This file is help.def, from which is created help.c.
It implements the builtin "help" 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 help.c

$BUILTIN help
$FUNCTION help_builtin
$DEPENDS_ON HELP_BUILTIN
$SHORT_DOC help [-dms] [pattern ...]
Display information about builtin commands.

Displays brief summaries of builtin commands.  If PATTERN is
specified, gives detailed help on all commands matching PATTERN,
otherwise the list of help topics is printed.

Options:
  -d	output short description for each topic
  -m	display usage in pseudo-manpage format
  -s	output only a short usage synopsis for each topic matching
	PATTERN

Arguments:
  PATTERN	Pattern specifiying a help topic

Exit Status:
Returns success unless PATTERN is not found or an invalid option is given.
$END

#include <config.h>

#if defined (HELP_BUILTIN)
#include <stdio.h>

#if defined (HAVE_UNISTD_H)
#  ifdef _MINIX
#    include <sys/types.h>
#  endif
#  include <unistd.h>
#endif

#include <errno.h>

#include <filecntl.h>

#include "../bashintl.h"

#include "../shell.h"
#include "../builtins.h"
#include "../pathexp.h"
#include "common.h"
#include "bashgetopt.h"

#include <glob/strmatch.h>
#include <glob/glob.h>

#ifndef errno
extern int errno;
#endif

extern const char * const bash_copyright;
extern const char * const bash_license;

static void show_builtin_command_help __P((void));
static int open_helpfile __P((char *));
static void show_desc __P((char *, int));
static void show_manpage __P((char *, int));
static void show_longdoc __P((int));

/* Print out a list of the known functions in the shell, and what they do.
   If LIST is supplied, print out the list which matches for each pattern
   specified. */
int
help_builtin (list)
     WORD_LIST *list;
{
  register int i;
  char *pattern, *name;
  int plen, match_found, sflag, dflag, mflag;

  dflag = sflag = mflag = 0;
  reset_internal_getopt ();
  while ((i = internal_getopt (list, "dms")) != -1)
    {
      switch (i)
	{
	case 'd':
	  dflag = 1;
	  break;
	case 'm':
	  mflag = 1;
	  break;
	case 's':
	  sflag = 1;
	  break;
	default:
	  builtin_usage ();
	  return (EX_USAGE);
	}
    }
  list = loptend;

  if (list == 0)
    {
      show_shell_version (0);
      show_builtin_command_help ();
      return (EXECUTION_SUCCESS);
    }

  /* We should consider making `help bash' do something. */

  if (glob_pattern_p (list->word->word))
    {
      printf (ngettext ("Shell commands matching keyword `", "Shell commands matching keywords `", (list->next ? 2 : 1)));
      print_word_list (list, ", ");
      printf ("'\n\n");
    }

  for (match_found = 0, pattern = ""; list; list = list->next)
    {
      pattern = list->word->word;
      plen = strlen (pattern);

      for (i = 0; name = shell_builtins[i].name; i++)
	{
	  QUIT;
	  if ((strncmp (pattern, name, plen) == 0) ||
	      (strmatch (pattern, name, FNMATCH_EXTFLAG) != FNM_NOMATCH))
	    {
	      match_found++;
	      if (dflag)
		{
		  show_desc (name, i);
		  continue;
		}
	      else if (mflag)
		{
		  show_manpage (name, i);
		  continue;
		}

	      printf ("%s: %s\n", name, shell_builtins[i].short_doc);

	      if (sflag == 0)
		show_longdoc (i);
	    }
	}
    }

  if (match_found == 0)
    {
      builtin_error (_("no help topics match `%s'.  Try `help help' or `man -k %s' or `info %s'."), pattern, pattern, pattern);
      return (EXECUTION_FAILURE);
    }

  fflush (stdout);
  return (EXECUTION_SUCCESS);
}

static int
open_helpfile (name)
     char *name;
{
  int fd;

  fd = open (name, O_RDONLY);
  if (fd == -1)
    {
      builtin_error (_("%s: cannot open: %s"), name, strerror (errno));
      return -1;
    }
  return fd;
}

