This document describes the GNU Readline Library, a utility for aiding in the consistency of user interface across discrete programs that need to provide a command line interface.

Copyright (C) 1988--2011 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.

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.

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.

Basic Behavior
==============

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 PROMPT and then reads and returns a single line of text from the user. If PROMPT is NULL or the empty string, no prompt is displayed. The line readline returns is allocated with malloc(); the caller should free() the line when it has finished with it. The declaration for readline in ANSI C is

     char *readline (const 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, rl_command_func_t *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 Custom Completers).

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.

Before declaring any functions that customize Readline's behavior, or using any functionality Readline provides in other code, an application writer should include the file <readline/readline.h> in any file that uses Readline's features.  Since some of the definitions in readline.h use the stdio library, the file <stdio.h> should be included before readline.h.

readline.h defines a C preprocessor variable that should be treated as an integer, RL_READLINE_VERSION, which may be used to conditionally compile application code depending on the installed Readline version.  The value is a hexadecimal encoding of the major and minor version numbers of the library, of the form 0xMMMM.  MM is the two-digit major version number; MM is the two-digit minor version number. For Readline 4.2, for example, the value of RL_READLINE_VERSION would be 0x0402.

Readline Typedefs
-----------------

For readabilty, we declare a number of new object types, all pointers to functions.

The reason for declaring these new types is to make it easier to write code describing pointers to C functions with appropriately prototyped arguments and return values.

For instance, say we want to declare a variable FUNC as a pointer to a function which takes two int arguments and returns an int (this is the type of all of the Readline bindable functions). Instead of the classic C declaration

int (*func)();

or the ANSI-C style declaration

int (*func)(int, int);

we may write

rl_command_func_t *func;

The full list of function pointer types available is

typedef int rl_command_func_t (int, int);

typedef char *rl_compentry_func_t (const char *, int);

typedef char **rl_completion_func_t (const char *, int, int);

typedef char *rl_quote_func_t (char *, int, char *);

typedef char *rl_dequote_func_t (char *, int);

typedef int rl_compignore_func_t (char **);

typedef void rl_compdisp_func_t (char **, int, int);

typedef int rl_hook_func_t (void);

typedef int rl_getc_func_t (FILE *);

typedef int rl_linebuf_func_t (char *, int);

typedef int rl_intfunc_t (int);

#define rl_ivoidfunc_t rl_hook_func_t

typedef int rl_icpfunc_t (char *);

typedef int rl_icppfunc_t (char **);

typedef void rl_voidfunc_t (void);

typedef void rl_vintfunc_t (int);

typedef void rl_vcpfunc_t (char *);

typedef void rl_vcppfunc_t (char **);

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 foo looks like

     int 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.

A command function should return 0 if its action completes successfully, and a non-zero value if some error occurs. This is the convention obeyed by all of the builtin Readline bindable command functions.

Readline Variables
==================

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 Allowing Undoing.  The function rl_extend_line_buffer is available to increase the memory allocated to rl_line_buffer.

 -- 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_num_chars_to_read
     Setting this to a positive value before calling readline() causes Readline to return after accepting that many characters, rather than reading up to a character bound to accept-line.

 -- 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: int rl_dispatching
     Set to a non-zero value if a function is being called from a key binding; zero otherwise.  Application functions can test this to discover whether they were called directly or by Readline's dispatching mechanism.

 -- Variable: int rl_erase_empty_line
     Setting this to a non-zero value causes Readline to completely erase the current line, including any prompt, any time a newline is typed as the only character on an otherwise-empty line.  The cursor is moved to the beginning of the newly-blank line.

 -- Variable: char * rl_prompt
     The prompt Readline uses.  This is set from the argument to readline(), and should not be assigned to directly. The rl_set_prompt() function (see Redisplay) may be used to modify the prompt string after calling readline().

 -- Variable: char * rl_display_prompt
     The string displayed as the prompt.  This is usually identical to RL_PROMPT, but may be changed temporarily by functions that use the prompt string as a message area, such as incremental search.

 -- Variable: int rl_already_prompted
     If an application wishes to display the prompt itself, rather than have Readline do it the first time readline() is called, it should set this variable to a non-zero value after displaying the prompt. The prompt must also be passed as the argument to readline() so the redisplay functions can update the display properly. The calling application is responsible for managing the value; Readline never sets it.

 -- Variable: const char * rl_library_version
     The version number of this revision of the library.

 -- Variable: int rl_readline_version
     An integer encoding the current version of the library.  The encoding is of the form 0xMMMM, where MM is the two-digit major version number, and MM is the two-digit minor version number. For example, for Readline-4.2, rl_readline_version would have the value 0x0402.

 -- Variable: int rl_gnu_readline_p
     Always set to 1, denoting that this is GNU readline rather than some emulation.

 -- Variable: const char * rl_terminal_name
     The terminal type, used for initialization.  If not set by the application, Readline sets this to the value of the TERM environment variable the first time it is called.

 -- Variable: const 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 Conditional Init Constructs).

 -- Variable: FILE * rl_instream
     The stdio stream from which Readline reads input. If NULL, Readline defaults to STDIN.

