Imported from ../bash-2.03.tar.gz.

[platform/upstream/bash.git] / subst.c

/* subst.c -- The part of the shell that does parameter, command, and
   globbing substitutions. */

/* Copyright (C) 1987,1989 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 2, 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. */

#include "config.h"

#include "bashtypes.h"
#include <stdio.h>
#include <pwd.h>
#include <signal.h>
#include <errno.h>

#if defined (HAVE_UNISTD_H)
#  include <unistd.h>
#endif

#include "bashansi.h"
#include "posixstat.h"

#include "shell.h"
#include "flags.h"
#include "jobs.h"
#include "execute_cmd.h"
#include "filecntl.h"
#include "trap.h"
#include "pathexp.h"
#include "mailcheck.h"

#if !defined (HAVE_RESTARTABLE_SYSCALLS)        /* for getc_with_restart */
#include "input.h"
#endif

#include "builtins/getopt.h"
#include "builtins/common.h"

#include <tilde/tilde.h>
#include <glob/fnmatch.h>

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

/* The size that strings change by. */
#define DEFAULT_INITIAL_ARRAY_SIZE 112
#define DEFAULT_ARRAY_SIZE 128

/* Variable types. */
#define VT_VARIABLE     0
#define VT_POSPARMS     1
#define VT_ARRAYVAR     2
#define VT_ARRAYMEMBER  3

/* Flags for quoted_strchr */
#define ST_BACKSL       0x01
#define ST_CTLESC       0x02

/* These defs make it easier to use the editor. */
#define LBRACE          '{'
#define RBRACE          '}'
#define LPAREN          '('
#define RPAREN          ')'

/* Process ID of the last command executed within command substitution. */
pid_t last_command_subst_pid = NO_PID;
pid_t current_command_subst_pid = NO_PID;

/* Extern functions and variables from different files. */
extern int last_command_exit_value, interactive, interactive_shell;
extern int subshell_environment, startup_state;
extern int dollar_dollar_pid;
extern int posixly_correct;
extern char *this_command_name;
extern struct fd_bitmap *current_fds_to_close;
extern int wordexp_only;

extern void getopts_reset ();

/* Non-zero means to allow unmatched globbed filenames to expand to
   a null file. */
int allow_null_glob_expansion;

/* Variables to keep track of which words in an expanded word list (the
   output of expand_word_list_internal) are the result of globbing
   expansions.  GLOB_ARGV_FLAGS is used by execute_cmd.c. */
char *glob_argv_flags;
static int glob_argv_flags_size;

static WORD_LIST expand_word_error, expand_word_fatal;
static char expand_param_error, expand_param_fatal;

static int doing_completion = 0;

static char *make_quoted_char ();
static void remove_quoted_nulls ();
static char *param_expand ();
static char *maybe_expand_string ();
static WORD_LIST *call_expand_word_internal ();
static WORD_LIST *expand_string_internal ();
static WORD_LIST *expand_word_internal (), *expand_word_list_internal ();
static WORD_LIST *expand_string_leave_quoted ();
static WORD_LIST *expand_string_for_rhs ();
static char *getifs ();
static WORD_LIST *word_list_split ();
static WORD_LIST *quote_list (), *dequote_list ();
static char *quote_escapes ();
static WORD_LIST *list_quote_escapes ();
static int unquoted_substring (), unquoted_member ();
static int do_assignment_internal ();
static char *string_extract_verbatim (), *string_extract ();
static char *string_extract_double_quoted (), *string_extract_single_quoted ();
static char *string_list_dollar_at (), *string_list_dollar_star ();
static inline int skip_single_quoted (), skip_double_quoted ();
static char *extract_delimited_string ();
static char *extract_dollar_brace_string ();

/* **************************************************************** */
/*                                                                  */
/*                      Utility Functions                           */
/*                                                                  */
/* **************************************************************** */

/* Cons a new string from STRING starting at START and ending at END,
   not including END. */
char *
substring (string, start, end)
     char *string;
     int start, end;
{
  register int len;
  register char *result;

  len = end - start;
  result = xmalloc (len + 1);
  strncpy (result, string + start, len);
  result[len] = '\0';
  return (result);
}

static char *
quoted_substring (string, start, end)
     char *string;
     int start, end;
{
  register int len, l;
  register char *result, *s, *r;

  len = end - start;

  /* Move to string[start], skipping quoted characters. */
  for (s = string, l = 0; *s && l < start; )
    {
      if (*s == CTLESC)
        {
          s++;
          continue;
        }
      l++;
      if (*s == 0)
        break;
    }

  r = result = xmalloc (2*len + 1);      /* save room for quotes */

  /* Copy LEN characters, including quote characters. */
  s = string + l;
  for (l = 0; l < len; s++)
    {
      if (*s == CTLESC)
        *r++ = *s++;
      *r++ = *s;
      l++;
      if (*s == 0)
        break;
    }
  *r = '\0';
  return result;
}

/* Find the first occurrence of character C in string S, obeying shell
   quoting rules.  If (FLAGS & ST_BACKSL) is non-zero, backslash-escaped
   characters are skipped.  If (FLAGS & ST_CTLESC) is non-zero, characters
   escaped with CTLESC are skipped. */
static inline char *
quoted_strchr (s, c, flags)
     char *s;
     int c, flags;
{
  register char *p;

  for (p = s; *p; p++)
    {
      if (((flags & ST_BACKSL) && *p == '\\')
            || ((flags & ST_CTLESC) && *p == CTLESC))
        {
          p++;
          if (*p == '\0')
            return ((char *)NULL);
          continue;
        }
      else if (*p == c)
        return p;
    }
  return ((char *)NULL);
}

/* Return 1 if CHARACTER appears in an unquoted portion of
   STRING.  Return 0 otherwise. */
static int
unquoted_member (character, string)
     int character;
     char *string;
{
  int sindex, c;

  for (sindex = 0; c = string[sindex]; )
    {
      if (c == character)
        return (1);

      switch (c)
        {
        default:
          sindex++;
          break;

        case '\\':
          sindex++;
          if (string[sindex])
            sindex++;
          break;

        case '\'':
          sindex = skip_single_quoted (string, ++sindex);
          break;

        case '"':
          sindex = skip_double_quoted (string, ++sindex);
          break;
        }
    }
  return (0);
}

/* Return 1 if SUBSTR appears in an unquoted portion of STRING. */
static int
unquoted_substring (substr, string)
     char *substr, *string;
{
  int sindex, c, sublen;

  if (substr == 0 || *substr == '\0')
    return (0);

  sublen = strlen (substr);
  for (sindex = 0; c = string[sindex]; )
    {
      if (STREQN (string + sindex, substr, sublen))
        return (1);

      switch (c)
        {
        case '\\':
          sindex++;

          if (string[sindex])
            sindex++;
          break;

        case '\'':
          sindex = skip_single_quoted (string, ++sindex);
          break;

        case '"':
          sindex = skip_double_quoted (string, ++sindex);
          break;

        default:
          sindex++;
          break;
        }
    }
  return (0);
}

/* Most of the substitutions must be done in parallel.  In order
   to avoid using tons of unclear goto's, I have some functions
   for manipulating malloc'ed strings.  They all take INDX, a
   pointer to an integer which is the offset into the string
   where manipulation is taking place.  They also take SIZE, a
   pointer to an integer which is the current length of the
   character array for this string. */

/* Append SOURCE to TARGET at INDEX.  SIZE is the current amount
   of space allocated to TARGET.  SOURCE can be NULL, in which
   case nothing happens.  Gets rid of SOURCE by freeing it.
   Returns TARGET in case the location has changed. */
inline char *
sub_append_string (source, target, indx, size)
     char *source, *target;
     int *indx, *size;
{
  if (source)
    {
      int srclen, n;

      srclen = STRLEN (source);
      if (srclen >= (int)(*size - *indx))
        {
          n = srclen + *indx;
          n = (n + DEFAULT_ARRAY_SIZE) - (n % DEFAULT_ARRAY_SIZE);
          target = xrealloc (target, (*size = n));
        }

      FASTCOPY (source, target + *indx, srclen);
      *indx += srclen;
      target[*indx] = '\0';

      free (source);
    }
  return (target);
}

#if 0
/* UNUSED */
/* Append the textual representation of NUMBER to TARGET.
   INDX and SIZE are as in SUB_APPEND_STRING. */
char *
sub_append_number (number, target, indx, size)
     int number, *indx, *size;
     char *target;
{
  char *temp;

  temp = itos (number);
  return (sub_append_string (temp, target, indx, size));
}
#endif

/* Extract a substring from STRING, starting at SINDEX and ending with
   one of the characters in CHARLIST.  Don't make the ending character
   part of the string.  Leave SINDEX pointing at the ending character.
   Understand about backslashes in the string.  If VARNAME is non-zero,
   and array variables have been compiled into the shell, everything
   between a `[' and a corresponding `]' is skipped over. */
static char *
string_extract (string, sindex, charlist, varname)
     char *string, *charlist;
     int *sindex, varname;
{
  register int c, i;
  char *temp;

  for (i = *sindex; c = string[i]; i++)
    {
      if (c == '\\')
        if (string[i + 1])
          i++;
        else
          break;
#if defined (ARRAY_VARS)
      else if (varname && c == '[')
        {
          int ni;
          /* If this is an array subscript, skip over it and continue. */
          ni = skipsubscript (string, i);
          if (string[ni] == ']')
            i = ni;
        }
#endif
      else if (MEMBER (c, charlist))
          break;
    }
  c = i - *sindex;
  temp = xmalloc (1 + c);
  strncpy (temp, string + *sindex, c);
  temp[c] = '\0';
  *sindex = i;
  return (temp);
}

/* Extract the contents of STRING as if it is enclosed in double quotes.
   SINDEX, when passed in, is the offset of the character immediately
   following the opening double quote; on exit, SINDEX is left pointing after
   the closing double quote.  If STRIPDQ is non-zero, unquoted double
   quotes are stripped and the string is terminated by a null byte.
   Backslashes between the embedded double quotes are processed.  If STRIPDQ
   is zero, an unquoted `"' terminates the string. */
static inline char *
string_extract_double_quoted (string, sindex, stripdq)
     char *string;
     int *sindex, stripdq;
{
  int c, j, i, t;
  char *temp, *ret;             /* The new string we return. */
  int pass_next, backquote, si; /* State variables for the machine. */
  int dquote;

  pass_next = backquote = dquote = 0;
  temp = xmalloc (1 + strlen (string) - *sindex);

  for (j = 0, i = *sindex; c = string[i]; i++)
    {
      /* Process a character that was quoted by a backslash. */
      if (pass_next)
        {
          /* Posix.2 sez:

             ``The backslash shall retain its special meaning as an escape
             character only when followed by one of the characters:
                $       `       "       \       <newline>''.

             If STRIPDQ is zero, we handle the double quotes here and let
             expand_word_internal handle the rest.  If STRIPDQ is non-zero,
             we have already been through one round of backslash stripping,
             and want to strip these backslashes only if DQUOTE is non-zero,
             indicating that we are inside an embedded double-quoted string. */

             /* If we are in an embedded quoted string, then don't strip
                backslashes before characters for which the backslash
                retains its special meaning, but remove backslashes in
                front of other characters.  If we are not in an
                embedded quoted string, don't strip backslashes at all.
                This mess is necessary because the string was already
                surrounded by double quotes (and sh has some really weird
                quoting rules).
                The returned string will be run through expansion as if
                it were double-quoted. */
          if ((stripdq == 0 && c != '"') ||
              (stripdq && ((dquote && strchr (slashify_in_quotes, c)) || dquote == 0)))
            temp[j++] = '\\';
          temp[j++] = c;
          pass_next = 0;
          continue;
        }

      /* A backslash protects the next character.  The code just above
         handles preserving the backslash in front of any character but
         a double quote. */
      if (c == '\\')
        {
          pass_next++;
          continue;
        }

      /* Inside backquotes, ``the portion of the quoted string from the
         initial backquote and the characters up to the next backquote
         that is not preceded by a backslash, having escape characters
         removed, defines that command''. */
      if (backquote)
        {
          if (c == '`')
            backquote = 0;
          temp[j++] = c;
          continue;
        }

      if (c == '`')
        {
          temp[j++] = c;
          backquote++;
          continue;
        }

      /* Pass everything between `$(' and the matching `)' or a quoted
         ${ ... } pair through according to the Posix.2 specification. */
      if (c == '$' && ((string[i + 1] == LPAREN) || (string[i + 1] == LBRACE)))
        {
          si = i + 2;
          if (string[i + 1] == LPAREN)
            ret = extract_delimited_string (string, &si, "$(", "(", ")"); /*)*/
          else
            ret = extract_dollar_brace_string (string, &si, 1);

          temp[j++] = '$';
          temp[j++] = string[i + 1];

          for (t = 0; ret[t]; t++, j++)
            temp[j] = ret[t];
          temp[j++] = string[si];

          i = si;
          free (ret);
          continue;
        }

      /* Add any character but a double quote to the quoted string we're
         accumulating. */
      if (c != '"')
        {
          temp[j++] = c;
          continue;
        }

      /* c == '"' */
      if (stripdq)
        {
          dquote ^= 1;
          continue;
        }

      break;
    }
  temp[j] = '\0';

  /* Point to after the closing quote. */
  if (c)
    i++;
  *sindex = i;

  return (temp);
}

/* This should really be another option to string_extract_double_quoted. */
static inline int
skip_double_quoted (string, sind)
     char *string;
     int sind;
{
  int c, j, i;
  char *ret;
  int pass_next, backquote, si;

  pass_next = backquote = 0;

  for (j = 0, i = sind; c = string[i]; i++)
    {
      if (pass_next)
        {
          pass_next = 0;
          continue;
        }
      else if (c == '\\')
        {
          pass_next++;
          continue;
        }
      else if (backquote)
        {
          if (c == '`')
            backquote = 0;
          continue;
        }
      else if (c == '`')
        {
          backquote++;
          continue;
        }
      else if (c == '$' && ((string[i + 1] == LPAREN) || (string[i + 1] == LBRACE)))
        {
          si = i + 2;
          if (string[i + 1] == LPAREN)
            ret = extract_delimited_string (string, &si, "$(", "(", ")");
          else
            ret = extract_dollar_brace_string (string, &si, 0);

          i = si;
          free (ret);
          continue;
        }
      else if (c != '"')
        continue;
      else
        break;
    }

  if (c)
    i++;

  return (i);
}

/* Extract the contents of STRING as if it is enclosed in single quotes.
   SINDEX, when passed in, is the offset of the character immediately
   following the opening single quote; on exit, SINDEX is left pointing after
   the closing single quote. */
static inline char *
string_extract_single_quoted (string, sindex)
     char *string;
     int *sindex;
{
  register int i, j;
  char *t;

  for (i = *sindex; string[i] && string[i] != '\''; i++)
    ;

  j = i - *sindex;
  t = xmalloc (1 + j);
  strncpy (t, string + *sindex, j);
  t[j] = '\0';

  if (string[i])
    i++;
  *sindex = i;

  return (t);
}

static inline int
skip_single_quoted (string, sind)
     char *string;
     int sind;
{
  register int i;

  for (i = sind; string[i] && string[i] != '\''; i++)
    ;
  if (string[i])
    i++;
  return i;
}

/* Just like string_extract, but doesn't hack backslashes or any of
   that other stuff.  Obeys quoting.  Used to do splitting on $IFS. */
static char *
string_extract_verbatim (string, sindex, charlist)
     char *string, *charlist;
     int *sindex;
{
  register int i = *sindex;
  int c;
  char *temp;

  if (charlist[0] == '\'' && charlist[1] == '\0')
    {
      temp = string_extract_single_quoted (string, sindex);
      --*sindex;        /* leave *sindex at separator character */
      return temp;
    }

  for (i = *sindex; c = string[i]; i++)
    {
      if (c == CTLESC)
        {
          i++;
          continue;
        }

      if (MEMBER (c, charlist))
        break;
    }

  c = i - *sindex;
  temp = xmalloc (1 + c);
  strncpy (temp, string + *sindex, c);
  temp[c] = '\0';
  *sindex = i;

  return (temp);
}

/* Extract the $( construct in STRING, and return a new string.
   Start extracting at (SINDEX) as if we had just seen "$(".
   Make (SINDEX) get the position of the matching ")". */
char *
extract_command_subst (string, sindex)
     char *string;
     int *sindex;
{
  return (extract_delimited_string (string, sindex, "$(", "(", ")"));
}

/* Extract the $[ construct in STRING, and return a new string.
   Start extracting at (SINDEX) as if we had just seen "$[".
   Make (SINDEX) get the position of the matching "]". */
char *
extract_arithmetic_subst (string, sindex)
     char *string;
     int *sindex;
{
  return (extract_delimited_string (string, sindex, "$[", "[", "]"));
}

#if defined (PROCESS_SUBSTITUTION)
/* Extract the <( or >( construct in STRING, and return a new string.
   Start extracting at (SINDEX) as if we had just seen "<(".
   Make (SINDEX) get the position of the matching ")". */ /*))*/
char *
extract_process_subst (string, starter, sindex)
     char *string;
     char *starter;
     int *sindex;
{
  return (extract_delimited_string (string, sindex, starter, "(", ")"));
}
#endif /* PROCESS_SUBSTITUTION */

#if defined (ARRAY_VARS)
char *
extract_array_assignment_list (string, sindex)
     char *string;
     int *sindex;
{
  return (extract_delimited_string (string, sindex, "(", (char *)NULL, ")"));
}
#endif

/* Extract and create a new string from the contents of STRING, a
   character string delimited with OPENER and CLOSER.  SINDEX is
   the address of an int describing the current offset in STRING;
   it should point to just after the first OPENER found.  On exit,
   SINDEX gets the position of the last character of the matching CLOSER.
   If OPENER is more than a single character, ALT_OPENER, if non-null,
   contains a character string that can also match CLOSER and thus
   needs to be skipped. */
static char *
extract_delimited_string (string, sindex, opener, alt_opener, closer)
     char *string;
     int *sindex;
     char *opener, *alt_opener, *closer;
{
  int i, c, si;
  char *t, *result;
  int pass_character, nesting_level;
  int len_closer, len_opener, len_alt_opener;

  len_opener = STRLEN (opener);
  len_alt_opener = STRLEN (alt_opener);
  len_closer = STRLEN (closer);

  pass_character = 0;

  nesting_level = 1;
  i = *sindex;

  while (nesting_level)
    {
      c = string[i];

      if (c == 0)
        break;

      if (pass_character)       /* previous char was backslash */
        {
          pass_character = 0;
          i++;
          continue;
        }

      if (c == CTLESC)
        {
          pass_character++;
          i++;
          continue;
        }

#if 0
      if (c == '\\' && delimiter == '"' &&
              (member (string[i], slashify_in_quotes)))
#else
      if (c == '\\')
#endif
        {
          pass_character++;
          i++;
          continue;
        }

      /* Process a nested OPENER. */
      if (STREQN (string + i, opener, len_opener))
        {
          si = i + len_opener;
          t = extract_delimited_string (string, &si, opener, alt_opener, closer);
          i = si + 1;
          FREE (t);
          continue;
        }

      /* Process a nested ALT_OPENER */
      if (len_alt_opener && STREQN (string + i, alt_opener, len_alt_opener))
        {
          si = i + len_alt_opener;
          t = extract_delimited_string (string, &si, alt_opener, alt_opener, closer);
          i = si + 1;
          FREE (t);
          continue;
        }

      /* If the current substring terminates the delimited string, decrement
         the nesting level. */
      if (STREQN (string + i, closer, len_closer))
        {
          i += len_closer - 1;  /* move to last char of the closer */
          nesting_level--;
          if (nesting_level == 0)
            break;
        }

      /* Pass old-style command substitution through verbatim. */
      if (c == '`')
        {
          si = i + 1;
          t = string_extract (string, &si, "`", 0);
          i = si + 1;
          FREE (t);
          continue;
        }

      /* Pass single-quoted strings through verbatim. */
      if (c == '\'')
        {
          si = i + 1;
          i = skip_single_quoted (string, si);
          continue;
        }

