_H_I_S_T_O_R_Y(3)                 Library Functions Manual                 _H_I_S_T_O_R_Y(3)

NNAAMMEE
       history - GNU History Library

CCOOPPYYRRIIGGHHTT
       The GNU History Library is Copyright (C) 1989-2025 by the Free Software
       Foundation, Inc.

DDEESSCCRRIIPPTTIIOONN
       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 when
       composing new ones.

       The History library provides functions that allow applications to their
       _h_i_s_t_o_r_y, the set of previously-typed lines, which it keeps in  a  list.
       Applications  can  choose  which lines to save into a history list, how
       many commands to save, save a history list to a file,  read  a  history
       list  from  a  file, and display lines from the history in various for-
       mats.

HHIISSTTOORRYY EEXXPPAANNSSIIOONN
       The history library supports a history expansion feature that is  iden-
       tical  to  the  history expansion in bbaasshh.  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  history list entry to use during substitution.  The second is to
       select portions of that entry to include into the current one.

       The entry selected from the history is the _e_v_e_n_t, and the  portions  of
       that entry that are acted upon are _w_o_r_d_s.  Various _m_o_d_i_f_i_e_r_s are avail-
       able  to  manipulate the selected words.  The entry is split into words
       in the same fashion as bbaasshh does when reading input,  so  that  several
       words  that  would  otherwise be separated are considered one word when
       surrounded by quotes (see the description of hhiissttoorryy__ttookkeenniizzee(()) below).
       The _e_v_e_n_t _d_e_s_i_g_n_a_t_o_r selects the event, the  optional  _w_o_r_d  _d_e_s_i_g_n_a_t_o_r
       selects words from the event, and various optional _m_o_d_i_f_i_e_r_s are avail-
       able to manipulate the selected words.

       History  expansions are introduced by the appearance of the history ex-
       pansion character, which is !! by default.  History expansions  may  ap-
       pear anywhere in the input, but do not nest.

       Only  backslash  (\\)  and single quotes can quote the history expansion
       character.

       There is a special abbreviation for substitution, active when the _q_u_i_c_k
       _s_u_b_s_t_i_t_u_t_i_o_n character (default ^^) is the first character on the  line.
       It  selects  the previous history list entry, using an event designator
       equivalent to !!!!, and substitutes one string for another in that entry.
       It is described below under EEvveenntt DDeessiiggnnaattoorrss.  This is the  only  his-
       tory  expansion  that does not begin with the history expansion charac-
       ter.

   EEvveenntt DDeessiiggnnaattoorrss
       An event designator is a reference to an entry  in  the  history  list.
       The event designator consists of the portion of the word beginning with
       the  history expansion character and ending with the word designator if
       present, or the end of the word.  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 bbllaannkk,
              newline, carriage return, =, or (.
       !!_n     Refer to history list entry _n.
       !!--_n    Refer to the current entry minus _n.
       !!!!     Refer to the previous entry.  This is a synonym for "!-1".
       !!_s_t_r_i_n_g
              Refer to the most recent command preceding the current  position
              in the history list starting with _s_t_r_i_n_g.
       !!??_s_t_r_i_n_g[[??]]
              Refer  to the most recent command preceding the current position
              in the history list containing _s_t_r_i_n_g.  The trailing  ??  may  be
              omitted  if  _s_t_r_i_n_g  is  followed  immediately by a newline.  If
              _s_t_r_i_n_g is missing, this uses the string  from  the  most  recent
              search; it is an error if there is no previous search string.
       ^^_s_t_r_i_n_g_1^^_s_t_r_i_n_g_2^^
              Quick  substitution.   Repeat  the  previous  command, replacing
              _s_t_r_i_n_g_1 with  _s_t_r_i_n_g_2.   Equivalent  to  "!!:s^_s_t_r_i_n_g_1^_s_t_r_i_n_g_2^"
              (see MMooddiiffiieerrss below).
       !!##     The entire command line typed so far.

   WWoorrdd DDeessiiggnnaattoorrss
       Word designators are used to select desired words from the event.  They
       are optional; if the word designator isn't supplied, the history expan-
       sion uses the entire 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 in-
       serted into the current line separated by single spaces.

