/* common.c - utility functions for all builtins */

/* Copyright (C) 1987-2021 Free Software Foundation, Inc.

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

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

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

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

#include <config.h>

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

#include <stdio.h>
#include <chartypes.h>
#include "../bashtypes.h"
#include "posixstat.h"
#include <signal.h>

#include <errno.h>

#if defined (PREFER_STDARG)
#  include <stdarg.h>
#else
#  include <varargs.h>
#endif

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

#define NEED_FPURGE_DECL

#include "../shell.h"
#include "maxpath.h"
#include "../flags.h"
#include "../parser.h"
#include "../jobs.h"
#include "../builtins.h"
#include "../input.h"
#include "../execute_cmd.h"
#include "../trap.h"
#include "bashgetopt.h"
#include "common.h"
#include "builtext.h"
#include <tilde/tilde.h>

#if defined (HISTORY)
#  include "../bashhist.h"
#endif

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

extern const char * const bash_getcwd_errstr;

/* Used by some builtins and the mainline code. */
sh_builtin_func_t *last_shell_builtin = (sh_builtin_func_t *)NULL;
sh_builtin_func_t *this_shell_builtin = (sh_builtin_func_t *)NULL;

/* **************************************************************** */
/*								    */
/*	     Error reporting, usage, and option processing	    */
/*								    */
/* **************************************************************** */

/* This is a lot like report_error (), but it is for shell builtins
   instead of shell control structures, and it won't ever exit the
   shell. */

static void
builtin_error_prolog ()
{
  char *name;

  name = get_name_for_error ();
  fprintf (stderr, "%s: ", name);

  if (interactive_shell == 0)
    fprintf (stderr, _("line %d: "), executing_line_number ());

  if (this_command_name && *this_command_name)
    fprintf (stderr, "%s: ", this_command_name);
}

void
#if defined (PREFER_STDARG)
builtin_error (const char *format, ...)
#else
builtin_error (format, va_alist)
     const char *format;
     va_dcl
#endif
{
  va_list args;

  builtin_error_prolog ();

  SH_VA_START (args, format);

  vfprintf (stderr, format, args);
  va_end (args);
  fprintf (stderr, "\n");
}

void
#if defined (PREFER_STDARG)
builtin_warning (const char *format, ...)
#else
builtin_warning (format, va_alist)
     const char *format;
     va_dcl
#endif
{
  va_list args;

  builtin_error_prolog ();
  fprintf (stderr, _("warning: "));

  SH_VA_START (args, format);

  vfprintf (stderr, format, args);
  va_end (args);
  fprintf (stderr, "\n");
}

/* Print a usage summary for the currently-executing builtin command. */
void
builtin_usage ()
{
  if (this_command_name && *this_command_name)
    fprintf (stderr, _("%s: usage: "), this_command_name);
  fprintf (stderr, "%s\n", _(current_builtin->short_doc));
  fflush (stderr);
}

/* Return if LIST is NULL else barf and jump to top_level.  Used by some
   builtins that do not accept arguments. */
void
no_args (list)
     WORD_LIST *list;
{
  if (list)
    {
      builtin_error (_("too many arguments"));
      top_level_cleanup ();
      jump_to_top_level (DISCARD);
    }
}

/* Check that no options were given to the currently-executing builtin,
   and return 0 if there were options. */
int
no_options (list)
     WORD_LIST *list;
{
  int opt;

  reset_internal_getopt ();
  if ((opt = internal_getopt (list, "")) != -1)
    {
      if (opt == GETOPT_HELP)
	{
	  builtin_help ();
	  return (2);
	}
      builtin_usage ();
      return (1);
    }
  return (0);
}

void
sh_needarg (s)
     char *s;
{
  builtin_error (_("%s: option requires an argument"), s);
}

void
sh_neednumarg (s)
     char *s;
{
  builtin_error (_("%s: numeric argument required"), s);
}

void
sh_notfound (s)
     char *s;
{
  builtin_error (_("%s: not found"), s);
}

/* Function called when one of the builtin commands detects an invalid
   option. */
void
sh_invalidopt (s)
     char *s;
{
  builtin_error (_("%s: invalid option"), s);
}

void
sh_invalidoptname (s)
     char *s;
{
  builtin_error (_("%s: invalid option name"), s);
}

void
sh_invalidid (s)
     char *s;
{
  builtin_error (_("`%s': not a valid identifier"), s);
}

void
sh_invalidnum (s)
     char *s;
{
  char *msg;

  if (*s == '0' && isdigit ((unsigned char)s[1]))
    msg = _("invalid octal number");
  else if (*s == '0' && s[1] == 'x')
    msg = _("invalid hex number");
  else
    msg = _("invalid number");
  builtin_error ("%s: %s", s, msg);
}

