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

Copyright (C) 1987, 1989, 1991 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 1, 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; see the file COPYING.  If not, write to the Free Software
Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.

$PRODUCES history.c

$BUILTIN history
$FUNCTION history_builtin
$DEPENDS_ON HISTORY
$SHORT_DOC history [n] [ [-awrn] [filename]]
Display the history list with line numbers.  Lines listed with
with a `*' have been modified.  Argument of N says to list only
the last N lines.  Argument `-w' means to write out the current
history file;  `-r' means to read it instead.  Argument `-a' means
to append history lines from this session to the history file.
Argument `-n' means to read all history lines not already read
from the history file.  If FILENAME is given, then use that file,
else if $HISTFILE has a value, use that, else use ~/.bash_history.
$END

#include "../shell.h"
#if defined (HISTORY)
#include <sys/types.h>
#include <sys/file.h>
#include "../filecntl.h"
#include "../posixstat.h"
#include "../bashhist.h"
#include <readline/history.h>

/* History.  Arg of -w FILENAME means write file, arg of -r FILENAME
   means read file.  Arg of N means only display that many items. */

history_builtin (list)
     WORD_LIST *list;
{
  register int i;
  int limited = 0, limit = 0;
  HIST_ENTRY **hlist;

  while (list)
    {
      char *arg = list->word->word;

      if ((arg[0] == '-') &&
	  (strlen (arg) == 2) &&
	  (member (arg[1], "rwan")))
	{
	  char *file;
	  int result = EXECUTION_SUCCESS;

	  if (list->next)
	    file = list->next->word->word;
	  else
	    file = get_string_value ("HISTFILE");

	  switch (arg[1])
	    {
	    case 'a':		/* Append `new' lines to file. */
	      {
		if (history_lines_this_session)
		  {
		    void using_history ();

		    if (history_lines_this_session < where_history ())
		      {
			/* If the filename was supplied, then create it
			   if it doesn't already exist. */
			if (file)
			  {
			    struct stat buf;

			    if (stat (file, &buf) == -1)
			      {
				int tem;

				tem = open (file, O_CREAT, 0666);
				close (tem);
			      }
			  }

			result =
			  append_history (history_lines_this_session, file);
			history_lines_in_file += history_lines_this_session;
			history_lines_this_session = 0;
		      }
		  }
		break;
	      }

	    case 'w':		/* Write entire history. */
	      {
		result = write_history (file);
		break;
	      }

	    case 'r':		/* Read entire file. */
	      {
		result = read_history (file);
		break;
	      }

	    case 'n':		/* Read `new' history from file. */
	      {
		/* Read all of the lines in the file that we haven't
		   already read. */
		using_history ();
		result = read_history_range (file, history_lines_in_file, -1);
		using_history ();
		history_lines_in_file = where_history ();

		break;
	      }
	    }
	  return (result ? EXECUTION_FAILURE : EXECUTION_SUCCESS);
	}
      else if (strcmp (list->word->word, "--") == 0)
	{
	  list = list->next;
	  break;
	}
      else if (*list->word->word == '-')
	{
	  bad_option (list->word->word);
	  builtin_error ("usage: history [n] [-rwan [filename]]");
	  return (EX_USAGE);
	}
      else
	break;
    }

  if (list)
    {
      limited = 1;
      limit = get_numeric_arg (list);
    }

  hlist = history_list ();

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

      if (limit < 0)
	limit = -limit;

      if (!limited)
	i = 0;
      else
	if ((i -= limit) < 0)
	  i = 0;

      while (hlist[i])
	{
	  QUIT;
	  printf ("%5d%c %s\n", i + history_base,
		  hlist[i]->data ? '*' : ' ', hlist[i]->line);
	  i++;
	}
    }
  return (EXECUTION_SUCCESS);
}
#endif /* HISTORY */