 -- Variable: FILE * rl_outstream
     The stdio stream to which Readline performs output. If NULL, Readline defaults to STDOUT.

 -- Variable: int rl_prefer_env_winsize
     If non-zero, Readline gives values found in the LINES and COLUMNS environment variables greater precedence than values fetched from the kernel when computing the screen dimensions.

 -- Variable: rl_command_func_t * rl_last_func
     The address of the last command function Readline executed.  May be used to test whether or not a function is being executed twice in succession, for example.

 -- Variable: rl_hook_func_t * rl_startup_hook
     If non-zero, this is the address of a function to call just before readline prints the first prompt.

 -- Variable: rl_hook_func_t * rl_pre_input_hook
     If non-zero, this is the address of a function to call after the first prompt has been printed and just before readline starts reading input characters.

 -- Variable: rl_hook_func_t * rl_event_hook
     If non-zero, this is the address of a function to call periodically when Readline is waiting for terminal input. By default, this will be called at most ten times a second if there is no keyboard input.

 -- Variable: rl_getc_func_t * 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 Character Input).

 -- Variable: rl_voidfunc_t * 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 Redisplay).

 -- Variable: rl_vintfunc_t * rl_prep_term_function
     If non-zero, Readline will call indirectly through this pointer to initialize the terminal.  The function takes a single argument, an int flag that says whether or not to use eight-bit characters. By default, this is set to rl_prep_terminal (see Terminal Management).

 -- Variable: rl_voidfunc_t * rl_deprep_term_function
     If non-zero, Readline will call indirectly through this pointer to reset the terminal.  This function should undo the effects of rl_prep_term_function. By default, this is set to rl_deprep_terminal (see Terminal Management).

 -- Variable: Keymap rl_executing_keymap
     This variable is set to the keymap (see Keymaps) in which the currently executing readline function was found.

 -- Variable: Keymap rl_binding_keymap
     This variable is set to the keymap (see Keymaps) in which the last key binding occurred.

 -- Variable: char * rl_executing_macro
     This variable is set to the text of any currently-executing macro.

 -- Variable: int rl_readline_state
     A variable with bit values that encapsulate the current Readline state. A bit is set with the RL_SETSTATE macro, and unset with the RL_UNSETSTATE macro.  Use the RL_ISSTATE macro to test whether a particular state bit is set.  Current state bits include:

     RL_STATE_NONE
          Readline has not yet been called, nor has it begun to intialize.

     RL_STATE_INITIALIZING
          Readline is initializing its internal data structures.

     RL_STATE_INITIALIZED
          Readline has completed its initialization.

     RL_STATE_TERMPREPPED
          Readline has modified the terminal modes to do its own input and redisplay.

     RL_STATE_READCMD
          Readline is reading a command from the keyboard.

     RL_STATE_METANEXT
          Readline is reading more input after reading the meta-prefix character.

     RL_STATE_DISPATCHING
          Readline is dispatching to a command.

     RL_STATE_MOREINPUT
          Readline is reading more input while executing an editing command.

     RL_STATE_ISEARCH
          Readline is performing an incremental history search.

     RL_STATE_NSEARCH
          Readline is performing a non-incremental history search.

     RL_STATE_SEARCH
          Readline is searching backward or forward through the history for a string.

     RL_STATE_NUMERICARG
          Readline is reading a numeric argument.

     RL_STATE_MACROINPUT
          Readline is currently getting its input from a previously-defined keyboard macro.

     RL_STATE_MACRODEF
          Readline is currently reading characters defining a keyboard macro.

     RL_STATE_OVERWRITE
          Readline is in overwrite mode.

     RL_STATE_COMPLETING
          Readline is performing word completion.

     RL_STATE_SIGHANDLER
          Readline is currently executing the readline signal handler.

     RL_STATE_UNDOING
          Readline is performing an undo.

     RL_STATE_INPUTPENDING
          Readline has input pending due to a call to rl_execute_next().

     RL_STATE_TTYCSAVED
          Readline has saved the values of the terminal's special characters.

     RL_STATE_CALLBACK
          Readline is currently using the alternate (callback) interface (see Alternate Interface).

     RL_STATE_VIMOTION
          Readline is reading the argument to a vi-mode "motion" command.

     RL_STATE_MULTIKEY
          Readline is reading a multiple-keystroke command.

     RL_STATE_VICMDONCE
          Readline has entered vi command (movement) mode at least one time during the current call to readline().

     RL_STATE_DONE
          Readline has read a key sequence bound to accept-line and is about to return the line to the caller.

 -- Variable: int rl_explicit_arg
     Set to a non-zero value if an explicit numeric argument was specified by the user.  Only valid in a bindable command function.

 -- Variable: int rl_numeric_arg
     Set to the value of any numeric argument explicitly specified by the user before executing the current Readline function.  Only valid in a bindable command function.

 -- Variable: int rl_editing_mode
     Set to a value denoting Readline's current editing mode.  A value of 1 means Readline is currently in emacs mode; 0 means that vi mode is active.

Readline Convenience Functions
==============================

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

     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 (const char *name, rl_command_func_t *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.

