HISTORY(3)                                                          HISTORY(3)



NNAAMMEE
       history - GNU History Library

CCOOPPYYRRIIGGHHTT
       The GNU History Library is Copyright (C) 1989-2011 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  in
       composing new ones.


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 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 _e_v_e_n_t, and the portions
       of  that  line  that  are  acted upon are _w_o_r_d_s.  Various _m_o_d_i_f_i_e_r_s are
       available to manipulate the selected words.  The line  is  broken  into
       words in the same fashion as bbaasshh 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 hhiissttoorryy__ttookkeenniizzee(())
       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.

   EEvveenntt DDeessiiggnnaattoorrss
       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  bbllaannkk,
              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'.
       !!_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 postition
              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.
       ^^_s_t_r_i_n_g_1^^_s_t_r_i_n_g_2^^
              Quick substitution.  Repeat the last 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 MMoodd--
              iiffiieerrss below).
       !!##     The entire command line typed so far.

   WWoorrdd DDeessiiggnnaattoorrss
       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.

       00 ((zzeerroo))
              The zeroth word.  For the shell, this is the command word.
       _n      The _nth word.
       ^^      The first argument.  That is, word 1.
       $$      The last argument.
       %%      The word matched by the most recent `?_s_t_r_i_n_g?' search.
       _x--_y    A range of words; `-_y' abbreviates `0-_y'.
       **      All  of  the words but the zeroth.  This is a synonym for `_1_-_$'.
              It is not an error to use ** if there is just  one  word  in  the
              event; the empty string is returned in that case.
       xx**     Abbreviates _x_-_$.
       xx--     Abbreviates _x_-_$ like xx**, but omits the last word.

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

   MMooddiiffiieerrss
       After the optional word designator, there may appear a sequence of  one
       or more of the following modifiers, each preceded by a `:'.

       hh      Remove a trailing file name component, leaving only the head.
       tt      Remove all leading file name 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.
       ss//_o_l_d//_n_e_w//
              Substitute  _n_e_w  for  the  first  occurrence of _o_l_d in the event
              line.  Any delimiter can be used  in  place  of  /.   The  final
              delimiter  is  optional if it is the last character of the event
              line.  The delimiter may be quoted in _o_l_d and _n_e_w with a  single
              backslash.   If & appears in _n_e_w, it is replaced by _o_l_d.  A sin-
              gle backslash will quote the &.  If _o_l_d is null, it  is  set  to
              the  last  _o_l_d substituted, or, if no previous history substitu-
              tions took place, the last _s_t_r_i_n_g in a !!??_s_t_r_i_n_g[[??]]  search.
       &&      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' 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
       The programmer using the History library has  available  functions  for
       remembering  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.

       If the programmer desires, he  can  use  the  Readline  library,  which
       includes some history manipulation by default, and has the added advan-
       tage of command line editing.

       Before declaring any functions  using  any  functionality  the  History
       library  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  pub-
       lic 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 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 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.

       _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
       element is returned so you can free  the  line,  data,  and  containing
       structure.

       _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
       associated 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
       returns 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
       returned.

       _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.

       _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
       individual 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
       input 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,  starting  from  hhiiss--
       ttoorryy__bbaassee.   If  there  is no entry there, or if _o_f_f_s_e_t is greater than
       the history length, return 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)
       Move the current history offset forward to the next history entry,  and
       return  the a pointer to that entry.  If there is no next entry, 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
       history 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
       entries, 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 a -1 is returned.

       _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 a -1 is returned.

       _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
       index  into  the  list.   If _d_i_r_e_c_t_i_o_n is negative, the search proceeds
       backward 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_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 ocurred 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 charac-
       ters.

       _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  hhiiss--
       ttoorryy__wwoorrdd__ddeelliimmiitteerrss  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__wwiittee__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),  timestamps  will
       not be written.

       _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
       default 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, single-quoted words are not scanned for the history expan-
       sion character.  The default value is 0.

       _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@ins.CWRU.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
       appears 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_@_i_n_s_._C_W_R_U_._E_d_u.



GNU History 6.2                 2010 August 12                      HISTORY(3)