       00 ((zzeerroo))
              The zeroth word.  For the shell, and  many  other  applications,
              this is the command word.
       _n      The _nth word.
       ^^      The first argument: word 1.
       $$      The  last  word.  This is usually the last argument, but expands
              to the zeroth word if there is only one word in the line.
       %%      The first word matched by the most recent "?_s_t_r_i_n_g?"  search, if
              the search string begins with a character  that  is  part  of  a
              word.   By  default,  searches begin at the end of each line and
              proceed to the beginning, so the first word matched is  the  one
              closest to the end of the line.
       _x--_y    A range of words; "-_y" abbreviates "0-_y".
       **      All  of  the words but the zeroth.  This is a synonym for "_1_-_$".
              It is not an error to use ** if there is just  one  word  in  the
              event; it expands to the empty string in that case.
       xx**     Abbreviates _x_-_$.
       xx--     Abbreviates _x_-_$ like xx**, but omits the last word.  If xx 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, equivalent to !!!!.

   MMooddiiffiieerrss
       After the optional word designator, the expansion  may  include  a  se-
       quence  of  one  or more of the following modifiers, each preceded by a
       ":".  These modify, or edit, the word or words selected from  the  his-
       tory event.

       hh      Remove a trailing filename component, leaving only the head.
       tt      Remove all leading filename components, leaving the tail.
       rr      Remove a trailing suffix of the form _._x_x_x, leaving the basename.
       ee      Remove all but the trailing suffix.
       pp      Print the new command but do not execute it.
       qq      Quote the substituted words, escaping further substitutions.
       xx      Quote  the  substituted words as with qq, but break into words at
              bbllaannkkss and newlines.  The qq and xx modifiers are mutually  exclu-
              sive; expansion uses the last one supplied.
       ss//_o_l_d//_n_e_w//
              Substitute  _n_e_w  for  the  first  occurrence of _o_l_d 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.  A single backslash quotes the delimiter in _o_l_d
              and _n_e_w.  If & appears in _n_e_w, it is replaced with _o_l_d.  A  sin-
              gle  backslash  quotes  the &.  If _o_l_d is null, it is set to the
              last _o_l_d substituted, or, if no previous  history  substitutions
              took place, the last _s_t_r_i_n_g in a !!??_s_t_r_i_n_g[[??]]  search.  If _n_e_w is
              null, each matching _o_l_d is deleted.
       &&      Repeat the previous substitution.
       gg      Cause changes to be applied over the entire event line.  This is
              used  in  conjunction  with "::ss" (e.g., "::ggss//_o_l_d//_n_e_w//") or "::&&".
              If used with "::ss", 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 aa may be used as a synonym for gg.
       GG      Apply the following "ss" or "&&" modifier once to each word in the
              event line.

PPRROOGGRRAAMMMMIINNGG WWIITTHH HHIISSTTOORRYY FFUUNNCCTTIIOONNSS
       This section describes how to use the History  library  in  other  pro-
       grams.

   IInnttrroodduuccttiioonn ttoo HHiissttoorryy
       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 _e_x_p_a_n_s_i_o_n 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 bbaasshh.

       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 _<_r_e_a_d_l_i_n_e_/_h_i_s_t_o_r_y_._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.

   HHiissttoorryy SSttoorraaggee
       The  history  list  is an array of history entries.  A history entry is
       declared as follows:

       _t_y_p_e_d_e_f _v_o_i_d _* hhiissttddaattaa__tt;;

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

       The history list itself might therefore be declared as

       _H_I_S_T___E_N_T_R_Y _*_* tthhee__hhiissttoorryy__lliisstt;;

       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 entry records. */
         int offset;           /* The current record. */
         int length;           /* Number of records in list. */
         int size;             /* Number of records allocated. */
         int flags;
       } HISTORY_STATE;

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

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

   IInniittiiaalliizziinngg HHiissttoorryy aanndd SSttaattee MMaannaaggeemmeenntt
       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.

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

       _H_I_S_T_O_R_Y___S_T_A_T_E _* hhiissttoorryy__ggeett__hhiissttoorryy__ssttaattee (_v_o_i_d)
       Return a structure describing the current state of the input history.

       _v_o_i_d hhiissttoorryy__sseett__hhiissttoorryy__ssttaattee (_H_I_S_T_O_R_Y___S_T_A_T_E _*_s_t_a_t_e)
       Set the state of the history list according to _s_t_a_t_e.