Selecting a Keymap
------------------

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 (void)
     Returns a new, empty keymap.  The space for the keymap is allocated with malloc(); the caller should free it by calling rl_free_keymap() when done.

 -- Function: Keymap rl_copy_keymap (Keymap map)
     Return a new keymap which is a copy of MAP.

 -- Function: Keymap rl_make_keymap (void)
     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 the data in KEYMAP. The caller should free KEYMAP.

 -- Function: void rl_free_keymap (Keymap keymap)
     Free all storage associated with KEYMAP.  This calls rl_discard_keymap to free subordindate keymaps and macros.

Readline has several internal keymaps.  These functions allow you to change which keymap is active.

 -- Function: Keymap rl_get_keymap (void)
     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 (const char *name)
     Return the keymap matching NAME.  NAME is one which would be supplied in a set keymap inputrc line (see 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 (see Readline Init File).

Binding Keys
------------

Key sequences are associate 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.

Since readline() installs a set of default key bindings the first time it is called, there is always the danger that a custom binding installed before the first call to readline() will be overridden. An alternate mechanism is to install custom key bindings in an initialization function assigned to the rl_startup_hook variable (see Readline Variables).

These functions manage key bindings.

 -- Function: int rl_bind_key (int key, rl_command_func_t *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, rl_command_func_t *function, Keymap map)
     Bind KEY to FUNCTION in MAP. Returns non-zero in the case of an invalid KEY.

 -- Function: int rl_bind_key_if_unbound (int key, rl_command_func_t *function)
     Binds KEY to FUNCTION if it is not already bound in the currently active keymap. Returns non-zero in the case of an invalid KEY or if KEY is already bound.

 -- Function: int rl_bind_key_if_unbound_in_map (int key, rl_command_func_t *function, Keymap map)
     Binds KEY to FUNCTION if it is not already bound in MAP. Returns non-zero in the case of an invalid KEY or if KEY is already bound.

 -- 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_unbind_function_in_map (rl_command_func_t *function, Keymap map)
     Unbind all keys that execute FUNCTION in MAP.

 -- Function: int rl_unbind_command_in_map (const char *command, Keymap map)
     Unbind all keys that are bound to COMMAND in MAP.

 -- Function: int rl_bind_keyseq (const char *keyseq, rl_command_func_t *function)
     Bind the key sequence represented by the string KEYSEQ to the function FUNCTION, beginning in the current keymap. This makes new keymaps as necessary. The return value is non-zero if KEYSEQ is invalid.

 -- Function: int rl_bind_keyseq_in_map (const char *keyseq, rl_command_func_t *function, Keymap map)
     Bind the key sequence represented by the string KEYSEQ to the function FUNCTION.  This makes new keymaps as necessary. Initial bindings are performed in MAP. The return value is non-zero if KEYSEQ is invalid.

 -- Function: int rl_set_key (const char *keyseq, rl_command_func_t *function, Keymap map)
     Equivalent to rl_bind_keyseq_in_map.

 -- Function: int rl_bind_keyseq_if_unbound (const char *keyseq, rl_command_func_t *function)
     Binds KEYSEQ to FUNCTION if it is not already bound in the currently active keymap. Returns non-zero in the case of an invalid KEYSEQ or if KEYSEQ is already bound.

 -- Function: int rl_bind_keyseq_if_unbound_in_map (const char *keyseq, rl_command_func_t *function, Keymap map)
     Binds KEYSEQ to FUNCTION if it is not already bound in MAP. Returns non-zero in the case of an invalid KEYSEQ or if KEYSEQ is already bound.

 -- Function: int rl_generic_bind (int type, const 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 (see Readline Init File).

 -- Function: int rl_read_init_file (const char *filename)
     Read keybindings and variable assignments from FILENAME (see Readline Init File).

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.  You may also associate a new function name with an arbitrary function.

 -- Function: rl_command_func_t * rl_named_function (const char *name)
     Return the function with name NAME.

 -- Function: rl_command_func_t * rl_function_of_keyseq (const 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 the int variable it points to (one of ISFUNC, ISKMAP, or ISMACR).

 -- Function: char ** rl_invoking_keyseqs (rl_command_func_t *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 (rl_command_func_t *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 (void)
     Print the names of all bindable Readline functions to rl_outstream.

 -- Function: const char ** rl_funmap_names (void)
     Return a NULL terminated array of known function names.  The array is sorted.  The array itself is allocated, but not the strings inside.  You should free the array, but not the pointers, using free or rl_free when you are done.

 -- Function: int rl_add_funmap_entry (const char *name, rl_command_func_t *function)
     Add NAME to the list of bindable Readline command names, and make FUNCTION the function to be called when NAME is invoked.

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.

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 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 (void)
     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 (void)
     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 rl_free_undo_list (void)
     Free the existing undo list.

 -- Function: int rl_do_undo (void)
     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.

Redisplay
---------

 -- Function: void rl_redisplay (void)
     Change what's displayed on the screen to reflect the current contents of rl_line_buffer.

 -- Function: int rl_forced_update_display (void)
     Force the line to be updated and redisplayed, whether or not Readline thinks the screen display is correct.