      /* Pass embedded double-quoted strings through verbatim as well. */
      if (c == '"')
        {
          si = i + 1;
          i = skip_double_quoted (string, si);
          continue;
        }

      i++;      /* move past this character, which was not special. */
    }

  if (c == 0 && nesting_level)
    {
      report_error ("bad substitution: no `%s' in %s", closer, string);
      jump_to_top_level (DISCARD);
    }

  si = i - *sindex - len_closer + 1;
  result = xmalloc (1 + si);
  strncpy (result, string + *sindex, si);
  result[si] = '\0';
  *sindex = i;

  return (result);
}

/* Extract a parameter expansion expression within ${ and } from STRING.
   Obey the Posix.2 rules for finding the ending `}': count braces while
   skipping over enclosed quoted strings and command substitutions.
   SINDEX is the address of an int describing the current offset in STRING;
   it should point to just after the first `{' found.  On exit, SINDEX
   gets the position of the matching `}'.  QUOTED is non-zero if this
   occurs inside double quotes. */
/* XXX -- this is very similar to extract_delimited_string -- XXX */
static char *
extract_dollar_brace_string (string, sindex, quoted)
     char *string;
     int *sindex, quoted;
{
  register int i, c, l;
  int pass_character, nesting_level, si;
  char *result, *t;

  pass_character = 0;

  nesting_level = 1;

  for (i = *sindex; (c = string[i]); i++)
    {
      if (pass_character)
        {
          pass_character = 0;
          continue;
        }

      /* CTLESCs and backslashes quote the next character. */
      if (c == CTLESC || c == '\\')
        {
          pass_character++;
          continue;
        }

      if (string[i] == '$' && string[i+1] == LBRACE)
        {
          nesting_level++;
          i++;
          continue;
        }

      if (c == RBRACE)
        {
          nesting_level--;
          if (nesting_level == 0)
            break;
          continue;
        }

      /* Pass the contents of old-style command substitutions through
         verbatim. */
      if (c == '`')
        {
          si = i + 1;
          t = string_extract (string, &si, "`", 0);
          i = si;
          free (t);
          continue;
        }

      /* Pass the contents of new-style command substitutions and
         arithmetic substitutions through verbatim. */
      if (string[i] == '$' && string[i+1] == LPAREN)
        {
          si = i + 2;
          t = extract_delimited_string (string, &si, "$(", "(", ")"); /*)*/
          i = si;
          free (t);
          continue;
        }

      /* Pass the contents of single-quoted and double-quoted strings
         through verbatim. */
      if (c == '\'' || c == '"')
        {
          si = i + 1;
          i = (c == '\'') ? skip_single_quoted (string, si)
                          : skip_double_quoted (string, si);
          /* skip_XXX_quoted leaves index one past close quote */
          i--;
          continue;
        }
    }

  if (c == 0 && nesting_level && doing_completion == 0)
    {
      report_error ("bad substitution: no ending `}' in %s", string);
      jump_to_top_level (DISCARD);
    }

  l = i - *sindex;
  result = xmalloc (1 + l);
  strncpy (result, string + *sindex, l);
  result[l] = '\0';
  *sindex = i;

  return (result);
}

/* Remove backslashes which are quoting backquotes from STRING.  Modifies
   STRING, and returns a pointer to it. */
char *
de_backslash (string)
     char *string;
{
  register int i, l;

  for (i = 0, l = strlen (string); i < l; i++)
    if (string[i] == '\\' && (string[i + 1] == '`' || string[i + 1] == '\\' ||
                              string[i + 1] == '$'))
      strcpy (string + i, string + i + 1);      /* XXX - should be memmove */
  return (string);
}

#if 0
/*UNUSED*/
/* Replace instances of \! in a string with !. */
void
unquote_bang (string)
     char *string;
{
  register int i, j;
  register char *temp;

  temp = xmalloc (1 + strlen (string));

  for (i = 0, j = 0; (temp[j] = string[i]); i++, j++)
    {
      if (string[i] == '\\' && string[i + 1] == '!')
        {
          temp[j] = '!';
          i++;
        }
    }
  strcpy (string, temp);
  free (temp);
}
#endif

#if defined (READLINE)
/* Return 1 if the portion of STRING ending at EINDEX is quoted (there is
   an unclosed quoted string), or if the character at EINDEX is quoted
   by a backslash. DOING_COMPLETION is used to flag that the various
   single and double-quoted string parsing functions should not return an
   error if there are unclosed quotes or braces. */

#define CQ_RETURN(x) do { doing_completion = 0; return (x); } while (0)

int
char_is_quoted (string, eindex)
     char *string;
     int eindex;
{
  int i, pass_next, quoted;

  doing_completion = 1;
  for (i = pass_next = quoted = 0; i <= eindex; i++)
    {
      if (pass_next)
        {
          pass_next = 0;
          if (i >= eindex)      /* XXX was if (i >= eindex - 1) */
            CQ_RETURN(1);
          continue;
        }
      else if (string[i] == '\'' || string[i] == '"')
        {
          i = (string[i] == '\'') ? skip_single_quoted (string, ++i)
                                  : skip_double_quoted (string, ++i);
          if (i > eindex)
            CQ_RETURN(1);
          i--;  /* the skip functions increment past the closing quote. */
        }
      else if (string[i] == '\\')
        {
          pass_next = 1;
          continue;
        }
    }
  CQ_RETURN(0);
}

int
unclosed_pair (string, eindex, openstr)
     char *string;
     int eindex;
     char *openstr;
{
  int i, pass_next, openc, olen;

  olen = strlen (openstr);
  for (i = pass_next = openc = 0; i <= eindex; i++)
    {
      if (pass_next)
        {
          pass_next = 0;
          if (i >= eindex)      /* XXX was if (i >= eindex - 1) */
            return 0;
          continue;
        }
      else if (STREQN (string + i, openstr, olen))
        {
          openc = 1 - openc;
          i += olen - 1;
        }
      else if (string[i] == '\'' || string[i] == '"')
        {
          i = (string[i] == '\'') ? skip_single_quoted (string, i)
                                  : skip_double_quoted (string, i);
          if (i > eindex)
            return 0;
        }
      else if (string[i] == '\\')
        {
          pass_next = 1;
          continue;
        }
    }
  return (openc);
}
#endif /* READLINE */

#if 0
/* UNUSED */
/* Extract the name of the variable to bind to from the assignment string. */
char *
assignment_name (string)
     char *string;
{
  int offset;
  char *temp;

  offset = assignment (string);
  if (offset == 0)
    return (char *)NULL;
  temp = xmalloc (offset + 1);
  strncpy (temp, string, offset);
  temp[offset] = '\0';
  return (temp);
}
#endif

/* **************************************************************** */
/*                                                                  */
/*     Functions to convert strings to WORD_LISTs and vice versa    */
/*                                                                  */
/* **************************************************************** */

/* Return a single string of all the words in LIST.  SEP is the separator
   to put between individual elements of LIST in the output string. */
static char *
string_list_internal (list, sep)
     WORD_LIST *list;
     char *sep;
{
  register WORD_LIST *t;
  char *result, *r;
  int word_len, sep_len, result_size;

  if (list == 0)
    return ((char *)NULL);

  /* This is nearly always called with either sep[0] == 0 or sep[1] == 0. */
  sep_len = STRLEN (sep);
  result_size = 0;

  for (t = list; t; t = t->next)
    {
      if (t != list)
        result_size += sep_len;
      result_size += strlen (t->word->word);
    }

  r = result = xmalloc (result_size + 1);

  for (t = list; t; t = t->next)
    {
      if (t != list && sep_len)
        {
          if (sep_len > 1)
            {
              FASTCOPY (sep, r, sep_len);
              r += sep_len;
            }
          else
            *r++ = sep[0];
        }

      word_len = strlen (t->word->word);
      FASTCOPY (t->word->word, r, word_len);
      r += word_len;
    }

  *r = '\0';
  return (result);
}

/* Return a single string of all the words present in LIST, separating
   each word with a space. */
char *
string_list (list)
     WORD_LIST *list;
{
  return (string_list_internal (list, " "));
}

/* Return a single string of all the words present in LIST, obeying the
   quoting rules for "$*", to wit: (P1003.2, draft 11, 3.5.2) "If the
   expansion [of $*] appears within a double quoted string, it expands
   to a single field with the value of each parameter separated by the
   first character of the IFS variable, or by a <space> if IFS is unset." */
static char *
string_list_dollar_star (list)
     WORD_LIST *list;
{
  char *ifs, sep[2];

  ifs = get_string_value ("IFS");

  sep[0] = (ifs == 0) ? ' ' : *ifs;
  sep[1] = '\0';

  return (string_list_internal (list, sep));
}

/* Turn $@ into a string.  If (quoted & (Q_HERE_DOCUMENT|Q_DOUBLE_QUOTES))
   is non-zero, the $@ appears within double quotes, and we should quote
   the list before converting it into a string.  If IFS is unset, and the
   word is not quoted, we just need to quote CTLESC and CTLNUL characters
   in the words in the list, because the default value of $IFS is
   <space><tab><newline>, IFS characters in the words in the list should
   also be split.  If IFS is null, and the word is not quoted, we need
   to quote the words in the list to preserve the positional parameters
   exactly. */
static char *
string_list_dollar_at (list, quoted)
     WORD_LIST *list;
     int quoted;
{
  char *ifs, sep[2];
  WORD_LIST *tlist;

  ifs = get_string_value ("IFS");

  sep[0] = (ifs == 0 || *ifs == 0) ? ' ' : *ifs;
  sep[1] = '\0';

  tlist = ((quoted & (Q_HERE_DOCUMENT|Q_DOUBLE_QUOTES)) || (ifs && *ifs == 0))
                ? quote_list (list)
                : list_quote_escapes (list);
  return (string_list_internal (tlist, sep));
}

/* Return the list of words present in STRING.  Separate the string into
   words at any of the characters found in SEPARATORS.  If QUOTED is
   non-zero then word in the list will have its quoted flag set, otherwise
   the quoted flag is left as make_word () deemed fit.

   This obeys the P1003.2 word splitting semantics.  If `separators' is
   exactly <space><tab><newline>, then the splitting algorithm is that of
   the Bourne shell, which treats any sequence of characters from `separators'
   as a delimiter.  If IFS is unset, which results in `separators' being set
   to "", no splitting occurs.  If separators has some other value, the
   following rules are applied (`IFS white space' means zero or more
   occurrences of <space>, <tab>, or <newline>, as long as those characters
   are in `separators'):

        1) IFS white space is ignored at the start and the end of the
           string.
        2) Each occurrence of a character in `separators' that is not
           IFS white space, along with any adjacent occurrences of
           IFS white space delimits a field.
        3) Any nonzero-length sequence of IFS white space delimits a field.
   */

/* BEWARE!  list_string strips null arguments.  Don't call it twice and
   expect to have "" preserved! */

/* This performs word splitting and quoted null character removal on
   STRING. */
#define issep(c)        (member ((c), separators))

WORD_LIST *
list_string (string, separators, quoted)
     register char *string, *separators;
     int quoted;
{
  WORD_LIST *result;
  WORD_DESC *t;
  char *current_word, *s;
  int sindex, sh_style_split;

  if (!string || !*string)
    return ((WORD_LIST *)NULL);

  sh_style_split =
    separators && *separators && (STREQ (separators, " \t\n"));

  /* Remove sequences of whitespace at the beginning of STRING, as
     long as those characters appear in IFS.  Do not do this if
     STRING is quoted or if there are no separator characters. */
  if (!quoted || !separators || !*separators)
    {
      for (s = string; *s && spctabnl (*s) && issep (*s); s++);

      if (!*s)
        return ((WORD_LIST *)NULL);

      string = s;
    }

  /* OK, now STRING points to a word that does not begin with white space.
     The splitting algorithm is:
        extract a word, stopping at a separator
        skip sequences of spc, tab, or nl as long as they are separators
     This obeys the field splitting rules in Posix.2. */
  for (result = (WORD_LIST *)NULL, sindex = 0; string[sindex]; )
    {
      current_word = string_extract_verbatim (string, &sindex, separators);
      if (current_word == 0)
        break;

      /* If we have a quoted empty string, add a quoted null argument.  We
         want to preserve the quoted null character iff this is a quoted
         empty string; otherwise the quoted null characters are removed
         below. */
      if (QUOTED_NULL (current_word))
        {
          t = make_bare_word ("");
          t->flags |= W_QUOTED;
          free (t->word);
          t->word = make_quoted_char ('\0');
          result = make_word_list (t, result);
        }
      else if (current_word[0] != '\0')
        {
          /* If we have something, then add it regardless.  However,
             perform quoted null character removal on the current word. */
          remove_quoted_nulls (current_word);
#if 0
          result = make_word_list (make_word (current_word), result);
#else
          result = add_string_to_list (current_word, result);
#endif    
          if (quoted & (Q_DOUBLE_QUOTES|Q_HERE_DOCUMENT))
            result->word->flags |= W_QUOTED;
        }

      /* If we're not doing sequences of separators in the traditional
         Bourne shell style, then add a quoted null argument. */
      else if (!sh_style_split && !spctabnl (string[sindex]))
        {
          t = make_bare_word ("");
          t->flags |= W_QUOTED;
          free (t->word);
          t->word = make_quoted_char ('\0');
          result = make_word_list (t, result);
        }

      free (current_word);

      /* Move past the current separator character. */
      if (string[sindex])
        sindex++;

      /* Now skip sequences of space, tab, or newline characters if they are
         in the list of separators. */
      while (string[sindex] && spctabnl (string[sindex]) && issep (string[sindex]))
        sindex++;
    }
  return (REVERSE_LIST (result, WORD_LIST *));
}

/* Parse a single word from STRING, using SEPARATORS to separate fields.
   ENDPTR is set to the first character after the word.  This is used by
   the `read' builtin.
   XXX - this function is very similar to list_string; they should be
         combined - XXX */
char *
get_word_from_string (stringp, separators, endptr)
     char **stringp, *separators, **endptr;
{
  register char *s;
  char *current_word;
  int sindex, sh_style_split;

  if (!stringp || !*stringp || !**stringp)
    return ((char *)NULL);

  s = *stringp;

  sh_style_split =
    separators && *separators && (STREQ (separators, " \t\n"));

  /* Remove sequences of whitespace at the beginning of STRING, as
     long as those characters appear in IFS. */
  if (sh_style_split || !separators || !*separators)
    {
      for (; *s && spctabnl (*s) && issep (*s); s++);

      /* If the string is nothing but whitespace, update it and return. */
      if (!*s)
        {
          *stringp = s;
          if (endptr)
            *endptr = s;
          return ((char *)NULL);
        }
    }

  /* OK, S points to a word that does not begin with white space.
     Now extract a word, stopping at a separator, save a pointer to
     the first character after the word, then skip sequences of spc,
     tab, or nl as long as they are separators.

     This obeys the field splitting rules in Posix.2. */
  sindex = 0;
  current_word = string_extract_verbatim (s, &sindex, separators);

  /* Set ENDPTR to the first character after the end of the word. */
  if (endptr)
    *endptr = s + sindex;

  /* Move past the current separator character. */
  if (s[sindex])
    sindex++;

  /* Now skip sequences of space, tab, or newline characters if they are
     in the list of separators. */
  while (s[sindex] && spctabnl (s[sindex]) && issep (s[sindex]))
    sindex++;

  /* Update STRING to point to the next field. */
  *stringp = s + sindex;
  return (current_word);
}

/* Remove IFS white space at the end of STRING.  Start at the end
   of the string and walk backwards until the beginning of the string
   or we find a character that's not IFS white space and not CTLESC.
   Only let CTLESC escape a white space character if SAW_ESCAPE is
   non-zero.  */
char *
strip_trailing_ifs_whitespace (string, separators, saw_escape)
     char *string, *separators;
     int saw_escape;
{
  char *s;

  s = string + STRLEN (string) - 1;
  while (s > string && ((spctabnl (*s) && issep (*s)) ||
                        (saw_escape && *s == CTLESC && spctabnl (s[1]))))
    s--;
  *++s = '\0';
  return string;
}

#if defined (ARRAY_VARS)
WORD_LIST *
list_string_with_quotes (string)
     char *string;
{
  WORD_LIST *list;
  char *token, *s;
  int c, i, tokstart, len;

  for (s = string; s && *s && spctabnl (*s); s++)
    ;
  if (s == 0 || *s == 0)
    return ((WORD_LIST *)NULL);

  tokstart = i = 0;
  list = (WORD_LIST *)NULL;
  while (1)
    {
      c = s[i];
      if (c == '\\')
        {
          i++;
          if (s[i])
            i++;
        }
      else if (c == '\'')
        i = skip_single_quoted (s, ++i);
      else if (c == '"')
        i = skip_double_quoted (s, ++i);
      else if (c == 0 || spctabnl (c))
        {
          /* We have found the end of a token.  Make a word out of it and
             add it to the word list. */
          len = i - tokstart;
          token = xmalloc (len + 1);
          strncpy (token, s + tokstart, len);
          token[len] = '\0';
#if 0
          list = make_word_list (make_word (token), list);
#else
          list = add_string_to_list (token, list);
#endif
          free (token);
          while (spctabnl (s[i]))
            i++;
          if (s[i])
            tokstart = i;
          else
            break;
        }
      else
        i++;    /* normal character */
    }
  return (REVERSE_LIST (list, WORD_LIST *));
}
#endif /* ARRAY_VARS */

/********************************************************/
/*                                                      */
/*      Functions to perform assignment statements      */
/*                                                      */
/********************************************************/

#if defined (ARRAY_VARS)
SHELL_VAR *
do_array_element_assignment (name, value)
     char *name, *value;
{
  char *t;
  int ind, ni;
  SHELL_VAR *entry;

  t = strchr (name, '[');
  if (t == 0)
    return ((SHELL_VAR *)NULL);
  ind = t - name;
  ni = skipsubscript (name, ind);
  if ((ALL_ELEMENT_SUB (t[1]) && t[2] == ']') || (ni <= ind + 1))
    {
      report_error ("%s: bad array subscript", name);
      return ((SHELL_VAR *)NULL);
    }
  *t++ = '\0';
  ind = array_expand_index (t, ni - ind);
  if (ind < 0)
    {
      t[-1] = '[';              /* restore original name */
      report_error ("%s: bad array subscript", name);
      return ((SHELL_VAR *)NULL);
    }
  entry = bind_array_variable (name, ind, value);
  t[-1] = '[';          /* restore original name */
  return (entry);
}
#endif /* ARRAY_VARS */

/* Given STRING, an assignment string, get the value of the right side
   of the `=', and bind it to the left side.  If EXPAND is true, then
   perform parameter expansion, command substitution, and arithmetic
   expansion on the right-hand side.  Perform tilde expansion in any
   case.  Do not perform word splitting on the result of expansion. */
static int
do_assignment_internal (string, expand)
     char *string;
     int expand;
{
  int offset;
  char *name, *value;
  SHELL_VAR *entry;
#if defined (ARRAY_VARS)
  char *t;
  int ni, assign_list = 0;
#endif

  offset = assignment (string);
  name = savestring (string);
  value = (char *)NULL;

  if (name[offset] == '=')
    {
      char *temp;

      name[offset] = 0;
      temp = name + offset + 1;

#if defined (ARRAY_VARS)
      if (expand && temp[0] == LPAREN && strchr (temp, RPAREN))
        {
          assign_list = ni = 1;
          value = extract_delimited_string (temp, &ni, "(", (char *)NULL, ")");
        }
      else
#endif

      /* Perform tilde expansion. */
      if (expand && temp[0])
        {
          temp = (strchr (temp, '~') && unquoted_member ('~', temp))
                        ? bash_tilde_expand (temp)
                        : savestring (temp);

          value = maybe_expand_string (temp, 0, expand_string_unsplit);
          free (temp);
        }
      else
        value = savestring (temp);
    }

  if (value == 0)
    {
      value = xmalloc (1);
      value[0] = '\0';
    }

  if (echo_command_at_execute)
#if defined (ARRAY_VARS)
    if (assign_list)
      fprintf (stderr, "%s%s=(%s)\n", indirection_level_string (), name, value);
    else
#endif
    fprintf (stderr, "%s%s=%s\n", indirection_level_string (), name, value);

#define ASSIGN_RETURN(r)        do { FREE (value); free (name); return (r); } while (0)

#if defined (ARRAY_VARS)
  if (t = strchr (name, '['))
    {
      if (assign_list)
        {
          report_error ("%s: cannot assign list to array member", name);
          ASSIGN_RETURN (0);
        }
      entry = do_array_element_assignment (name, value);
      if (entry == 0)
        ASSIGN_RETURN (0);
    }
  else if (assign_list)
    entry = assign_array_from_string (name, value);
  else
#endif /* ARRAY_VARS */
  entry = bind_variable (name, value);

  stupidly_hack_special_variables (name);

  if (entry)
    entry->attributes &= ~att_invisible;

  /* Return 1 if the assignment seems to have been performed correctly. */
  ASSIGN_RETURN (entry ? ((entry->attributes & att_readonly) == 0) : 0);
}

/* Perform the assignment statement in STRING, and expand the
   right side by doing command and parameter expansion. */
int
do_assignment (string)
     char *string;
{
  return do_assignment_internal (string, 1);
}

