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

Copyright (C) 1987-2025 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 specifying 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 "../bashansi.h"

#include "../bashintl.h"

#include "../shell.h"
#include "../builtins.h"
#include "../execute_cmd.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 (void);
static int open_helpfile (const char *);
static void show_desc (char *, int);
static void show_manpage (char *, int);
static void show_longdoc (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 (WORD_LIST *list)
{
  register int i;
  char *pattern, *name;
  int match_found, sflag, dflag, mflag, m, pass, this_found;
  size_t plen;

  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;
	CASE_HELPOPT;
	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) == 1)
    {
      printf ("%s", ngettext ("Shell commands matching keyword `", "Shell commands matching keywords `", (list->next ? 2 : 1)));
      print_word_list (list, ", ");
      printf ("%s", _("'\n\n"));
    }

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

      for (pass = 1, this_found = 0; pass < 3; pass++)
	{
	  for (i = 0; name = shell_builtins[i].name; i++)
	    {
	      QUIT;

	      /* First pass: look for exact string or pattern matches.
		 Second pass: look for prefix matches like bash-4.2 */
	      if (pass == 1)
	        m = (strcmp (pattern, name) == 0) ||
		    (strmatch (pattern, name, FNMATCH_EXTFLAG) != FNM_NOMATCH);
	      else
		m = strncmp (pattern, name, plen) == 0;

	      if (m)
	        {
	          this_found = 1;
	          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 (pass == 1 && this_found == 1)
	    break;
	}
    }

  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);
    }

  return (sh_chkwrite (EXECUTION_SUCCESS));
}

void
builtin_help (void)
{
  int ind;

  current_builtin = builtin_address_internal (this_command_name, 0);
  if (current_builtin == 0)
    return;

  ind = current_builtin - shell_builtins;
  printf ("%s: %s\n", this_command_name, _(shell_builtins[ind].short_doc));
  show_longdoc (ind);  
}

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

  fd = open (name, O_RDONLY);
  if (fd == -1)
    {
      builtin_error ("%s: %s: %s", name, _("cannot open"), 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 (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 if (doc)
    for (j = 0; doc[j]; j++)
      printf ("%*s%s\n", BASE_INDENT, " ", _(doc[j]));
}

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

  doc = 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;
      r = zmapfd (fd, &line, doc[0]);
      if (r < 0)
	{
	  builtin_error ("%s: %s: %s", doc[0], _("read error"), strerror (errno));
	  free (line);
	  line = (char *)NULL;
	}
      close (fd);
    }
  else
    line = doc ? doc[0] : (char *)NULL;

  printf ("%s - ", name);
  /* Don't assume LINE ends with a newline. */
  for (j = 0; line && line[j] && line[j] != '\n'; j++)
    putchar (line[j]);
  putchar ('\n');
  
  fflush (stdout);

  if (usefile)
    free (line);
}

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

  doc = 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;
      r = zmapfd (fd, &line, doc[0]);
      if (r < 0)
	{
	  builtin_error ("%s: %s: %s", doc[0], _("read error"), strerror (errno));
	  free (line);
	  line = (char *)NULL;
	}
      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;
    }
  /* If the line doesn't end with a newline, e.g., if it's a loadable builtin,
     add one. */
  if (line[j] != '\n')
    putchar ('\n');
  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
dispcolumn (int i, char *buf, size_t bufsize, int width, int height)
{
  int j;
  size_t dispcols;
  char *helpdoc;

  /* first column */
  helpdoc = _(shell_builtins[i].short_doc);

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

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

  /* second column */
  helpdoc = _(shell_builtins[i+height].short_doc);

  buf[0] = (shell_builtins[i+height].flags & BUILTIN_ENABLED) ? ' ' : '*';
  strncpy (buf + 1, helpdoc, width - 3);
  buf[width - 3] = '>';		/* indicate truncation */
  buf[width - 2] = '\0';

  printf ("%s\n", buf);
}

#if defined (HANDLE_MULTIBYTE)
static void
wdispcolumn (int i, char *buf, size_t bufsize, int width, int height)
{
  int j;
  int dispcols, dispchars;
  char *helpdoc;
  wchar_t *wcstr;
  size_t slen, n;