void
sh_invalidsig (s)
     char *s;
{
  builtin_error (_("%s: invalid signal specification"), s);
}

void
sh_badpid (s)
     char *s;
{
  builtin_error (_("`%s': not a pid or valid job spec"), s);
}

void
sh_readonly (s)
     const char *s;
{
  builtin_error (_("%s: readonly variable"), s);
}

void
sh_noassign (s)
     const char *s;
{
  internal_error (_("%s: cannot assign"), s);	/* XXX */
}

void
sh_erange (s, desc)
     char *s, *desc;
{
  if (s)
    builtin_error (_("%s: %s out of range"), s, desc ? desc : _("argument"));
  else
    builtin_error (_("%s out of range"), desc ? desc : _("argument"));
}

#if defined (JOB_CONTROL)
void
sh_badjob (s)
     char *s;
{
  builtin_error (_("%s: no such job"), s);
}

void
sh_nojobs (s)
     char *s;
{
  if (s)
    builtin_error (_("%s: no job control"), s);
  else
    builtin_error (_("no job control"));
}
#endif

#if defined (RESTRICTED_SHELL)
void
sh_restricted (s)
     char *s;
{
  if (s)
    builtin_error (_("%s: restricted"), s);
  else
    builtin_error (_("restricted"));
}
#endif

void
sh_notbuiltin (s)
     char *s;
{
  builtin_error (_("%s: not a shell builtin"), s);
}

void
sh_wrerror ()
{
#if defined (DONT_REPORT_BROKEN_PIPE_WRITE_ERRORS) && defined (EPIPE)
  if (errno != EPIPE)
#endif /* DONT_REPORT_BROKEN_PIPE_WRITE_ERRORS && EPIPE */
  builtin_error (_("write error: %s"), strerror (errno));
}

void
sh_ttyerror (set)
     int set;
{
  if (set)
    builtin_error (_("error setting terminal attributes: %s"), strerror (errno));
  else
    builtin_error (_("error getting terminal attributes: %s"), strerror (errno));
}

int
sh_chkwrite (s)
     int s;
{
  QUIT;
  fflush (stdout);
  QUIT;
  if (ferror (stdout))
    {
      sh_wrerror ();
      fpurge (stdout);
      clearerr (stdout);
      return (EXECUTION_FAILURE);
    }
  return (s);
}

/* **************************************************************** */
/*								    */
/*	     Shell positional parameter manipulation		    */
/*								    */
/* **************************************************************** */

/* Convert a WORD_LIST into a C-style argv.  Return the number of elements
   in the list in *IP, if IP is non-null.  A convenience function for
   loadable builtins; also used by `test'. */
char **
make_builtin_argv (list, ip)
     WORD_LIST *list;
     int *ip;
{
  char **argv;

  argv = strvec_from_word_list (list, 0, 1, ip);
  argv[0] = this_command_name;
  return argv;
}

/* Remember LIST in $1 ... $9, and REST_OF_ARGS.  If DESTRUCTIVE is
   non-zero, then discard whatever the existing arguments are, else
   only discard the ones that are to be replaced.  Set POSPARAM_COUNT
   to the number of args assigned (length of LIST). */
void
remember_args (list, destructive)
     WORD_LIST *list;
     int destructive;
{
  register int i;

  posparam_count = 0;

  for (i = 1; i < 10; i++)
    {
      if ((destructive || list) && dollar_vars[i])
	{
	  free (dollar_vars[i]);
	  dollar_vars[i] = (char *)NULL;
	}

      if (list)
	{
	  dollar_vars[posparam_count = i] = savestring (list->word->word);
	  list = list->next;
	}
    }

  /* If arguments remain, assign them to REST_OF_ARGS.
     Note that copy_word_list (NULL) returns NULL, and
     that dispose_words (NULL) does nothing. */
  if (destructive || list)
    {
      dispose_words (rest_of_args);
      rest_of_args = copy_word_list (list);
      posparam_count += list_length (list);
    }

  if (destructive)
    set_dollar_vars_changed ();

  invalidate_cached_quoted_dollar_at ();
}

void
shift_args (times)
     int times;
{
  WORD_LIST *temp;
  int count;

  if (times <= 0)		/* caller should check */
    return;

  while (times-- > 0)
    {
      if (dollar_vars[1])
	free (dollar_vars[1]);

      for (count = 1; count < 9; count++)
	dollar_vars[count] = dollar_vars[count + 1];

      if (rest_of_args)
	{
	  temp = rest_of_args;
	  dollar_vars[9] = savestring (temp->word->word);
	  rest_of_args = rest_of_args->next;
	  temp->next = (WORD_LIST *)NULL;
	  dispose_words (temp);
	}
      else
	dollar_vars[9] = (char *)NULL;

      posparam_count--;
    }
}

int
number_of_args ()
{
#if 0
  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++;

if (n != posparam_count)
  itrace("number_of_args: n (%d) != posparam_count (%d)", n, posparam_count);
#else
  return posparam_count;
#endif
}

static int changed_dollar_vars;