 -- Function: int rl_on_new_line (void)
     Tell the update functions that we have moved onto a new (empty) line, usually after ouputting a newline.

 -- Function: int rl_on_new_line_with_prompt (void)
     Tell the update functions that we have moved onto a new line, with RL_PROMPT already displayed. This could be used by applications that want to output the prompt string themselves, but still need Readline to know the prompt string length for redisplay. It should be used after setting RL_ALREADY_PROMPTED.

 -- Function: int rl_reset_line_state (void)
     Reset the display state to a clean state and redisplay the current line starting on a new line.

 -- Function: int rl_crlf (void)
     Move the cursor to the start of the next screen line.

 -- Function: int rl_show_char (int c)
     Display character C on rl_outstream. If Readline has not been set to display meta characters directly, this will convert meta characters to a meta-prefixed key sequence. This is intended for use by applications which wish to do their own redisplay.

 -- Function: int rl_message (const char *, ...)
     The arguments are a format string as would be supplied to printf, possibly containing conversion specifications such as %d, and any additional arguments necessary to satisfy the conversion specifications. The resulting string is displayed in the echo area.  The echo area is also used to display numeric arguments and search strings. You should call rl_save_prompt to save the prompt information before calling this function.

 -- Function: int rl_clear_message (void)
     Clear the message in the echo area.  If the prompt was saved with a call to rl_save_prompt before the last call to rl_message, call rl_restore_prompt before calling this function.

 -- Function: void rl_save_prompt (void)
     Save the local Readline prompt display state in preparation for displaying a new message in the message area with rl_message().

 -- Function: void rl_restore_prompt (void)
     Restore the local Readline prompt display state saved by the most recent call to rl_save_prompt. if rl_save_prompt was called to save the prompt before a call to rl_message, this function should be called before the corresponding call to rl_clear_message.

 -- Function: int rl_expand_prompt (char *prompt)
     Expand any special character sequences in PROMPT and set up the local Readline prompt redisplay variables. This function is called by readline().  It may also be called to expand the primary prompt if the rl_on_new_line_with_prompt() function or rl_already_prompted variable is used. It returns the number of visible characters on the last line of the (possibly multi-line) prompt. Applications may indicate that the prompt contains characters that take up no physical screen space when displayed by bracketing a sequence of such characters with the special markers RL_PROMPT_START_IGNORE and RL_PROMPT_END_IGNORE (declared in readline.h.  This may be used to embed terminal-specific escape sequences in prompts.

 -- Function: int rl_set_prompt (const char *prompt)
     Make Readline use PROMPT for subsequent redisplay.  This calls rl_expand_prompt() to expand the prompt and sets rl_prompt to the result.

Modifying Text
--------------

 -- Function: int rl_insert_text (const char *text)
     Insert TEXT into the line at the current cursor position. Returns the number of characters inserted.

 -- Function: int rl_delete_text (int start, int end)
     Delete the text between START and END in the current line. Returns the number of characters deleted.

 -- 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_push_macro_input (char *macro)
     Cause MACRO to be inserted into the line, as if it had been invoked by a key bound to a macro.  Not especially useful; use rl_insert_text() instead.

Character Input
---------------

 -- Function: int rl_read_key (void)
     Return the next character available from Readline's current input stream. This handles input inserted into the input stream via RL_PENDING_INPUT (see Readline Variables) and rl_stuff_char(), macros, and characters read from the keyboard. While waiting for input, this function will call any function assigned to the rl_event_hook variable.

 -- Function: int rl_getc (FILE *stream)
     Return the next character available from STREAM, which is assumed to be 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().  Up to 512 characters may be pushed back. rl_stuff_char returns 1 if the character was successfully inserted; 0 otherwise.

 -- Function: int rl_execute_next (int c)
     Make C be the next command to be executed when rl_read_key() is called.  This sets RL_PENDING_INPUT.

 -- Function: int rl_clear_pending_input (void)
     Unset RL_PENDING_INPUT, effectively negating the effect of any previous call to rl_execute_next().  This works only if the pending input has not already been read with rl_read_key().

 -- Function: int rl_set_keyboard_input_timeout (int u)
     While waiting for keyboard input in rl_read_key(), Readline will wait for U microseconds for input before calling any function assigned to rl_event_hook.  U must be greater than or equal to zero (a zero-length timeout is equivalent to a poll). The default waiting period is one-tenth of a second. Returns the old timeout value.

Terminal Management
-------------------

 -- Function: void rl_prep_terminal (int meta_flag)
     Modify the terminal settings for Readline's use, so readline() can read a single character at a time from the keyboard. The META_FLAG argument should be non-zero if Readline should read eight-bit input.

 -- Function: void rl_deprep_terminal (void)
     Undo the effects of rl_prep_terminal(), leaving the terminal in the state in which it was before the most recent call to rl_prep_terminal().

 -- Function: void rl_tty_set_default_bindings (Keymap kmap)
     Read the operating system's terminal editing characters (as would be displayed by stty) to their Readline equivalents. The bindings are performed in KMAP.

 -- Function: void rl_tty_unset_default_bindings (Keymap kmap)
     Reset the bindings manipulated by rl_tty_set_default_bindings so that the terminal editing characters are bound to rl_insert. The bindings are performed in KMAP.

