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READLINE(3)		   Library Functions Manual		   READLINE(3)



NAME
       readline - get a line from a user with editing

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

       char *
       readline (const char *prompt);

COPYRIGHT
       Readline is Copyright (C) 1989-2020 Free Software Foundation,  Inc.

DESCRIPTION
       readline will read a line from the terminal and return it, using prompt
       as a prompt.  If prompt is NULL or the empty string, no prompt  is  is‐
       sued.   The  line returned is allocated with malloc(3); the caller must
       free it when finished.  The line returned has  the  final  newline  re‐
       moved, so only the text of the line remains.

       readline	 offers	 editing  capabilities	while the user is entering the
       line.  By default, the line editing commands are similar	 to  those  of
       emacs.  A vi-style line editing interface is also available.

       This  manual  page describes only the most basic use of readline.  Much
       more functionality is available; see The GNU Readline Library  and  The
       GNU History Library for additional information.

RETURN VALUE
       readline	 returns  the text of the line read.  A blank line returns the
       empty string.  If EOF is encountered while reading a line, and the line
       is  empty,  NULL is returned.  If an EOF is read with a non-empty line,
       it is treated as a newline.

NOTATION
       An Emacs-style notation is used to denote keystrokes.  Control keys are
       denoted	by C-key, e.g., C-n means Control-N.  Similarly, meta keys are
       denoted by M-key, so M-x means Meta-X.  (On keyboards  without  a  meta
       key,  M-x means ESC x, i.e., press the Escape key then the x key.  This
       makes ESC the meta prefix.  The combination M-C-x means	ESC-Control-x,
       or  press the Escape key then hold the Control key while pressing the x
       key.)

       Readline commands may be given numeric arguments, which normally act as
       a  repeat  count.   Sometimes,  however, it is the sign of the argument
       that is significant.  Passing a negative argument  to  a	 command  that
       acts  in the forward direction (e.g., kill-line) causes that command to
       act in a backward direction.  Commands whose  behavior  with  arguments
       deviates from this are noted below.

       When  a command is described as killing text, the text deleted is saved
       for possible future retrieval (yanking).	 The killed text is saved in a
       kill ring.  Consecutive kills cause the text to be accumulated into one
       unit, which can be yanked all at once.  Commands which do not kill text
       separate the chunks of text on the kill ring.

INITIALIZATION FILE
       Readline	 is  customized	 by putting commands in an initialization file
       (the inputrc file).  The name of this file is taken from the  value  of
       the  INPUTRC  environment variable.  If that variable is unset, the de‐
       fault is ~/.inputrc.  If that file  does not exist or cannot  be	 read,
       the  ultimate  default  is /etc/inputrc.	 When a program which uses the
       readline library starts up, the init file is read, and the key bindings
       and  variables  are set.	 There are only a few basic constructs allowed
       in the readline init file.  Blank lines are ignored.   Lines  beginning
       with  a	# are comments.	 Lines beginning with a $ indicate conditional
       constructs.  Other lines denote key  bindings  and  variable  settings.
       Each program using this library may add its own commands and bindings.

       For example, placing

	      M-Control-u: universal-argument
       or
	      C-Meta-u: universal-argument

       into  the inputrc would make M-C-u execute the readline command univer‐
       sal-argument.

       The following symbolic character names are recognized while  processing
       key  bindings:  DEL,  ESC,  ESCAPE,  LFD, NEWLINE, RET, RETURN, RUBOUT,
       SPACE, SPC, and TAB.

       In addition to command names, readline allows keys to  be  bound	 to  a
       string that is inserted when the key is pressed (a macro).

   Key Bindings
       The  syntax for controlling key bindings in the inputrc file is simple.
       All that is required is the name of the command or the text of a	 macro
       and a key sequence to which it should be bound.	The name may be speci‐
       fied in one of two ways: as a symbolic key name, possibly with Meta- or
       Control- prefixes, or as a key sequence.	 The name and key sequence are
       separated by a colon.  There can be no whitespace between the name  and
       the colon.

       When using the form keyname:function-name or macro, keyname is the name
       of a key spelled out in English.	 For example:

	      Control-u: universal-argument
	      Meta-Rubout: backward-kill-word
	      Control-o: "> output"

       In the above example, C-u is bound to the function  universal-argument,
       M-DEL  is bound to the function backward-kill-word, and C-o is bound to
       run the macro expressed on the right hand side (that is, to insert  the
       text ``> output'' into the line).

       In  the	second	form,  "keyseq":function-name or macro, keyseq differs
       from keyname above in that strings denoting an entire key sequence  may
       be  specified  by  placing the sequence within double quotes.  Some GNU
       Emacs style key escapes can be used, as in the following	 example,  but
       the symbolic character names are not recognized.

	      "\C-u": universal-argument
	      "\C-x\C-r": re-read-init-file
	      "\e[11~": "Function Key 1"

       In this example, C-u is again bound to the function universal-argument.
       C-x C-r is bound to the function re-read-init-file, and ESC [ 1 1 ~  is
       bound to insert the text ``Function Key 1''.

       The  full set of GNU Emacs style escape sequences available when speci‐
       fying key sequences is
	      \C-    control prefix
	      \M-    meta prefix
	      \e     an escape character
	      \\     backslash
	      \"     literal ", a double quote
	      \'     literal ', a single quote

       In addition to the GNU Emacs style escape sequences, a  second  set  of
       backslash escapes is available:
	      \a     alert (bell)
	      \b     backspace
	      \d     delete
	      \f     form feed
	      \n     newline
	      \r     carriage return
	      \t     horizontal tab
	      \v     vertical tab
	      \nnn   the  eight-bit  character	whose value is the octal value
		     nnn (one to three digits)
	      \xHH   the eight-bit character whose value  is  the  hexadecimal
		     value HH (one or two hex digits)

       When  entering  the  text of a macro, single or double quotes should be
       used to indicate a macro definition.  Unquoted text is assumed to be  a
       function	 name.	 In  the  macro	 body, the backslash escapes described
       above are expanded.  Backslash will quote any other  character  in  the
       macro text, including " and '.

       Bash  allows the current readline key bindings to be displayed or modi‐
       fied with the bind builtin command.  The editing mode may  be  switched
       during  interactive  use by using the -o option to the set builtin com‐
       mand.  Other programs using this library	 provide  similar  mechanisms.
       The  inputrc  file may be edited and re-read if a program does not pro‐
       vide any other means to incorporate new bindings.

   Variables
       Readline has variables that can be used to further customize its behav‐
       ior.  A variable may be set in the inputrc file with a statement of the
       form

	      set variable-name value

       Except where noted, readline variables can take the values  On  or  Off
       (without	 regard	 to  case).   Unrecognized variable names are ignored.
       When a variable value is read, empty or null values, "on"  (case-insen‐
       sitive), and "1" are equivalent to On.  All other values are equivalent
       to Off.	The variables and their default values are:

       active-region-start-color
	      A string variable that controls the text	color  and  background
	      when  displaying the text in the active region (see the descrip‐
	      tion of enable-active-region below).  This string must not  take
	      up any physical character positions on the display, so it should
	      consist only of terminal escape sequences.  It is output to  the
	      terminal	before displaying the text in the active region.  This
	      variable is reset to the default	value  whenever	 the  terminal
	      type  changes.   The  default  value is the string that puts the
	      terminal in standout mode, as obtained from the terminal's  ter‐
	      minfo description.  A sample value might be "\e[01;33m".
       active-region-end-color
	      A	 string	 variable  that	 "undoes"  the	effects	 of active-re‐
	      gion-start-color and restores "normal" terminal display  appear‐
	      ance  after  displaying  text in the active region.  This string
	      must not take up any physical character positions	 on  the  dis‐
	      play,  so	 it  should consist only of terminal escape sequences.
	      It is output to the terminal after displaying the	 text  in  the
	      active  region.	This  variable	is  reset to the default value
	      whenever the terminal type changes.  The default	value  is  the
	      string  that  restores  the  terminal from standout mode, as ob‐
	      tained from the terminal's terminfo description.	A sample value
	      might be "\e[0m".
       bell-style (audible)
	      Controls	what  happens when readline wants to ring the terminal
	      bell.  If set to none, readline never rings the bell.  If set to
	      visible,	readline  uses a visible bell if one is available.  If
	      set to audible, readline attempts to ring the terminal's bell.
       bind-tty-special-chars (On)
	      If set to On (the default), readline attempts to bind  the  con‐
	      trol  characters	  treated  specially  by the kernel's terminal
	      driver to their readline equivalents.
       blink-matching-paren (Off)
	      If set to On, readline attempts to briefly move the cursor to an
	      opening parenthesis when a closing parenthesis is inserted.
       colored-completion-prefix (Off)
	      If  set  to  On, when listing completions, readline displays the
	      common prefix of the set of possible completions using a differ‐
	      ent  color.   The	 color definitions are taken from the value of
	      the LS_COLORS environment variable.  If there is a color defini‐
	      tion  in $LS_COLORS for the custom suffix "readline-colored-com‐
	      pletion-prefix", readline uses this color for the common	prefix
	      instead of its default.
       colored-stats (Off)
	      If  set to On, readline displays possible completions using dif‐
	      ferent colors to indicate their file type.   The	color  defini‐
	      tions  are  taken	 from  the  value of the LS_COLORS environment
	      variable.
       comment-begin (``#'')
	      The string that is inserted in vi mode when  the	insert-comment
	      command is executed.  This command is bound to M-# in emacs mode
	      and to # in vi command mode.
       completion-display-width (-1)
	      The number of screen columns used to  display  possible  matches
	      when  performing completion.  The value is ignored if it is less
	      than 0 or greater than the terminal screen width.	 A value of  0
	      will  cause  matches  to be displayed one per line.  The default
	      value is -1.
       completion-ignore-case (Off)
	      If set to On, readline performs filename matching and completion
	      in a case-insensitive fashion.
       completion-map-case (Off)
	      If  set  to  On, and completion-ignore-case is enabled, readline
	      treats hyphens (-) and underscores (_) as equivalent  when  per‐
	      forming case-insensitive filename matching and completion.
       completion-prefix-display-length (0)
	      The  length in characters of the common prefix of a list of pos‐
	      sible completions that is displayed without modification.	  When
	      set  to  a  value greater than zero, common prefixes longer than
	      this value are replaced with an ellipsis when displaying	possi‐
	      ble completions.
       completion-query-items (100)
	      This  determines when the user is queried about viewing the num‐
	      ber of possible completions generated  by	 the  possible-comple‐
	      tions  command.  It may be set to any integer value greater than
	      or equal to zero.	 If the	 number	 of  possible  completions  is
	      greater  than  or	 equal to the value of this variable, readline
	      will ask whether or not the user wishes to view them;  otherwise
	      they are simply listed on the terminal.  A negative value causes
	      readline to never ask.
       convert-meta (On)
	      If set to On, readline will convert characters with  the	eighth
	      bit set to an ASCII key sequence by stripping the eighth bit and
	      prefixing it with an escape character (in effect,	 using	escape
	      as  the  meta prefix).  The default is On, but readline will set
	      it to Off if the locale  contains	 eight-bit  characters.	  This
	      variable	is  dependent on the LC_CTYPE locale category, and may
	      change if the locale is changed.
       disable-completion (Off)
	      If set to On, readline will inhibit word completion.  Completion
	      characters  will	be  inserted into the line as if they had been
	      mapped to self-insert.
       echo-control-characters (On)
	      When set to On, on operating systems that indicate they  support
	      it, readline echoes a character corresponding to a signal gener‐
	      ated from the keyboard.
       editing-mode (emacs)
	      Controls whether readline begins with a set of key bindings sim‐
	      ilar to Emacs or vi.  editing-mode can be set to either emacs or
	      vi.
       emacs-mode-string (@)
	      If the show-mode-in-prompt variable is enabled, this  string  is
	      displayed immediately before the last line of the primary prompt
	      when emacs editing mode is active.  The value is expanded like a
	      key  binding,  so the standard set of meta- and control prefixes
	      and backslash escape sequences is available.  Use the \1 and  \2
	      escapes  to  begin and end sequences of non-printing characters,
	      which can be used to embed a terminal control sequence into  the
	      mode string.
       enable-active-region (On)
	      The  point  is the current cursor position, and mark refers to a
	      saved cursor position.  The text between the point and  mark  is
	      referred	to  as	the  region.  When this variable is set to On,
	      readline allows certain commands to designate the region as  ac‐
	      tive.   When  the region is active, readline highlights the text
	      in the region using the value of the  active-region-start-color,
	      which  defaults to the string that enables the terminal's stand‐
	      out mode.	 The active region shows the text inserted  by	brack‐
	      eted-paste  and  any matching text found by incremental and non-
	      incremental history searches.
       enable-bracketed-paste (On)
	      When set to On, readline configures the terminal to insert  each
	      paste  into the editing buffer as a single string of characters,
	      instead of treating each character as if it had been  read  from
	      the keyboard.  This prevents readline from executing any editing
	      commands bound to key sequences appearing in the pasted text.
       enable-keypad (Off)
	      When set to On, readline will try to enable the application key‐
	      pad when it is called.  Some systems need this to enable the ar‐
	      row keys.
       enable-meta-key (On)
	      When set to On, readline will try to enable  any	meta  modifier
	      key  the	terminal claims to support when it is called.  On many
	      terminals, the meta key is used to send eight-bit characters.
       expand-tilde (Off)
	      If set to On, tilde expansion is	performed  when	 readline  at‐
	      tempts word completion.
       history-preserve-point (Off)
	      If  set  to  On, the history code attempts to place point at the
	      same location on each history line retrieved with	 previous-his‐
	      tory or next-history.
       history-size (unset)
	      Set  the	maximum number of history entries saved in the history
	      list.  If set to zero, any existing history entries are  deleted
	      and no new entries are saved.  If set to a value less than zero,
	      the number of history entries is not limited.  By	 default,  the
	      number of history entries is not limited.	 If an attempt is made
	      to set history-size to a non-numeric value, the  maximum	number
	      of history entries will be set to 500.
       horizontal-scroll-mode (Off)
	      When  set	 to  On, makes readline use a single line for display,
	      scrolling the input horizontally on a single screen line when it
	      becomes  longer  than the screen width rather than wrapping to a
	      new line.	 This setting is automatically enabled	for  terminals
	      of height 1.
       input-meta (Off)
	      If  set to On, readline will enable eight-bit input (that is, it
	      will not clear the eighth bit in the characters it  reads),  re‐
	      gardless	of  what the terminal claims it can support.  The name
	      meta-flag is a synonym for this variable.	 The default  is  Off,
	      but  readline will set it to On if the locale contains eight-bit
	      characters.  This variable is dependent on the  LC_CTYPE	locale
	      category, and may change if the locale is changed.
       isearch-terminators (``C-[ C-J'')
	      The  string  of  characters that should terminate an incremental
	      search without subsequently executing the character  as  a  com‐
	      mand.   If this variable has not been given a value, the charac‐
	      ters ESC and C-J will terminate an incremental search.
       keymap (emacs)
	      Set the current readline keymap.	The set of legal keymap	 names
	      is  emacs,  emacs-standard, emacs-meta, emacs-ctlx, vi, vi-move,
	      vi-command, and vi-insert.   vi  is  equivalent  to  vi-command;
	      emacs  is	 equivalent  to	 emacs-standard.  The default value is
	      emacs.  The value	 of  editing-mode  also	 affects  the  default
	      keymap.
       keyseq-timeout (500)
	      Specifies	 the  duration readline will wait for a character when
	      reading an ambiguous key sequence (one that can form a  complete
	      key sequence using the input read so far, or can take additional
	      input to complete a longer key sequence).	 If no	input  is  re‐
	      ceived  within  the  timeout,  readline will use the shorter but
	      complete key sequence.  The value is specified in	 milliseconds,
	      so  a value of 1000 means that readline will wait one second for
	      additional input.	 If this variable is set to a value less  than
	      or  equal to zero, or to a non-numeric value, readline will wait
	      until another key is pressed to decide  which  key  sequence  to
	      complete.
       mark-directories (On)
	      If set to On, completed directory names have a slash appended.
       mark-modified-lines (Off)
	      If  set  to  On,	history lines that have been modified are dis‐
	      played with a preceding asterisk (*).
       mark-symlinked-directories (Off)
	      If set to On, completed names which are symbolic links to direc‐
	      tories  have  a slash appended (subject to the value of mark-di‐
	      rectories).
       match-hidden-files (On)
	      This variable, when set to On, causes readline  to  match	 files
	      whose  names  begin  with	 a  `.' (hidden files) when performing
	      filename completion.  If set to Off, the	leading	 `.'  must  be
	      supplied by the user in the filename to be completed.
       menu-complete-display-prefix (Off)
	      If  set to On, menu completion displays the common prefix of the
	      list of possible completions (which may be empty) before cycling
	      through the list.
       output-meta (Off)
	      If  set  to On, readline will display characters with the eighth
	      bit set directly rather than as a meta-prefixed escape sequence.
	      The default is Off, but readline will set it to On if the locale
	      contains eight-bit characters.  This variable  is	 dependent  on
	      the  LC_CTYPE  locale  category, and may change if the locale is
	      changed.
       page-completions (On)
	      If set to On, readline uses an internal more-like pager to  dis‐
	      play a screenful of possible completions at a time.
       print-completions-horizontally (Off)
	      If  set  to  On,	readline will display completions with matches
	      sorted horizontally in alphabetical order, rather than down  the
	      screen.
       revert-all-at-newline (Off)
	      If  set  to  On, readline will undo all changes to history lines
	      before returning when accept-line is executed.  By default, his‐
	      tory  lines  may	be  modified  and retain individual undo lists
	      across calls to readline.
       show-all-if-ambiguous (Off)
	      This alters the default behavior of  the	completion  functions.
	      If set to On, words which have more than one possible completion
	      cause the matches to be listed immediately  instead  of  ringing
	      the bell.
       show-all-if-unmodified (Off)
	      This  alters the default behavior of the completion functions in
	      a fashion similar to show-all-if-ambiguous.  If set to On, words
	      which  have more than one possible completion without any possi‐
	      ble partial completion (the possible completions don't  share  a
	      common  prefix)  cause  the matches to be listed immediately in‐
	      stead of ringing the bell.
       show-mode-in-prompt (Off)
	      If set to On, add a string to the beginning of the prompt	 indi‐
	      cating  the  editing  mode:  emacs, vi command, or vi insertion.
	      The mode strings are user-settable (e.g., emacs-mode-string).
       skip-completed-text (Off)
	      If set to On, this alters the default completion	behavior  when
	      inserting	 a  single match into the line.	 It's only active when
	      performing completion in the middle  of  a  word.	  If  enabled,
	      readline	does  not  insert  characters from the completion that
	      match characters after point in the  word	 being	completed,  so
	      portions of the word following the cursor are not duplicated.
       vi-cmd-mode-string ((cmd))
	      If  the  show-mode-in-prompt variable is enabled, this string is
	      displayed immediately before the last line of the primary prompt
	      when  vi	editing mode is active and in command mode.  The value
	      is expanded like a key binding, so the standard set of meta- and
	      control  prefixes	 and  backslash escape sequences is available.
	      Use the \1 and \2 escapes to begin and  end  sequences  of  non-
	      printing	characters, which can be used to embed a terminal con‐
	      trol sequence into the mode string.
       vi-ins-mode-string ((ins))
	      If the show-mode-in-prompt variable is enabled, this  string  is
	      displayed immediately before the last line of the primary prompt
	      when vi editing mode is active and in insertion mode.  The value
	      is expanded like a key binding, so the standard set of meta- and
	      control prefixes and backslash escape  sequences	is  available.
	      Use  the	\1  and	 \2 escapes to begin and end sequences of non-
	      printing characters, which can be used to embed a terminal  con‐
	      trol sequence into the mode string.
       visible-stats (Off)
	      If  set to On, a character denoting a file's type as reported by
	      stat(2) is appended to the filename when listing	possible  com‐
	      pletions.

