_complete_internal ()} with an argument of
+@samp{?}.
+@end deftypefun
+
+@deftypefun 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 @code{rl_complete ()}.
+This calls @code{rl_complete_internal ()} with an argument of @samp{*}.
+@end deftypefun
+
+@deftypefun {char **} completion_matches (char *text, CPFunction *entry_func)
+Returns an array of @code{(char *)} which is a list of completions for
+@var{text}. If there are no completions, returns @code{(char **)NULL}.
+The first entry in the returned array is the substitution for @var{text}.
+The remaining entries are the possible completions. The array is
+terminated with a @code{NULL} pointer.
+
+@var{entry_func} is a function of two args, and returns a
+@code{(char *)}. The first argument is @var{text}. The second is a
+state argument; it is zero on the first call, and non-zero on subsequent
+calls. @var{entry_func} returns a @code{NULL} pointer to the caller
+when there are no more matches.
+@end deftypefun
+
+@deftypefun {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.
+@end deftypefun
+
+@deftypefun {char *} username_completion_function (char *text, int state)
+A completion generator for usernames. @var{text} contains a partial
+username preceded by a random character (usually @samp{~}). As with all
+completion generators, @var{state} is zero on the first call and non-zero
+for subsequent calls.
+@end deftypefun
+
+@node Completion Variables
+@subsection Completion Variables
+
+@deftypevar {Function *} rl_completion_entry_function
+A pointer to the generator function for @code{completion_matches ()}.
+@code{NULL} means to use @code{filename_entry_function ()}, the default
+filename completer.
+@end deftypevar
+
+@deftypevar {CPPFunction *} rl_attempted_completion_function
+A pointer to an alternative function to create matches.
+The function is called with @var{text}, @var{start}, and @var{end}.
+@var{start} and @var{end} are indices in @code{rl_line_buffer} saying
+what the boundaries of @var{text} are. If this function exists and
+returns @code{NULL}, or if this variable is set to @code{NULL}, then
+@code{rl_complete ()} will call the value of
+@code{rl_completion_entry_function} to generate matches, otherwise the
+array of strings returned will be used.
+@end deftypevar
+
+@deftypevar {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 @code{rl_filename_quote_characters}
+appears in a completed filename. The function is called with
+@var{text}, @var{match_type}, and @var{quote_pointer}. The @var{text}
+is the filename to be quoted. The @var{match_type} is either
+@code{SINGLE_MATCH}, if there is only one completion match, or
+@code{MULT_MATCH}. Some functions use this to decide whether or not to
+insert a closing quote character. The @var{quote_pointer} is a pointer
+to any opening quote character the user typed. Some functions choose
+to reset this character.
+@end deftypevar
+
+@deftypevar {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 @var{text}, the text of the word
+to be dequoted, and @var{quote_char}, which is the quoting character
+that delimits the filename (usually @samp{'} or @samp{"}). If
+@var{quote_char} is zero, the filename was not in an embedded string.
+@end deftypevar
+
+@deftypevar {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: @var{text}, the text of the line, and @var{index}, the
+index of the character in the line. It is used to decide whether a
+character found in @code{rl_completer_word_break_characters} should be
+used to break words for the completer.
+@end deftypevar
+
+@deftypevar 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.
+@end deftypevar
+
+@deftypevar {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.,
+@code{" \t\n\"\\'`@@$><=;|&@{("}.
+@end deftypevar
+
+@deftypevar {char *} rl_basic_quote_characters
+List of quote characters which can cause a word break.
+@end deftypevar
+
+@deftypevar {char *} rl_completer_word_break_characters
+The list of characters that signal a break between words for
+@code{rl_complete_internal ()}. The default list is the value of
+@code{rl_basic_word_break_characters}.
+@end deftypevar
+
+@deftypevar {char *} rl_completer_quote_characters
+List of characters which can be used to quote a substring of the line.
+Completion occurs on the entire substring, and within the substring
+@code{rl_completer_word_break_characters} are treated as any other character,
+unless they also appear within this list.
+@end deftypevar
+
+@deftypevar {char *} rl_filename_quote_characters
+A list of characters that cause a filename to be quoted by the completer
+when they appear in a completed filename. The default is empty.
+@end deftypevar
+
+@deftypevar {char *} rl_special_prefixes
+The list of characters that are word break characters, but should be
+left in @var{text} when it is passed to the completion function.
+Programs can use this to help determine what kind of completing to do.
+For instance, Bash sets this variable to "$@@" so that it can complete
+shell variables and hostnames.
+@end deftypevar
+
+@deftypevar {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 (@samp{ }). Setting this to the null
+character (@samp{\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.
+@end deftypevar
+
+@deftypevar int rl_ignore_completion_duplicates
+If non-zero, then disallow duplicates in the matches. Default is 1.
+@end deftypevar
+
+@deftypevar int rl_filename_completion_desired
+Non-zero means that the results of the matches are to be treated as
+filenames. This is @emph{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.
+@end deftypevar
+
+@deftypevar 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
+@code{rl_filename_quote_chars}. This is @emph{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 @code{rl_filename_quoting_function}.
+@end deftypevar
+
+@deftypevar int rl_inhibit_completion
+If this variable is non-zero, completion is inhibited. The completion
+character will be inserted as any other bound to @code{self-insert}.
+@end deftypevar
+
+@deftypevar {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 @code{NULL} terminated array of matches.
+The first element (@code{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.
+@end deftypevar
+
+@deftypevar {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.
+@end deftypevar
+
+@node A Short Completion Example
+@subsection A Short Completion Example
+
+Here is a small application demonstrating the use of the GNU Readline
+library. It is called @code{fileman}, and the source code resides in
+@file{examples/fileman.c}. This sample application provides
+completion of command names, line editing features, and access to the
+history list.
+
+@page
+@smallexample
+/* 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);
+@}
+@end smallexample
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