 -- Function: int rl_reset_terminal (const char *terminal_name)
     Reinitialize Readline's idea of the terminal settings using TERMINAL_NAME as the terminal type (e.g., vt100). If TERMINAL_NAME is NULL, the value of the TERM environment variable is used.

Utility Functions
-----------------

 -- Function: int rl_save_state (struct readline_state *sp)
     Save a snapshot of Readline's internal state to SP. The contents of the READLINE_STATE structure are documented in readline.h. The caller is responsible for allocating the structure.

 -- Function: int rl_restore_state (struct readline_state *sp)
     Restore Readline's internal state to that stored in SP, which must have been saved by a call to rl_save_state. The contents of the READLINE_STATE structure are documented in readline.h. The caller is responsible for freeing the structure.

 -- Function: void rl_free (void *mem)
     Deallocate the memory pointed to by MEM.  MEM must have been allocated by malloc.

 -- Function: void rl_replace_line (const char *text, int clear_undo)
     Replace the contents of rl_line_buffer with TEXT. The point and mark are preserved, if possible. If CLEAR_UNDO is non-zero, the undo list associated with the current line is cleared.

 -- Function: void 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 (void)
     Initialize or re-initialize Readline's internal state. It's not strictly necessary to call this; readline() calls it before reading any input.

 -- Function: int rl_ding (void)
     Ring the terminal bell, obeying the setting of bell-style.

 -- Function: int rl_alphabetic (int c)
     Return 1 if C is an alphabetic character.

 -- Function: void rl_display_match_list (char **matches, int len, int max)
     A convenience function for displaying a list of strings in columnar format on Readline's output stream.  matches is the list of strings, in argv format, such as a list of completion matches. len is the number of strings in matches, and max is the length of the longest string in matches.  This function uses the setting of print-completions-horizontally to select how the matches are displayed (see Readline Init File Syntax). When displaying completions, this function sets the number of columns used for display to the value of completion-display-width, the value of the environment variable COLUMNS, or the screen width, in that order.

The following are implemented as macros, defined in chardefs.h. Applications should refrain from using them.

 -- Function: int _rl_uppercase_p (int c)
     Return 1 if C is an uppercase alphabetic character.

 -- Function: int _rl_lowercase_p (int c)
     Return 1 if C is a lowercase alphabetic character.

 -- Function: int _rl_digit_p (int c)
     Return 1 if C is a numeric character.

 -- Function: int _rl_to_upper (int c)
     If C is a lowercase alphabetic character, return the corresponding uppercase character.

 -- Function: int _rl_to_lower (int c)
     If C is an uppercase alphabetic character, return the corresponding lowercase character.

 -- Function: int _rl_digit_value (int c)
     If C is a number, return the value it represents.

Miscellaneous Functions
-----------------------

 -- Function: int rl_macro_bind (const char *keyseq, const char *macro, Keymap map)
     Bind the key sequence KEYSEQ to invoke the macro MACRO. The binding is performed in MAP.  When KEYSEQ is invoked, the MACRO will be inserted into the line.  This function is deprecated; use rl_generic_bind() instead.

 -- Function: void rl_macro_dumper (int readable)
     Print the key sequences bound to macros and their values, using the current keymap, 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: int rl_variable_bind (const char *variable, const char *value)
     Make the Readline variable VARIABLE have VALUE. This behaves as if the readline command set VARIABLE VALUE had been executed in an inputrc file (see Readline Init File Syntax).

 -- Function: char * rl_variable_value (const char *variable)
     Return a string representing the value of the Readline variable VARIABLE. For boolean variables, this string is either on or off.

 -- Function: void rl_variable_dumper (int readable)
     Print the readline variable names and their current values 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: int rl_set_paren_blink_timeout (int u)
     Set the time interval (in microseconds) that Readline waits when showing a balancing character when blink-matching-paren has been enabled.

 -- Function: char * rl_get_termcap (const char *cap)
     Retrieve the string value of the termcap capability CAP. Readline fetches the termcap entry for the current terminal name and uses those capabilities to move around the screen line and perform other terminal-specific operations, like erasing a line.  Readline does not use all of a terminal's capabilities, and this function will return values for only those capabilities Readline uses.

Alternate Interface
-------------------

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 (const char *prompt, rl_vcpfunc_t *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 function to call when a complete line of input has been entered. The function takes the text of the line as an argument.

 -- Function: void rl_callback_read_char (void)
     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. Before calling the LHANDLER function, the terminal settings are reset to the values they had before calling rl_callback_handler_install. If the LHANDLER function returns, the terminal settings are modified for Readline's use again. EOF is  indicated by calling LHANDLER with a NULL line.

 -- Function: void rl_callback_handler_remove (void)
     Restore the terminal to its initial state and remove the line handler. This may be called from within a callback as well as independently. If the LHANDLER installed by rl_callback_handler_install does not exit the program, either this function or the function referred to by the value of rl_deprep_term_function should be called before the program exits to reset the terminal settings.