   Conditional Constructs
       Readline	 implements  a	facility  similar in spirit to the conditional
       compilation features of the C preprocessor which	 allows	 key  bindings
       and  variable  settings	to be performed as the result of tests.	 There
       are four parser directives used.

       $if    The $if construct allows bindings to be made based on the	 edit‐
	      ing  mode,  the  terminal	 being	used, or the application using
	      readline.	 The text of the test, after any comparison  operator,
	      extends to the end of the line; unless otherwise noted, no char‐
	      acters are required to isolate it.

	      mode   The mode= form of the  $if	 directive  is	used  to  test
		     whether  readline	is  in	emacs or vi mode.  This may be
		     used in conjunction with the set keymap command, for  in‐
		     stance,  to set bindings in the emacs-standard and emacs-
		     ctlx keymaps only if readline is starting	out  in	 emacs
		     mode.

	      term   The  term=	 form may be used to include terminal-specific
		     key bindings, perhaps to bind the key sequences output by
		     the terminal's function keys.  The word on the right side
		     of the = is tested against the full name of the  terminal
		     and  the portion of the terminal name before the first -.
		     This allows sun to match both sun and  sun-cmd,  for  in‐
		     stance.

	      version
		     The  version  test	 may  be  used	to perform comparisons
		     against specific readline versions.  The version  expands
		     to	 the  current readline version.	 The set of comparison
		     operators includes =, (and ==), !=, <=,  >=,  <,  and  >.
		     The  version number supplied on the right side of the op‐
		     erator consists of a major version	 number,  an  optional
		     decimal point, and an optional minor version (e.g., 7.1).
		     If the minor version is omitted, it is assumed to	be  0.
		     The operator may be separated from the string version and
		     from the version number argument by whitespace.

	      application
		     The application construct is used to include application-
		     specific  settings.   Each program using the readline li‐
		     brary sets the application name,  and  an	initialization
		     file can test for a particular value.  This could be used
		     to bind key sequences to functions useful for a  specific
		     program.	For instance, the following command adds a key
		     sequence that quotes the  current	or  previous  word  in
		     bash:

		     $if Bash
		     # Quote the current or previous word
		     "\C-xq": "\eb\"\ef\""
		     $endif

	      variable
		     The variable construct provides simple equality tests for
		     readline variables and values.  The permitted  comparison
		     operators	are  =, ==, and !=.  The variable name must be
		     separated from the comparison operator by whitespace; the
		     operator  may  be	separated  from the value on the right
		     hand side by whitespace.  Both string and	boolean	 vari‐
		     ables  may	 be  tested.  Boolean variables must be tested
		     against the values on and off.

       $endif This command, as seen in the previous example, terminates an $if
	      command.

       $else  Commands in this branch of the $if directive are executed if the
	      test fails.

       $include
	      This directive takes a single filename as an argument and	 reads
	      commands	and bindings from that file.  For example, the follow‐
	      ing directive would read /etc/inputrc:

	      $include	/etc/inputrc

SEARCHING
       Readline provides commands for searching through	 the  command  history
       for  lines  containing a specified string.  There are two search modes:
       incremental and non-incremental.

       Incremental searches begin before the  user  has	 finished  typing  the
       search  string.	As each character of the search string is typed, read‐
       line displays the next entry from the history matching the string typed
       so  far.	  An  incremental  search  requires only as many characters as
       needed to find the desired history entry.  To search  backward  in  the
       history for a particular string, type C-r.  Typing C-s searches forward
       through the history.  The  characters  present  in  the	value  of  the
       isearch-terminators  variable  are  used	 to  terminate	an incremental
       search.	If that variable has not been assigned a value the Escape  and
       C-J characters will terminate an incremental search.  C-G will abort an
       incremental search and restore the original line.  When the  search  is
       terminated,  the history entry containing the search string becomes the
       current line.

       To find other matching entries in the history list, type C-s or C-r  as
       appropriate.   This  will search backward or forward in the history for
       the next line matching the search string typed so far.  Any  other  key
       sequence bound to a readline command will terminate the search and exe‐
       cute that command.  For instance, a newline will terminate  the	search
       and  accept  the	 line,	thereby executing the command from the history
       list.  A movement command will terminate the search, make the last line
       found the current line, and begin editing.

       Non-incremental	searches read the entire search string before starting
       to search for matching history lines.  The search string may  be	 typed
       by the user or be part of the contents of the current line.

EDITING COMMANDS
       The  following  is  a list of the names of the commands and the default
       key sequences to which they are bound.  Command names without an accom‐
       panying key sequence are unbound by default.

       In the following descriptions, point refers to the current cursor posi‐
       tion, and mark refers to a cursor position saved by the	set-mark  com‐
       mand.   The  text  between the point and mark is referred to as the re‐
       gion.