  /* first column */
  helpdoc = _(shell_builtins[i].short_doc);

  wcstr = 0;
  slen = mbstowcs ((wchar_t *)0, helpdoc, 0);
  if (slen == -1)
    {
      dispcolumn (i, buf, bufsize, width, height);
      return;
    }

  /* No bigger than the passed max width */
  if (slen >= width)
    slen = width - 2;
  wcstr = (wchar_t *)xmalloc (sizeof (wchar_t) * (width + 2));
  n = mbstowcs (wcstr+1, helpdoc, slen + 1);
  wcstr[n+1] = L'\0';

  /* Turn tabs and newlines into spaces for column display, since wcwidth
     returns -1 for them */
  for (j = 1; j < n; j++)
    if (wcstr[j] == L'\n' || wcstr[j] == L'\t')
      wcstr[j] = L' ';

  /* dispchars == number of characters that will be displayed */
  dispchars = wcsnwidth (wcstr+1, slen, width - 2);
  /* dispcols == number of columns required to display DISPCHARS */
  dispcols = wcswidth (wcstr+1, dispchars) + 1;	/* +1 for ' ' or '*' */

  wcstr[0] = (shell_builtins[i].flags & BUILTIN_ENABLED) ? L' ' : L'*';

  if (dispcols >= width-2)
    {
      wcstr[dispchars] = L'>';		/* indicate truncation */
      wcstr[dispchars+1] = L'\0';
    }

  printf ("%ls", wcstr);
  if (((i << 1) >= num_shell_builtins) || (i+height >= num_shell_builtins))
    {
      printf ("\n");
      free (wcstr);
      return;
    }

  /* at least one space */
  for (j = dispcols; j < width; j++)
    putc (' ', stdout);

  /* second column */
  helpdoc = _(shell_builtins[i+height].short_doc);
  slen = mbstowcs ((wchar_t *)0, helpdoc, 0);
  if (slen == -1)
    {
      /* for now */
      printf ("%c%s\n", (shell_builtins[i+height].flags & BUILTIN_ENABLED) ? ' ' : '*', helpdoc);
      free (wcstr);
      return;
    }

  /* Reuse wcstr since it is already width wide chars long */
  if (slen >= width)
    slen = width - 2;
  n = mbstowcs (wcstr+1, helpdoc, slen + 1);
  wcstr[n+1] = L'\0';		/* make sure null-terminated */

  /* Turn tabs and newlines into spaces for column display */
  for (j = 1; j < n; j++)
    if (wcstr[j] == L'\n' || wcstr[j] == L'\t')
      wcstr[j] = L' ';

  /* dispchars == number of characters that will be displayed */
  dispchars = wcsnwidth (wcstr+1, slen, width - 2);
  dispcols = wcswidth (wcstr+1, dispchars) + 1;	/* +1 for ' ' or '*' */
  
  wcstr[0] = (shell_builtins[i+height].flags & BUILTIN_ENABLED) ? L' ' : L'*';

  /* The dispchars-1 is there for terminals that behave strangely when you
     have \n in the nth column for terminal width n; this is what bash-4.3
     did. */
  if (dispcols >= width - 2)
    {
      wcstr[dispchars-1] = L'>';		/* indicate truncation */
      wcstr[dispchars] = L'\0';
    }

  printf ("%ls\n", wcstr);

  free (wcstr);
}
#endif /* HANDLE_MULTIBYTE */

static void
show_builtin_command_help (void)
{
  int i;
  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"));

  width = default_columns ();

  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;

#if defined (HANDLE_MULTIBYTE)
      if (MB_CUR_MAX > 1)
	wdispcolumn (i, blurb, sizeof (blurb), width, height);
      else
#endif
	dispcolumn (i, blurb, sizeof (blurb), width, height);
    }
}
#endif /* HELP_BUILTIN */
