This file is history.def, from which is created history.c.
It implements the builtin "history" in Bash.

Copyright (C) 1987-2009 Free Software Foundation, Inc.

This file is part of GNU Bash, the Bourne Again SHell.

Bash is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

Bash is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with Bash.  If not, see <http://www.gnu.org/licenses/>.

$PRODUCES history.c

$BUILTIN history
$FUNCTION history_builtin
$DEPENDS_ON HISTORY
$SHORT_DOC history [-c] [-d offset] [n] or history -anrw [filename] or 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 offset OFFSET.

  -a	append history lines from this session to the history file
  -n	read all history lines not already read from the history file
  -r	read the history file and append the contents to the history
	list
  -w	write the current history to the history file
	and append them to the history list

  -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.
$END

#include <config.h>

#if defined (HISTORY)
#include "../bashtypes.h"
#if ! defined(_MINIX) && defined (HAVE_SYS_FILE_H)
#  include <sys/file.h>
#endif
#include "posixstat.h"
#include "filecntl.h"
#include <errno.h>
#include <stdio.h>
#if defined (HAVE_UNISTD_H)
#  include <unistd.h>
#endif

#include "../bashansi.h"
#include "../bashintl.h"

#include "../shell.h"
#include "../bashhist.h"
#include <readline/history.h>
#include "bashgetopt.h"
#include "common.h"

#if !defined (errno)
extern int errno;
#endif

extern int current_command_line_count;
extern int force_append_history;	/* shopt -s histappend */

static char *histtime __P((HIST_ENTRY *, const char *));
static int display_history __P((WORD_LIST *));
static void push_history __P((WORD_LIST *));
static int expand_and_print_history __P((WORD_LIST *));

#define AFLAG	0x01
#define RFLAG	0x02
#define WFLAG	0x04
#define NFLAG	0x08
#define SFLAG	0x10
#define PFLAG	0x20
#define CFLAG	0x40
#define DFLAG	0x80

int
history_builtin (list)
     WORD_LIST *list;
{
  int flags, opt, result, old_history_lines, obase;
  char *filename, *delete_arg;
  intmax_t delete_offset;

  flags = 0;
  reset_internal_getopt ();
  while ((opt = internal_getopt (list, "acd:npsrw")) != -1)
    {
      switch (opt)
	{
	case 'a':
	  flags |= AFLAG;
	  break;
	case 'c':
	  flags |= CFLAG;
	  break;
	case 'n':
	  flags |= NFLAG;
	  break;
	case 'r':
	  flags |= RFLAG;
	  break;
	case 'w':
	  flags |= WFLAG;
	  break;
	case 's':
	  flags |= SFLAG;
	  break;
	case 'd':
	  flags |= DFLAG;
	  delete_arg = list_optarg;
	  break;
	case 'p':
#if defined (BANG_HISTORY)
	  flags |= PFLAG;
#endif
	  break;
	default:
	  builtin_usage ();
	  return (EX_USAGE);
	}
    }
  list = loptend;

  opt = flags & (AFLAG|RFLAG|WFLAG|NFLAG);
  if (opt && opt != AFLAG && opt != RFLAG && opt != WFLAG && opt != NFLAG)
    {
      builtin_error (_("cannot use more than one of -anrw"));
      return (EXECUTION_FAILURE);
    }

  /* clear the history, but allow other arguments to add to it again. */
  if (flags & CFLAG)
    {
      bash_clear_history ();
      if (list == 0)
	return (EXECUTION_SUCCESS);
    }

  if (flags & SFLAG)
    {
      if (list)
	push_history (list);
      return (EXECUTION_SUCCESS);
    }
#if defined (BANG_HISTORY)
  else if (flags & PFLAG)
    {
      if (list)
	return (expand_and_print_history (list));
      return (sh_chkwrite (EXECUTION_SUCCESS));
    }
#endif
  else if (flags & DFLAG)
    {
      if ((legal_number (delete_arg, &delete_offset) == 0)
	  || (delete_offset < history_base)
	  || (delete_offset > (history_base + history_length)))
	{
	  sh_erange (delete_arg, _("history position"));
	  return (EXECUTION_FAILURE);
	}
      opt = delete_offset;
      result = bash_delete_histent (opt - history_base);
      /* Since remove_history changes history_length, this can happen if
	 we delete the last history entry. */
      if (where_history () > history_length)
	history_set_pos (history_length);
      return (result ? EXECUTION_SUCCESS : EXECUTION_FAILURE);
    }
  else if ((flags & (AFLAG|RFLAG|NFLAG|WFLAG|CFLAG)) == 0)
    {
      result = display_history (list);
      return (sh_chkwrite (result));
    }

  filename = list ? list->word->word : get_string_value ("HISTFILE");
  result = EXECUTION_SUCCESS;

  if (flags & AFLAG)		/* Append session's history to file. */
    result = maybe_append_history (filename);
  else if (flags & WFLAG)	/* Write entire history. */
    result = write_history (filename);
  else if (flags & RFLAG)	/* Read entire file. */
    result = read_history (filename);
  else if (flags & NFLAG)	/* Read `new' history from file. */
    {
      /* Read all of the lines in the file that we haven't already read. */
      old_history_lines = history_lines_in_file;
      obase = history_base;

      using_history ();
      result = read_history_range (filename, history_lines_in_file, -1);
      using_history ();

      history_lines_in_file = where_history ();