   HHiissttoorryy LLiisstt MMaannaaggeemmeenntt
       These functions manage individual entries on the history list,  or  set
       parameters managing the list itself.

       _v_o_i_d aadddd__hhiissttoorryy (_c_o_n_s_t _c_h_a_r _*_s_t_r_i_n_g)
       Place _s_t_r_i_n_g at the end of the history list.  The associated data field
       (if  any) is set to NNUULLLL.  If the maximum number of history entries has
       been set using ssttiiffllee__hhiissttoorryy(()), and the new number of history  entries
       would exceed that maximum, the oldest history entry is removed.

       _v_o_i_d aadddd__hhiissttoorryy__ttiimmee (_c_o_n_s_t _c_h_a_r _*_s_t_r_i_n_g)
       Change  the time stamp associated with the most recent history entry to
       _s_t_r_i_n_g.

       _H_I_S_T___E_N_T_R_Y _* rreemmoovvee__hhiissttoorryy (_i_n_t _w_h_i_c_h)
       Remove history entry at offset _w_h_i_c_h from the history.  The removed el-
       ement is returned so you can free the line, data, and containing struc-
       ture.

       _h_i_s_t_d_a_t_a___t ffrreeee__hhiissttoorryy__eennttrryy (_H_I_S_T___E_N_T_R_Y _*_h_i_s_t_e_n_t)
       Free the history entry _h_i_s_t_e_n_t and any history library private data as-
       sociated with it.  Returns the application-specific data so the  caller
       can dispose of it.

       _H_I_S_T___E_N_T_R_Y  _* rreeppllaaccee__hhiissttoorryy__eennttrryy (_i_n_t _w_h_i_c_h_, _c_o_n_s_t _c_h_a_r _*_l_i_n_e_, _h_i_s_t_-
       _d_a_t_a___t _d_a_t_a)
       Make the history entry at offset _w_h_i_c_h have _l_i_n_e and  _d_a_t_a.   This  re-
       turns  the  old entry so the caller can dispose of any application-spe-
       cific data.  In the case of an invalid _w_h_i_c_h, a  NNUULLLL  pointer  is  re-
       turned.

       _v_o_i_d cclleeaarr__hhiissttoorryy (_v_o_i_d)
       Clear the history list by deleting all the entries.

       _v_o_i_d ssttiiffllee__hhiissttoorryy (_i_n_t _m_a_x)
       Stifle  the  history  list, remembering only the last _m_a_x entries.  The
       history list will contain only _m_a_x entries at a time.

       _i_n_t uunnssttiiffllee__hhiissttoorryy (_v_o_i_d)
       Stop stifling the history.  This  returns  the  previously-set  maximum
       number  of  history  entries (as set by ssttiiffllee__hhiissttoorryy(())).  history was
       stifled.  The value is positive if the history was stifled, negative if
       it wasn't.

       _i_n_t hhiissttoorryy__iiss__ssttiifflleedd (_v_o_i_d)
       Returns non-zero if the history is stifled, zero if it is not.

   IInnffoorrmmaattiioonn AAbboouutt tthhee HHiissttoorryy LLiisstt
       These functions return information about the entire history list or in-
       dividual list entries.

       _H_I_S_T___E_N_T_R_Y _*_* hhiissttoorryy__lliisstt (_v_o_i_d)
       Return a NNUULLLL terminated array of _H_I_S_T___E_N_T_R_Y _* which is the current in-
       put history.  Element 0 of this list is  the  beginning  of  time.   If
       there is no history, return NNUULLLL.

       _i_n_t wwhheerree__hhiissttoorryy (_v_o_i_d)
       Returns the offset of the current history element.

       _H_I_S_T___E_N_T_R_Y _* ccuurrrreenntt__hhiissttoorryy (_v_o_i_d)
       Return  the  history  entry  at  the current position, as determined by
       wwhheerree__hhiissttoorryy(()).  If there is no entry there, return a NNUULLLL pointer.

       _H_I_S_T___E_N_T_R_Y _* hhiissttoorryy__ggeett (_i_n_t _o_f_f_s_e_t)
       Return the history entry at position _o_f_f_s_e_t.  The range of valid values
       of _o_f_f_s_e_t starts at hhiissttoorryy__bbaassee and ends at hhiissttoorryy__lleennggtthh  -  1.   If
       there  is  no entry there, or if _o_f_f_s_e_t is outside the valid range, re-
       turn a NNUULLLL pointer.