A Readline Example
------------------

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 (_rl_uppercase_p (rl_line_buffer[i]))
             rl_line_buffer[i] = _rl_to_lower (rl_line_buffer[i]);
           else if (_rl_lowercase_p (rl_line_buffer[i]))
             rl_line_buffer[i] = _rl_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);
     }

Readline Signal Handling
========================

Signals are asynchronous events sent to a process by the Unix kernel, sometimes on behalf of another process.  They are intended to indicate exceptional events, like a user pressing the interrupt key on his terminal, or a network connection being broken.  There is a class of signals that can be sent to the process currently reading input from the keyboard.  Since Readline changes the terminal attributes when it is called, it needs to perform special processing when such a signal is received in order to restore the terminal to a sane state, or provide application writers with functions to do so manually.

Readline contains an internal signal handler that is installed for a number of signals (SIGINT, SIGQUIT, SIGTERM, SIGALRM, SIGTSTP, SIGTTIN, and SIGTTOU). When one of these signals is received, the signal handler will reset the terminal attributes to those that were in effect before readline() was called, reset the signal handling to what it was before readline() was called, and resend the signal to the calling application. If and when the calling application's signal handler returns, Readline will reinitialize the terminal and continue to accept input. When a SIGINT is received, the Readline signal handler performs some additional work, which will cause any partially-entered line to be aborted (see the description of rl_free_line_state() below).

There is an additional Readline signal handler, for SIGWINCH, which the kernel sends to a process whenever the terminal's size changes (for example, if a user resizes an xterm).  The Readline SIGWINCH handler updates Readline's internal screen size information, and then calls any SIGWINCH signal handler the calling application has installed. Readline calls the application's SIGWINCH signal handler without resetting the terminal to its original state.  If the application's signal handler does more than update its idea of the terminal size and return (for example, a longjmp back to a main processing loop), it must call rl_cleanup_after_signal() (described below), to restore the terminal state.

Readline provides two variables that allow application writers to control whether or not it will catch certain signals and act on them when they are received.  It is important that applications change the values of these variables only when calling readline(), not in a signal handler, so Readline's internal signal state is not corrupted.

 -- Variable: int rl_catch_signals
     If this variable is non-zero, Readline will install signal handlers for SIGINT, SIGQUIT, SIGTERM, SIGALRM, SIGTSTP, SIGTTIN, and SIGTTOU.

     The default value of rl_catch_signals is 1.

 -- Variable: int rl_catch_sigwinch
     If this variable is non-zero, Readline will install a signal handler for SIGWINCH.

     The default value of rl_catch_sigwinch is 1.

If an application does not wish to have Readline catch any signals, or to handle signals other than those Readline catches (SIGHUP, for example), Readline provides convenience functions to do the necessary terminal and internal state cleanup upon receipt of a signal.

 -- Function: void rl_cleanup_after_signal (void)
     This function will reset the state of the terminal to what it was before readline() was called, and remove the Readline signal handlers for all signals, depending on the values of rl_catch_signals and rl_catch_sigwinch.

 -- Function: void rl_free_line_state (void)
     This will free any partial state associated with the current input line (undo information, any partial history entry, any partially-entered keyboard macro, and any partially-entered numeric argument).  This should be called before rl_cleanup_after_signal().  The Readline signal handler for SIGINT calls this to abort the current input line.

 -- Function: void rl_reset_after_signal (void)
     This will reinitialize the terminal and reinstall any Readline signal handlers, depending on the values of rl_catch_signals and rl_catch_sigwinch.

If an application does not wish Readline to catch SIGWINCH, it may call rl_resize_terminal() or rl_set_screen_size() to force Readline to update its idea of the terminal size when a SIGWINCH is received.

 -- Function: void rl_echo_signal_char (int sig)
     If an application wishes to install its own signal handlers, but still have readline display characters that generate signals, calling this function with SIG set to SIGINT, SIGQUIT, or SIGTSTP will display the character generating that signal.

 -- Function: void rl_resize_terminal (void)
     Update Readline's internal screen size by reading values from the kernel.

 -- Function: void rl_set_screen_size (int rows, int cols)
     Set Readline's idea of the terminal size to ROWS rows and COLS columns.  If either ROWS or COLUMNS is less than or equal to 0, Readline's idea of that terminal dimension is unchanged.

If an application does not want to install a SIGWINCH handler, but is still interested in the screen dimensions, Readline's idea of the screen size may be queried.

 -- Function: void rl_get_screen_size (int *rows, int *cols)
     Return Readline's idea of the terminal's size in the variables pointed to by the arguments.

 -- Function: void rl_reset_screen_size (void)
     Cause Readline to reobtain the screen size and recalculate its dimensions.

The following functions install and remove Readline's signal handlers.

 -- Function: int rl_set_signals (void)
     Install Readline's signal handler for SIGINT, SIGQUIT, SIGTERM, SIGALRM, SIGTSTP, SIGTTIN, SIGTTOU, and SIGWINCH, depending on the values of rl_catch_signals and rl_catch_sigwinch.

 -- Function: int rl_clear_signals (void)
     Remove all of the Readline signal handlers installed by rl_set_signals().

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.

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:

 1. The user-interface function rl_complete().  This function is called with the same arguments as other bindable Readline functions: COUNT and INVOKING_KEY. It isolates the word to be completed and calls rl_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.