/* Given STRING, an assignment string, get the value of the right side
   of the `=', and bind it to the left side.  Do not do command and
   parameter substitution on the right hand side. */
int
do_assignment_no_expand (string)
     char *string;
{
  return do_assignment_internal (string, 0);
}

/***************************************************
 *                                                 *
 *  Functions to manage the positional parameters  *
 *                                                 *
 ***************************************************/

/* Return the word list that corresponds to `$*'. */
WORD_LIST *
list_rest_of_args ()
{
  register WORD_LIST *list, *args;
  int i;

  /* Break out of the loop as soon as one of the dollar variables is null. */
  for (i = 1, list = (WORD_LIST *)NULL; i < 10 && dollar_vars[i]; i++)
    list = make_word_list (make_bare_word (dollar_vars[i]), list);

  for (args = rest_of_args; args; args = args->next)
    list = make_word_list (make_bare_word (args->word->word), list);

  return (REVERSE_LIST (list, WORD_LIST *));
}

int
number_of_args ()
{
  register WORD_LIST *list;
  int n;

  for (n = 0; n < 9 && dollar_vars[n+1]; n++)
    ;
  for (list = rest_of_args; list; list = list->next)
    n++;
  return n;
}

/* Return the value of a positional parameter.  This handles values > 10. */
char *
get_dollar_var_value (ind)
     int ind;
{
  char *temp;
  WORD_LIST *p;

  if (ind < 10)
    temp = dollar_vars[ind] ? savestring (dollar_vars[ind]) : (char *)NULL;
  else  /* We want something like ${11} */
    {
      ind -= 10;
      for (p = rest_of_args; p && ind--; p = p->next)
        ;
      temp = p ? savestring (p->word->word) : (char *)NULL;
    }
  return (temp);
}

/* Make a single large string out of the dollar digit variables,
   and the rest_of_args.  If DOLLAR_STAR is 1, then obey the special
   case of "$*" with respect to IFS. */
char *
string_rest_of_args (dollar_star)
     int dollar_star;
{
  register WORD_LIST *list;
  char *string;

  list = list_rest_of_args ();
  string = dollar_star ? string_list_dollar_star (list) : string_list (list);
  dispose_words (list);
  return (string);
}

/* Return a string containing the positional parameters from START to
   END, inclusive.  If STRING[0] == '*', we obey the rules for $*,
   which only makes a difference if QUOTED is non-zero. */
static char *
pos_params (string, start, end, quoted)
     char *string;
     int start, end, quoted;
{
  WORD_LIST *save, *params, *h, *t;
  char *ret;
  int i;

  save = params = list_rest_of_args ();
  if (save == 0)
    return ((char *)NULL);

  for (i = 1; params && i < start; i++)
    params = params->next;
  if (params == 0)
    return ((char *)NULL);
  for (h = t = params; params && i < end; i++)
    {
      t = params;
      params = params->next;
    }

  t->next = (WORD_LIST *)NULL;
  if (string[0] == '*')
    ret = (quoted & (Q_HERE_DOCUMENT|Q_DOUBLE_QUOTES)) ? string_list_dollar_star (h) : string_list (h);
  else
    ret = string_list ((quoted & (Q_HERE_DOCUMENT|Q_DOUBLE_QUOTES)) ? quote_list (h) : h);
  t->next = params;

  dispose_words (save);
  return (ret);
}

/******************************************************************/
/*                                                                */
/*      Functions to expand strings to strings or WORD_LISTs      */
/*                                                                */
/******************************************************************/

#if defined (PROCESS_SUBSTITUTION)
#define EXP_CHAR(s) (s == '$' || s == '`' || s == '<' || s == '>' || s == CTLESC)
#else
#define EXP_CHAR(s) (s == '$' || s == '`' || s == CTLESC)
#endif

/* If there are any characters in STRING that require full expansion,
   then call FUNC to expand STRING; otherwise just perform quote
   removal if necessary.  This returns a new string. */
static char *
maybe_expand_string (string, quoted, func)
     char *string;
     int quoted;
     WORD_LIST *(*func)();
{
  WORD_LIST *list;
  int i, saw_quote;
  char *ret;

  for (i = saw_quote = 0; string[i]; i++)
    {
      if (EXP_CHAR (string[i]))
        break;
      else if (string[i] == '\'' || string[i] == '\\' || string[i] == '"')
        saw_quote = 1;
    }

  if (string[i])
    {
      list = (*func) (string, quoted);
      if (list)
        {
          ret = string_list (list);
          dispose_words (list);
        }
      else
        ret = (char *)NULL;
    }
  else if (saw_quote && ((quoted & (Q_HERE_DOCUMENT|Q_DOUBLE_QUOTES)) == 0))
    ret = string_quote_removal (string, quoted);
  else
    ret = savestring (string);
  return ret;
}

static inline char *
expand_string_to_string (string, quoted, func)
     char *string;
     int quoted;
     WORD_LIST *(*func)();
{
  WORD_LIST *list;
  char *ret;

  if (string == 0 || *string == '\0')
    return ((char *)NULL);

  list = (*func) (string, quoted);
  if (list)
    {
      ret = string_list (list);
      dispose_words (list);
    }
  else
    ret = (char *)NULL;

  return (ret);
}

#if defined (COND_COMMAND)
/* Just remove backslashes in STRING.  Returns a new string. */
char *
remove_backslashes (string)
     char *string;
{
  char *r, *ret, *s;

  r = ret = xmalloc (strlen (string) + 1);
  for (s = string; s && *s; )
    {
      if (*s == '\\')
        s++;
      if (*s == 0)
        break;
      *r++ = *s++;
    }
  *r = '\0';
  return ret;
}

/* This needs better error handling. */
/* Expand W for use as an argument to a unary or binary operator in a
   [[...]] expression.  If SPECIAL is nonzero, this is the rhs argument
   to the != or == operator, and should be treated as a pattern.  In
   this case, we quote the string specially for the globbing code.  The
   caller is responsible for removing the backslashes if the unquoted
   words is needed later. */   
char *
cond_expand_word (w, special)
     WORD_DESC *w;
     int special;
{
  char *r, *p;
  WORD_LIST *l;

  if (w->word == 0 || w->word[0] == '\0')
    return ((char *)NULL);

  l = call_expand_word_internal (w, 0, 0, (int *)0, (int *)0);
  if (l)
    {
      if (special == 0)
        {
          dequote_list (l);
          r = string_list (l);
        }
      else
        {
          p = string_list (l);
          r = quote_string_for_globbing (p, QGLOB_CVTNULL);
          free (p);
        }
      dispose_words (l);
    }
  else
    r = (char *)NULL;

  return r;
}
#endif

/* Call expand_word_internal to expand W and handle error returns.
   A convenience function for functions that don't want to handle
   any errors or free any memory before aborting. */
static WORD_LIST *
call_expand_word_internal (w, q, i, c, e)
     WORD_DESC *w;
     int q, i, *c, *e;
{
  WORD_LIST *result;

  result = expand_word_internal (w, q, i, c, e);
  if (result == &expand_word_error)
    {
      /* By convention, each time this error is returned, w->word has
         already been freed. */
      w->word = (char *)NULL;
      jump_to_top_level (DISCARD);
      /* NOTREACHED */
    }
  else if (result == &expand_word_fatal)
    jump_to_top_level (FORCE_EOF);
    /* NOTREACHED */
  else
    return (result);
}

/* Perform parameter expansion, command substitution, and arithmetic
   expansion on STRING, as if it were a word.  Leave the result quoted. */
static WORD_LIST *
expand_string_internal (string, quoted)
     char *string;
     int quoted;
{
  WORD_DESC td;
  WORD_LIST *tresult;

  if (string == 0 || *string == 0)
    return ((WORD_LIST *)NULL);

  bzero ((char *)&td, sizeof (td));
  td.word = string;
  tresult = call_expand_word_internal (&td, quoted, 0, (int *)NULL, (int *)NULL);
  return (tresult);
}

/* Expand STRING by performing parameter expansion, command substitution,
   and arithmetic expansion.  Dequote the resulting WORD_LIST before
   returning it, but do not perform word splitting.  The call to
   remove_quoted_nulls () is in here because word splitting normally
   takes care of quote removal. */
WORD_LIST *
expand_string_unsplit (string, quoted)
     char *string;
     int quoted;
{
  WORD_LIST *value;

  if (!string || !*string)
    return ((WORD_LIST *)NULL);

  value = expand_string_internal (string, quoted);
  if (value)
    {
      if (value->word)
        remove_quoted_nulls (value->word->word);
      dequote_list (value);
    }
  return (value);
}

/* Expand STRING just as if you were expanding a word, but do not dequote
   the resultant WORD_LIST.  This is called only from within this file,
   and is used to correctly preserve quoted characters when expanding
   things like ${1+"$@"}.  This does parameter expansion, command
   substitution, arithmetic expansion, and word splitting. */
static WORD_LIST *
expand_string_leave_quoted (string, quoted)
     char *string;
     int quoted;
{
  WORD_LIST *tlist;
  WORD_LIST *tresult;

  if (string == 0 || *string == '\0')
    return ((WORD_LIST *)NULL);

  tlist = expand_string_internal (string, quoted);

  if (tlist)
    {
      tresult = word_list_split (tlist);
      dispose_words (tlist);
      return (tresult);
    }
  return ((WORD_LIST *)NULL);
}

/* This does not perform word splitting or dequote the WORD_LIST
   it returns. */
static WORD_LIST *
expand_string_for_rhs (string, quoted, dollar_at_p, has_dollar_at)
     char *string;
     int quoted, *dollar_at_p, *has_dollar_at;
{
  WORD_DESC td;
  WORD_LIST *tresult;

  if (string == 0 || *string == '\0')
    return (WORD_LIST *)NULL;

  bzero ((char *)&td, sizeof (td));
  td.word = string;
  tresult = call_expand_word_internal (&td, quoted, 1, dollar_at_p, has_dollar_at);
  return (tresult);
}

/* Expand STRING just as if you were expanding a word.  This also returns
   a list of words.  Note that filename globbing is *NOT* done for word
   or string expansion, just when the shell is expanding a command.  This
   does parameter expansion, command substitution, arithmetic expansion,
   and word splitting.  Dequote the resultant WORD_LIST before returning. */
WORD_LIST *
expand_string (string, quoted)
     char *string;
     int quoted;
{
  WORD_LIST *result;

  if (!string || !*string)
    return ((WORD_LIST *)NULL);

  result = expand_string_leave_quoted (string, quoted);
  return (result ? dequote_list (result) : result);
}

/***************************************************
 *                                                 *
 *      Functions to handle quoting chars          *
 *                                                 *
 ***************************************************/

/* Conventions:

     A string with s[0] == CTLNUL && s[1] == 0 is a quoted null string.
     The parser passes CTLNUL as CTLESC CTLNUL. */

/* The parser passes us CTLESC as CTLESC CTLESC and CTLNUL as CTLESC CTLNUL.
   This is necessary to make unquoted CTLESC and CTLNUL characters in the
   data stream pass through properly.
   Here we remove doubled CTLESC characters inside quoted strings before
   quoting the entire string, so we do not double the number of CTLESC
   characters. */
static char *
remove_quoted_escapes (string)
     char *string;
{
  register char *s;
  int docopy;
  char *t, *t1;

  if (string == NULL)
    return (string);

  t1 = t = xmalloc (strlen (string) + 1);
  for (docopy = 0, s = string; *s; s++, t1++)
    {
      if (*s == CTLESC && (s[1] == CTLESC || s[1] == CTLNUL))
        {
          s++;
          docopy = 1;
        }
      *t1 = *s;
    }
  *t1 = '\0';
  if (docopy)
    strcpy (string, t);
  free (t);
  return (string);
}

/* Quote escape characters in string s, but no other characters.  This is
   used to protect CTLESC and CTLNUL in variable values from the rest of
   the word expansion process after the variable is expanded. */
static char *
quote_escapes (string)
     char *string;
{
  register char *s, *t;
  char *result;

  result = xmalloc ((strlen (string) * 2) + 1);
  for (s = string, t = result; *s; )
    {
      if (*s == CTLESC || *s == CTLNUL)
        *t++ = CTLESC;
      *t++ = *s++;
    }
  *t = '\0';
  return (result);
}

static WORD_LIST *
list_quote_escapes (list)
     WORD_LIST *list;
{
  register WORD_LIST *w;
  char *t;

  for (w = list; w; w = w->next)
    {
      t = w->word->word;
      w->word->word = quote_escapes (t);
      free (t);
    }
  return list;
}

#ifdef INCLUDE_UNUSED
static char *
dequote_escapes (string)
     char *string;
{
  register char *s, *t;
  char *result;

  result = xmalloc (strlen (string) + 1);
  for (s = string, t = result; *s; )
    {
      if (*s == CTLESC && (s[1] == CTLESC || s[1] == CTLNUL))
        {
          s++;
          if (*s == '\0')
            break;
        }
      *t++ = *s++;
    }
  *t = '\0';
  return result;
}
#endif

static WORD_LIST *
dequote_list (list)
     WORD_LIST *list;
{
  register char *s;
  register WORD_LIST *tlist;

  for (tlist = list; tlist; tlist = tlist->next)
    {
      s = dequote_string (tlist->word->word);
      free (tlist->word->word);
      tlist->word->word = s;
    }
  return list;
}

static char *
make_quoted_char (c)
     int c;
{
  char *temp;

  temp = xmalloc (3);
  if (c == 0)
    {
      temp[0] = CTLNUL;
      temp[1] = '\0';
    }
  else
    {
      temp[0] = CTLESC;
      temp[1] = c;
      temp[2] = '\0';
    }
  return (temp);
}

/* Quote STRING.  Return a new string. */
char *
quote_string (string)
     char *string;
{
  register char *t;
  char *result;

  if (*string == 0)
    {
      result = xmalloc (2);
      result[0] = CTLNUL;
      result[1] = '\0';
    }
  else
    {
      result = xmalloc ((strlen (string) * 2) + 1);

      for (t = result; *string; )
        {
          *t++ = CTLESC;
          *t++ = *string++;
        }
      *t = '\0';
    }
  return (result);
}

/* De-quoted quoted characters in STRING. */
char *
dequote_string (string)
     char *string;
{
  register char *t;
  char *result;

  result = xmalloc (strlen (string) + 1);

  if (QUOTED_NULL (string))
    {
      result[0] = '\0';
      return (result);
    }

  /* If no character in the string can be quoted, don't bother examining
     each character.  Just return a copy of the string passed to us. */
  if (strchr (string, CTLESC) == NULL)          /* XXX */
    {                                           /* XXX */
      strcpy (result, string);                  /* XXX */
      return (result);                          /* XXX */
    }

  for (t = result; *string; string++, t++)
    {
      if (*string == CTLESC)
        {
          string++;

          if (!*string)
            break;
        }

      *t = *string;
    }

  *t = '\0';
  return (result);
}

/* Quote the entire WORD_LIST list. */
static WORD_LIST *
quote_list (list)
     WORD_LIST *list;
{
  register WORD_LIST *w;
  char *t;

  for (w = list; w; w = w->next)
    {
      t = w->word->word;
      w->word->word = quote_string (t);
      free (t);
      w->word->flags |= W_QUOTED;
    }
  return list;
}

/* Perform quoted null character removal on STRING.  We don't allow any
   quoted null characters in the middle or at the ends of strings because
   of how expand_word_internal works.  remove_quoted_nulls () turns
   STRING into an empty string iff it only consists of a quoted null,
   and removes all unquoted CTLNUL characters. */
/*
#define remove_quoted_nulls(string) \
  do { if (QUOTED_NULL (string)) string[0] ='\0'; } while (0)
*/
static void
remove_quoted_nulls (string)
     char *string;
{
  char *nstr, *s, *p;

  nstr = savestring (string);
  nstr[0] = '\0';
  for (p = nstr, s = string; *s; s++)
    {
      if (*s == CTLESC)
        {
          *p++ = *s++;  /* CTLESC */
          if (*s == 0)
            break;
          *p++ = *s;    /* quoted char */
          continue;
        }
      if (*s == CTLNUL)
        continue;
      *p++ = *s;
    }
  *p = '\0';
  strcpy (string, nstr);
  free (nstr);
}

/* Perform quoted null character removal on each element of LIST.
   This modifies LIST. */
void
word_list_remove_quoted_nulls (list)
     WORD_LIST *list;
{
  register WORD_LIST *t;

  for (t = list; t; t = t->next)
    remove_quoted_nulls (t->word->word);
}

/* **************************************************************** */
/*                                                                  */
/*         Functions for Matching and Removing Patterns             */
/*                                                                  */
/* **************************************************************** */

/* Remove the portion of PARAM matched by PATTERN according to OP, where OP
   can have one of 4 values:
        RP_LONG_LEFT    remove longest matching portion at start of PARAM
        RP_SHORT_LEFT   remove shortest matching portion at start of PARAM
        RP_LONG_RIGHT   remove longest matching portion at end of PARAM
        RP_SHORT_RIGHT  remove shortest matching portion at end of PARAM
*/

#define RP_LONG_LEFT    1
#define RP_SHORT_LEFT   2
#define RP_LONG_RIGHT   3
#define RP_SHORT_RIGHT  4

static char *
remove_pattern (param, pattern, op)
     char *param, *pattern;
     int op;
{
  register int len;
  register char *end;
  register char *p, *ret, c;

  if (param == NULL || *param == '\0')
    return (param);
  if (pattern == NULL || *pattern == '\0')      /* minor optimization */
    return (savestring (param));

  len = STRLEN (param);
  end = param + len;

  switch (op)
    {
      case RP_LONG_LEFT:        /* remove longest match at start */
        for (p = end; p >= param; p--)
          {
            c = *p; *p = '\0';
            if (fnmatch (pattern, param, FNMATCH_EXTFLAG) != FNM_NOMATCH)
              {
                *p = c;
                return (savestring (p));
              }
            *p = c;
          }
        break;

      case RP_SHORT_LEFT:       /* remove shortest match at start */
        for (p = param; p <= end; p++)
          {
            c = *p; *p = '\0';
            if (fnmatch (pattern, param, FNMATCH_EXTFLAG) != FNM_NOMATCH)
              {
                *p = c;
                return (savestring (p));
              }
            *p = c;
          }
        break;

      case RP_LONG_RIGHT:       /* remove longest match at end */
        for (p = param; p <= end; p++)
          {
            if (fnmatch (pattern, p, FNMATCH_EXTFLAG) != FNM_NOMATCH)
              {
                c = *p; *p = '\0';
                ret = savestring (param);
                *p = c;
                return (ret);
              }
          }
        break;

      case RP_SHORT_RIGHT:      /* remove shortest match at end */
        for (p = end; p >= param; p--)
          {
            if (fnmatch (pattern, p, FNMATCH_EXTFLAG) != FNM_NOMATCH)
              {
                c = *p; *p = '\0';
                ret = savestring (param);
                *p = c;
                return (ret);
              }
          }
        break;
    }
  return (savestring (param));  /* no match, return original string */
}

/* Return 1 of the first character of STRING could match the first
   character of pattern PAT.  Used to avoid n2 calls to fnmatch(). */
static int
match_pattern_char (pat, string)
     char *pat, *string;
{
  char c;

  if (*string == 0)
    return (0);

  switch (c = *pat++)
    {
    default:
      return (*string == c);
    case '\\':
      return (*string == *pat);
    case '?':
      return (*string == LPAREN ? 1 : (*string != '\0'));
    case '*':
      return (1);
    case '+':
    case '!':
    case '@':
      return (*string == LPAREN ? 1 : (*string == c));
    case '[':
      return (*string != '\0');
    }
}