       _t_i_m_e___t hhiissttoorryy__ggeett__ttiimmee (_H_I_S_T___E_N_T_R_Y _*)
       Return the time stamp associated with the history entry passed  as  the
       argument.

       _i_n_t hhiissttoorryy__ttoottaall__bbyytteess (_v_o_i_d)
       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.

   MMoovviinngg AArroouunndd tthhee HHiissttoorryy LLiisstt
       These functions allow the current index into the history list to be set
       or changed.

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

       _H_I_S_T___E_N_T_R_Y _* pprreevviioouuss__hhiissttoorryy (_v_o_i_d)
       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 NNUULLLL pointer.

       _H_I_S_T___E_N_T_R_Y _* nneexxtt__hhiissttoorryy (_v_o_i_d)
       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 NNUULLLL pointer.

   SSeeaarrcchhiinngg tthhee HHiissttoorryy LLiisstt
       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 _a_n_-
       _c_h_o_r_e_d, meaning that the string must match at the beginning of the his-
       tory entry.

       _i_n_t hhiissttoorryy__sseeaarrcchh (_c_o_n_s_t _c_h_a_r _*_s_t_r_i_n_g_, _i_n_t _d_i_r_e_c_t_i_o_n)
       Search the history for _s_t_r_i_n_g, starting at the current history  offset.
       If  _d_i_r_e_c_t_i_o_n  is  less than 0, then the search is through previous en-
       tries, otherwise through subsequent entries.  If _s_t_r_i_n_g 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 _s_t_r_i_n_g was found.
       Otherwise, nothing is changed, and the function returns -1.

       _i_n_t hhiissttoorryy__sseeaarrcchh__pprreeffiixx (_c_o_n_s_t _c_h_a_r _*_s_t_r_i_n_g_, _i_n_t _d_i_r_e_c_t_i_o_n)
       Search the history for _s_t_r_i_n_g, starting at the current history  offset.
       The  search is anchored: matching lines must begin with _s_t_r_i_n_g.  If _d_i_-
       _r_e_c_t_i_o_n is less than 0, then the search is  through  previous  entries,
       otherwise  through  subsequent  entries.   If _s_t_r_i_n_g is found, then the
       current history index is set to that entry, and the return value is  0.
       Otherwise, nothing is changed, and the function returns -1.

       _i_n_t hhiissttoorryy__sseeaarrcchh__ppooss (_c_o_n_s_t _c_h_a_r _*_s_t_r_i_n_g_, _i_n_t _d_i_r_e_c_t_i_o_n_, _i_n_t _p_o_s)
       Search for _s_t_r_i_n_g in the history list, starting at _p_o_s, an absolute in-
       dex into the list.  If _d_i_r_e_c_t_i_o_n is negative, the search proceeds back-
       ward  from  _p_o_s,  otherwise forward.  Returns the absolute index of the
       history element where _s_t_r_i_n_g was found, or -1 otherwise.

   MMaannaaggiinngg tthhee HHiissttoorryy FFiillee
       The History library can read the history from and write it to  a  file.
       This section documents the functions for managing a history file.

       _i_n_t rreeaadd__hhiissttoorryy (_c_o_n_s_t _c_h_a_r _*_f_i_l_e_n_a_m_e)
       Add the contents of _f_i_l_e_n_a_m_e to the history list, a line at a time.  If
       _f_i_l_e_n_a_m_e  is NNUULLLL, then read from _~_/_._h_i_s_t_o_r_y.  Returns 0 if successful,
       or eerrrrnnoo if not.

       _i_n_t rreeaadd__hhiissttoorryy__rraannggee (_c_o_n_s_t _c_h_a_r _*_f_i_l_e_n_a_m_e_, _i_n_t _f_r_o_m_, _i_n_t _t_o)
       Read a range of lines from _f_i_l_e_n_a_m_e, adding them to the  history  list.
       Start  reading  at  line _f_r_o_m and end at _t_o.  If _f_r_o_m is zero, start at
       the beginning.  If _t_o is less than _f_r_o_m, then read until the end of the
       file.  If _f_i_l_e_n_a_m_e is NNUULLLL, then read from _~_/_._h_i_s_t_o_r_y.   Returns  0  if
       successful, or eerrrrnnoo if not.