 2. The internal function rl_completion_matches() uses an application-supplied generator function to generate the list of possible matches, and then returns the array of these matches. The caller should place the address of its generator function in rl_completion_entry_function.

 3. The generator function is called repeatedly from rl_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.  The generator function returns (char *)NULL to inform rl_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. Such a generator function is referred to as an application-specific completion function.

 -- 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 rl_completion_matches()).  The default is to do filename completion.

 -- Variable: rl_compentry_func_t * rl_completion_entry_function
     This is a pointer to the generator function for rl_completion_matches(). If the value of rl_completion_entry_function is NULL then the default filename generator function, rl_filename_completion_function(), is used. An application-specific completion function is a function whose address is assigned to rl_completion_entry_function and whose return values are used to  generate possible completions.

Completion Functions
--------------------

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.  @ is similar to !, but possible completions are not listed if the possible completions share a common prefix.

 -- 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 rl_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: int rl_completion_mode (rl_command_func_t *cfunc)
     Returns the apppriate value to pass to rl_complete_internal() depending on whether CFUNC was called twice in succession and the values of the show-all-if-ambiguous and show-all-if-unmodified variables. Application-specific completion functions may use this function to present the same interface as rl_complete().

 -- Function: char ** rl_completion_matches (const char *text, rl_compentry_func_t *entry_func)
     Returns an array of strings which is a list of completions for TEXT.  If there are no completions, returns 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 * rl_filename_completion_function (const char *text, int state)
     A generator function for filename completion in the general case. TEXT is a partial filename. The Bash source is a useful reference for writing application-specific completion functions (the Bash completion functions call this and other Readline functions).

 -- Function: char * rl_username_completion_function (const 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.

Completion Variables
--------------------

 -- Variable: rl_compentry_func_t * rl_completion_entry_function
     A pointer to the generator function for rl_completion_matches(). NULL means to use rl_filename_completion_function(), the default filename completer.

 -- Variable: rl_completion_func_t * 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 defining the boundaries of TEXT, which is a character string. 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. If this function sets the rl_attempted_completion_over variable to a non-zero value, Readline will not perform its default completion even if this function returns no matches.

 -- Variable: rl_quote_func_t * 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: rl_dequote_func_t * 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: rl_linebuf_func_t * 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: rl_compignore_func_t * 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: rl_icppfunc_t * rl_directory_completion_hook
     This function, if defined, is allowed to modify the directory portion of filenames Readline completes. It could be used to expand symbolic links or shell variables in pathnames. It is called with the address of a string (the current directory name) as an argument, and may modify that string. If the string is replaced with a new string, the old value should be freed. Any modified directory name should have a trailing slash. The modified value will be used as part of the completion, replacing the directory portion of the pathname the user typed. At the least, even if no other expansion is performed, this function should remove any quote characters from the directory name, because its result will be passed directly to opendir(). The directory completion hook returns an integer that should be non-zero if the function modifies its directory argument. The function should not modify the directory argument if it returns 0.

 -- Variable: rl_dequote_func_t * rl_filename_rewrite_hook
     If non-zero, this is the address of a function called when reading directory entries from the filesystem for completion and comparing them to the partial word to be completed.  The function should perform any necesary application or system-specific conversion on the filename, such as converting between character sets or converting from a filesystem format to a character input format. The function takes two arguments: FNAME, the filename to be converted, and FNLEN, its length in bytes. It must either return its first argument (if no conversion takes place) or the converted filename in newly-allocated memory.  The converted form is used to compare against the word to be completed, and, if it matches, is added to the list of matches.  Readline will free the allocated string.

 -- Variable: rl_compdisp_func_t * rl_completion_display_matches_hook
     If non-zero, then this is the address of a function to call when completing a word would normally display the list of possible matches. This function is called in lieu of Readline displaying the list. It takes three arguments: (char **MATCHES, int NUM_MATCHES, int MAX_LENGTH) where MATCHES is the array of matching strings, NUM_MATCHES is the number of strings in that array, and MAX_LENGTH is the length of the longest string in that array. Readline provides a convenience function, rl_display_match_list, that takes care of doing the display to Readline's output stream.  That function may be called from this hook.

 -- Variable: const 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: " \t\n\"\\'`@$><=;|&{(".

 -- Variable: const char * rl_basic_quote_characters
     A list of quote characters which can cause a word break.

 -- Variable: const 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: rl_cpvfunc_t * rl_completion_word_break_hook
     If non-zero, this is the address of a function to call when Readline is deciding where to separate words for word completion.  It should return a character string like rl_completer_word_break_characters to be used to perform the current completion.  The function may choose to set rl_completer_word_break_characters itself.  If the function returns NULL, rl_completer_word_break_characters is used.

 -- Variable: const char * rl_completer_quote_characters
     A 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: const 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 the null string.

 -- Variable: const 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_query_items
     Up to this many items will be displayed in response to a possible-completions call.  After that, readline asks the user if she is sure she wants to see them all.  The default value is 100.  A negative value indicates that Readline should never ask the user.