/* Have the dollar variables been reset to new values since we last
   checked? */
int
dollar_vars_changed ()
{
  return (changed_dollar_vars);
}

void
set_dollar_vars_unchanged ()
{
  changed_dollar_vars = 0;
}

void
set_dollar_vars_changed ()
{
  if (variable_context)
    changed_dollar_vars |= ARGS_FUNC;
  else if (this_shell_builtin == set_builtin)
    changed_dollar_vars |= ARGS_SETBLTIN;
  else
    changed_dollar_vars |= ARGS_INVOC;
}

/* **************************************************************** */
/*								    */
/*		Validating numeric input and arguments		    */
/*								    */
/* **************************************************************** */

/* Read a numeric arg for this_command_name, the name of the shell builtin
   that wants it.  LIST is the word list that the arg is to come from.
   Accept only the numeric argument; report an error if other arguments
   follow.  If FATAL is 1, call throw_to_top_level, which exits the
   shell; if it's 2, call jump_to_top_level (DISCARD), which aborts the
   current command; if FATAL is 0, return an indication of an invalid
   number by setting *NUMOK == 0 and return -1. */
int
get_numeric_arg (list, fatal, count)
     WORD_LIST *list;
     int fatal;
     intmax_t *count;
{
  char *arg;

  if (count)
    *count = 1;

  if (list && list->word && ISOPTION (list->word->word, '-'))
    list = list->next;

  if (list)
    {
      arg = list->word->word;
      if (arg == 0 || (legal_number (arg, count) == 0))
	{
	  sh_neednumarg (list->word->word ? list->word->word : "`'");
	  if (fatal == 0)
	    return 0;
	  else if (fatal == 1)		/* fatal == 1; abort */
	    throw_to_top_level ();
	  else				/* fatal == 2; discard current command */
	    {
	      top_level_cleanup ();
	      jump_to_top_level (DISCARD);
	    }
	}
      no_args (list->next);
    }

  return (1);
}

/* Get an eight-bit status value from LIST */
int
get_exitstat (list)
     WORD_LIST *list;
{
  int status;
  intmax_t sval;
  char *arg;

  if (list && list->word && ISOPTION (list->word->word, '-'))
    list = list->next;

  if (list == 0)
    {
      /* If we're not running the DEBUG trap, the return builtin, when not
	 given any arguments, uses the value of $? before the trap ran.  If
	 given an argument, return uses it.  This means that the trap can't
	 change $?.  The DEBUG trap gets to change $?, though, since that is
	 part of its reason for existing, and because the extended debug mode
	 does things with the return value. */
      if (this_shell_builtin == return_builtin && running_trap > 0 && running_trap != DEBUG_TRAP+1)
	return (trap_saved_exit_value);
      return (last_command_exit_value);
    }

  arg = list->word->word;
  if (arg == 0 || legal_number (arg, &sval) == 0)
    {
      sh_neednumarg (list->word->word ? list->word->word : "`'");
      return EX_BADUSAGE;
    }
  no_args (list->next);

  status = sval & 255;
  return status;
}

/* Return the octal number parsed from STRING, or -1 to indicate
   that the string contained a bad number. */
int
read_octal (string)
     char *string;
{
  int result, digits;

  result = digits = 0;
  while (*string && ISOCTAL (*string))
    {
      digits++;
      result = (result * 8) + (*string++ - '0');
      if (result > 07777)
	return -1;
    }

  if (digits == 0 || *string)
    result = -1;

  return (result);
}

/* **************************************************************** */
/*								    */
/*	     Manipulating the current working directory		    */
/*								    */
/* **************************************************************** */

/* Return a consed string which is the current working directory.
   FOR_WHOM is the name of the caller for error printing.  */
char *the_current_working_directory = (char *)NULL;

char *
get_working_directory (for_whom)
     char *for_whom;
{
  if (no_symbolic_links)
    {
      FREE (the_current_working_directory);
      the_current_working_directory = (char *)NULL;
    }

  if (the_current_working_directory == 0)
    {
#if defined (GETCWD_BROKEN)
      the_current_working_directory = getcwd (0, PATH_MAX);
#else
      the_current_working_directory = getcwd (0, 0);
#endif
      if (the_current_working_directory == 0)
	{
	  fprintf (stderr, _("%s: error retrieving current directory: %s: %s\n"),
		   (for_whom && *for_whom) ? for_whom : get_name_for_error (),
		   _(bash_getcwd_errstr), strerror (errno));
	  return (char *)NULL;
	}
    }

  return (savestring (the_current_working_directory));
}

/* Make NAME our internal idea of the current working directory. */
void
set_working_directory (name)
     char *name;
{
  FREE (the_current_working_directory);
  the_current_working_directory = savestring (name);
}