       _i_n_t wwrriittee__hhiissttoorryy (_c_o_n_s_t _c_h_a_r _*_f_i_l_e_n_a_m_e)
       Write  the  current history to _f_i_l_e_n_a_m_e, overwriting _f_i_l_e_n_a_m_e if neces-
       sary.  If _f_i_l_e_n_a_m_e is NNUULLLL, then write the history list to  _~_/_._h_i_s_t_o_r_y.
       Returns 0 on success, or eerrrrnnoo on a read or write error.

       _i_n_t aappppeenndd__hhiissttoorryy (_i_n_t _n_e_l_e_m_e_n_t_s_, _c_o_n_s_t _c_h_a_r _*_f_i_l_e_n_a_m_e)
       Append the last _n_e_l_e_m_e_n_t_s of the history list to _f_i_l_e_n_a_m_e.  If _f_i_l_e_n_a_m_e
       is  NNUULLLL, then append to _~_/_._h_i_s_t_o_r_y.  Returns 0 on success, or eerrrrnnoo on
       a read or write error.

       _i_n_t hhiissttoorryy__ttrruunnccaattee__ffiillee (_c_o_n_s_t _c_h_a_r _*_f_i_l_e_n_a_m_e_, _i_n_t _n_l_i_n_e_s)
       Truncate the history file _f_i_l_e_n_a_m_e, leaving only the last _n_l_i_n_e_s lines.
       If _f_i_l_e_n_a_m_e is NNUULLLL, then _~_/_._h_i_s_t_o_r_y is truncated.  Returns 0  on  suc-
       cess, or eerrrrnnoo on failure.

   HHiissttoorryy EExxppaannssiioonn
       These functions implement history expansion.

       _i_n_t hhiissttoorryy__eexxppaanndd (_c_o_n_s_t _c_h_a_r _*_s_t_r_i_n_g_, _c_h_a_r _*_*_o_u_t_p_u_t)
       Expand  _s_t_r_i_n_g,  placing the result into _o_u_t_p_u_t, 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 ::pp modifier.
       If  an  error occurred in expansion, then _o_u_t_p_u_t contains a descriptive
       error message.

       _c_h_a_r _* ggeett__hhiissttoorryy__eevveenntt (_c_o_n_s_t _c_h_a_r _*_s_t_r_i_n_g_, _i_n_t _*_c_i_n_d_e_x_, _i_n_t _q_c_h_a_r)
       Returns the text of the history event beginning at  _s_t_r_i_n_g  +  _*_c_i_n_d_e_x.
       _*_c_i_n_d_e_x is modified to point to after the event specifier.  At function
       entry,  _c_i_n_d_e_x  points to the index into _s_t_r_i_n_g where the history event
       specification begins.  _q_c_h_a_r is a character that is allowed to end  the
       event specification in addition to the "normal" terminating characters.

       _c_h_a_r _*_* hhiissttoorryy__ttookkeenniizzee (_c_o_n_s_t _c_h_a_r _*_s_t_r_i_n_g)
       Return  an  array  of  tokens  parsed  out of _s_t_r_i_n_g, much as the shell
       might.  The tokens are split on the characters in the  hhiissttoorryy__wwoorrdd__ddee--
       lliimmiitteerrss variable, and shell quoting conventions are obeyed.

       _c_h_a_r _* hhiissttoorryy__aarrgg__eexxttrraacctt (_i_n_t _f_i_r_s_t_, _i_n_t _l_a_s_t_, _c_o_n_s_t _c_h_a_r _*_s_t_r_i_n_g)
       Extract a string segment consisting of the _f_i_r_s_t through _l_a_s_t arguments
       present in _s_t_r_i_n_g.  Arguments are split using hhiissttoorryy__ttookkeenniizzee(()).

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

       _i_n_t hhiissttoorryy__bbaassee
       The logical offset of the first entry in the history list.

       _i_n_t hhiissttoorryy__lleennggtthh
       The number of entries currently stored in the history list.

       _i_n_t hhiissttoorryy__mmaaxx__eennttrriieess
       The maximum number of history entries.  This must be changed using ssttii--
       ffllee__hhiissttoorryy(()).

       _i_n_t hhiissttoorryy__wwrriittee__ttiimmeessttaammppss
       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
       _h_i_s_t_o_r_y___c_o_m_m_e_n_t___c_h_a_r to delimit timestamp entries in the history  file.
       If  that  variable does not have a value (the default), the history li-
       brary will not write timestamps.