      /* If we're rewriting the history file at shell exit rather than just
	 appending the lines from this session to it, the question is whether
	 we reset history_lines_this_session to 0, losing any history entries
	 we had before we read the new entries from the history file, or
	 whether we count the new entries we just read from the file as
	 history lines added during this session.
	 Right now, we do the latter.  This will cause these history entries
	 to be written to the history file along with any intermediate entries
	 we add when we do a `history -a', but the alternative is losing
	 them altogether. */
      if (force_append_history == 0)
	history_lines_this_session += history_lines_in_file - old_history_lines +
				    history_base - obase;
    }

  return (result ? EXECUTION_FAILURE : EXECUTION_SUCCESS);
}

/* Accessors for HIST_ENTRY lists that are called HLIST. */
#define histline(i) (hlist[(i)]->line)
#define histdata(i) (hlist[(i)]->data)

static char *
histtime (hlist, histtimefmt)
     HIST_ENTRY *hlist;
     const char *histtimefmt;
{
  static char timestr[128];
  time_t t;

  t = history_get_time (hlist);
  if (t)
    strftime (timestr, sizeof (timestr), histtimefmt, localtime (&t));
  else
    strcpy (timestr, "??");
  return timestr;
}

static int
display_history (list)
     WORD_LIST *list;
{
  register int i;
  intmax_t limit;
  HIST_ENTRY **hlist;
  char *histtimefmt, *timestr;

  if (list)
    {
      if (get_numeric_arg (list, 0, &limit) == 0)
	return (EXECUTION_FAILURE);

      if (limit < 0)
	limit = -limit;
    }
  else
    limit = -1;

  hlist = history_list ();

  if (hlist)
    {
      for (i = 0;  hlist[i]; i++)
	;

      if (0 <= limit && limit < i)
	i -= limit;
      else
	i = 0;

      histtimefmt = get_string_value ("HISTTIMEFORMAT");

      while (hlist[i])
	{
	  QUIT;

	  timestr = (histtimefmt && *histtimefmt) ? histtime (hlist[i], histtimefmt) : (char *)NULL;
	  printf ("%5d%c %s%s\n", i + history_base,
		  histdata(i) ? '*' : ' ',
		  ((timestr && *timestr) ? timestr : ""),
		  histline(i));
	  i++;
	}
    }

  return (EXECUTION_SUCCESS);
}

/* Remove the last entry in the history list and add each argument in
   LIST to the history. */
static void
push_history (list)
     WORD_LIST *list;
{
  char *s;

  /* Delete the last history entry if it was a single entry added to the
     history list (generally the `history -s' itself), or if `history -s'
     is being used in a compound command and the compound command was
     added to the history as a single element (command-oriented history).
     If you don't want history -s to remove the compound command from the
     history, change #if 0 to #if 1 below. */
#if 0
  if (hist_last_line_pushed == 0 && hist_last_line_added && bash_delete_last_history () == 0)
#else
  if (hist_last_line_pushed == 0 &&
	(hist_last_line_added ||
	  (current_command_line_count > 0 && current_command_first_line_saved && command_oriented_history))
      && bash_delete_last_history () == 0)
#endif
      return;

  s = string_list (list);
  /* Call check_add_history with FORCE set to 1 to skip the check against
     current_command_line_count.  If history -s is used in a compound
     command, the above code will delete the compound command's history
     entry and this call will add the line to the history as a separate
     entry.  Without FORCE=1, if current_command_line_count were > 1, the
     line would be appended to the entry before the just-deleted entry. */
  check_add_history (s, 1);	/* obeys HISTCONTROL, HISTIGNORE */

  hist_last_line_pushed = 1;	/* XXX */
  free (s);
}

#if defined (BANG_HISTORY)
static int
expand_and_print_history (list)
     WORD_LIST *list;
{
  char *s;
  int r, result;

  if (hist_last_line_pushed == 0 && hist_last_line_added && bash_delete_last_history () == 0)
    return EXECUTION_FAILURE;
  result = EXECUTION_SUCCESS;
  while (list)
    {
      r = history_expand (list->word->word, &s);
      if (r < 0)
	{
	  builtin_error (_("%s: history expansion failed"), list->word->word);
	  result = EXECUTION_FAILURE;
	}
      else
	{
	  fputs (s, stdout);
	  putchar ('\n');
	}
      FREE (s);
      list = list->next;
    }
  fflush (stdout);
  return result;
}
#endif /* BANG_HISTORY */
#endif /* HISTORY */