   Commands for Moving
       beginning-of-line (C-a)
	      Move to the start of the current line.
       end-of-line (C-e)
	      Move to the end of the line.
       forward-char (C-f)
	      Move forward a character.
       backward-char (C-b)
	      Move back a character.
       forward-word (M-f)
	      Move forward to the end of the next word.	 Words are composed of
	      alphanumeric characters (letters and digits).
       backward-word (M-b)
	      Move  back  to the start of the current or previous word.	 Words
	      are composed of alphanumeric characters (letters and digits).
       previous-screen-line
	      Attempt to move point to the same physical screen column on  the
	      previous	physical  screen  line. This will not have the desired
	      effect if the current readline line does not take up  more  than
	      one  physical line or if point is not greater than the length of
	      the prompt plus the screen width.
       next-screen-line
	      Attempt to move point to the same physical screen column on  the
	      next physical screen line. This will not have the desired effect
	      if the current readline line does not  take  up  more  than  one
	      physical	line  or if the length of the current readline line is
	      not greater than the length of the prompt plus the screen width.
       clear-display (M-C-l)
	      Clear the screen and, if	possible,  the	terminal's  scrollback
	      buffer,  then  redraw the current line, leaving the current line
	      at the top of the screen.
       clear-screen (C-l)
	      Clear the screen, then redraw the current line, leaving the cur‐
	      rent  line  at the top of the screen.  With an argument, refresh
	      the current line without clearing the screen.
       redraw-current-line
	      Refresh the current line.

   Commands for Manipulating the History
       accept-line (Newline, Return)
	      Accept the line regardless of where the cursor is.  If this line
	      is non-empty, it may be added to the history list for future re‐
	      call with add_history().	If the	line  is  a  modified  history
	      line, the history line is restored to its original state.
       previous-history (C-p)
	      Fetch the previous command from the history list, moving back in
	      the list.
       next-history (C-n)
	      Fetch the next command from the history list, moving forward  in
	      the list.
       beginning-of-history (M-<)
	      Move to the first line in the history.
       end-of-history (M->)
	      Move  to	the end of the input history, i.e., the line currently
	      being entered.
       operate-and-get-next (C-o)
	      Accept the current line for return to the calling application as
	      if  a newline had been entered, and fetch the next line relative
	      to the current line from the history for editing.	 A numeric ar‐
	      gument,  if supplied, specifies the history entry to use instead
	      of the current line.
       fetch-history
	      With a numeric argument, fetch that entry from the history  list
	      and make it the current line.  Without an argument, move back to
	      the first entry in the history list.
       reverse-search-history (C-r)
	      Search backward starting at the current  line  and  moving  `up'
	      through  the  history  as	 necessary.   This  is	an incremental
	      search.
       forward-search-history (C-s)
	      Search forward starting at the current line  and	moving	`down'
	      through  the  history  as	 necessary.   This  is	an incremental
	      search.
       non-incremental-reverse-search-history (M-p)
	      Search backward through the history starting at the current line
	      using  a	non-incremental	 search	 for  a string supplied by the
	      user.
       non-incremental-forward-search-history (M-n)
	      Search forward  through  the  history  using  a  non-incremental
	      search for a string supplied by the user.
       history-search-backward
	      Search backward through the history for the string of characters
	      between the start of the current line and the current cursor po‐
	      sition  (the point).  The search string must match at the begin‐
	      ning of a history line.  This is a non-incremental search.
       history-search-forward
	      Search forward through the history for the string of  characters
	      between the start of the current line and the point.  The search
	      string must match at the beginning of a history line.  This is a
	      non-incremental search.
       history-substring-search-backward
	      Search backward through the history for the string of characters
	      between the start of the current line and the current cursor po‐
	      sition  (the  point).  The search string may match anywhere in a
	      history line.  This is a non-incremental search.
       history-substring-search-forward
	      Search forward through the history for the string of  characters
	      between the start of the current line and the point.  The search
	      string may match anywhere in a history line.  This is a  non-in‐
	      cremental search.
       yank-nth-arg (M-C-y)
	      Insert  the  first argument to the previous command (usually the
	      second word on the previous line) at point.  With an argument n,
	      insert  the nth word from the previous command (the words in the
	      previous command begin with word 0).  A  negative	 argument  in‐
	      serts  the  nth word from the end of the previous command.  Once
	      the argument n is computed, the argument is extracted as if  the
	      "!n" history expansion had been specified.
       yank-last-arg (M-., M-_)
	      Insert  the last argument to the previous command (the last word
	      of the previous history entry).  With a numeric argument, behave
	      exactly  like  yank-nth-arg.   Successive calls to yank-last-arg
	      move back through the history list, inserting the last word  (or
	      the  word	 specified  by the argument to the first call) of each
	      line in turn.  Any numeric argument supplied to these successive
	      calls  determines	 the direction to move through the history.  A
	      negative argument switches the  direction	 through  the  history
	      (back or forward).  The history expansion facilities are used to
	      extract the last argument, as if the "!$" history expansion  had
	      been specified.

   Commands for Changing Text
       end-of-file (usually C-d)
	      The  character  indicating  end-of-file  as set, for example, by
	      ``stty''.	 If this character is read when there are  no  charac‐
	      ters  on	the  line,  and point is at the beginning of the line,
	      readline interprets it as the end of input and returns EOF.
       delete-char (C-d)
	      Delete the character at point.  If this function is bound to the
	      same character as the tty EOF character, as C-d commonly is, see
	      above for the effects.
       backward-delete-char (Rubout)
	      Delete the character behind the cursor.  When  given  a  numeric
	      argument, save the deleted text on the kill ring.
       forward-backward-delete-char
	      Delete  the  character under the cursor, unless the cursor is at
	      the end of the line, in which case the character behind the cur‐
	      sor is deleted.
       quoted-insert (C-q, C-v)
	      Add the next character that you type to the line verbatim.  This
	      is how to insert characters like C-q, for example.
       tab-insert (M-TAB)
	      Insert a tab character.
       self-insert (a, b, A, 1, !, ...)
	      Insert the character typed.
       transpose-chars (C-t)
	      Drag the character before point forward over  the	 character  at
	      point,  moving point forward as well.  If point is at the end of
	      the line, then this transposes the two characters before	point.
	      Negative arguments have no effect.
       transpose-words (M-t)
	      Drag  the	 word  before  point past the word after point, moving
	      point over that word as well.  If point is at  the  end  of  the
	      line, this transposes the last two words on the line.
       upcase-word (M-u)
	      Uppercase	 the current (or following) word.  With a negative ar‐
	      gument, uppercase the previous word, but do not move point.
       downcase-word (M-l)
	      Lowercase the current (or following) word.  With a negative  ar‐
	      gument, lowercase the previous word, but do not move point.
       capitalize-word (M-c)
	      Capitalize the current (or following) word.  With a negative ar‐
	      gument, capitalize the previous word, but do not move point.
       overwrite-mode
	      Toggle overwrite mode.  With an explicit positive numeric	 argu‐
	      ment, switches to overwrite mode.	 With an explicit non-positive
	      numeric argument, switches to insert mode.  This command affects
	      only  emacs mode; vi mode does overwrite differently.  Each call
	      to readline() starts in insert mode.  In overwrite mode, charac‐
	      ters  bound to self-insert replace the text at point rather than
	      pushing the text	to  the	 right.	  Characters  bound  to	 back‐
	      ward-delete-char	replace	 the  character	 before	 point	with a
	      space.  By default, this command is unbound.

   Killing and Yanking
       kill-line (C-k)
	      Kill the text from point to the end of the line.
       backward-kill-line (C-x Rubout)
	      Kill backward to the beginning of the line.
       unix-line-discard (C-u)
	      Kill backward from point to the  beginning  of  the  line.   The
	      killed text is saved on the kill-ring.
       kill-whole-line
	      Kill  all	 characters on the current line, no matter where point
	      is.
       kill-word (M-d)
	      Kill from point the end of  the  current	word,  or  if  between
	      words,  to  the  end  of the next word.  Word boundaries are the
	      same as those used by forward-word.
       backward-kill-word (M-Rubout)
	      Kill the word behind point.  Word boundaries  are	 the  same  as
	      those used by backward-word.
       unix-word-rubout (C-w)
	      Kill  the	 word behind point, using white space as a word bound‐
	      ary.  The killed text is saved on the kill-ring.
       unix-filename-rubout
	      Kill the word behind point, using	 white	space  and  the	 slash
	      character	 as  the word boundaries.  The killed text is saved on
	      the kill-ring.
       delete-horizontal-space (M-\)
	      Delete all spaces and tabs around point.
       kill-region
	      Kill the text between the point and  mark	 (saved	 cursor	 posi‐
	      tion).  This text is referred to as the region.
       copy-region-as-kill
	      Copy the text in the region to the kill buffer.
       copy-backward-word
	      Copy  the word before point to the kill buffer.  The word bound‐
	      aries are the same as backward-word.
       copy-forward-word
	      Copy the word following point to	the  kill  buffer.   The  word
	      boundaries are the same as forward-word.
       yank (C-y)
	      Yank the top of the kill ring into the buffer at point.
       yank-pop (M-y)
	      Rotate  the kill ring, and yank the new top.  Only works follow‐
	      ing yank or yank-pop.