/* Match PAT anywhere in STRING and return the match boundaries.
   This returns 1 in case of a successful match, 0 otherwise.  SP
   and EP are pointers into the string where the match begins and
   ends, respectively.  MTYPE controls what kind of match is attempted.
   MATCH_BEG and MATCH_END anchor the match at the beginning and end
   of the string, respectively.  The longest match is returned. */
static int
match_pattern (string, pat, mtype, sp, ep)
     char *string, *pat;
     int mtype;
     char **sp, **ep;
{
  int c;
  register char *p, *p1;
  char *end;

  if (string == 0 || *string == 0 || pat == 0 || *pat == 0)
    return (0);

  end = string + STRLEN (string);

  switch (mtype)
    {
    case MATCH_ANY:
      for (p = string; p <= end; p++)
        {
          if (match_pattern_char (pat, p))
            {
              for (p1 = end; p1 >= p; p1--)
                {
                  c = *p1; *p1 = '\0';
                  if (fnmatch (pat, p, FNMATCH_EXTFLAG) == 0)
                    {
                      *p1 = c;
                      *sp = p;
                      *ep = p1;
                      return 1;
                    }
                  *p1 = c;
                }
            }
        }
      return (0);

    case MATCH_BEG:
      if (match_pattern_char (pat, string) == 0)
        return (0);
      for (p = end; p >= string; p--)
        {
          c = *p; *p = '\0';
          if (fnmatch (pat, string, FNMATCH_EXTFLAG) == 0)
            {
              *p = c;
              *sp = string;
              *ep = p;
              return 1;
            }
          *p = c;
        }
      return (0);

    case MATCH_END:
      for (p = string; p <= end; p++)
        if (fnmatch (pat, p, FNMATCH_EXTFLAG) == 0)
          {
            *sp = p;
            *ep = end;
            return 1;
          }
      return (0);
    }

  return (0);
}

static int
getpatspec (c, value)
     int c;
     char *value;
{
  if (c == '#')
    return ((*value == '#') ? RP_LONG_LEFT : RP_SHORT_LEFT);
  else  /* c == '%' */
    return ((*value == '%') ? RP_LONG_RIGHT : RP_SHORT_RIGHT);
}

/* Posix.2 says that the WORD should be run through tilde expansion,
   parameter expansion, command substitution and arithmetic expansion.
   This leaves the result quoted, so quote_string_for_globbing () has
   to be called to fix it up for fnmatch ().  If QUOTED is non-zero,
   it means that the entire expression was enclosed in double quotes.
   This means that quoting characters in the pattern do not make any
   special pattern characters quoted.  For example, the `*' in the
   following retains its special meaning: "${foo#'*'}". */
static char *
getpattern (value, quoted, expandpat)
     char *value;
     int quoted, expandpat;
{
  char *pat, *tword;
  WORD_LIST *l;
  int i;

  tword = strchr (value, '~') ? bash_tilde_expand (value) : savestring (value);

  /* expand_string_internal () leaves WORD quoted and does not perform
     word splitting. */
  if (expandpat && (quoted & (Q_HERE_DOCUMENT|Q_DOUBLE_QUOTES)) && *tword)
    {
      i = 0;
      pat = string_extract_double_quoted (tword, &i, 1);
      free (tword);
      tword = pat;
    }

  /* There is a problem here:  how to handle single or double quotes in the
     pattern string when the whole expression is between double quotes? */
#if 0
  l = *tword ? expand_string_for_rhs (tword, quoted, (int *)NULL, (int *)NULL)
#else
  l = *tword ? expand_string_for_rhs (tword,
                                      (quoted & (Q_HERE_DOCUMENT|Q_DOUBLE_QUOTES)) ? Q_NOQUOTE : quoted,
                                      (int *)NULL, (int *)NULL)
#endif
             : (WORD_LIST *)0;
  free (tword);
  pat = string_list (l);
  dispose_words (l);
  if (pat)
    {
      tword = quote_string_for_globbing (pat, QGLOB_CVTNULL);
      free (pat);
      pat = tword;
    }
  return (pat);
}

/* Handle removing a pattern from a string as a result of ${name%[%]value}
   or ${name#[#]value}. */
static char *
parameter_brace_remove_pattern (value, temp, c, quoted)
     char *value, *temp;
     int c, quoted;
{
  int patspec;
  char *pattern, *tword;

  patspec = getpatspec (c, value);
  if (patspec == RP_LONG_LEFT || patspec == RP_LONG_RIGHT)
    value++;

  pattern = getpattern (value, quoted, 1);

  tword = remove_pattern (temp, pattern, patspec);

  FREE (pattern);
  return (tword);
}

static char *
list_remove_pattern (list, pattern, patspec, type, quoted)
     WORD_LIST *list;
     char *pattern;
     int patspec, type, quoted;
{
  WORD_LIST *new, *l;
  WORD_DESC *w;
  char *tword;

  for (new = (WORD_LIST *)NULL, l = list; l; l = l->next)
    {
      tword = remove_pattern (l->word->word, pattern, patspec);
      w = make_bare_word (tword);
      free (tword);
      new = make_word_list (w, new);
    }

  l = REVERSE_LIST (new, WORD_LIST *);
  if (type == '*')
    tword = (quoted & (Q_HERE_DOCUMENT|Q_DOUBLE_QUOTES)) ? string_list_dollar_star (l) : string_list (l);
  else
    tword = string_list ((quoted & (Q_HERE_DOCUMENT|Q_DOUBLE_QUOTES)) ? quote_list (l) : l);

  dispose_words (l);
  return (tword);
}

static char *
parameter_list_remove_pattern (value, type, c, quoted)
     char *value;
     int type, c, quoted;
{
  int patspec;
  char *pattern, *ret;
  WORD_LIST *list;

  patspec = getpatspec (c, value);
  if (patspec == RP_LONG_LEFT || patspec == RP_LONG_RIGHT)
    value++;

  pattern = getpattern (value, quoted, 1);

  list = list_rest_of_args ();
  ret = list_remove_pattern (list, pattern, patspec, type, quoted);
  dispose_words (list);
  FREE (pattern);
  return (ret);
}

#if defined (ARRAY_VARS)
static char *
array_remove_pattern (value, aspec, aval, c, quoted)
     char *value, *aspec, *aval;        /* AVAL == evaluated ASPEC */
     int c, quoted;
{
  SHELL_VAR *var;
  int len, patspec;
  char *ret, *t, *pattern;
  WORD_LIST *l;

  var = array_variable_part (aspec, &t, &len);
  if (var == 0)
    return ((char *)NULL);

  patspec = getpatspec (c, value);
  if (patspec == RP_LONG_LEFT || patspec == RP_LONG_RIGHT)
    value++;

  pattern = getpattern (value, quoted, 1);

  if (ALL_ELEMENT_SUB (t[0]) && t[1] == ']')
    {
      if (array_p (var) == 0)
        {
          report_error ("%s: bad array subscript", aspec);
          FREE (pattern);
          return ((char *)NULL);
        }
      l = array_to_word_list (array_cell (var));
      if (l == 0)
        return ((char *)NULL);
      ret = list_remove_pattern (l, pattern, patspec, t[0], quoted);
      dispose_words (l);
    }
  else
    {
      ret = remove_pattern (aval, pattern, patspec);
      if (ret)
        {
          t = quote_escapes (ret);
          free (ret);
          ret = t;
        }
    }

  FREE (pattern);
  return ret;
}
#endif /* ARRAY_VARS */

/*******************************************
 *                                         *
 *      Functions to expand WORD_DESCs     *
 *                                         *
 *******************************************/

/* Expand WORD, performing word splitting on the result.  This does
   parameter expansion, command substitution, arithmetic expansion,
   word splitting, and quote removal. */

WORD_LIST *
expand_word (word, quoted)
     WORD_DESC *word;
     int quoted;
{
  WORD_LIST *result, *tresult;

  tresult = call_expand_word_internal (word, quoted, 0, (int *)NULL, (int *)NULL);
  result = word_list_split (tresult);
  dispose_words (tresult);
  return (result ? dequote_list (result) : result);
}

/* Expand WORD, but do not perform word splitting on the result.  This
   does parameter expansion, command substitution, arithmetic expansion,
   and quote removal. */
WORD_LIST *
expand_word_no_split (word, quoted)
     WORD_DESC *word;
     int quoted;
{
  WORD_LIST *result;

  result = call_expand_word_internal (word, quoted, 0, (int *)NULL, (int *)NULL);
  return (result ? dequote_list (result) : result);
}

/* Perform shell expansions on WORD, but do not perform word splitting or
   quote removal on the result. */
WORD_LIST *
expand_word_leave_quoted (word, quoted)
     WORD_DESC *word;
     int quoted;
{
  return (call_expand_word_internal (word, quoted, 0, (int *)NULL, (int *)NULL));
}

#if defined (PROCESS_SUBSTITUTION)

/*****************************************************************/
/*                                                               */
/*                  Hacking Process Substitution                 */
/*                                                               */
/*****************************************************************/

#if !defined (HAVE_DEV_FD)
/* Named pipes must be removed explicitly with `unlink'.  This keeps a list
   of FIFOs the shell has open.  unlink_fifo_list will walk the list and
   unlink all of them. add_fifo_list adds the name of an open FIFO to the
   list.  NFIFO is a count of the number of FIFOs in the list. */
#define FIFO_INCR 20
extern char *mktemp ();

static char **fifo_list = (char **)NULL;
static int nfifo;
static int fifo_list_size;

static void
add_fifo_list (pathname)
     char *pathname;
{
  if (nfifo >= fifo_list_size - 1)
    {
      fifo_list_size += FIFO_INCR;
      fifo_list = (char **)xrealloc (fifo_list,
                                     fifo_list_size * sizeof (char *));
    }

  fifo_list[nfifo++] = savestring (pathname);
}

void
unlink_fifo_list ()
{
  if (nfifo == 0)
    return;

  while (nfifo--)
    {
      unlink (fifo_list[nfifo]);
      free (fifo_list[nfifo]);
      fifo_list[nfifo] = (char *)NULL;
    }
  nfifo = 0;
}

static char *
make_named_pipe ()
{
  char *tname;

  tname = mktemp (savestring ("/tmp/sh-np-XXXXXX"));
  if (mkfifo (tname, 0600) < 0)
    {
      free (tname);
      return ((char *)NULL);
    }

  add_fifo_list (tname);
  return (tname);
}

#else /* HAVE_DEV_FD */

/* DEV_FD_LIST is a bitmap of file descriptors attached to pipes the shell
   has open to children.  NFDS is a count of the number of bits currently
   set in DEV_FD_LIST.  TOTFDS is a count of the highest possible number
   of open files. */
static char *dev_fd_list = (char *)NULL;
static int nfds;
static int totfds;      /* The highest possible number of open files. */

static void
add_fifo_list (fd)
     int fd;
{
  if (!dev_fd_list || fd >= totfds)
    {
      int ofds;

      ofds = totfds;
      totfds = getdtablesize ();
      if (totfds < 0 || totfds > 256)
        totfds = 256;
      if (fd > totfds)
        totfds = fd + 2;

      dev_fd_list = xrealloc (dev_fd_list, totfds);
      bzero (dev_fd_list + ofds, totfds - ofds);
    }

  dev_fd_list[fd] = 1;
  nfds++;
}

void
unlink_fifo_list ()
{
  register int i;

  if (nfds == 0)
    return;

  for (i = 0; nfds && i < totfds; i++)
    if (dev_fd_list[i])
      {
        close (i);
        dev_fd_list[i] = 0;
        nfds--;
      }

  nfds = 0;
}

#if defined (NOTDEF)
print_dev_fd_list ()
{
  register int i;

  fprintf (stderr, "pid %d: dev_fd_list:", getpid ());
  fflush (stderr);

  for (i = 0; i < totfds; i++)
    {
      if (dev_fd_list[i])
        fprintf (stderr, " %d", i);
    }
  fprintf (stderr, "\n");
}
#endif /* NOTDEF */

static char *
make_dev_fd_filename (fd)
     int fd;
{
  char *ret;

  ret = xmalloc (sizeof (DEV_FD_PREFIX) + 4);
  sprintf (ret, "%s%d", DEV_FD_PREFIX, fd);
  add_fifo_list (fd);
  return (ret);
}

#endif /* HAVE_DEV_FD */

/* Return a filename that will open a connection to the process defined by
   executing STRING.  HAVE_DEV_FD, if defined, means open a pipe and return
   a filename in /dev/fd corresponding to a descriptor that is one of the
   ends of the pipe.  If not defined, we use named pipes on systems that have
   them.  Systems without /dev/fd and named pipes are out of luck.

   OPEN_FOR_READ_IN_CHILD, if 1, means open the named pipe for reading or
   use the read end of the pipe and dup that file descriptor to fd 0 in
   the child.  If OPEN_FOR_READ_IN_CHILD is 0, we open the named pipe for
   writing or use the write end of the pipe in the child, and dup that
   file descriptor to fd 1 in the child.  The parent does the opposite. */

static char *
process_substitute (string, open_for_read_in_child)
     char *string;
     int open_for_read_in_child;
{
  char *pathname;
  int fd, result;
  pid_t old_pid, pid;
#if defined (HAVE_DEV_FD)
  int parent_pipe_fd, child_pipe_fd;
  int fildes[2];
#endif /* HAVE_DEV_FD */
#if defined (JOB_CONTROL)
  pid_t old_pipeline_pgrp;
#endif

  if (!string || !*string || wordexp_only)
    return ((char *)NULL);

#if !defined (HAVE_DEV_FD)
  pathname = make_named_pipe ();
#else /* HAVE_DEV_FD */
  if (pipe (fildes) < 0)
    {
      sys_error ("cannot make pipe for process substitution");
      return ((char *)NULL);
    }
  /* If OPEN_FOR_READ_IN_CHILD == 1, we want to use the write end of
     the pipe in the parent, otherwise the read end. */
  parent_pipe_fd = fildes[open_for_read_in_child];
  child_pipe_fd = fildes[1 - open_for_read_in_child];
  /* Move the parent end of the pipe to some high file descriptor, to
     avoid clashes with FDs used by the script. */
  parent_pipe_fd = move_to_high_fd (parent_pipe_fd, 1, 64);

  pathname = make_dev_fd_filename (parent_pipe_fd);
#endif /* HAVE_DEV_FD */

  if (!pathname)
    {
      sys_error ("cannot make pipe for process substitution");
      return ((char *)NULL);
    }

  old_pid = last_made_pid;

#if defined (JOB_CONTROL)
  old_pipeline_pgrp = pipeline_pgrp;
  pipeline_pgrp = shell_pgrp;
#if 0
  cleanup_the_pipeline ();
#else
  save_pipeline (1);
#endif
#endif /* JOB_CONTROL */

  pid = make_child ((char *)NULL, 1);
  if (pid == 0)
    {
      reset_terminating_signals ();     /* XXX */
      /* Cancel traps, in trap.c. */
      restore_original_signals ();
      setup_async_signals ();
      subshell_environment = SUBSHELL_COMSUB;
    }

#if defined (JOB_CONTROL)
  set_sigchld_handler ();
  stop_making_children ();
  pipeline_pgrp = old_pipeline_pgrp;
#endif /* JOB_CONTROL */

  if (pid < 0)
    {
      sys_error ("cannot make child for process substitution");
      free (pathname);
#if defined (HAVE_DEV_FD)
      close (parent_pipe_fd);
      close (child_pipe_fd);
#endif /* HAVE_DEV_FD */
      return ((char *)NULL);
    }

  if (pid > 0)
    {
#if defined (JOB_CONTROL)
      restore_pipeline (1);
#endif

      last_made_pid = old_pid;

#if defined (JOB_CONTROL) && defined (PGRP_PIPE)
      close_pgrp_pipe ();
#endif /* JOB_CONTROL && PGRP_PIPE */

#if defined (HAVE_DEV_FD)
      close (child_pipe_fd);
#endif /* HAVE_DEV_FD */

      return (pathname);
    }

  set_sigint_handler ();

#if defined (JOB_CONTROL)
  set_job_control (0);
#endif /* JOB_CONTROL */

#if !defined (HAVE_DEV_FD)
  /* Open the named pipe in the child. */
  fd = open (pathname, open_for_read_in_child ? O_RDONLY|O_NONBLOCK : O_WRONLY);
  if (fd < 0)
    {
      sys_error ("cannot open named pipe %s for %s", pathname,
        open_for_read_in_child ? "reading" : "writing");
      exit (127);
    }
#else /* HAVE_DEV_FD */
  fd = child_pipe_fd;
#endif /* HAVE_DEV_FD */

  if (dup2 (fd, open_for_read_in_child ? 0 : 1) < 0)
    {
      sys_error ("cannot duplicate named pipe %s as fd %d", pathname,
        open_for_read_in_child ? 0 : 1);
      exit (127);
    }

  close (fd);

  /* Need to close any files that this process has open to pipes inherited
     from its parent. */
  if (current_fds_to_close)
    {
      close_fd_bitmap (current_fds_to_close);
      current_fds_to_close = (struct fd_bitmap *)NULL;
    }

#if defined (HAVE_DEV_FD)
  /* Make sure we close the parent's end of the pipe and clear the slot
     in the fd list so it is not closed later, if reallocated by, for
     instance, pipe(2). */
  close (parent_pipe_fd);
  dev_fd_list[parent_pipe_fd] = 0;
#endif /* HAVE_DEV_FD */

  result = parse_and_execute (string, "process substitution", (SEVAL_NONINT|SEVAL_NOHIST));

#if !defined (HAVE_DEV_FD)
  /* Make sure we close the named pipe in the child before we exit. */
  close (open_for_read_in_child ? 0 : 1);
#endif /* !HAVE_DEV_FD */

  exit (result);
  /*NOTREACHED*/
}
#endif /* PROCESS_SUBSTITUTION */

/***********************************/
/*                                 */
/*      Command Substitution       */
/*                                 */
/***********************************/

static char *
read_comsub (fd, quoted)
     int fd, quoted;
{
  char *istring, buf[128], *bufp;
  int bufn, istring_index, istring_size, c;

  istring = (char *)NULL;
  istring_index = istring_size = bufn = 0;

  /* Read the output of the command through the pipe. */
  while (1)
    {
      if (fd < 0)
        break;
      if (--bufn <= 0)
        {
          while ((bufn = read (fd, buf, sizeof(buf))) < 0 && errno == EINTR)
            ;
          if (bufn <= 0) 
            break;
          bufp = buf;
        }
      c = *bufp++;

      /* Add the character to ISTRING, possibly after resizing it. */
      RESIZE_MALLOCED_BUFFER (istring, istring_index, 2, istring_size, DEFAULT_ARRAY_SIZE);

      if ((quoted & (Q_HERE_DOCUMENT|Q_DOUBLE_QUOTES)) || c == CTLESC || c == CTLNUL)
        istring[istring_index++] = CTLESC;

      istring[istring_index++] = c;
    }

  if (istring)
    istring[istring_index] = '\0';

  /* If we read no output, just return now and save ourselves some
     trouble. */
  if (istring_index == 0)
    {
      FREE (istring);
      return (char *)NULL;
    }

  /* Strip trailing newlines from the output of the command. */
  if (quoted & (Q_HERE_DOCUMENT|Q_DOUBLE_QUOTES))
    {
      while (istring_index > 0)
        {
          if (istring[istring_index - 1] == '\n')
            {
              --istring_index;

              /* If the newline was quoted, remove the quoting char. */
              if (istring[istring_index - 1] == CTLESC)
                --istring_index;
            }
          else
            break;
        }
      istring[istring_index] = '\0';
    }
  else
    strip_trailing (istring, istring_index - 1, 1);

  return istring;
}

/* Perform command substitution on STRING.  This returns a string,
   possibly quoted. */
static char *
command_substitute (string, quoted)
     char *string;
     int quoted;
{
  pid_t pid, old_pid, old_pipeline_pgrp;
  char *istring;
  int result, fildes[2];

  istring = (char *)NULL;

  /* Don't fork () if there is no need to.  In the case of no command to
     run, just return NULL. */
  if (!string || !*string || (string[0] == '\n' && !string[1]))
    return ((char *)NULL);

  if (wordexp_only && read_but_dont_execute)
    {
      last_command_exit_value = 125;
      jump_to_top_level (EXITPROG);
    }

  /* Pipe the output of executing STRING into the current shell. */
  if (pipe (fildes) < 0)
    {
      sys_error ("cannot make pipes for command substitution");
      goto error_exit;
    }

  old_pid = last_made_pid;
#if defined (JOB_CONTROL)
  old_pipeline_pgrp = pipeline_pgrp;
  pipeline_pgrp = shell_pgrp;
  cleanup_the_pipeline ();
#endif

  pid = make_child ((char *)NULL, 0);
  if (pid == 0)
    /* Reset the signal handlers in the child, but don't free the
       trap strings. */
    reset_signal_handlers ();

#if defined (JOB_CONTROL)
  set_sigchld_handler ();
  stop_making_children ();
  pipeline_pgrp = old_pipeline_pgrp;
#endif /* JOB_CONTROL */

  if (pid < 0)
    {
      sys_error ("cannot make child for command substitution");
    error_exit:

      FREE (istring);
      close (fildes[0]);
      close (fildes[1]);
      return ((char *)NULL);
    }

  if (pid == 0)
    {
      set_sigint_handler ();    /* XXX */
#if defined (JOB_CONTROL)
      set_job_control (0);
#endif
      if (dup2 (fildes[1], 1) < 0)
        {
          sys_error ("command_substitute: cannot duplicate pipe as fd 1");
          exit (EXECUTION_FAILURE);
        }