       _c_h_a_r hhiissttoorryy__eexxppaannssiioonn__cchhaarr
       The character that introduces a history event.  The default is !!.  Set-
       ting this to 0 inhibits history expansion.

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

       _c_h_a_r hhiissttoorryy__ccoommmmeenntt__cchhaarr
       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.

       _c_h_a_r _* hhiissttoorryy__wwoorrdd__ddeelliimmiitteerrss
       The  characters  that  separate tokens for hhiissttoorryy__ttookkeenniizzee(()).  The de-
       fault value is "" \\tt\\nn(())<<>>;;&&||"".

       _c_h_a_r _* hhiissttoorryy__nnoo__eexxppaanndd__cchhaarrss
       The list of characters which inhibit history expansion if found immedi-
       ately following hhiissttoorryy__eexxppaannssiioonn__cchhaarr.  The  default  is  space,  tab,
       newline, \\rr, and ==.

       _c_h_a_r _* hhiissttoorryy__sseeaarrcchh__ddeelliimmiitteerr__cchhaarrss
       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.

       _i_n_t hhiissttoorryy__qquuootteess__iinnhhiibbiitt__eexxppaannssiioonn
       If  non-zero, the history expansion code implements shell-like quoting:
       single-quoted words are not scanned for the history expansion character
       or the history comment character, and double-quoted words may have his-
       tory expansion performed, since single quotes are  not  special  within
       double quotes.  The default value is 0.

       _i_n_t hhiissttoorryy__qquuoottiinngg__ssttaattee
       An  application may set this variable to indicate that the current line
       being expanded is subject to existing quoting.  If set  to  _',  history
       expansion  assumes that the line is single-quoted and inhibit expansion
       until it reads an unquoted closing single quote; if set to  _",  history
       expansion  assumes the line is double quoted until it reads an unquoted
       closing double quote.  If set to zero, the default,  history  expansion
       assumes  the  line is not quoted and treats quote characters within the
       line as described above.  This is only effective if  hhiissttoorryy__qquuootteess__iinn--
       hhiibbiitt__eexxppaannssiioonn is set.

       _r_l___l_i_n_e_b_u_f___f_u_n_c___t _* hhiissttoorryy__iinnhhiibbiitt__eexxppaannssiioonn__ffuunnccttiioonn
       This  should  be  set to the address of a function that takes two argu-
       ments: a cchhaarr ** (_s_t_r_i_n_g) and an iinntt index into  that  string  (_i).   It
       should  return  a  non-zero  value if the history expansion starting at
       _s_t_r_i_n_g_[_i_] should not be performed; zero  if  the  expansion  should  be
       done.   It  is  intended for use by applications like bbaasshh that use the
       history expansion character for additional purposes.  By default,  this
       variable is set to NNUULLLL.

FFIILLEESS
       _~_/_._h_i_s_t_o_r_y
              Default filename for reading and writing saved history

SSEEEE AALLSSOO
       _T_h_e _G_n_u _R_e_a_d_l_i_n_e _L_i_b_r_a_r_y, Brian Fox and Chet Ramey
       _T_h_e _G_n_u _H_i_s_t_o_r_y _L_i_b_r_a_r_y, Brian Fox and Chet Ramey
       _b_a_s_h(1)
       _r_e_a_d_l_i_n_e(3)

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

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

BBUUGG RREEPPOORRTTSS
       If  you  find  a bug in the hhiissttoorryy 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 hhiissttoorryy library that you have.

       Once  you have determined that a bug actually exists, mail a bug report
       to _b_u_g_-_r_e_a_d_l_i_n_e@_g_n_u_._o_r_g.  If you have a fix, you are  welcome  to  mail
       that  as  well!   Suggestions  and  "philosophical"  bug reports may be
       mailed to  _b_u_g_-_r_e_a_d_l_i_n_e@_g_n_u_._o_r_g  or  posted  to  the  Usenet  newsgroup
       ggnnuu..bbaasshh..bbuugg.

       Comments and bug reports concerning this manual page should be directed
       to _c_h_e_t_._r_a_m_e_y_@_c_a_s_e_._e_d_u.

GNU History 8.3                2024 December 31                     _H_I_S_T_O_R_Y(3)