HISTORY(3)                      Library Functions Manual                     HISTORY(3)

NAME
       history - GNU History Library

COPYRIGHT
       The  GNU History Library is Copyright (C) 1989-2014 by the Free Software Founda‐
       tion, Inc.

DESCRIPTION
       Many programs read input from the user a  line  at  a  time.   The  GNU  History
       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  identical  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 second 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 several 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 history 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.
       ^string1^string2^
              Quick  substitution.   Repeat  the  last  command, replacing string1 with
              string2.  Equivalent to ``!!:s/string1/string2/'' (see Modifiers 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  begin‐
       ning  of  the  line,  with  the first word being denoted by 0 (zero).  Words are
       inserted into the current line separated 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 expand to the
              zeroth word if there is only one word in the line.
       %      The word matched by the most recent `?string?' search.
       x-y    A range of words; `-y' abbreviates `0-y'.
       *      All of the words but the zeroth.  This is a synonym for `1-$'.  It is not
              an error to use * if there is just one  word  in  the  event;  the  empty
              string is returned in that case.
       x*     Abbreviates x-$.
       x-     Abbreviates x-$ like x*, but omits the last word.

       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 `:'.

       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.
       s/old/new/
              Substitute new for the first occurrence of old 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  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.
       &      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' modifier once to each word in the event line.

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

   Introduction to History
       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 his‐
       tory expansion function is available which provides for a consistent user inter‐
       face across different programs.

       The  user  using  programs written with the History library has the benefit 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.

       If  the programmer desires, he can 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 library pro‐
       vides in other code, an  application  writer  should  include  the  file  <read‐
       line/history.h>  in  any file that uses the History library's features.  It sup‐
       plies extern declarations for all of the library's public  functions  and  vari‐
       ables, 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 structure:

       /*
        * 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.

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

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

       HIST_ENTRY  *  replace_history_entry  (int  which,  const char *line, histdata_t
       data)
       Make the history entry at offset which have line and data.  This returns the old
       entry  so  the caller can dispose of any application-specific data.  In the case
       of an invalid which, a NULL pointer is returned.

       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.

       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  individual
       list entries.

       HIST_ENTRY ** history_list (void)
       Return  a  NULL terminated array of HIST_ENTRY * which is the current input his‐
       tory.  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_his‐
       tory().  If there is no entry there, return a NULL pointer.

       HIST_ENTRY * history_get (int offset)
       Return the history entry at position offset,  starting  from  history_base.   If
       there is no entry there, or if offset is greater than the history length, return
       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, increment 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  containing  a
       specific  string.  Searching may be performed both forward and backward from the
       current history position.  The search may be anchored, meaning that  the  string
       must match at the beginning of the history 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 entries, 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 direction is less
       than 0, then the search is through previous entries,  otherwise  through  subse‐
       quent  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 index into
       the list.  If direction is negative, the search proceeds backward from pos, oth‐
       erwise  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 sec‐
       tion 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 necessary.  If
       filename is NULL, then write the history list to ~/.history.  Returns 0 on  suc‐
       cess, 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 success, 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  expan‐
                     sion 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 executed, as
                     with the :p modifier.
       If an error ocurred in expansion, then output contains a descriptive error  mes‐
       sage.

       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 characters.

       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_delimiters 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 His‐
       tory 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 stifle_his‐
       tory().

       int history_wite_timestamps
       If non-zero, timestamps are written to the history file, so  they  can  be  pre‐
       served  between  sessions.   The default value is 0, meaning that timestamps 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 !.  Setting  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  default  value
       is " \t\n()<>;&|".

       char * history_no_expand_chars
       The list of characters which inhibit history expansion if found immediately fol‐
       lowing 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 expansion char‐
       acter 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 arguments: 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 appears in the latest ver‐
       sion 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-read‐
       line@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 6.3                       2015 May 24                            HISTORY(3)

history: history [-c] [-d szám] [n] vagy history -anrw [fájlnév] vagy history -ps arg [arg...]
    Display or manipulate the history list.
    
    Display the history list with line numbers, prefixing each modified
    entry with a `*'.  An argument of N lists only the last N entries.
    
    Options:
      -c        clear the history list by deleting all of the entries
      -d offset delete the history entry at position OFFSET.
    
      -a        append history lines from this session to the history file
      -n        read all history lines not already read from the history file
                and append them to the history list
      -r        read the history file and append the contents to the history
                list
      -w        write the current history to the history file
    
      -p        perform history expansion on each ARG and display the result
                without storing it in the history list
      -s        append the ARGs to the history list as a single entry
    
    If FILENAME is given, it is used as the history file.  Otherwise,
    if HISTFILE has a value, that is used, else ~/.bash_history.
    
    If the HISTTIMEFORMAT variable is set and not null, its value is used
    as a format string for strftime(3) to print the time stamp associated
    with each displayed history entry.  No time stamps are printed otherwise.
    
    Exit Status:
    Returns success unless an invalid option is given or an error occurs.