      /* If standard output is closed in the parent shell
         (such as after `exec >&-'), file descriptor 1 will be
         the lowest available file descriptor, and end up in
         fildes[0].  This can happen for stdin and stderr as well,
         but stdout is more important -- it will cause no output
         to be generated from this command. */
      if ((fildes[1] != fileno (stdin)) &&
          (fildes[1] != fileno (stdout)) &&
          (fildes[1] != fileno (stderr)))
        close (fildes[1]);

      if ((fildes[0] != fileno (stdin)) &&
          (fildes[0] != fileno (stdout)) &&
          (fildes[0] != fileno (stderr)))
        close (fildes[0]);

      /* The currently executing shell is not interactive. */
      interactive = 0;

      /* This is a subshell environment. */
      subshell_environment = SUBSHELL_COMSUB;

      /* Command substitution does not inherit the -e flag. */
      exit_immediately_on_error = 0;

      remove_quoted_escapes (string);

      startup_state = 2;        /* see if we can avoid a fork */
      /* Give command substitution a place to jump back to on failure,
         so we don't go back up to main (). */
      result = setjmp (top_level);

      if (result == EXITPROG)
        exit (last_command_exit_value);
      else if (result)
        exit (EXECUTION_FAILURE);
      else
        exit (parse_and_execute (string, "command substitution", SEVAL_NOHIST));
    }
  else
    {
#if defined (JOB_CONTROL) && defined (PGRP_PIPE)
      close_pgrp_pipe ();
#endif /* JOB_CONTROL && PGRP_PIPE */

      close (fildes[1]);

      istring = read_comsub (fildes[0], quoted);

      close (fildes[0]);

      current_command_subst_pid = pid;
      last_command_exit_value = wait_for (pid);
      last_command_subst_pid = pid;
      last_made_pid = old_pid;

#if defined (JOB_CONTROL)
      /* If last_command_exit_value > 128, then the substituted command
         was terminated by a signal.  If that signal was SIGINT, then send
         SIGINT to ourselves.  This will break out of loops, for instance. */
      if (last_command_exit_value == (128 + SIGINT))
        kill (getpid (), SIGINT);

      /* wait_for gives the terminal back to shell_pgrp.  If some other
         process group should have it, give it away to that group here.
         pipeline_pgrp is non-zero only while we are constructing a
         pipline, so what we are concerned about is whether or not that
         pipeline was started in the background.  A pipeline started in
         the background should never get the tty back here. */
#if 0
      if (interactive && pipeline_pgrp != (pid_t)0 && pipeline_pgrp != last_asynchronous_pid)
#else
      if (interactive && pipeline_pgrp != (pid_t)0 && subshell_environment != SUBSHELL_ASYNC)
#endif
        give_terminal_to (pipeline_pgrp);
#endif /* JOB_CONTROL */

      return (istring);
    }
}

/********************************************************
 *                                                      *
 *      Utility functions for parameter expansion       *
 *                                                      *
 ********************************************************/

/* Utility functions to manage arrays and their contents for expansion */

#if defined (ARRAY_VARS)
int
valid_array_reference (name)
     char *name;
{
  char *t;
  int r, len;

  t = strchr (name, '[');
  if (t)
    {
      *t = '\0';
      r = legal_identifier (name);
      *t = '[';
      if (r == 0)
        return 0;
      /* Check for a properly-terminated non-blank subscript. */
      len = skipsubscript (t, 0);
      if (t[len] != ']' || len == 1)
        return 0;
      for (r = 1; r < len; r++)
        if (whitespace (t[r]) == 0)
          return 1;
      return 0;
    }
  return 0;
}

/* Expand the array index beginning at S and extending LEN characters. */
int
array_expand_index (s, len)
     char *s;
     int len;
{
  char *exp, *t;
  int val, expok;

  exp = xmalloc (len);
  strncpy (exp, s, len - 1);
  exp[len - 1] = '\0';
  t = maybe_expand_string (exp, 0, expand_string);
  this_command_name = (char *)NULL;
  val = evalexp (t, &expok);
  free (t);
  free (exp);
  if (expok == 0)
    jump_to_top_level (DISCARD);
  return val;
}

/* Return the variable specified by S without any subscript.  If non-null,
   return the index of the start of the subscript in *SUBP.  If non-null,
   the length of the subscript is returned in *LENP. */
SHELL_VAR *
array_variable_part (s, subp, lenp)
     char *s, **subp;
     int *lenp;
{
  char *t;
  int ind, ni;
  SHELL_VAR *var;

  t = strchr (s, '[');
  ind = t - s;
  ni = skipsubscript (s, ind);
  if (ni <= ind + 1 || s[ni] != ']')
    {
      report_error ("%s: bad array subscript", s);
      return ((SHELL_VAR *)NULL);
    }

  *t = '\0';
  var = find_variable (s);
  *t++ = '[';

  if (subp)
    *subp = t;
  if (lenp)
    *lenp = ni - ind;
  return var;
}

static char *
array_value_internal (s, quoted, allow_all)
     char *s;
     int quoted, allow_all;
{
  int len, ind;
  char *retval, *t, *temp;
  WORD_LIST *l, *list;
  SHELL_VAR *var;

  var = array_variable_part (s, &t, &len);

  if (var == 0)
    return (char *)NULL;

  if (ALL_ELEMENT_SUB (t[0]) && t[1] == ']')
    {
      if (array_p (var) == 0 || allow_all == 0)
        {
          report_error ("%s: bad array subscript", s);
          return ((char *)NULL);
        }
      l = array_to_word_list (array_cell (var));
      if (l == (WORD_LIST *)NULL)
        return ((char *) NULL);

#if 0
      if (t[0] == '*')          /* ${name[*]} */
        retval = (quoted & (Q_HERE_DOCUMENT|Q_DOUBLE_QUOTES)) ? string_list_dollar_star (l) : string_list (l);
      else                      /* ${name[@]} */
        retval = string_list ((quoted & (Q_HERE_DOCUMENT|Q_DOUBLE_QUOTES)) ? quote_list (l) : l);
#else
      if (t[0] == '*' && (quoted & (Q_HERE_DOCUMENT|Q_DOUBLE_QUOTES)))
        {
          temp = string_list_dollar_star (l);
          retval = quote_string (temp);
          free (temp);
        }
      else      /* ${name[@]} or unquoted ${name[*]} */
        retval = string_list_dollar_at (l, quoted);
#endif

      dispose_words (l);
    }
  else
    {
      ind = array_expand_index (t, len);
      if (ind < 0)
        {
          report_error ("%s: bad array subscript", var->name);
          return ((char *)NULL);
        }
      if (array_p (var) == 0)
        return (ind == 0 ? savestring (value_cell (var)) : (char *)NULL);
      retval = array_reference (array_cell (var), ind);
      if (retval)
        retval = quote_escapes (retval);
    }

  return retval;
}

static char *
array_value (s, quoted)
     char *s;
     int quoted;
{
  return (array_value_internal (s, quoted, 1));
}

/* Return the value of the array indexing expression S as a single string.
   If ALLOW_ALL is 0, do not allow `@' and `*' subscripts.  This is used
   by other parts of the shell such as the arithmetic expression evaluator
   in expr.c. */
char *
get_array_value (s, allow_all)
     char *s;
     int allow_all;
{
  return (array_value_internal (s, 0, allow_all));
}

static int
array_length_reference (s)
     char *s;
{
  int ind, len;
  char *t;
  ARRAY *array;
  SHELL_VAR *var;

  var = array_variable_part (s, &t, &len);

  /* If unbound variables should generate an error, report one and return
     failure. */
  if ((var == 0 || array_p (var) == 0) && unbound_vars_is_error)
    {
      ind = *--t;
      *t = '\0';
      report_error ("%s: unbound variable", s);
      *t++ = (char)ind;
      return (-1);
    }
  else if (var == 0)
    return 0;
  else if (array_p (var) == 0)
    return 1;

  array = array_cell (var);

  if (ALL_ELEMENT_SUB (t[0]) && t[1] == ']')
    return (array_num_elements (array));

  ind = array_expand_index (t, len);
  if (ind < 0)
    {
      report_error ("%s: bad array subscript", t);
      return (-1);
    }
  t = array_reference (array, ind);
  len = STRLEN (t);

  return (len);
}
#endif /* ARRAY_VARS */

static int
valid_brace_expansion_word (name, var_is_special)
     char *name;
     int var_is_special;
{
  if (digit (*name) && all_digits (name))
    return 1;
  else if (var_is_special)
    return 1;
#if defined (ARRAY_VARS)
  else if (valid_array_reference (name))
    return 1;
#endif /* ARRAY_VARS */
  else if (legal_identifier (name))
    return 1;
  else
    return 0;
}

/* Parameter expand NAME, and return a new string which is the expansion,
   or NULL if there was no expansion.
   VAR_IS_SPECIAL is non-zero if NAME is one of the special variables in
   the shell, e.g., "@", "$", "*", etc.  QUOTED, if non-zero, means that
   NAME was found inside of a double-quoted expression. */
static char *
parameter_brace_expand_word (name, var_is_special, quoted)
     char *name;
     int var_is_special, quoted;
{
  char *temp, *tt;
  int arg_index;
  SHELL_VAR *var;
  WORD_LIST *l;

  /* Handle multiple digit arguments, as in ${11}. */
  if (digit (*name))
    {
      arg_index = atoi (name);
      temp = get_dollar_var_value (arg_index);
    }
  else if (var_is_special)      /* ${@} */
    {
      int sindex;
      tt = xmalloc (2 + strlen (name));
      tt[sindex = 0] = '$';
      strcpy (tt + 1, name);
#if 0
      l = expand_string_leave_quoted (tt, quoted);
      free (tt);
      temp = string_list (l);
      dispose_words (l);
#else
      temp = param_expand (tt, &sindex, quoted, (int *)NULL, (int *)NULL,
                           (int *)NULL, (int *)NULL, 0);
      free (tt);
#endif
    }
#if defined (ARRAY_VARS)
  else if (valid_array_reference (name))
    {
      temp = array_value (name, quoted);
    }
#endif
  else if (var = find_variable (name))
    {
      if (var && invisible_p (var) == 0)
        {
#if defined (ARRAY_VARS)
          temp = array_p (var) ? array_reference (array_cell (var), 0) : value_cell (var);
#else
          temp = value_cell (var);
#endif

          if (temp)
            temp = quote_escapes (temp);

          if (tempvar_p (var))
            dispose_variable (var);
        }
      else
        temp = (char *)NULL;
    }
  else
    temp = (char *)NULL;

  return (temp);
}

/* Expand an indirect reference to a variable: ${!NAME} expands to the
   value of the variable whose name is the value of NAME. */
static char *
parameter_brace_expand_indir (name, var_is_special, quoted)
     char *name;
     int var_is_special, quoted;
{
  char *temp, *t;

  t = parameter_brace_expand_word (name, var_is_special, quoted);
  if (t == 0)
    return (t);
  temp = parameter_brace_expand_word (t, t[0] == '@' && t[1] == '\0', quoted);
  free (t);
  return temp;
}

/* Expand the right side of a parameter expansion of the form ${NAMEcVALUE},
   depending on the value of C, the separating character.  C can be one of
   "-", "+", or "=".  QUOTED is true if the entire brace expression occurs
   between double quotes. */
static char *
parameter_brace_expand_rhs (name, value, c, quoted, qdollaratp, hasdollarat)
     char *name, *value;
     int c, quoted, *qdollaratp, *hasdollarat;
{
  WORD_LIST *l;
  char *t, *t1, *temp;
  int hasdol;

  temp = (*value == '~' || (strchr (value, '~') && unquoted_substring ("=~", value)))
        ? bash_tilde_expand (value)
        : savestring (value);

  /* If the entire expression is between double quotes, we want to treat
     the value as a double-quoted string, with the exception that we strip
     embedded unescaped double quotes. */
  if ((quoted & (Q_HERE_DOCUMENT|Q_DOUBLE_QUOTES)) && *temp)
    {
      hasdol = 0;
      t = string_extract_double_quoted (temp, &hasdol, 1);
      free (temp);
      temp = t;
    }

  hasdol = 0;
  /* XXX was 0 not quoted */
  l = *temp ? expand_string_for_rhs (temp, quoted, &hasdol, (int *)NULL)
            : (WORD_LIST *)0;
  if (hasdollarat)
    *hasdollarat = hasdol || (l && l->next);
  free (temp);
  if (l)
    {
      /* The expansion of TEMP returned something.  We need to treat things
          slightly differently if HASDOL is non-zero. */
      temp = string_list (l);
      /* If l->next is not null, we know that TEMP contained "$@", since that
         is the only expansion that creates more than one word. */
      if ((hasdol && quoted) || l->next)
        *qdollaratp = 1;
      dispose_words (l);
    }
  else if ((quoted & (Q_HERE_DOCUMENT|Q_DOUBLE_QUOTES)) && hasdol)
    {
      /* The brace expansion occurred between double quotes and there was
         a $@ in TEMP.  It does not matter if the $@ is quoted, as long as
         it does not expand to anything.  In this case, we want to return
         a quoted empty string. */
      temp = xmalloc (2);
      temp[0] = CTLNUL;
      temp[1] = '\0';
    }
  else
    temp = (char *)NULL;

  if (c == '-' || c == '+')
    return (temp);

  /* c == '=' */
  t = temp ? savestring (temp) : savestring ("");
  t1 = dequote_string (t);
  free (t);
  bind_variable (name, t1);
  free (t1);
  return (temp);
}

/* Deal with the right hand side of a ${name:?value} expansion in the case
   that NAME is null or not set.  If VALUE is non-null it is expanded and
   used as the error message to print, otherwise a standard message is
   printed. */
static void
parameter_brace_expand_error (name, value)
     char *name, *value;
{
  WORD_LIST *l;
  char *temp;

  if (value && *value)
    {
      l = expand_string (value, 0);
      temp =  string_list (l);
      report_error ("%s: %s", name, temp ? temp : "");  /* XXX was value not "" */
      FREE (temp);
      dispose_words (l);
    }
  else
    report_error ("%s: parameter null or not set", name);

  /* Free the data we have allocated during this expansion, since we
     are about to longjmp out. */
  free (name);
  FREE (value);
}

/* Return 1 if NAME is something for which parameter_brace_expand_length is
   OK to do. */
static int
valid_length_expression (name)
     char *name;
{
  return (!name[1] ||                                           /* ${#} */
          ((name[1] == '@' || name[1] == '*') && !name[2]) ||   /* ${#@}, ${#*} */
          (member (name[1], "-?$!#") && !name[2]) ||            /* ${#-}, etc. */
          (digit (name[1]) && all_digits (name + 1)) ||         /* ${#11} */
#if defined (ARRAY_VARS)
          valid_array_reference (name + 1) ||                   /* ${#a[7]} */
#endif
          legal_identifier (name + 1));                         /* ${#PS1} */
}

/* Handle the parameter brace expansion that requires us to return the
   length of a parameter. */
static int
parameter_brace_expand_length (name)
     char *name;
{
  char *t, *newname;
  int number;
  WORD_LIST *list;
#if defined (ARRAY_VARS)
  SHELL_VAR *var;
#endif

  if (name[1] == '\0')                  /* ${#} */
    number = number_of_args ();
  else if ((name[1] == '@' || name[1] == '*') && name[2] == '\0')       /* ${#@}, ${#*} */
    number = number_of_args ();
  else if (member (name[1], "-?$!#") && name[2] == '\0')
    {
      /* Take the lengths of some of the shell's special parameters. */
      switch (name[1])
        {
        case '-':
          t = which_set_flags ();
          break;
        case '?':
          t = itos (last_command_exit_value);
          break;
        case '$':
          t = itos (dollar_dollar_pid);
          break;
        case '!':
          if (last_asynchronous_pid == NO_PID)
            t = (char *)NULL;
          else
            t = itos ((int)last_asynchronous_pid);
          break;
        case '#':
          t = itos (number_of_args ());
          break;
        }
      number = STRLEN (t);
      FREE (t);
    }
#if defined (ARRAY_VARS)
  else if (valid_array_reference (name + 1))
    number = array_length_reference (name + 1);
#endif /* ARRAY_VARS */
  else
    {
      number = 0;

      if (digit (name[1]))              /* ${#1} */
        {
          t = get_dollar_var_value (atoi (name + 1));
          number = STRLEN (t);
          FREE (t);
        }
#if defined (ARRAY_VARS)
      else if ((var = find_variable (name + 1)) && array_p (var))
        {
          t = array_reference (array_cell (var), 0);
          number = STRLEN (t);
        }
#endif
      else                              /* ${#PS1} */
        {
          newname = savestring (name);
          newname[0] = '$';
          list = expand_string (newname, Q_DOUBLE_QUOTES);
          t = list ? string_list (list) : (char *)NULL;
          free (newname);
          if (list)
            dispose_words (list);

          number = STRLEN (t);
          FREE (t);
        }
    }

  return (number);
}

/* Verify and limit the start and end of the desired substring.  If
   VTYPE == 0, a regular shell variable is being used; if it is 1,
   then the positional parameters are being used; if it is 2, then
   VALUE is really a pointer to an array variable that should be used.
   Return value is 1 if both values were OK, 0 if there was a problem
   with an invalid expression, or -1 if the values were out of range. */
static int
verify_substring_values (value, substr, vtype, e1p, e2p)
     char *value, *substr;
     int vtype, *e1p, *e2p;
{
  char *t, *temp1;
  int len, expok;
#if defined (ARRAY_VARS)
 ARRAY *a;
#endif

  t = strchr (substr, ':');
  if (t)
    *t = '\0';
  temp1 = maybe_expand_string (substr, Q_DOUBLE_QUOTES, expand_string);
  *e1p = evalexp (temp1, &expok);
  free (temp1);
  if (expok == 0)
    return (0);

  switch (vtype)
    {
    case VT_VARIABLE:
    case VT_ARRAYMEMBER:
      len = strlen (value);
      break;
    case VT_POSPARMS:
      len = number_of_args () + 1;
      break;
#if defined (ARRAY_VARS)
    case VT_ARRAYVAR:
      a = (ARRAY *)value;
      len = array_num_elements (a) + 1;
      break;
#endif
    }

  if (*e1p < 0)         /* negative offsets count from end */
    *e1p += len;

  if (*e1p >= len || *e1p < 0)
    return (-1);

  if (t)
    {
      t++;
      temp1 = maybe_expand_string (t, Q_DOUBLE_QUOTES, expand_string);
      t[-1] = ':';
      *e2p = evalexp (temp1, &expok);
      free (temp1);
      if (expok == 0)
        return (0);
      if (*e2p < 0)
        {
          internal_error ("%s: substring expression < 0", t);
          return (0);
        }
      *e2p += *e1p;             /* want E2 chars starting at E1 */
      if (*e2p > len)
        *e2p = len;
    }
  else
    *e2p = len;

  return (1);
}

/* Return the type of variable specified by VARNAME (simple variable,
   positional param, or array variable).  Also return the value specified
   by VARNAME (value of a variable or a reference to an array element). */
static int
get_var_and_type (varname, value, varp, valp)
     char *varname, *value;
     SHELL_VAR **varp;
     char **valp;
{
  int vtype;
  char *temp;
#if defined (ARRAY_VARS)
  SHELL_VAR *v;
#endif

  vtype = (varname[0] == '@' || varname[0] == '*') && varname[1] == '\0';       /* VT_POSPARMS */
  *varp = (SHELL_VAR *)NULL;

#if defined (ARRAY_VARS)
  if (valid_array_reference (varname))
    {
      v = array_variable_part (varname, &temp, (int *)0);
      if (v && array_p (v))
        {
          if ((temp[0] == '@' || temp[0] == '*') && temp[1] == ']')
            {
              vtype = VT_ARRAYVAR;
              *valp = (char *)array_cell (v);
            }
          else
            {
              vtype = VT_ARRAYMEMBER;
              *valp = array_value (varname, 1);
            }
          *varp = v;
        }
      else
        return -1;
    }
  else if ((v = find_variable (varname)) && array_p (v))
    {
      vtype = VT_VARIABLE;
      *varp = v;
      *valp = array_reference (array_cell (v), 0);
    }
  else
#endif
  *valp = value;

  return vtype;
}

/******************************************************/
/*                                                    */
/* Functions to extract substrings of variable values */
/*                                                    */
/******************************************************/