   Numeric Arguments
       digit-argument (M-0, M-1, ..., M--)
	      Add this digit to the argument already accumulating, or start  a
	      new argument.  M-- starts a negative argument.
       universal-argument
	      This  is another way to specify an argument.  If this command is
	      followed by one or more digits, optionally with a leading	 minus
	      sign,  those digits define the argument.	If the command is fol‐
	      lowed by digits, executing universal-argument again ends the nu‐
	      meric argument, but is otherwise ignored.	 As a special case, if
	      this command is immediately followed by a character that is nei‐
	      ther a digit or minus sign, the argument count for the next com‐
	      mand is multiplied by four.  The	argument  count	 is  initially
	      one,  so	executing this function the first time makes the argu‐
	      ment count four, a second time makes the argument count sixteen,
	      and so on.

   Completing
       complete (TAB)
	      Attempt to perform completion on the text before point.  The ac‐
	      tual completion performed is  application-specific.   Bash,  for
	      instance,	 attempts  completion  treating the text as a variable
	      (if the text begins with $), username (if the text  begins  with
	      ~),  hostname (if the text begins with @), or command (including
	      aliases and functions) in turn.  If none	of  these  produces  a
	      match,  filename	completion  is	attempted.   Gdb, on the other
	      hand, allows completion of program functions and variables,  and
	      only attempts filename completion under certain circumstances.
       possible-completions (M-?)
	      List  the	 possible  completions of the text before point.  When
	      displaying completions, readline 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.
       insert-completions (M-*)
	      Insert  all completions of the text before point that would have
	      been generated by possible-completions.
       menu-complete
	      Similar to complete, but replaces the word to be completed  with
	      a	 single match from the list of possible completions.  Repeated
	      execution of menu-complete steps through the  list  of  possible
	      completions,  inserting  each  match in turn.  At the end of the
	      list of completions, the bell is rung (subject to the setting of
	      bell-style) and the original text is restored.  An argument of n
	      moves n positions forward in the list of matches; a negative ar‐
	      gument may be used to move backward through the list.  This com‐
	      mand is intended to be bound to TAB, but is unbound by default.
       menu-complete-backward
	      Identical to menu-complete, but moves backward through the  list
	      of  possible  completions,  as if menu-complete had been given a
	      negative argument.  This command is unbound by default.
       delete-char-or-list
	      Deletes the character under the cursor if not at	the  beginning
	      or  end  of  the	line (like delete-char).  If at the end of the
	      line, behaves identically to possible-completions.

   Keyboard Macros
       start-kbd-macro (C-x ()
	      Begin saving the characters  typed  into	the  current  keyboard
	      macro.
       end-kbd-macro (C-x ))
	      Stop saving the characters typed into the current keyboard macro
	      and store the definition.
       call-last-kbd-macro (C-x e)
	      Re-execute the last keyboard macro defined, by making the	 char‐
	      acters in the macro appear as if typed at the keyboard.
       print-last-kbd-macro ()
	      Print  the  last keyboard macro defined in a format suitable for
	      the inputrc file.

   Miscellaneous
       re-read-init-file (C-x C-r)
	      Read in the contents of the inputrc file,	 and  incorporate  any
	      bindings or variable assignments found there.
       abort (C-g)
	      Abort  the  current editing command and ring the terminal's bell
	      (subject to the setting of bell-style).
       do-lowercase-version (M-A, M-B, M-x, ...)
	      If the metafied character x is uppercase, run the	 command  that
	      is bound to the corresponding metafied lowercase character.  The
	      behavior is undefined if x is already lowercase.
       prefix-meta (ESC)
	      Metafy the next character typed.	ESC f is equivalent to Meta-f.
       undo (C-_, C-x C-u)
	      Incremental undo, separately remembered for each line.
       revert-line (M-r)
	      Undo all changes made to this line.  This is like executing  the
	      undo  command  enough  times  to	return the line to its initial
	      state.
       tilde-expand (M-&)
	      Perform tilde expansion on the current word.
       set-mark (C-@, M-<space>)
	      Set the mark to the point.  If a numeric argument	 is  supplied,
	      the mark is set to that position.
       exchange-point-and-mark (C-x C-x)
	      Swap  the	 point	with the mark.	The current cursor position is
	      set to the saved position, and the old cursor position is	 saved
	      as the mark.
       character-search (C-])
	      A character is read and point is moved to the next occurrence of
	      that character.  A negative argument searches for	 previous  oc‐
	      currences.
       character-search-backward (M-C-])
	      A	 character  is	read and point is moved to the previous occur‐
	      rence of that character.	A negative argument searches for  sub‐
	      sequent occurrences.
       skip-csi-sequence
	      Read  enough  characters to consume a multi-key sequence such as
	      those defined for keys like Home and End.	 Such sequences	 begin
	      with a Control Sequence Indicator (CSI), usually ESC-[.  If this
	      sequence is bound to "\[", keys producing	 such  sequences  will
	      have  no	effect	unless explicitly bound to a readline command,
	      instead of inserting stray characters into the  editing  buffer.
	      This is unbound by default, but usually bound to ESC-[.
       insert-comment (M-#)
	      Without  a  numeric  argument,  the  value  of the readline com‐
	      ment-begin variable is inserted at the beginning of the  current
	      line.  If a numeric argument is supplied, this command acts as a
	      toggle: if the characters at the beginning of the	 line  do  not
	      match  the value of comment-begin, the value is inserted, other‐
	      wise the characters in comment-begin are deleted from the begin‐
	      ning  of the line.  In either case, the line is accepted as if a
	      newline had been typed.	The  default  value  of	 comment-begin
	      makes  the  current line a shell comment.	 If a numeric argument
	      causes the comment character to be removed, the line will be ex‐
	      ecuted by the shell.
       dump-functions
	      Print  all  of the functions and their key bindings to the read‐
	      line output stream.  If a numeric argument is supplied, the out‐
	      put  is  formatted  in such a way that it can be made part of an
	      inputrc file.
       dump-variables
	      Print all of the settable variables  and	their  values  to  the
	      readline	output stream.	If a numeric argument is supplied, the
	      output is formatted in such a way that it can be made part of an
	      inputrc file.
       dump-macros
	      Print  all of the readline key sequences bound to macros and the
	      strings they output.  If a numeric  argument  is	supplied,  the
	      output is formatted in such a way that it can be made part of an
	      inputrc file.
       emacs-editing-mode (C-e)
	      When in vi command mode, this causes a switch to	emacs  editing
	      mode.
       vi-editing-mode (M-C-j)
	      When  in	emacs editing mode, this causes a switch to vi editing
	      mode.

DEFAULT KEY BINDINGS
       The following is a list of the default emacs and vi bindings.   Charac‐
       ters  with the eighth bit set are written as M-<character>, and are re‐
       ferred to as metafied characters.  The printable ASCII  characters  not
       mentioned  in  the  list	 of  emacs  standard bindings are bound to the
       self-insert function, which just inserts the given character  into  the
       input line.  In vi insertion mode, all characters not specifically men‐
       tioned are bound to self-insert.	 Characters assigned to signal genera‐
       tion by stty(1) or the terminal driver, such as C-Z or C-C, retain that
       function.  Upper and lower case metafied characters are	bound  to  the
       same  function in the emacs mode meta keymap.  The remaining characters
       are unbound, which causes readline to ring the  bell  (subject  to  the
       setting of the bell-style variable).