/* By convention, enforced by mkbuiltins.c, if separate help files are being
   used, the long_doc array contains one string -- the full pathname of the
   help file for this builtin.  */
static void
show_longdoc (i)
     int i;
{
  register int j;
  char * const *doc;
  int fd;

  doc = shell_builtins[i].long_doc;

  if (doc && doc[0] && *doc[0] == '/' && doc[1] == (char *)NULL)
    {
      fd = open_helpfile (doc[0]);
      if (fd < 0)
	return;
      zcatfd (fd, 1, doc[0]);
      close (fd);
    }
  else
    for (j = 0; doc[j]; j++)
      printf ("%*s%s\n", BASE_INDENT, " ", _(doc[j]));
}

static void
show_desc (name, i)
     char *name;
     int i;
{
  register int j;
  char **doc, *line;
  int fd, usefile;

  doc = (char **)shell_builtins[i].long_doc;

  usefile = (doc && doc[0] && *doc[0] == '/' && doc[1] == (char *)NULL);
  if (usefile)
    {
      fd = open_helpfile (doc[0]);
      if (fd < 0)
	return;
      zmapfd (fd, &line, doc[0]);
      close (fd);
    }
  else
    line = doc ? doc[0] : (char *)NULL;

  printf ("%s - ", name);
  for (j = 0; line && line[j]; j++)
    {
      putchar (line[j]);
      if (line[j] == '\n')
	break;
    }
  
  fflush (stdout);

  if (usefile)
    free (line);
}

/* Print builtin help in pseudo-manpage format. */
static void
show_manpage (name, i)
     char *name;
     int i;
{
  register int j;
  char **doc, *line;
  int fd, usefile;

  doc = (char **)shell_builtins[i].long_doc;

  usefile = (doc && doc[0] && *doc[0] == '/' && doc[1] == (char *)NULL);
  if (usefile)
    {
      fd = open_helpfile (doc[0]);
      if (fd < 0)
	return;
      zmapfd (fd, &line, doc[0]);
      close (fd);
    }
  else
    line = doc ? _(doc[0]) : (char *)NULL;

  /* NAME */
  printf ("NAME\n");
  printf ("%*s%s - ", BASE_INDENT, " ", name);
  for (j = 0; line && line[j]; j++)
    {
      putchar (line[j]);
      if (line[j] == '\n')
	break;
    }
  printf ("\n");

  /* SYNOPSIS */
  printf ("SYNOPSIS\n");
  printf ("%*s%s\n\n", BASE_INDENT, " ", shell_builtins[i].short_doc);

  /* DESCRIPTION */
  printf ("DESCRIPTION\n");
  if (usefile == 0)
    {
      for (j = 0; doc[j]; j++)
        printf ("%*s%s\n", BASE_INDENT, " ", _(doc[j]));
    }
  else
    {
      for (j = 0; line && line[j]; j++)
	{
	  putchar (line[j]);
	  if (line[j] == '\n')
	    printf ("%*s", BASE_INDENT, " ");
	}
    }
  putchar ('\n');

  /* SEE ALSO */
  printf ("SEE ALSO\n");
  printf ("%*sbash(1)\n\n", BASE_INDENT, " ");

  /* IMPLEMENTATION */
  printf ("IMPLEMENTATION\n");
  printf ("%*s", BASE_INDENT, " ");
  show_shell_version (0);
  printf ("%*s", BASE_INDENT, " ");
  printf ("%s\n", _(bash_copyright));
  printf ("%*s", BASE_INDENT, " ");
  printf ("%s\n", _(bash_license));

  fflush (stdout);
  if (usefile)
    free (line);
}

static void
show_builtin_command_help ()
{
  int i, j;
  int height, width;
  char *t, blurb[128];

  printf (
_("These shell commands are defined internally.  Type `help' to see this list.\n\
Type `help name' to find out more about the function `name'.\n\
Use `info bash' to find out more about the shell in general.\n\
Use `man -k' or `info' to find out more about commands not in this list.\n\
\n\
A star (*) next to a name means that the command is disabled.\n\
\n"));

  t = get_string_value ("COLUMNS");
  width = (t && *t) ? atoi (t) : 80;
  if (width <= 0)
    width = 80;

  width /= 2;
  if (width > sizeof (blurb))
    width = sizeof (blurb);
  if (width <= 3)
    width = 40;
  height = (num_shell_builtins + 1) / 2;	/* number of rows */

  for (i = 0; i < height; i++)
    {
      QUIT;

      /* first column */
      blurb[0] = (shell_builtins[i].flags & BUILTIN_ENABLED) ? ' ' : '*';
      strncpy (blurb + 1, shell_builtins[i].short_doc, width - 2);
      blurb[width - 2] = '>';		/* indicate truncation */
      blurb[width - 1] = '\0';
      printf ("%s", blurb);
      if (((i << 1) >= num_shell_builtins) || (i+height >= num_shell_builtins))
	{
	  printf ("\n");
	  break;
	}

      /* two spaces */
      for (j = strlen (blurb); j < width; j++)
        putc (' ', stdout);

      /* second column */
      blurb[0] = (shell_builtins[i+height].flags & BUILTIN_ENABLED) ? ' ' : '*';
      strncpy (blurb + 1, shell_builtins[i+height].short_doc, width - 3);
      blurb[width - 3] = '>';		/* indicate truncation */
      blurb[width - 2] = '\0';
      printf ("%s\n", blurb);
    }
}
#endif /* HELP_BUILTIN */