/* Process a variable substring expansion: ${name:e1[:e2]}.  If VARNAME
   is `@', use the positional parameters; otherwise, use the value of
   VARNAME.  If VARNAME is an array variable, use the array elements. */

static char *
parameter_brace_substring (varname, value, substr, quoted)
     char *varname, *value, *substr;
     int quoted;
{
  int e1, e2, vtype, r;
  char *temp, *val;
  SHELL_VAR *v;

  if (value == 0)
    return ((char *)NULL);

  this_command_name = varname;

  vtype = get_var_and_type (varname, value, &v, &val);
  if (vtype == -1)
    return ((char *)NULL);

  r = verify_substring_values (val, substr, vtype, &e1, &e2);
  if (r <= 0)
    {
      if (val && vtype == VT_ARRAYMEMBER)
        free (val);
      return ((r == 0) ? &expand_param_error : (char *)NULL);
    }

  switch (vtype)
    {
    case VT_VARIABLE:
    case VT_ARRAYMEMBER:
      temp = quoted ? quoted_substring (value, e1, e2) : substring (value, e1, e2);
      break;
    case VT_POSPARMS:
      temp = pos_params (varname, e1, e2, quoted);
      break;
#if defined (ARRAY_VARS)
    case VT_ARRAYVAR:
      temp = array_subrange (array_cell (v), e1, e2, quoted);
      break;
#endif
    }

  return temp;
}

/****************************************************************/
/*                                                              */
/* Functions to perform pattern substitution on variable values */
/*                                                              */
/****************************************************************/

char *
pat_subst (string, pat, rep, mflags)
     char *string, *pat, *rep;
     int mflags;
{
  char *ret, *s, *e, *str;
  int rsize, rptr, l, replen, mtype;

  mtype = mflags & MATCH_TYPEMASK;

  /* Special cases:
   *    1.  A null pattern with mtype == MATCH_BEG means to prefix STRING
   *        with REP and return the result.
   *    2.  A null pattern with mtype == MATCH_END means to append REP to
   *        STRING and return the result.
   */
  if ((pat == 0 || *pat == 0) && (mtype == MATCH_BEG || mtype == MATCH_END))
    {
      replen = STRLEN (rep);
      l = strlen (string);
      ret = xmalloc (replen + l + 2);
      if (mtype == MATCH_BEG)
        {
          strcpy (ret, rep);
          strcpy (ret + replen, string);
        }
      else
        {
          strcpy (ret, string);
          strcpy (ret + l, rep);
        }
      return (ret);
    }

  ret = xmalloc (rsize = 64);
  ret[0] = '\0';

  for (replen = STRLEN (rep), rptr = 0, str = string;;)
    {
      if (match_pattern (str, pat, mtype, &s, &e) == 0)
        break;
      l = s - str;
      RESIZE_MALLOCED_BUFFER (ret, rptr, (l + replen), rsize, 64);

      /* OK, now copy the leading unmatched portion of the string (from
         str to s) to ret starting at rptr (the current offset).  Then copy
         the replacement string at ret + rptr + (s - str).  Increment
         rptr (if necessary) and str and go on. */
      if (l)
        {
          strncpy (ret + rptr, str, l);
          rptr += l;
        }
      if (replen)
        {
          strncpy (ret + rptr, rep, replen);
          rptr += replen;
        }
      str = e;          /* e == end of match */
      if (((mflags & MATCH_GLOBREP) == 0) || mtype != MATCH_ANY)
        break;
    }

  /* Now copy the unmatched portion of the input string */
  if (*str)
    {
      RESIZE_MALLOCED_BUFFER (ret, rptr, STRLEN(str) + 1, rsize, 64);
      strcpy (ret + rptr, str);
    }
  else
    ret[rptr] = '\0';

  return ret;
}

/* Do pattern match and replacement on the positional parameters. */
static char *
pos_params_pat_subst (string, pat, rep, mflags)
     char *string, *pat, *rep;
     int mflags;
{
  WORD_LIST *save, *params;
  WORD_DESC *w;
  char *ret;

  save = params = list_rest_of_args ();
  if (save == 0)
    return ((char *)NULL);

  for ( ; params; params = params->next)
    {
      ret = pat_subst (params->word->word, pat, rep, mflags);
      w = make_bare_word (ret);
      dispose_word (params->word);
      params->word = w;
      FREE (ret);
    }

  ret = string_list ((mflags & MATCH_QUOTED) ? quote_list (save) : save);
  dispose_words (save);

  return (ret);
}

/* Perform pattern substitution on VALUE, which is the expansion of
   VARNAME.  PATSUB is an expression supplying the pattern to match
   and the string to substitute.  QUOTED is a flags word containing
   the type of quoting currently in effect. */
static char *
parameter_brace_patsub (varname, value, patsub, quoted)
     char *varname, *value, *patsub;
     int quoted;
{
  int vtype, mflags;
  char *val, *temp, *pat, *rep, *p;
  SHELL_VAR *v;

  if (value == 0)
    return ((char *)NULL);

  this_command_name = varname;

  vtype = get_var_and_type (varname, value, &v, &val);
  if (vtype == -1)
    return ((char *)NULL);

  mflags = 0;
  if (*patsub == '/')
    {
      mflags |= MATCH_GLOBREP;
      patsub++;
    }

  if (quoted & (Q_HERE_DOCUMENT|Q_DOUBLE_QUOTES))
    mflags |= MATCH_QUOTED;

  if (rep = quoted_strchr (patsub, '/', ST_BACKSL))
    *rep++ = '\0';
  else
    rep = (char *)NULL;

  if (rep && *rep == '\0')
    rep = (char *)NULL;

  /* Expand PAT and REP for command, variable and parameter, arithmetic,
     and process substitution.  Also perform quote removal.  Do not
     perform word splitting or filename generation. */
#if 0
  pat = maybe_expand_string (patsub, quoted, expand_string_unsplit);
#else
  pat = maybe_expand_string (patsub, (quoted & ~Q_DOUBLE_QUOTES), expand_string_unsplit);
#endif
  if (rep)
    {
      if ((mflags & MATCH_QUOTED) == 0)
        rep = maybe_expand_string (rep, quoted, expand_string_unsplit);
      else
        rep = expand_string_to_string (rep, quoted, expand_string_unsplit);
    }

  p = pat;
  if (pat && pat[0] == '#')
    {
      mflags |= MATCH_BEG;
      p++;
    }
  else if (pat && pat[0] == '%')
    {
      mflags |= MATCH_END;
      p++;
    }
  else
    mflags |= MATCH_ANY;

  /* OK, we now want to substitute REP for PAT in VAL.  If
     flags & MATCH_GLOBREP is non-zero, the substitution is done
     everywhere, otherwise only the first occurrence of PAT is
     replaced. */
  switch (vtype)
    {
    case VT_VARIABLE:
    case VT_ARRAYMEMBER:
      temp = pat_subst (val, p, rep, mflags);
      break;
    case VT_POSPARMS:
      temp = pos_params_pat_subst (val, p, rep, mflags);
      break;
#if defined (ARRAY_VARS)
    case VT_ARRAYVAR:
      temp = array_pat_subst (array_cell (v), p, rep, mflags);
      break;
#endif
    }

  if (val && v && array_p (v) && vtype == VT_ARRAYMEMBER)
    free (val);

  FREE (pat);
  FREE (rep);

  return temp;
}

/****************************************************************/
/*                                                              */
/*      Functions to perform parameter expansion on a string    */
/*                                                              */
/****************************************************************/

/* ${[#][!]name[[:]#[#]%[%]-=?+[word][:e1[:e2]]]} */
static char *
parameter_brace_expand (string, indexp, quoted, quoted_dollar_atp, contains_dollar_at)
     char *string;
     int *indexp, quoted, *quoted_dollar_atp, *contains_dollar_at;
{
  int check_nullness, var_is_set, var_is_null, var_is_special;
  int want_substring, want_indir, want_patsub;
  char *name, *value, *temp, *temp1;
  int t_index, sindex, c, number;

  value = (char *)NULL;
  var_is_set = var_is_null = var_is_special = check_nullness = 0;
  want_substring = want_indir = want_patsub = 0;

  sindex = *indexp;
  t_index = ++sindex;
  name = string_extract (string, &t_index, "#%:-=?+/}", 1);

  /* If the name really consists of a special variable, then make sure
     that we have the entire name.  We don't allow indirect references
     to special variables except `#', `?', `@' and `*'. */
  if ((sindex == t_index &&
        (string[t_index] == '-' ||
         string[t_index] == '?' ||
         string[t_index] == '#')) ||
      (sindex == t_index - 1 && string[sindex] == '!' &&
        (string[t_index] == '#' ||
         string[t_index] == '?' ||
         string[t_index] == '@' ||
         string[t_index] == '*')))
    {
      t_index++;
      free (name);
      temp1 = string_extract (string, &t_index, "#%:-=?+/}", 0);
      name = xmalloc (3 + (strlen (temp1)));
      *name = string[sindex];
      if (string[sindex] == '!')
        {
          /* indirect reference of $#, $?, $@, or $* */
          name[1] = string[sindex + 1];
          strcpy (name + 2, temp1);
        }
      else      
        strcpy (name + 1, temp1);
      free (temp1);
    }
  sindex = t_index;

  /* Find out what character ended the variable name.  Then
     do the appropriate thing. */
  if (c = string[sindex])
    sindex++;

  /* If c is followed by one of the valid parameter expansion
     characters, move past it as normal.  If not, assume that
     a substring specification is being given, and do not move
     past it. */
  if (c == ':' && member (string[sindex], "-=?+"))
    {
      check_nullness++;
      if (c = string[sindex])
        sindex++;
    }
  else if (c == ':' && string[sindex] != RBRACE)
    want_substring = 1;
  else if (c == '/' && string[sindex] != RBRACE)
    want_patsub = 1;

  /* Catch the valid and invalid brace expressions that made it through the
     tests above. */
  /* ${#-} is a valid expansion and means to take the length of $-.
     Similarly for ${#?} and ${##}... */
  if (name[0] == '#' && name[1] == '\0' && check_nullness == 0 &&
        member (c, "-?#") && string[sindex] == RBRACE)
    {
      name = xrealloc (name, 3);
      name[1] = c;
      name[2] = '\0';
      c = string[sindex++];
    }

  /* ...but ${#%}, ${#:}, ${#=}, ${#+}, and ${#/} are errors. */
  if (name[0] == '#' && name[1] == '\0' && check_nullness == 0 &&
        member (c, "%:=+/") && string[sindex] == RBRACE)
    {
      temp = (char *)NULL;
      goto bad_substitution;
    }

  /* Indirect expansion begins with a `!'.  A valid indirect expansion is
     either a variable name, one of the positional parameters or a special
     variable that expands to one of the positional parameters. */
  want_indir = *name == '!' &&
    (legal_variable_starter (name[1]) || digit (name[1]) || member (name[1], "#?@*"));

  /* Determine the value of this variable. */

  /* Check for special variables, directly referenced. */
  if ((digit (*name) && all_digits (name)) ||
      (name[1] == '\0' && member (*name, "#-?$!@*")) ||
      (want_indir && name[2] == '\0' && member (name[1], "#?@*")))
    var_is_special++;

  /* Check for special expansion things, like the length of a parameter */
  if (*name == '#' && name[1])
    {
      /* If we are not pointing at the character just after the
         closing brace, then we haven't gotten all of the name.
         Since it begins with a special character, this is a bad
         substitution.  Also check NAME for validity before trying
         to go on. */
      if (string[sindex - 1] != RBRACE || (valid_length_expression (name) == 0))
        {
          temp = (char *)NULL;
          goto bad_substitution;
        }

      number = parameter_brace_expand_length (name);
      free (name);

      *indexp = sindex;
      return ((number < 0) ? &expand_param_error : itos (number));
    }

  /* ${@} is identical to $@. */
  if (name[0] == '@' && name[1] == '\0')
    {
      if ((quoted & (Q_HERE_DOCUMENT|Q_DOUBLE_QUOTES)) && quoted_dollar_atp)
        *quoted_dollar_atp = 1;

      if (contains_dollar_at)
        *contains_dollar_at = 1;
    }

  /* Make sure that NAME is valid before trying to go on. */
  if (valid_brace_expansion_word (want_indir ? name + 1 : name,
                                        var_is_special) == 0)
    {
      temp = (char *)NULL;
      goto bad_substitution;
    }

  if (want_indir)
    temp = parameter_brace_expand_indir (name + 1, var_is_special, quoted);
  else
    temp = parameter_brace_expand_word (name, var_is_special, quoted);

#if defined (ARRAY_VARS)
#if 0
  if ((quoted & (Q_HERE_DOCUMENT|Q_DOUBLE_QUOTES)) && valid_array_reference (name))
#else
  if (valid_array_reference (name))
#endif
    {
      temp1 = strchr (name, '[');
      if (temp1 && temp1[1] == '@' && temp1[2] == ']')
        {
          if ((quoted & (Q_HERE_DOCUMENT|Q_DOUBLE_QUOTES)) && quoted_dollar_atp)
            *quoted_dollar_atp = 1;
          if (contains_dollar_at)
            *contains_dollar_at = 1;
        }       /* [ */
      /* ${array[*]}, when unquoted, should be treated like ${array[@]},
         which should result in separate words even when IFS is unset. */
      if (temp1 && temp1[1] == '*' && temp1[2] == ']' && quoted == 0)
        {
          if (contains_dollar_at)
            *contains_dollar_at = 1;
        }
    }
#endif

  var_is_set = temp != (char *)0;
  var_is_null = check_nullness && (var_is_set == 0 || *temp == 0);

  /* Get the rest of the stuff inside the braces. */
  if (c && c != RBRACE)
    {
      /* Extract the contents of the ${ ... } expansion
         according to the Posix.2 rules. */
      value = extract_dollar_brace_string (string, &sindex, quoted);
      if (string[sindex] == RBRACE)
        sindex++;
      else
        goto bad_substitution;
    }
  else
    value = (char *)NULL;

  *indexp = sindex;

  /* If this is a substring spec, process it and add the result. */
  if (want_substring)
    {
      temp1 = parameter_brace_substring (name, temp, value, quoted);
      FREE (name);
      FREE (value);
      FREE (temp);
      return (temp1);
    }
  else if (want_patsub)
    {
      temp1 = parameter_brace_patsub (name, temp, value, quoted);
      FREE (name);
      FREE (value);
      FREE (temp);
      return (temp1);
    }

  /* Do the right thing based on which character ended the variable name. */
  switch (c)
    {
    default:
    case '\0':
    bad_substitution:
      report_error ("%s: bad substitution", string ? string : "??");
      FREE (value);
      FREE (temp);
      free (name);
      return &expand_param_error;

    case RBRACE:
      if (var_is_set == 0 && unbound_vars_is_error)
        {
          report_error ("%s: unbound variable", name);
          FREE (value);
          FREE (temp);
          free (name);
          last_command_exit_value = EXECUTION_FAILURE;
          return (interactive_shell ? &expand_param_error : &expand_param_fatal);
        }
      break;

    case '#':   /* ${param#[#]pattern} */
    case '%':   /* ${param%[%]pattern} */
      if (value == 0 || *value == '\0' || temp == 0 || *temp == '\0')
        {
          FREE (value);
          break;
        }
      if ((name[0] == '@' || name[0] == '*') && name[1] == '\0')
        temp1 = parameter_list_remove_pattern (value, name[0], c, quoted);
#if defined (ARRAY_VARS)
      else if (valid_array_reference (name))
        temp1 = array_remove_pattern (value, name, temp, c, quoted);
#endif
      else
        temp1 = parameter_brace_remove_pattern (value, temp, c, quoted);
      free (temp);
      free (value);
      temp = temp1;
      break;

    case '-':
    case '=':
    case '?':
    case '+':
      if (var_is_set && var_is_null == 0)
        {
          /* We don't want the value of the named variable for
             anything, just the value of the right hand side. */
          if (c == '+')
            {
              FREE (temp);
              if (value)
                {
                  temp = parameter_brace_expand_rhs (name, value, c,
                                                     quoted,
                                                     quoted_dollar_atp,
                                                     contains_dollar_at);
                  free (value);
                }
              else
                temp = (char *)NULL;
            }
          else
            {
              FREE (value);
            }
          /* Otherwise do nothing; just use the value in TEMP. */
        }
      else      /* VAR not set or VAR is NULL. */
        {
          FREE (temp);
          temp = (char *)NULL;
          if (c == '=' && var_is_special)
            {
              report_error ("$%s: cannot assign in this way", name);
              free (name);
              free (value);
              return &expand_param_error;
            }
          else if (c == '?')
            {
              parameter_brace_expand_error (name, value);
              return (interactive ? &expand_param_error : &expand_param_fatal);
            }
          else if (c != '+')
            temp = parameter_brace_expand_rhs (name, value, c, quoted,
                                               quoted_dollar_atp,
                                               contains_dollar_at);
          free (value);
        }
      break;
    }
  free (name);
  return (temp);
}

/* Expand a single ${xxx} expansion.  The braces are optional.  When
   the braces are used, parameter_brace_expand() does the work,
   possibly calling param_expand recursively. */
static char *
param_expand (string, sindex, quoted, expanded_something,
              contains_dollar_at, quoted_dollar_at_p, had_quoted_null_p,
              pflags)
     char *string;
     int *sindex, quoted, *expanded_something, *contains_dollar_at;
     int *quoted_dollar_at_p, *had_quoted_null_p, pflags;
{
  char *temp, *temp1;
  int zindex, number, c, t_index, expok;
  SHELL_VAR *var;
  WORD_LIST *list, *tlist;

  zindex = *sindex;
  c = string[++zindex];

  temp = (char *)NULL;

  /* Do simple cases first. Switch on what follows '$'. */
  switch (c)
    {
    /* $0 .. $9? */
    case '0':
    case '1':
    case '2':
    case '3':
    case '4':
    case '5':
    case '6':
    case '7':
    case '8':
    case '9':
      temp1 = dollar_vars[digit_value (c)];
      if (unbound_vars_is_error && temp1 == (char *)NULL)
        {
          report_error ("$%c: unbound variable", c);
          last_command_exit_value = EXECUTION_FAILURE;
          return (interactive_shell ? &expand_param_error : &expand_param_fatal);
        }
      temp = temp1 ? savestring (temp1) : (char *)NULL;
      break;

    /* $$ -- pid of the invoking shell. */
    case '$':
      temp = itos (dollar_dollar_pid);
      break;

    /* $# -- number of positional parameters. */
    case '#':
      temp = itos (number_of_args ());
      break;

    /* $? -- return value of the last synchronous command. */
    case '?':
      temp = itos (last_command_exit_value);
      break;

    /* $- -- flags supplied to the shell on invocation or by `set'. */
    case '-':
      temp = which_set_flags ();
      break;

      /* $! -- Pid of the last asynchronous command. */
    case '!':
      /* If no asynchronous pids have been created, expand to nothing.
         If `set -u' has been executed, and no async processes have
         been created, this is an expansion error. */
      if (last_asynchronous_pid == NO_PID)
        {
          if (expanded_something)
            *expanded_something = 0;
          temp = (char *)NULL;
          if (unbound_vars_is_error)
            {
              report_error ("$%c: unbound variable", c);
              last_command_exit_value = EXECUTION_FAILURE;
              return (interactive_shell ? &expand_param_error : &expand_param_fatal);
            }
        }
      else
        temp = itos ((int)last_asynchronous_pid);
      break;

    /* The only difference between this and $@ is when the arg is quoted. */
    case '*':           /* `$*' */
      list = list_rest_of_args ();

      /* If there are no command-line arguments, this should just
         disappear if there are other characters in the expansion,
         even if it's quoted. */
      if ((quoted & (Q_HERE_DOCUMENT|Q_DOUBLE_QUOTES)) && list == 0)
        temp = (char *)NULL;
      else if (quoted & (Q_HERE_DOCUMENT|Q_DOUBLE_QUOTES))
        {
          /* If we have "$*" we want to make a string of the positional
             parameters, separated by the first character of $IFS, and
             quote the whole string, including the separators.  If IFS
             is unset, the parameters are separated by ' '; if $IFS is
             null, the parameters are concatenated. */
          temp = string_list_dollar_star (list);
          temp1 = quote_string (temp);
          free (temp);
          temp = temp1;
        }
      else
        {
          /* If the $* is not quoted it is identical to $@ */
          temp = string_list_dollar_at (list, quoted);
          if (contains_dollar_at)
            *contains_dollar_at = 1;
        }

      dispose_words (list);
      break;

    /* When we have "$@" what we want is "$1" "$2" "$3" ... This
       means that we have to turn quoting off after we split into
       the individually quoted arguments so that the final split
       on the first character of $IFS is still done.  */
    case '@':           /* `$@' */
      list = list_rest_of_args ();