   Emacs Mode
	     Emacs Standard bindings

	     "C-@"  set-mark
	     "C-A"  beginning-of-line
	     "C-B"  backward-char
	     "C-D"  delete-char
	     "C-E"  end-of-line
	     "C-F"  forward-char
	     "C-G"  abort
	     "C-H"  backward-delete-char
	     "C-I"  complete
	     "C-J"  accept-line
	     "C-K"  kill-line
	     "C-L"  clear-screen
	     "C-M"  accept-line
	     "C-N"  next-history
	     "C-P"  previous-history
	     "C-Q"  quoted-insert
	     "C-R"  reverse-search-history
	     "C-S"  forward-search-history
	     "C-T"  transpose-chars
	     "C-U"  unix-line-discard
	     "C-V"  quoted-insert
	     "C-W"  unix-word-rubout
	     "C-Y"  yank
	     "C-]"  character-search
	     "C-_"  undo
	     " " to "/"	 self-insert
	     "0"  to "9"  self-insert
	     ":"  to "~"  self-insert
	     "C-?"  backward-delete-char

	     Emacs Meta bindings

	     "M-C-G"  abort
	     "M-C-H"  backward-kill-word
	     "M-C-I"  tab-insert
	     "M-C-J"  vi-editing-mode
	     "M-C-L"  clear-display
	     "M-C-M"  vi-editing-mode
	     "M-C-R"  revert-line
	     "M-C-Y"  yank-nth-arg
	     "M-C-["  complete
	     "M-C-]"  character-search-backward
	     "M-space"	set-mark
	     "M-#"  insert-comment
	     "M-&"  tilde-expand
	     "M-*"  insert-completions
	     "M--"  digit-argument
	     "M-."  yank-last-arg
	     "M-0"  digit-argument
	     "M-1"  digit-argument
	     "M-2"  digit-argument
	     "M-3"  digit-argument
	     "M-4"  digit-argument
	     "M-5"  digit-argument
	     "M-6"  digit-argument
	     "M-7"  digit-argument
	     "M-8"  digit-argument
	     "M-9"  digit-argument
	     "M-<"  beginning-of-history
	     "M-="  possible-completions
	     "M->"  end-of-history
	     "M-?"  possible-completions
	     "M-B"  backward-word
	     "M-C"  capitalize-word
	     "M-D"  kill-word
	     "M-F"  forward-word
	     "M-L"  downcase-word
	     "M-N"  non-incremental-forward-search-history
	     "M-P"  non-incremental-reverse-search-history
	     "M-R"  revert-line
	     "M-T"  transpose-words
	     "M-U"  upcase-word
	     "M-Y"  yank-pop
	     "M-\"  delete-horizontal-space
	     "M-~"  tilde-expand
	     "M-C-?"  backward-kill-word
	     "M-_"  yank-last-arg

	     Emacs Control-X bindings

	     "C-XC-G"  abort
	     "C-XC-R"  re-read-init-file
	     "C-XC-U"  undo
	     "C-XC-X"  exchange-point-and-mark
	     "C-X("  start-kbd-macro
	     "C-X)"  end-kbd-macro
	     "C-XE"  call-last-kbd-macro
	     "C-XC-?"  backward-kill-line


   VI Mode bindings
	     VI Insert Mode functions

	     "C-D"  vi-eof-maybe
	     "C-H"  backward-delete-char
	     "C-I"  complete
	     "C-J"  accept-line
	     "C-M"  accept-line
	     "C-R"  reverse-search-history
	     "C-S"  forward-search-history
	     "C-T"  transpose-chars
	     "C-U"  unix-line-discard
	     "C-V"  quoted-insert
	     "C-W"  unix-word-rubout
	     "C-Y"  yank
	     "C-["  vi-movement-mode
	     "C-_"  undo
	     " " to "~"	 self-insert
	     "C-?"  backward-delete-char

	     VI Command Mode functions

	     "C-D"  vi-eof-maybe
	     "C-E"  emacs-editing-mode
	     "C-G"  abort
	     "C-H"  backward-char
	     "C-J"  accept-line
	     "C-K"  kill-line
	     "C-L"  clear-screen
	     "C-M"  accept-line
	     "C-N"  next-history
	     "C-P"  previous-history
	     "C-Q"  quoted-insert
	     "C-R"  reverse-search-history
	     "C-S"  forward-search-history
	     "C-T"  transpose-chars
	     "C-U"  unix-line-discard
	     "C-V"  quoted-insert
	     "C-W"  unix-word-rubout
	     "C-Y"  yank
	     "C-_"  vi-undo
	     " "  forward-char
	     "#"  insert-comment
	     "$"  end-of-line
	     "%"  vi-match
	     "&"  vi-tilde-expand
	     "*"  vi-complete
	     "+"  next-history
	     ","  vi-char-search
	     "-"  previous-history
	     "."  vi-redo
	     "/"  vi-search
	     "0"  beginning-of-line
	     "1" to "9"	 vi-arg-digit
	     ";"  vi-char-search
	     "="  vi-complete
	     "?"  vi-search
	     "A"  vi-append-eol
	     "B"  vi-prev-word
	     "C"  vi-change-to
	     "D"  vi-delete-to
	     "E"  vi-end-word
	     "F"  vi-char-search
	     "G"  vi-fetch-history
	     "I"  vi-insert-beg
	     "N"  vi-search-again
	     "P"  vi-put
	     "R"  vi-replace
	     "S"  vi-subst
	     "T"  vi-char-search
	     "U"  revert-line
	     "W"  vi-next-word
	     "X"  backward-delete-char
	     "Y"  vi-yank-to
	     "\"  vi-complete
	     "^"  vi-first-print
	     "_"  vi-yank-arg
	     "`"  vi-goto-mark
	     "a"  vi-append-mode
	     "b"  vi-prev-word
	     "c"  vi-change-to
	     "d"  vi-delete-to
	     "e"  vi-end-word
	     "f"  vi-char-search
	     "h"  backward-char
	     "i"  vi-insertion-mode
	     "j"  next-history
	     "k"  prev-history
	     "l"  forward-char
	     "m"  vi-set-mark
	     "n"  vi-search-again
	     "p"  vi-put
	     "r"  vi-change-char
	     "s"  vi-subst
	     "t"  vi-char-search
	     "u"  vi-undo
	     "w"  vi-next-word
	     "x"  vi-delete
	     "y"  vi-yank-to
	     "|"  vi-column
	     "~"  vi-change-case

SEE ALSO
       The Gnu Readline Library, Brian Fox and Chet Ramey
       The Gnu History Library, Brian Fox and Chet Ramey
       bash(1)

FILES
       ~/.inputrc
	      Individual readline initialization file

AUTHORS
       Brian Fox, Free Software Foundation
       bfox@gnu.org

       Chet Ramey, Case Western Reserve University
       chet.ramey@case.edu

BUG REPORTS
       If  you	find  a bug in readline, you should report it.	But first, you
       should make sure that it really is a bug, and that it  appears  in  the
       latest version of the readline library that you have.

       Once  you have determined that a bug actually exists, mail a bug report
       to bug-readline@gnu.org.	 If you have a fix, you are  welcome  to  mail
       that  as	 well!	 Suggestions  and  `philosophical'  bug reports may be
       mailed to  bug-readline@gnu.org	or  posted  to	the  Usenet  newsgroup
       gnu.bash.bug.

       Comments and bug reports concerning this manual page should be directed
       to chet.ramey@case.edu.

BUGS
       It's too big and too slow.



GNU Readline 8.2	       2022 September 19		   READLINE(3)

HISTORY(3)		   Library Functions Manual		    HISTORY(3)



NAME
       history - GNU History Library

COPYRIGHT
       The GNU History Library is Copyright (C) 1989-2020 by the Free Software
       Foundation, Inc.

DESCRIPTION
       Many programs read input from the user a line at a time.	 The GNU  His‐
       tory  library is able to keep track of those lines, associate arbitrary
       data with each line, and utilize information  from  previous  lines  in
       composing new ones.

HISTORY EXPANSION
       The  history library supports a history expansion feature that is iden‐
       tical to the history expansion in bash.	This  section  describes  what
       syntax features are available.

       History expansions introduce words from the history list into the input
       stream, making it easy to repeat commands, insert the  arguments	 to  a
       previous command into the current input line, or fix errors in previous
       commands quickly.

       History expansion is usually performed  immediately  after  a  complete
       line  is read.  It takes place in two parts.  The first is to determine
       which line from the history list to use during substitution.  The  sec‐
       ond  is	to select portions of that line for inclusion into the current
       one.  The line selected from the history is the event, and the portions
       of  that	 line  that  are  acted upon are words.	 Various modifiers are
       available to manipulate the selected words.  The line  is  broken  into
       words in the same fashion as bash does when reading input, so that sev‐
       eral words that would otherwise be separated are	 considered  one  word
       when  surrounded	 by  quotes (see the description of history_tokenize()
       below).	History expansions are introduced by  the  appearance  of  the
       history expansion character, which is ! by default.  Only backslash (\)
       and single quotes can quote the history expansion character.