 -- 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 application-specific completion functions to provide the ``most sensible word separator character'' according to an application-specific command line syntax specification.

 -- Variable: int rl_completion_suppress_append
     If non-zero, RL_COMPLETION_APPEND_CHARACTER is not appended to matches at the end of the command line, as described above. It is set to 0 before any application-specific completion function is called, and may only be changed within such a function.

 -- Variable: int rl_completion_quote_character
     When Readline is completing quoted text, as delimited by one of the characters in RL_COMPLETER_QUOTE_CHARACTERS, it sets this variable to the quoting character found. This is set before any application-specific completion function is called.

 -- Variable: int rl_completion_suppress_quote
     If non-zero, Readline does not append a matching quote character when performing completion on a quoted string. It is set to 0 before any application-specific completion function is called, and may only be changed within such a function.

 -- Variable: int rl_completion_found_quote
     When Readline is completing quoted text, it sets this variable to a non-zero value if the word being completed contains or is delimited by any quoting characters, including backslashes. This is set before any application-specific completion function is called.

 -- Variable: int rl_completion_mark_symlink_dirs
     If non-zero, a slash will be appended to completed filenames that are symbolic links to directory names, subject to the value of the user-settable MARK-DIRECTORIES variable. This variable exists so that application-specific completion functions can override the user's global preference (set via the MARK-SYMLINKED-DIRECTORIES Readline variable) if appropriate. This variable is set to the user's preference before any application-specific completion function is called, so unless that function modifies the value, the user's preferences are honored.

 -- Variable: int rl_ignore_completion_duplicates
     If non-zero, then duplicates in the matches are removed. The 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 when completion is attempted, and can only be changed within an application-specific completion function.  If it is set to a non-zero value by such a function, directory names have a slash appended and Readline attempts to quote completed filenames if they contain any characters in rl_filename_quote_characters and rl_filename_quoting_desired is set to a non-zero value.

 -- 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 when completion is attempted, and can only be changed within an application-specific completion function. The quoting is effected via a call to the function pointed to by rl_filename_quoting_function.

 -- Variable: int rl_attempted_completion_over
     If an application-specific completion function assigned to rl_attempted_completion_function sets this variable to a non-zero value, Readline will not perform its default filename completion even if the application's completion function returns no matches. It should be set only by an application's completion function.

 -- Variable: int rl_sort_completion_matches
     If an application sets this variable to 0, Readline will not sort the list of completions (which implies that it cannot remove any duplicate completions).  The default value is 1, which means that Readline will sort the completions and, depending on the value of rl_ignore_completion_duplicates, will attempt to remove duplicate matches.

 -- Variable: int rl_completion_type
     Set to a character describing the type of completion Readline is currently attempting; see the description of rl_complete_internal() (see Completion Functions) for the list of characters. This is set to the appropriate value before any application-specific completion function is called, allowing such functions to present the same interface as rl_complete().

 -- Variable: int rl_completion_invoking_key
     Set to the final character in the key sequence that invoked one of the completion functions that call rl_complete_internal().  This is set to the appropriate value before any application-specific completion function is called.

 -- Variable: int rl_inhibit_completion
     If this variable is non-zero, completion is inhibited.  The completion character will be inserted as any other bound to self-insert.

A Short Completion Example
--------------------------

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. */

     #ifdef HAVE_CONFIG_H
     #  include <config.h>
     #endif

     #include <sys/types.h>
     #ifdef HAVE_SYS_FILE_H
     #  include <sys/file.h>
     #endif
     #include <sys/stat.h>

     #ifdef HAVE_UNISTD_H
     #  include <unistd.h>
     #endif

     #include <fcntl.h>
     #include <stdio.h>
     #include <errno.h>

     #if defined (HAVE_STRING_H)
     #  include <string.h>
     #else /* !HAVE_STRING_H */
     #  include <strings.h>
     #endif /* !HAVE_STRING_H */

     #ifdef HAVE_STDLIB_H
     #  include <stdlib.h>
     #endif

     #include <time.h>

     #include <readline/readline.h>
     #include <readline/history.h>

     extern char *xmalloc PARAMS((size_t));

     /* The names of functions that actually do the manipulation. */
     int com_list PARAMS((char *));
     int com_view PARAMS((char *));
     int com_rename PARAMS((char *));
     int com_stat PARAMS((char *));
     int com_pwd PARAMS((char *));
     int com_delete PARAMS((char *));
     int com_help PARAMS((char *));
     int com_cd PARAMS((char *));
     int com_quit PARAMS((char *));

     /* A structure which contains information on the commands this program
        can understand. */

     typedef struct {
       char *name;			/* User printable name of the function. */
       rl_icpfunc_t *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, (rl_icpfunc_t *)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)
          char *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 PARAMS((const char *, int));
     char **fileman_completion PARAMS((const char *, int, int));

     /* 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 = 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)
          const 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 = rl_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)
          const 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;

     #if defined (__MSDOS__)
       /* more.com doesn't grok slashes in pathnames */
       sprintf (syscom, "less %s", arg);
     #else
       sprintf (syscom, "more %s", arg);
     #endif
       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 = getcwd (dir, sizeof(dir) - 1);
       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);
     }