      /* We want to flag the fact that we saw this.  We can't turn
         off quoting entirely, because other characters in the
         string might need it (consider "\"$@\""), but we need some
         way to signal that the final split on the first character
         of $IFS should be done, even though QUOTED is 1. */
      if (quoted_dollar_at_p && (quoted & (Q_HERE_DOCUMENT|Q_DOUBLE_QUOTES)))
        *quoted_dollar_at_p = 1;
      if (contains_dollar_at)
        *contains_dollar_at = 1;

      /* We want to separate the positional parameters with the first
         character of $IFS in case $IFS is something other than a space.
         We also want to make sure that splitting is done no matter what --
         according to POSIX.2, this expands to a list of the positional
         parameters no matter what IFS is set to. */
      temp = string_list_dollar_at (list, quoted);

      dispose_words (list);
      break;

    case LBRACE:
      temp = parameter_brace_expand (string, &zindex, quoted,
                                     quoted_dollar_at_p,
                                     contains_dollar_at);
      if (temp == &expand_param_error || temp == &expand_param_fatal)
        return (temp);

      /* XXX */
      /* quoted nulls should be removed if there is anything else
         in the string. */
      /* Note that we saw the quoted null so we can add one back at
         the end of this function if there are no other characters
         in the string, discard TEMP, and go on. */
      if (temp && QUOTED_NULL (temp))
        {
          if (had_quoted_null_p)
            *had_quoted_null_p = 1;
          free (temp);
          temp = (char *)NULL;
        }

      goto return0;

    /* Do command or arithmetic substitution. */
    case LPAREN:
      /* We have to extract the contents of this paren substitution. */
      t_index = zindex + 1;
      temp = extract_command_subst (string, &t_index);
      zindex = t_index;

      /* For Posix.2-style `$(( ))' arithmetic substitution,
         extract the expression and pass it to the evaluator. */
      if (temp && *temp == LPAREN)
        {
          char *temp2;
          temp1 = temp + 1;
          temp2 = savestring (temp1);
          t_index = strlen (temp2) - 1;

          if (temp2[t_index] != RPAREN)
            {
              free (temp2);
              goto comsub;
            }

          /* Cut off ending `)' */
          temp2[t_index] = '\0';

          /* Expand variables found inside the expression. */
          temp1 = maybe_expand_string (temp2, Q_DOUBLE_QUOTES, expand_string);
          free (temp2);

arithsub:
          /* No error messages. */
          this_command_name = (char *)NULL;
          number = evalexp (temp1, &expok);
          free (temp);
          free (temp1);
          if (expok == 0)
            {
              if (interactive_shell == 0 && posixly_correct)
                {
                  last_command_exit_value = EXECUTION_FAILURE;
                  return (&expand_param_fatal);
                }
              else
                return (&expand_param_error);
            }
          temp = itos (number);
          break;
        }

comsub:
      temp1 = command_substitute (temp, quoted);
      FREE (temp);
      temp = temp1;
      break;

    /* Do POSIX.2d9-style arithmetic substitution.  This will probably go
       away in a future bash release. */
    case '[':
      /* We have to extract the contents of this arithmetic substitution. */
      t_index = zindex + 1;
      temp = extract_arithmetic_subst (string, &t_index);
      zindex = t_index;

       /* Do initial variable expansion. */
      temp1 = maybe_expand_string (temp, Q_DOUBLE_QUOTES, expand_string);

      goto arithsub;

    default:
      /* Find the variable in VARIABLE_LIST. */
      temp = (char *)NULL;

      for (t_index = zindex; (c = string[zindex]) && legal_variable_char (c); zindex++)
        ;
      temp1 = (zindex > t_index) ? substring (string, t_index, zindex) : (char *)NULL;

      /* If this isn't a variable name, then just output the `$'. */
      if (temp1 == 0 || *temp1 == '\0')
        {
          FREE (temp1);
          temp = xmalloc (2);
          temp[0] = '$';
          temp[1] = '\0';
          if (expanded_something)
            *expanded_something = 0;
          goto return0;
        }

      /* If the variable exists, return its value cell. */
      var = find_variable (temp1);

      if (var && invisible_p (var) == 0 && value_cell (var))
        {
#if defined (ARRAY_VARS)
          if (array_p (var))
            {
              temp = array_reference (array_cell (var), 0);
              if (temp)
                temp = quote_escapes (temp);
            }
          else
#endif
          temp = quote_escapes (value_cell (var));
          free (temp1);
          if (tempvar_p (var))          /* XXX */
            {
              dispose_variable (var);   /* XXX */
              var = (SHELL_VAR *)NULL;
            }
          goto return0;
        }

      temp = (char *)NULL;

      if (unbound_vars_is_error)
        report_error ("%s: unbound variable", temp1);
      else
        {
          free (temp1);
          goto return0;
        }

      free (temp1);
      last_command_exit_value = EXECUTION_FAILURE;
      return ((unbound_vars_is_error && interactive_shell == 0)
                ? &expand_param_fatal
                : &expand_param_error);
    }

  if (string[zindex])
    zindex++;

return0:
  *sindex = zindex;
  return (temp);
}

/* Make a word list which is the result of parameter and variable
   expansion, command substitution, arithmetic substitution, and
   quote removal of WORD.  Return a pointer to a WORD_LIST which is
   the result of the expansion.  If WORD contains a null word, the
   word list returned is also null.

   QUOTED contains flag values defined in shell.h.

   ISEXP is used to tell expand_word_internal that the word should be
   treated as the result of an expansion.  This has implications for
   how IFS characters in the word are treated.

   CONTAINS_DOLLAR_AT and EXPANDED_SOMETHING are return values; when non-null
   they point to an integer value which receives information about expansion.
   CONTAINS_DOLLAR_AT gets non-zero if WORD contained "$@", else zero.
   EXPANDED_SOMETHING get non-zero if WORD contained any parameter expansions,
   else zero.

   This only does word splitting in the case of $@ expansion.  In that
   case, we split on ' '. */

/* Values for the local variable quoted_state. */
#define UNQUOTED         0
#define PARTIALLY_QUOTED 1
#define WHOLLY_QUOTED    2

static WORD_LIST *
expand_word_internal (word, quoted, isexp, contains_dollar_at, expanded_something)
     WORD_DESC *word;
     int quoted, isexp;
     int *contains_dollar_at;
     int *expanded_something;
{
  WORD_LIST *list;
  WORD_DESC *tword;
  SHELL_VAR *var;

  /* The intermediate string that we build while expanding. */
  char *istring;

  /* The current size of the above object. */
  int istring_size;

  /* Index into ISTRING. */
  int istring_index;

  /* Temporary string storage. */
  char *temp, *temp1;

  /* The text of WORD. */
  register char *string;

  /* The index into STRING. */
  int sindex;

  /* This gets 1 if we see a $@ while quoted. */
  int quoted_dollar_at;

  /* One of UNQUOTED, PARTIALLY_QUOTED, or WHOLLY_QUOTED, depending on
     whether WORD contains no quoting characters, a partially quoted
     string (e.g., "xx"ab), or is fully quoted (e.g., "xxab"). */
  int quoted_state;

  int had_quoted_null;
  int has_dollar_at;

  register int c;               /* Current character. */
  int number;                   /* Temporary number value. */
  int t_index;                  /* For calls to string_extract_xxx. */

  char ifscmap[256];

  istring = xmalloc (istring_size = DEFAULT_INITIAL_ARRAY_SIZE);
  istring[istring_index = 0] = '\0';
  quoted_dollar_at = had_quoted_null = has_dollar_at = 0;
  quoted_state = UNQUOTED;

  string = word->word;
  if (string == 0)
    goto finished_with_string;

  if (contains_dollar_at)
    *contains_dollar_at = 0;

  /* Cache a bitmap of characters in IFS for quoting IFS characters that are
     not part of an expansion.  POSIX.2 says this is a must. */
  temp = getifs ();
  bzero (ifscmap, sizeof (ifscmap));
  for (temp1 = temp; temp1 && *temp1; temp1++)
#if 0
    /* This check compensates for what I think is a parsing problem -- the
       end brace matching algorithms for ${...} expressions differ between
       parse.y and subst.c.  For instance, the parser passes
       ${abc:-G { I } K } as one word when it should be three. */
    if (*temp1 != ' ' && *temp1 != '\t' && *temp1 != '\n')
#endif
      ifscmap[*temp1] = 1;

  /* Begin the expansion. */

  for (sindex = 0; ;)
    {
      c = string[sindex];

      /* Case on toplevel character. */
      switch (c)
        {
        case '\0':
          goto finished_with_string;

        case CTLESC:
          temp = xmalloc (3);
          temp[0] = CTLESC;
          temp[1] = c = string[++sindex];
          temp[2] = '\0';

dollar_add_string:
          if (string[sindex])
            sindex++;

add_string:
          if (temp)
            {
              istring = sub_append_string (temp, istring, &istring_index, &istring_size);
              temp = (char *)0;
            }

          break;

#if defined (PROCESS_SUBSTITUTION)
          /* Process substitution. */
        case '<':
        case '>':
          {
            if (string[++sindex] != LPAREN || (quoted & (Q_HERE_DOCUMENT|Q_DOUBLE_QUOTES)) || posixly_correct)
              {
                sindex--;
                goto add_character;
              }
            else
              t_index = sindex + 1; /* skip past both '<' and LPAREN */

            temp1 = extract_process_subst (string, (c == '<') ? "<(" : ">(", &t_index); /*))*/
            sindex = t_index;

            /* If the process substitution specification is `<()', we want to
               open the pipe for writing in the child and produce output; if
               it is `>()', we want to open the pipe for reading in the child
               and consume input. */
            temp = temp1 ? process_substitute (temp1, (c == '>')) : (char *)0;

            FREE (temp1);

            goto dollar_add_string;
          }
#endif /* PROCESS_SUBSTITUTION */

        case '$':
          if (expanded_something)
            *expanded_something = 1;

          has_dollar_at = 0;
          temp = param_expand (string, &sindex, quoted, expanded_something,
                               &has_dollar_at, &quoted_dollar_at,
                               &had_quoted_null, 0);

          if (temp == &expand_param_error || temp == &expand_param_fatal)
            {
              free (string);
              free (istring);
              return ((temp == &expand_param_error) ? &expand_word_error
                                                    : &expand_word_fatal);
            }
          if (contains_dollar_at && has_dollar_at)
            *contains_dollar_at = 1;
          goto add_string;
          break;

        case '`':               /* Backquoted command substitution. */
          {
            sindex++;

            if (expanded_something)
              *expanded_something = 1;

            temp = string_extract (string, &sindex, "`", 0);
            de_backslash (temp);
            temp1 = command_substitute (temp, quoted);
            FREE (temp);
            temp = temp1;
            goto dollar_add_string;
          }

        case '\\':
          if (string[sindex + 1] == '\n')
            {
              sindex += 2;
              continue;
            }

          c = string[++sindex];

          if (quoted & Q_HERE_DOCUMENT)
            temp1 = slashify_in_here_document;
          else if (quoted & Q_DOUBLE_QUOTES)
            temp1 = slashify_in_quotes;
          else
            temp1 = "";

          if ((quoted & (Q_HERE_DOCUMENT|Q_DOUBLE_QUOTES)) && member (c, temp1) == 0)
            {
              temp = xmalloc (3);
              temp[0] = '\\'; temp[1] = c; temp[2] = '\0';
            }
          else
            /* This character is quoted, so add it in quoted mode. */
            temp = make_quoted_char (c);

          if (c)
            sindex++;
          goto add_string;

        case '"':
          if (quoted & (Q_DOUBLE_QUOTES|Q_HERE_DOCUMENT|Q_NOQUOTE))
            goto add_character;

          t_index = ++sindex;
          temp = string_extract_double_quoted (string, &sindex, 0);

          /* If the quotes surrounded the entire string, then the
             whole word was quoted. */
          quoted_state = (t_index == 1 && string[sindex] == '\0')
                            ? WHOLLY_QUOTED
                            : PARTIALLY_QUOTED;

          if (temp && *temp)
            {
              tword = make_word (temp);         /* XXX */
              free (temp);
              temp = (char *)NULL;

              has_dollar_at = 0;
              list = expand_word_internal (tword, Q_DOUBLE_QUOTES, 0, &has_dollar_at, (int *)NULL);

              if (list == &expand_word_error || list == &expand_word_fatal)
                {
                  free (istring);
                  free (string);
                  /* expand_word_internal has already freed temp_word->word
                     for us because of the way it prints error messages. */
                  tword->word = (char *)NULL;
                  dispose_word (tword);
                  return list;
                }

              dispose_word (tword);

              /* "$@" (a double-quoted dollar-at) expands into nothing,
                 not even a NULL word, when there are no positional
                 parameters. */
              if (list == 0 && has_dollar_at)
                {
                  quoted_dollar_at++;
                  break;
                }

              /* If we get "$@", we know we have expanded something, so we
                 need to remember it for the final split on $IFS.  This is
                 a special case; it's the only case where a quoted string
                 can expand into more than one word.  It's going to come back
                 from the above call to expand_word_internal as a list with
                 a single word, in which all characters are quoted and
                 separated by blanks.  What we want to do is to turn it back
                 into a list for the next piece of code. */
              if (list)
                dequote_list (list);

              if (has_dollar_at)
                {
                  quoted_dollar_at++;
                  if (contains_dollar_at)
                    *contains_dollar_at = 1;
                  if (expanded_something)
                    *expanded_something = 1;
                }
            }
          else
            {
              /* What we have is "".  This is a minor optimization. */
              free (temp);
              list = (WORD_LIST *)NULL;
            }

          /* The code above *might* return a list (consider the case of "$@",
             where it returns "$1", "$2", etc.).  We can't throw away the
             rest of the list, and we have to make sure each word gets added
             as quoted.  We test on tresult->next:  if it is non-NULL, we
             quote the whole list, save it to a string with string_list, and
             add that string. We don't need to quote the results of this
             (and it would be wrong, since that would quote the separators
             as well), so we go directly to add_string. */
          if (list)
            {
              if (list->next)
                {
                  /* Testing quoted_dollar_at makes sure that "$@" is
                     split correctly when $IFS does not contain a space. */
                  temp = quoted_dollar_at
                                ? string_list_dollar_at (list, Q_DOUBLE_QUOTES)
                                : string_list (quote_list (list));
                  dispose_words (list);
                  goto add_string;
                }
              else
                {
                  temp = savestring (list->word->word);
                  dispose_words (list);
#if 1
                  /* If the string is not a quoted null string, we want
                     to remove any embedded unquoted CTLNUL characters.
                     We do not want to turn quoted null strings back into
                     the empty string, though.  We do this because we
                     want to remove any quoted nulls from expansions that
                     contain other characters.  For example, if we have
                     x"$*"y or "x$*y" and there are no positional parameters,
                     the $* should expand into nothing. */                   
                  if (QUOTED_NULL (temp) == 0)
                    remove_quoted_nulls (temp); /* XXX */
#endif
                }
            }
          else
            temp = (char *)NULL;

          /* We do not want to add quoted nulls to strings that are only
             partially quoted; we can throw them away. */
          if (temp == 0 && quoted_state == PARTIALLY_QUOTED)
            continue;

        add_quoted_string:

          if (temp)
            {
              temp1 = temp;
              temp = quote_string (temp);
              free (temp1);
            }
          else
            {
              /* Add NULL arg. */
              temp = xmalloc (2);
              temp[0] = CTLNUL;
              temp[1] = '\0';
            }
          goto add_string;
          /* break; */

        case '\'':
          if (quoted & (Q_DOUBLE_QUOTES|Q_HERE_DOCUMENT|Q_NOQUOTE))
            goto add_character;

          t_index = ++sindex;
          temp = string_extract_single_quoted (string, &sindex);

          /* If the entire STRING was surrounded by single quotes,
             then the string is wholly quoted. */
          quoted_state = (t_index == 1 && string[sindex] == '\0')
                            ? WHOLLY_QUOTED
                            : PARTIALLY_QUOTED;

          /* If all we had was '', it is a null expansion. */
          if (*temp == '\0')
            {
              free (temp);
              temp = (char *)NULL;
            }
          else
            remove_quoted_escapes (temp);

          /* We do not want to add quoted nulls to strings that are only
             partially quoted; such nulls are discarded. */
          if (temp == 0 && (quoted_state == PARTIALLY_QUOTED))
            continue;

          goto add_quoted_string;
          /* break; */

        default:
          /* This is the fix for " $@ " */
          if ((quoted & (Q_HERE_DOCUMENT|Q_DOUBLE_QUOTES)) || (isexp == 0 && ifscmap[c]))
            {
              temp = make_quoted_char (c);
              goto dollar_add_string;
            }

        add_character:
          RESIZE_MALLOCED_BUFFER (istring, istring_index, 1, istring_size,
                                  DEFAULT_ARRAY_SIZE);
          istring[istring_index++] = c;
          istring[istring_index] = '\0';

          /* Next character. */
          sindex++;
        }
    }

finished_with_string:
  /* OK, we're ready to return.  If we have a quoted string, and
     quoted_dollar_at is not set, we do no splitting at all; otherwise
     we split on ' '.  The routines that call this will handle what to
     do if nothing has been expanded. */

  /* Partially and wholly quoted strings which expand to the empty
     string are retained as an empty arguments.  Unquoted strings
     which expand to the empty string are discarded.  The single
     exception is the case of expanding "$@" when there are no
     positional parameters.  In that case, we discard the expansion. */

  /* Because of how the code that handles "" and '' in partially
     quoted strings works, we need to make ISTRING into a QUOTED_NULL
     if we saw quoting characters, but the expansion was empty.
     "" and '' are tossed away before we get to this point when
     processing partially quoted strings.  This makes "" and $xxx""
     equivalent when xxx is unset.  We also look to see whether we
     saw a quoted null from a ${} expansion and add one back if we
     need to. */

  /* If we expand to nothing and there were no single or double quotes
     in the word, we throw it away.  Otherwise, we return a NULL word.
     The single exception is for $@ surrounded by double quotes when
     there are no positional parameters.  In that case, we also throw
     the word away. */

  if (*istring == '\0')
    {
      if (quoted_dollar_at == 0 && (had_quoted_null || quoted_state == PARTIALLY_QUOTED))
        {
          istring[0] = CTLNUL;
          istring[1] = '\0';
          tword = make_bare_word (istring);
          list = make_word_list (tword, (WORD_LIST *)NULL);
          if (quoted & (Q_HERE_DOCUMENT|Q_DOUBLE_QUOTES))
            tword->flags |= W_QUOTED;
        }
      /* According to sh, ksh, and Posix.2, if a word expands into nothing
         and a double-quoted "$@" appears anywhere in it, then the entire
         word is removed. */
      else  if (quoted_state == UNQUOTED || quoted_dollar_at)
        list = (WORD_LIST *)NULL;
#if 0
      else
        {
          tword = make_bare_word (istring);
          list = make_word_list (tword, (WORD_LIST *)NULL);
          if (quoted & (Q_HERE_DOCUMENT|Q_DOUBLE_QUOTES))
            tword->flags |= W_QUOTED;
        }
#endif
    }
  else if (word->flags & W_NOSPLIT)
    {
      tword = make_bare_word (istring);
      list = make_word_list (tword, (WORD_LIST *)NULL);
      if (word->flags & W_ASSIGNMENT)
        tword->flags |= W_ASSIGNMENT;   /* XXX */
      if (word->flags & W_NOGLOB)
        tword->flags |= W_NOGLOB;       /* XXX */
      if (quoted & (Q_HERE_DOCUMENT|Q_DOUBLE_QUOTES))
        tword->flags |= W_QUOTED;
    }
  else
    {
      char *ifs_chars;

      ifs_chars = (quoted_dollar_at || has_dollar_at) ? getifs () : (char *)NULL;

      /* If we have $@, we need to split the results no matter what.  If
         IFS is unset or NULL, string_list_dollar_at has separated the
         positional parameters with a space, so we split on space (we have
         set ifs_chars to " \t\n" above if ifs is unset).  If IFS is set,
         string_list_dollar_at has separated the positional parameters
         with the first character of $IFS, so we split on $IFS. */
      if (has_dollar_at && ifs_chars)
        list = list_string (istring, *ifs_chars ? ifs_chars : " ", 1);
      else
        {
          tword = make_bare_word (istring);
          list = make_word_list (tword, (WORD_LIST *)NULL);
          if ((quoted & (Q_DOUBLE_QUOTES|Q_HERE_DOCUMENT)) || (quoted_state == WHOLLY_QUOTED))
            tword->flags |= W_QUOTED;
          if (word->flags & W_ASSIGNMENT)
            tword->flags |= W_ASSIGNMENT;
          if (word->flags & W_NOGLOB)
            tword->flags |= W_NOGLOB;
        }
    }

  free (istring);
  return (list);
}

/* **************************************************************** */
/*                                                                  */
/*                 Functions for Quote Removal                      */
/*                                                                  */
/* **************************************************************** */