   Event Designators
       An event designator is a reference to a command line entry in the  his‐
       tory  list.   Unless  the reference is absolute, events are relative to
       the current position in the history list.

       !      Start a history substitution, except when followed by  a	blank,
	      newline, = or (.
       !n     Refer to command line n.
       !-n    Refer to the current command minus n.
       !!     Refer to the previous command.  This is a synonym for `!-1'.
       !string
	      Refer  to the most recent command preceding the current position
	      in the history list starting with string.
       !?string[?]
	      Refer to the most recent command preceding the current  position
	      in  the  history	list containing string.	 The trailing ? may be
	      omitted if string is followed  immediately  by  a	 newline.   If
	      string  is  missing,  the	 string from the most recent search is
	      used; it is an error if there is no previous search string.
       ^string1^string2^
	      Quick substitution.  Repeat the last command, replacing  string1
	      with string2.  Equivalent to ``!!:s^string1^string2^'' (see Mod‐
	      ifiers below).
       !#     The entire command line typed so far.

   Word Designators
       Word designators are used to select desired words from the event.  A  :
       separates  the event specification from the word designator.  It may be
       omitted if the word designator begins with a ^, $, *, -, or  %.	 Words
       are  numbered from the beginning of the line, with the first word being
       denoted by 0 (zero).  Words are inserted into the  current  line	 sepa‐
       rated by single spaces.

       0 (zero)
	      The zeroth word.	For the shell, this is the command word.
       n      The nth word.
       ^      The first argument.  That is, word 1.
       $      The  last word.  This is usually the last argument, but will ex‐
	      pand to the zeroth word if there is only one word in the line.
       %      The first word matched by the most recent `?string?' search,  if
	      the  search  string  begins  with	 a character that is part of a
	      word.
       x-y    A range of words; `-y' abbreviates `0-y'.
       *      All of the words but the zeroth.	This is a synonym  for	`1-$'.
	      It  is  not  an  error to use * if there is just one word in the
	      event; the empty string is returned in that case.
       x*     Abbreviates x-$.
       x-     Abbreviates x-$ like x*, but omits the last word.	 If x is miss‐
	      ing, it defaults to 0.

       If  a  word  designator is supplied without an event specification, the
       previous command is used as the event.

   Modifiers
       After the optional word designator, there may appear a sequence of  one
       or more of the following modifiers, each preceded by a `:'.  These mod‐
       ify, or edit, the word or words selected from the history event.

       h      Remove a trailing file name component, leaving only the head.
       t      Remove all leading file name components, leaving the tail.
       r      Remove a trailing suffix of the form .xxx, leaving the basename.
       e      Remove all but the trailing suffix.
       p      Print the new command but do not execute it.
       q      Quote the substituted words, escaping further substitutions.
       x      Quote the substituted words as with q, but break into  words  at
	      blanks  and newlines.  The q and x modifiers are mutually exclu‐
	      sive; the last one supplied is used.
       s/old/new/
	      Substitute new for the first occurrence  of  old	in  the	 event
	      line.  Any character may be used as the delimiter in place of /.
	      The final delimiter is optional if it is the last	 character  of
	      the event line.  The delimiter may be quoted in old and new with
	      a single backslash.  If & appears in new, it is replaced by old.
	      A	 single backslash will quote the &.  If old is null, it is set
	      to the last old substituted, or, if no previous history  substi‐
	      tutions  took  place,  the last string in a !?string[?]  search.
	      If new is null, each matching old is deleted.
       &      Repeat the previous substitution.
       g      Cause changes to be applied over the entire event line.  This is
	      used  in	conjunction  with `:s' (e.g., `:gs/old/new/') or `:&'.
	      If used with `:s', any delimiter can be used in place of /,  and
	      the  final  delimiter is optional if it is the last character of
	      the event line.  An a may be used as a synonym for g.
       G      Apply the following `s' or `&' modifier once to each word in the
	      event line.

PROGRAMMING WITH HISTORY FUNCTIONS
       This  section  describes	 how  to use the History library in other pro‐
       grams.

   Introduction to History
       A programmer using the History library has available functions for  re‐
       membering  lines	 on  a history list, associating arbitrary data with a
       line, removing lines from the list, searching through the  list	for  a
       line  containing	 an arbitrary text string, and referencing any line in
       the list directly.  In addition, a history expansion function is avail‐
       able  which  provides  for a consistent user interface across different
       programs.

       The user using programs written with the History library has the	 bene‐
       fit  of	a  consistent user interface with a set of well-known commands
       for manipulating the text of previous lines and using that text in  new
       commands.  The basic history manipulation commands are identical to the
       history substitution provided by bash.

       The programmer can also use the readline library, which	includes  some
       history manipulation by default, and has the added advantage of command
       line editing.

       Before declaring any functions using any functionality the History  li‐
       brary  provides in other code, an application writer should include the
       file <readline/history.h> in any file that uses the  History  library's
       features.   It  supplies	 extern	 declarations for all of the library's
       public functions and variables, and declares all	 of  the  public  data
       structures.

   History Storage
       The  history  list  is an array of history entries.  A history entry is
       declared as follows:

       typedef void * histdata_t;

       typedef struct _hist_entry {
	 char *line;
	 char *timestamp;
	 histdata_t data;
       } HIST_ENTRY;

       The history list itself might therefore be declared as

       HIST_ENTRY ** the_history_list;

       The state of the History library is encapsulated into a	single	struc‐
       ture:

       /*
	* A structure used to pass around the current state of the history.
	*/
       typedef struct _hist_state {
	 HIST_ENTRY **entries; /* Pointer to the entries themselves. */
	 int offset;	       /* The location pointer within this array. */
	 int length;	       /* Number of elements within this array. */
	 int size;	       /* Number of slots allocated to this array. */
	 int flags;
       } HISTORY_STATE;

       If the flags member includes HS_STIFLED, the history has been stifled.

History Functions
       This  section  describes the calling sequence for the various functions
       exported by the GNU History library.

   Initializing History and State Management
       This section describes functions used  to  initialize  and  manage  the
       state of the History library when you want to use the history functions
       in your program.

       void using_history (void)
       Begin a session in which the history functions  might  be  used.	  This
       initializes the interactive variables.

       HISTORY_STATE * history_get_history_state (void)
       Return a structure describing the current state of the input history.

       void history_set_history_state (HISTORY_STATE *state)
       Set the state of the history list according to state.


   History List Management
       These  functions	 manage individual entries on the history list, or set
       parameters managing the list itself.

       void add_history (const char *string)
       Place string at the end of the history list.  The associated data field
       (if  any) is set to NULL.  If the maximum number of history entries has
       been set using stifle_history(), and the new number of history  entries
       would exceed that maximum, the oldest history entry is removed.

       void add_history_time (const char *string)
       Change  the time stamp associated with the most recent history entry to
       string.

       HIST_ENTRY * remove_history (int which)
       Remove history entry at offset which from the history.  The removed el‐
       ement is returned so you can free the line, data, and containing struc‐
       ture.

       histdata_t free_history_entry (HIST_ENTRY *histent)
       Free the history entry histent and any history library private data as‐
       sociated	 with it.  Returns the application-specific data so the caller
       can dispose of it.

       HIST_ENTRY * replace_history_entry (int which, const char *line,	 hist‐
       data_t data)
       Make  the  history  entry at offset which have line and data.  This re‐
       turns the old entry so the caller can dispose of	 any  application-spe‐
       cific  data.   In  the  case of an invalid which, a NULL pointer is re‐
       turned.

       void clear_history (void)
       Clear the history list by deleting all the entries.

       void stifle_history (int max)
       Stifle the history list, remembering only the last  max	entries.   The
       history list will contain only max entries at a time.

       int unstifle_history (void)
       Stop  stifling  the  history.   This returns the previously-set maximum
       number of history entries (as set by  stifle_history()).	  history  was
       stifled.	 The value is positive if the history was stifled, negative if
       it wasn't.

       int history_is_stifled (void)
       Returns non-zero if the history is stifled, zero if it is not.


   Information About the History List
       These functions return information about the entire history list or in‐
       dividual list entries.

       HIST_ENTRY ** history_list (void)
       Return a NULL terminated array of HIST_ENTRY * which is the current in‐
       put history.  Element 0 of this list is	the  beginning	of  time.   If
       there is no history, return NULL.

       int where_history (void)
       Returns the offset of the current history element.

       HIST_ENTRY * current_history (void)
       Return  the  history  entry  at	the current position, as determined by
       where_history().	 If there is no entry there, return a NULL pointer.