/* Perform quote removal on STRING.  If QUOTED > 0, assume we are obeying the
   backslash quoting rules for within double quotes. */
char *
string_quote_removal (string, quoted)
     char *string;
     int quoted;
{
  char *r, *result_string, *temp;
  int sindex, tindex, c, dquote;

  /* The result can be no longer than the original string. */
  r = result_string = xmalloc (strlen (string) + 1);

  for (dquote = sindex = 0; c = string[sindex];)
    {
      switch (c)
        {
        case '\\':
          c = string[++sindex];
          if (((quoted & (Q_HERE_DOCUMENT|Q_DOUBLE_QUOTES)) || dquote) && member (c, slashify_in_quotes) == 0)
            *r++ = '\\';
          /* FALLTHROUGH */

        default:
          *r++ = c;
          sindex++;
          break;

        case '\'':
          if ((quoted & (Q_HERE_DOCUMENT|Q_DOUBLE_QUOTES)) || dquote)
            {
              *r++ = c;
              sindex++;
              break;
            }
          tindex = sindex + 1;
          temp = string_extract_single_quoted (string, &tindex);
          if (temp)
            {
              strcpy (r, temp);
              r += strlen (r);
              free (temp);
            }
          sindex = tindex;
          break;

        case '"':
          dquote = 1 - dquote;
          sindex++;
          break;
        }
    }
    *r = '\0';
    return (result_string);
}

#if 0
/* UNUSED */
/* Perform quote removal on word WORD.  This allocates and returns a new
   WORD_DESC *. */
WORD_DESC *
word_quote_removal (word, quoted)
     WORD_DESC *word;
     int quoted;
{
  WORD_DESC *w;
  char *t;

  t = string_quote_removal (word->word, quoted);
  w = make_bare_word (t);
  free (t);
  return (w);
}

/* Perform quote removal on all words in LIST.  If QUOTED is non-zero,
   the members of the list are treated as if they are surrounded by
   double quotes.  Return a new list, or NULL if LIST is NULL. */
WORD_LIST *
word_list_quote_removal (list, quoted)
     WORD_LIST *list;
     int quoted;
{
  WORD_LIST *result, *t, *tresult;

  for (t = list, result = (WORD_LIST *)NULL; t; t = t->next)
    {
      tresult = (WORD_LIST *)xmalloc (sizeof (WORD_LIST));
      tresult->word = word_quote_removal (t->word, quoted);
      tresult->next = (WORD_LIST *)NULL;
      result = (WORD_LIST *) list_append (result, tresult);
    }
  return (result);
}
#endif

/*******************************************
 *                                         *
 *    Functions to perform word splitting  *
 *                                         *
 *******************************************/

static char *
getifs ()
{
  SHELL_VAR *ifs;

  ifs = find_variable ("IFS");
  /* If IFS is unset, it defaults to " \t\n". */
  return (ifs ? value_cell (ifs) : " \t\n");
}

/* This splits a single word into a WORD LIST on $IFS, but only if the word
   is not quoted.  list_string () performs quote removal for us, even if we
   don't do any splitting. */
WORD_LIST *
word_split (w)
     WORD_DESC *w;
{
  WORD_LIST *result;
  SHELL_VAR *ifs;
  char *ifs_chars;

  if (w)
    {
      ifs = find_variable ("IFS");
      /* If IFS is unset, it defaults to " \t\n". */
      ifs_chars = ifs ? value_cell (ifs) : " \t\n";

      if ((w->flags & W_QUOTED) || !ifs_chars)
        ifs_chars = "";

      result = list_string (w->word, ifs_chars, w->flags & W_QUOTED);

      if (ifs && tempvar_p (ifs))       /* XXX */
        dispose_variable (ifs);         /* XXX */
    }
  else
    result = (WORD_LIST *)NULL;

  return (result);
}

/* Perform word splitting on LIST and return the RESULT.  It is possible
   to return (WORD_LIST *)NULL. */
static WORD_LIST *
word_list_split (list)
     WORD_LIST *list;
{
  WORD_LIST *result, *t, *tresult;

  for (t = list, result = (WORD_LIST *)NULL; t; t = t->next)
    {
      tresult = word_split (t->word);
      result = (WORD_LIST *) list_append (result, tresult);
    }
  return (result);
}

/**************************************************
 *                                                *
 *    Functions to expand an entire WORD_LIST     *
 *                                                *
 **************************************************/

/* Put NLIST (which is a WORD_LIST * of only one element) at the front of
   ELIST, and set ELIST to the new list. */
#define PREPEND_LIST(nlist, elist) \
        do { nlist->next = elist; elist = nlist; } while (0)

static WORD_LIST *varlist = (WORD_LIST *)NULL;

/* Separate out any initial variable assignments from TLIST.  If set -k has
   been executed, remove all assignment statements from TLIST.  Initial
   variable assignments and other environment assignments are placed
   on VARLIST. */
static WORD_LIST *
separate_out_assignments (tlist)
     WORD_LIST *tlist;
{
  register WORD_LIST *vp, *lp;

  if (!tlist)
    return ((WORD_LIST *)NULL);

  if (varlist)
    dispose_words (varlist);    /* Clean up after previous error */

  varlist = (WORD_LIST *)NULL;
  vp = lp = tlist;

  /* Separate out variable assignments at the start of the command.
     Loop invariant: vp->next == lp
     Loop postcondition:
        lp = list of words left after assignment statements skipped
        tlist = original list of words
  */
  while (lp && (lp->word->flags & W_ASSIGNMENT))
    {
      vp = lp;
      lp = lp->next;
    }

  /* If lp != tlist, we have some initial assignment statements. */
  /* We make VARLIST point to the list of assignment words and
     TLIST point to the remaining words.  */
  if (lp != tlist)
    {
      varlist = tlist;
      /* ASSERT(vp->next == lp); */
      vp->next = (WORD_LIST *)NULL;     /* terminate variable list */
      tlist = lp;                       /* remainder of word list */
    }

  /* vp == end of variable list */
  /* tlist == remainder of original word list without variable assignments */
  if (!tlist)
    /* All the words in tlist were assignment statements */
    return ((WORD_LIST *)NULL);

  /* ASSERT(tlist != NULL); */
  /* ASSERT((tlist->word->flags & W_ASSIGNMENT) == 0); */

  /* If the -k option is in effect, we need to go through the remaining
     words, separate out the assignment words, and place them on VARLIST. */
  if (place_keywords_in_env)
    {
      WORD_LIST *tp;    /* tp == running pointer into tlist */

      tp = tlist;
      lp = tlist->next;

      /* Loop Invariant: tp->next == lp */
      /* Loop postcondition: tlist == word list without assignment statements */
      while (lp)
        {
          if (lp->word->flags & W_ASSIGNMENT)
            {
              /* Found an assignment statement, add this word to end of
                 varlist (vp). */
              if (!varlist)
                varlist = vp = lp;
              else
                {
                  vp->next = lp;
                  vp = lp;
                }

              /* Remove the word pointed to by LP from TLIST. */
              tp->next = lp->next;
              /* ASSERT(vp == lp); */
              lp->next = (WORD_LIST *)NULL;
              lp = tp->next;
            }
          else
            {
              tp = lp;
              lp = lp->next;
            }
        }
    }
  return (tlist);
}

#define WEXP_VARASSIGN  0x001
#define WEXP_BRACEEXP   0x002
#define WEXP_TILDEEXP   0x004
#define WEXP_PARAMEXP   0x008
#define WEXP_PATHEXP    0x010

/* All of the expansions, including variable assignments at the start of
   the list. */
#define WEXP_ALL        (WEXP_VARASSIGN|WEXP_BRACEEXP|WEXP_TILDEEXP|WEXP_PARAMEXP|WEXP_PATHEXP)

/* All of the expansions except variable assignments at the start of
   the list. */
#define WEXP_NOVARS     (WEXP_BRACEEXP|WEXP_TILDEEXP|WEXP_PARAMEXP|WEXP_PATHEXP)

/* All of the `shell expansions': brace expansion, tilde expansion, parameter
   expansion, command substitution, arithmetic expansion, word splitting, and
   quote removal. */
#define WEXP_SHELLEXP   (WEXP_BRACEEXP|WEXP_TILDEEXP|WEXP_PARAMEXP)

/* Take the list of words in LIST and do the various substitutions.  Return
   a new list of words which is the expanded list, and without things like
   variable assignments. */

WORD_LIST *
expand_words (list)
     WORD_LIST *list;
{
  return (expand_word_list_internal (list, WEXP_ALL));
}

/* Same as expand_words (), but doesn't hack variable or environment
   variables. */
WORD_LIST *
expand_words_no_vars (list)
     WORD_LIST *list;
{
  return (expand_word_list_internal (list, WEXP_NOVARS));
}

WORD_LIST *
expand_words_shellexp (list)
     WORD_LIST *list;
{
  return (expand_word_list_internal (list, WEXP_SHELLEXP));
}

static WORD_LIST *
glob_expand_word_list (tlist, eflags)
     WORD_LIST *tlist;
     int eflags;
{
  char **glob_array, *temp_string;
  register int glob_index;
  WORD_LIST *glob_list, *output_list, *disposables, *next;
  WORD_DESC *tword;

  output_list = disposables = (WORD_LIST *)NULL;
  glob_array = (char **)NULL;
  while (tlist)
    {
      /* For each word, either globbing is attempted or the word is
         added to orig_list.  If globbing succeeds, the results are
         added to orig_list and the word (tlist) is added to the list
         of disposable words.  If globbing fails and failed glob
         expansions are left unchanged (the shell default), the
         original word is added to orig_list.  If globbing fails and
         failed glob expansions are removed, the original word is
         added to the list of disposable words.  orig_list ends up
         in reverse order and requires a call to reverse_list to
         be set right.  After all words are examined, the disposable
         words are freed. */
      next = tlist->next;

      /* If the word isn't an assignment and contains an unquoted
         pattern matching character, then glob it. */
#if 0
      if ((tlist->word->flags & W_ASSIGNMENT) == 0 &&
#else
      if ((tlist->word->flags & W_NOGLOB) == 0 &&
#endif
          unquoted_glob_pattern_p (tlist->word->word))
        {
          glob_array = shell_glob_filename (tlist->word->word);

          /* Handle error cases.
             I don't think we should report errors like "No such file
             or directory".  However, I would like to report errors
             like "Read failed". */

          if (GLOB_FAILED (glob_array))
            {
              glob_array = (char **) xmalloc (sizeof (char *));
              glob_array[0] = (char *)NULL;
            }

          /* Dequote the current word in case we have to use it. */
          if (glob_array[0] == NULL)
            {
              temp_string = dequote_string (tlist->word->word);
              free (tlist->word->word);
              tlist->word->word = temp_string;
            }

          /* Make the array into a word list. */
          glob_list = (WORD_LIST *)NULL;
          for (glob_index = 0; glob_array[glob_index]; glob_index++)
            {
              tword = make_bare_word (glob_array[glob_index]);
              tword->flags |= W_GLOBEXP;        /* XXX */
              glob_list = make_word_list (tword, glob_list);
            }

          if (glob_list)
            {
              output_list = (WORD_LIST *)list_append (glob_list, output_list);
              PREPEND_LIST (tlist, disposables);
            }
          else if (allow_null_glob_expansion == 0)
            {
              /* Failed glob expressions are left unchanged. */
              PREPEND_LIST (tlist, output_list);
            }
          else
            {
              /* Failed glob expressions are removed. */
              PREPEND_LIST (tlist, disposables);
            }
        }
      else
        {
          /* Dequote the string. */
          temp_string = dequote_string (tlist->word->word);
          free (tlist->word->word);
          tlist->word->word = temp_string;
          PREPEND_LIST (tlist, output_list);
        }

      free_array (glob_array);
      glob_array = (char **)NULL;

      tlist = next;
    }

  if (disposables)
    dispose_words (disposables);

  if (output_list)
    output_list = REVERSE_LIST (output_list, WORD_LIST *);

  return (output_list);
}

#if defined (BRACE_EXPANSION)
static WORD_LIST *
brace_expand_word_list (tlist, eflags)
     WORD_LIST *tlist;
     int eflags;
{
  register char **expansions;
  char *temp_string;
  WORD_LIST *disposables, *output_list, *next;
  WORD_DESC *w;
  int eindex;

  for (disposables = output_list = (WORD_LIST *)NULL; tlist; tlist = next)
    {
      next = tlist->next;

      /* Only do brace expansion if the word has a brace character.  If
         not, just add the word list element to BRACES and continue.  In
         the common case, at least when running shell scripts, this will
         degenerate to a bunch of calls to `strchr', and then what is
         basically a reversal of TLIST into BRACES, which is corrected
         by a call to reverse_list () on BRACES when the end of TLIST
         is reached. */
      if (strchr (tlist->word->word, LBRACE))
        {
          expansions = brace_expand (tlist->word->word);

          for (eindex = 0; temp_string = expansions[eindex]; eindex++)
            {
              w = make_word (temp_string);
              /* If brace expansion didn't change the word, preserve
                 the flags.  We may want to preserve the flags
                 unconditionally someday -- XXX */
              if (STREQ (temp_string, tlist->word->word))
                w->flags = tlist->word->flags;
              output_list = make_word_list (w, output_list);
              free (expansions[eindex]);
            }
          free (expansions);

          /* Add TLIST to the list of words to be freed after brace
             expansion has been performed. */
          PREPEND_LIST (tlist, disposables);
        }
      else
        PREPEND_LIST (tlist, output_list);
    }

  if (disposables)
    dispose_words (disposables);

  if (output_list)
    output_list = REVERSE_LIST (output_list, WORD_LIST *);

  return (output_list);
}
#endif

static WORD_LIST *
shell_expand_word_list (tlist, eflags)
     WORD_LIST *tlist;
     int eflags;
{
  WORD_LIST *expanded, *orig_list, *new_list, *next, *temp_list;
  int expanded_something, has_dollar_at;
  char *temp_string;

  /* We do tilde expansion all the time.  This is what 1003.2 says. */
  new_list = (WORD_LIST *)NULL;
  for (orig_list = tlist; tlist; tlist = next)
    {
      temp_string = tlist->word->word;

      next = tlist->next;

      /* Posix.2 section 3.6.1 says that tildes following `=' in words
         which are not assignment statements are not expanded.  We do
         this only if POSIXLY_CORRECT is enabled.  Essentially, we do
         tilde expansion on unquoted assignment statements (flags include
         W_ASSIGNMENT but not W_QUOTED). */
      if (temp_string[0] == '~' ||
            (((tlist->word->flags & (W_ASSIGNMENT|W_QUOTED)) == W_ASSIGNMENT) &&
             posixly_correct == 0 &&
             strchr (temp_string, '~') &&
             (unquoted_substring ("=~", temp_string) || unquoted_substring (":~", temp_string))))
        {
          tlist->word->word = bash_tilde_expand (temp_string);
          free (temp_string);
        }

      expanded_something = 0;
      expanded = expand_word_internal
        (tlist->word, 0, 0, &has_dollar_at, &expanded_something);

      if (expanded == &expand_word_error || expanded == &expand_word_fatal)
        {
          /* By convention, each time this error is returned,
             tlist->word->word has already been freed. */
          tlist->word->word = (char *)NULL;

          /* Dispose our copy of the original list. */
          dispose_words (orig_list);
          /* Dispose the new list we're building. */
          dispose_words (new_list);

          if (expanded == &expand_word_error)
            jump_to_top_level (DISCARD);
          else
            jump_to_top_level (FORCE_EOF);
        }

      /* Don't split words marked W_NOSPLIT. */
      if (expanded_something && (tlist->word->flags & W_NOSPLIT) == 0)
        {
          temp_list = word_list_split (expanded);
          dispose_words (expanded);
        }
      else
        {
          /* If no parameter expansion, command substitution, process
             substitution, or arithmetic substitution took place, then
             do not do word splitting.  We still have to remove quoted
             null characters from the result. */
          word_list_remove_quoted_nulls (expanded);
          temp_list = expanded;
        }

      expanded = REVERSE_LIST (temp_list, WORD_LIST *);
      new_list = (WORD_LIST *)list_append (expanded, new_list);
    }

  if (orig_list)  
    dispose_words (orig_list);

  if (new_list)
    new_list = REVERSE_LIST (new_list, WORD_LIST *);

  return (new_list);
}

/* The workhorse for expand_words () and expand_words_no_vars ().
   First arg is LIST, a WORD_LIST of words.
   Second arg EFLAGS is a flags word controlling which expansions are
   performed.

   This does all of the substitutions: brace expansion, tilde expansion,
   parameter expansion, command substitution, arithmetic expansion,
   process substitution, word splitting, and pathname expansion, according
   to the bits set in EFLAGS.  Words with the W_QUOTED or W_NOSPLIT bits
   set, or for which no expansion is done, do not undergo word splitting.
   Words with the W_NOGLOB bit set do not undergo pathname expansion. */
static WORD_LIST *
expand_word_list_internal (list, eflags)
     WORD_LIST *list;
     int eflags;
{
  WORD_LIST *new_list, *temp_list;
  int tint;

  if (list == 0)
    return ((WORD_LIST *)NULL);

  new_list = copy_word_list (list);

  if (eflags & WEXP_VARASSIGN)
    {
      new_list = separate_out_assignments (new_list);
      if (new_list == 0)
        {
          if (varlist)
            {
              /* All the words were variable assignments, so they are placed
                 into the shell's environment. */
              for (temp_list = varlist; temp_list; temp_list = temp_list->next)
                {
                  this_command_name = (char *)NULL;     /* no arithmetic errors */
                  tint = do_assignment (temp_list->word->word);
                  /* Variable assignment errors in non-interactive shells
                     running in Posix.2 mode cause the shell to exit. */
                  if (tint == 0 && interactive_shell == 0 && posixly_correct)
                    {
                      last_command_exit_value = EXECUTION_FAILURE;
                      jump_to_top_level (FORCE_EOF);
                    }
                }
              dispose_words (varlist);
              varlist = (WORD_LIST *)NULL;
            }
          return ((WORD_LIST *)NULL);
        }
    }

  /* Begin expanding the words that remain.  The expansions take place on
     things that aren't really variable assignments. */

#if defined (BRACE_EXPANSION)
  /* Do brace expansion on this word if there are any brace characters
     in the string. */
  if ((eflags & WEXP_BRACEEXP) && brace_expansion && new_list)
    new_list = brace_expand_word_list (new_list, eflags);
#endif /* BRACE_EXPANSION */

  /* Perform the `normal' shell expansions: tilde expansion, parameter and
     variable substitution, command substitution, arithmetic expansion,
     and word splitting. */
  new_list = shell_expand_word_list (new_list, eflags);

  /* Okay, we're almost done.  Now let's just do some filename
     globbing. */
  if (new_list)
    {
      if ((eflags & WEXP_PATHEXP) && disallow_filename_globbing == 0)
        /* Glob expand the word list unless globbing has been disabled. */
        new_list = glob_expand_word_list (new_list, eflags);
      else
        /* Dequote the words, because we're not performing globbing. */
        new_list = dequote_list (new_list);
    }

  if ((eflags & WEXP_VARASSIGN) && varlist)
    {
      Function *assign_func;

      /* If the remainder of the words expand to nothing, Posix.2 requires
         that the variable and environment assignments affect the shell's
         environment. */
      assign_func = new_list ? assign_in_env : do_assignment;

      for (temp_list = varlist; temp_list; temp_list = temp_list->next)
        {
          this_command_name = (char *)NULL;
          tint = (*assign_func) (temp_list->word->word);
          /* Variable assignment errors in non-interactive shells running
             in Posix.2 mode cause the shell to exit. */
          if (tint == 0 && assign_func == do_assignment &&
                interactive_shell == 0 && posixly_correct)
            {
              last_command_exit_value = EXECUTION_FAILURE;
              jump_to_top_level (FORCE_EOF);
            }
        }

      dispose_words (varlist);
      varlist = (WORD_LIST *)NULL;
    }

#if 0
  tint = list_length (new_list) + 1;
  RESIZE_MALLOCED_BUFFER (glob_argv_flags, 0, tint, glob_argv_flags_size, 16);
  for (tint = 0, temp_list = new_list; temp_list; temp_list = temp_list->next)
    glob_argv_flags[tint++] = (temp_list->word->flags & W_GLOBEXP) ? '1' : '0';
  glob_argv_flags[tint] = '\0';
#endif

  return (new_list);
}