       HIST_ENTRY * history_get (int offset)
       Return the history entry at position offset.  The range of valid values
       of  offset  starts  at history_base and ends at history_length - 1.  If
       there is no entry there, or if offset is outside the valid  range,  re‐
       turn a NULL pointer.

       time_t history_get_time (HIST_ENTRY *)
       Return  the  time stamp associated with the history entry passed as the
       argument.

       int history_total_bytes (void)
       Return the number of bytes that the primary history entries are	using.
       This  function  returns	the sum of the lengths of all the lines in the
       history.


   Moving Around the History List
       These functions allow the current index into the history list to be set
       or changed.

       int history_set_pos (int pos)
       Set the current history offset to pos, an absolute index into the list.
       Returns 1 on success, 0 if pos is less than zero or  greater  than  the
       number of history entries.

       HIST_ENTRY * previous_history (void)
       Back  up	 the current history offset to the previous history entry, and
       return a pointer to that entry.	If there is no previous entry,	return
       a NULL pointer.

       HIST_ENTRY * next_history (void)
       If  the	current history offset refers to a valid history entry, incre‐
       ment the current history offset.	 If the	 possibly-incremented  history
       offset refers to a valid history entry, return a pointer to that entry;
       otherwise, return a NULL pointer.


   Searching the History List
       These functions allow searching of the history list  for	 entries  con‐
       taining a specific string.  Searching may be performed both forward and
       backward from the current history position.   The  search  may  be  an‐
       chored, meaning that the string must match at the beginning of the his‐
       tory entry.

       int history_search (const char *string, int direction)
       Search the history for string, starting at the current history  offset.
       If  direction  is  less than 0, then the search is through previous en‐
       tries, otherwise through subsequent entries.  If string is found,  then
       the  current  history index is set to that history entry, and the value
       returned is the offset in the line of the entry where string was found.
       Otherwise, nothing is changed, and a -1 is returned.

       int history_search_prefix (const char *string, int direction)
       Search  the history for string, starting at the current history offset.
       The search is anchored: matching lines must begin with string.  If  di‐
       rection	is  less  than 0, then the search is through previous entries,
       otherwise through subsequent entries.  If string	 is  found,  then  the
       current	history index is set to that entry, and the return value is 0.
       Otherwise, nothing is changed, and a -1 is returned.

       int history_search_pos (const char *string, int direction, int pos)
       Search for string in the history list, starting at pos, an absolute in‐
       dex into the list.  If direction is negative, the search proceeds back‐
       ward from pos, otherwise forward.  Returns the absolute	index  of  the
       history element where string was found, or -1 otherwise.


   Managing the History File
       The  History  library can read the history from and write it to a file.
       This section documents the functions for managing a history file.

       int read_history (const char *filename)
       Add the contents of filename to the history list, a line at a time.  If
       filename	 is NULL, then read from ~/.history.  Returns 0 if successful,
       or errno if not.

       int read_history_range (const char *filename, int from, int to)
       Read a range of lines from filename, adding them to the	history	 list.
       Start  reading  at  line from and end at to.  If from is zero, start at
       the beginning.  If to is less than from, then read until the end of the
       file.   If  filename  is NULL, then read from ~/.history.  Returns 0 if
       successful, or errno if not.

       int write_history (const char *filename)
       Write the current history to filename, overwriting filename  if	neces‐
       sary.   If filename is NULL, then write the history list to ~/.history.
       Returns 0 on success, or errno on a read or write error.


       int append_history (int nelements, const char *filename)
       Append the last nelements of the history list to filename.  If filename
       is  NULL, then append to ~/.history.  Returns 0 on success, or errno on
       a read or write error.

       int history_truncate_file (const char *filename, int nlines)
       Truncate the history file filename, leaving only the last nlines lines.
       If  filename  is NULL, then ~/.history is truncated.  Returns 0 on suc‐
       cess, or errno on failure.


   History Expansion
       These functions implement history expansion.

       int history_expand (char *string, char **output)
       Expand string, placing the result into output, a pointer to  a  string.
       Returns:
	      0	     If	 no  expansions	 took place (or, if the only change in
		     the text was the removal of escape	 characters  preceding
		     the history expansion character);
	      1	     if expansions did take place;
	      -1     if there was an error in expansion;
	      2	     if	 the  returned	line should be displayed, but not exe‐
		     cuted, as with the :p modifier.
       If an error occurred in expansion, then output contains	a  descriptive
       error message.

       char * get_history_event (const char *string, int *cindex, int qchar)
       Returns	the  text  of the history event beginning at string + *cindex.
       *cindex is modified to point to after the event specifier.  At function
       entry,  cindex  points to the index into string where the history event
       specification begins.  qchar is a character that is allowed to end  the
       event  specification  in addition to the ``normal'' terminating charac‐
       ters.

       char ** history_tokenize (const char *string)
       Return an array of tokens parsed out  of	 string,  much	as  the	 shell
       might.	The tokens are split on the characters in the history_word_de‐
       limiters variable, and shell quoting conventions are obeyed.

       char * history_arg_extract (int first, int last, const char *string)
       Extract a string segment consisting of the first through last arguments
       present in string.  Arguments are split using history_tokenize().


   History Variables
       This section describes the externally-visible variables exported by the
       GNU History Library.

       int history_base
       The logical offset of the first entry in the history list.

       int history_length
       The number of entries currently stored in the history list.

       int history_max_entries
       The maximum number of history entries.  This must be changed using sti‐
       fle_history().

       int history_write_timestamps
       If non-zero, timestamps are written to the history file, so they can be
       preserved between sessions.  The default value is 0, meaning that time‐
       stamps  are  not saved.	The current timestamp format uses the value of
       history_comment_char to delimit timestamp entries in the history	 file.
       If  that	 variable does not have a value (the default), timestamps will
       not be written.

       char history_expansion_char
       The character that introduces a history event.  The default is !.  Set‐
       ting this to 0 inhibits history expansion.

       char history_subst_char
       The character that invokes word substitution if found at the start of a
       line.  The default is ^.

       char history_comment_char
       During tokenization, if this character is seen as the  first  character
       of  a  word,  then it and all subsequent characters up to a newline are
       ignored, suppressing history expansion for the remainder of  the	 line.
       This is disabled by default.

       char * history_word_delimiters
       The  characters	that  separate tokens for history_tokenize().  The de‐
       fault value is " \t\n()<>;&|".

       char * history_no_expand_chars
       The list of characters which inhibit history expansion if found immedi‐
       ately  following	 history_expansion_char.   The	default is space, tab,
       newline, \r, and =.

       char * history_search_delimiter_chars
       The list of additional characters which can delimit  a  history	search
       string,	in  addition to space, tab, : and ? in the case of a substring
       search.	The default is empty.

       int history_quotes_inhibit_expansion
       If non-zero, double-quoted words are not scanned for the history expan‐
       sion  character or the history comment character.  The default value is
       0.

       rl_linebuf_func_t * history_inhibit_expansion_function
       This should be set to the address of a function that  takes  two	 argu‐
       ments:  a  char	*  (string) and an int index into that string (i).  It
       should return a non-zero value if the  history  expansion  starting  at
       string[i]  should  not  be  performed;  zero if the expansion should be
       done.  It is intended for use by applications like bash	that  use  the
       history	expansion character for additional purposes.  By default, this
       variable is set to NULL.

FILES
       ~/.history
	      Default filename for reading and writing saved history

SEE ALSO
       The Gnu Readline Library, Brian Fox and Chet Ramey
       The Gnu History Library, Brian Fox and Chet Ramey
       bash(1)
       readline(3)

AUTHORS
       Brian Fox, Free Software Foundation
       bfox@gnu.org

       Chet Ramey, Case Western Reserve University
       chet.ramey@case.edu

BUG REPORTS
       If you find a bug in the history library, you should  report  it.   But
       first,  you  should  make sure that it really is a bug, and that it ap‐
       pears in the latest version of the history library that you have.

       Once you have determined that a bug actually exists, mail a bug	report
       to  bug-readline@gnu.org.   If  you have a fix, you are welcome to mail
       that as well!  Suggestions  and	`philosophical'	 bug  reports  may  be
       mailed  to  bug-readline@gnu.org	 or  posted  to	 the  Usenet newsgroup
       gnu.bash.bug.

       Comments and bug reports concerning this manual page should be directed
       to chet.ramey@case.edu.



GNU History 8.1			 2020 July 17			    HISTORY(3)