/* **************************************************************** */
/*								    */
/*	     	Job control support functions			    */
/*								    */
/* **************************************************************** */

#if defined (JOB_CONTROL)
int
get_job_by_name (name, flags)
     const char *name;
     int flags;
{
  register int i, wl, cl, match, job;
  register PROCESS *p;
  register JOB *j;

  job = NO_JOB;
  wl = strlen (name);
  for (i = js.j_jobslots - 1; i >= 0; i--)
    {
      j = get_job_by_jid (i);
      if (j == 0 || ((flags & JM_STOPPED) && J_JOBSTATE(j) != JSTOPPED))
        continue;

      p = j->pipe;
      do
        {
	  if (flags & JM_EXACT)
	    {
	      cl = strlen (p->command);
	      match = STREQN (p->command, name, cl);
	    }
	  else if (flags & JM_SUBSTRING)
	    match = strcasestr (p->command, name) != (char *)0;
	  else
	    match = STREQN (p->command, name, wl);

	  if (match == 0)
	    {
	      p = p->next;
	      continue;
	    }
	  else if (flags & JM_FIRSTMATCH)
	    return i;		/* return first match */
	  else if (job != NO_JOB)
	    {
	      if (this_shell_builtin)
	        builtin_error (_("%s: ambiguous job spec"), name);
	      else
	        internal_error (_("%s: ambiguous job spec"), name);
	      return (DUP_JOB);
	    }
	  else
	    job = i;
        }
      while (p != j->pipe);
    }

  return (job);
}

/* Return the job spec found in LIST. */
int
get_job_spec (list)
     WORD_LIST *list;
{
  register char *word;
  int job, jflags;

  if (list == 0)
    return (js.j_current);

  word = list->word->word;

  if (*word == '\0')
    return (NO_JOB);

  if (*word == '%')
    word++;

  if (DIGIT (*word) && all_digits (word))
    {
      job = atoi (word);
      return ((job < 0 || job > js.j_jobslots) ? NO_JOB : job - 1);
    }

  jflags = 0;
  switch (*word)
    {
    case 0:
    case '%':
    case '+':
      return (js.j_current);

    case '-':
      return (js.j_previous);

    case '?':			/* Substring search requested. */
      jflags |= JM_SUBSTRING;
      word++;
      /* FALLTHROUGH */

    default:
      return get_job_by_name (word, jflags);
    }
}
#endif /* JOB_CONTROL */

/*
 * NOTE:  `kill' calls this function with forcecols == 0
 */
int
display_signal_list (list, forcecols)
     WORD_LIST *list;
     int forcecols;
{
  register int i, column;
  char *name;
  int result, signum, dflags;
  intmax_t lsignum;

  result = EXECUTION_SUCCESS;
  if (!list)
    {
      for (i = 1, column = 0; i < NSIG; i++)
	{
	  name = signal_name (i);
	  if (STREQN (name, "SIGJUNK", 7) || STREQN (name, "Unknown", 7))
	    continue;

	  if (posixly_correct && !forcecols)
	    {
	      /* This is for the kill builtin.  POSIX.2 says the signal names
		 are displayed without the `SIG' prefix. */
	      if (STREQN (name, "SIG", 3))
		name += 3;
	      printf ("%s%s", name, (i == NSIG - 1) ? "" : " ");
	    }
	  else
	    {
	      printf ("%2d) %s", i, name);

	      if (++column < 5)
		printf ("\t");
	      else
		{
		  printf ("\n");
		  column = 0;
		}
	    }
	}

      if ((posixly_correct && !forcecols) || column != 0)
	printf ("\n");
      return result;
    }

  /* List individual signal names or numbers. */
  while (list)
    {
      if (legal_number (list->word->word, &lsignum))
	{
	  /* This is specified by Posix.2 so that exit statuses can be
	     mapped into signal numbers. */
	  if (lsignum > 128)
	    lsignum -= 128;
	  if (lsignum < 0 || lsignum >= NSIG)
	    {
	      sh_invalidsig (list->word->word);
	      result = EXECUTION_FAILURE;
	      list = list->next;
	      continue;
	    }

	  signum = lsignum;
	  name = signal_name (signum);
	  if (STREQN (name, "SIGJUNK", 7) || STREQN (name, "Unknown", 7))
	    {
	      list = list->next;
	      continue;
	    }
	  /* POSIX.2 says that `kill -l signum' prints the signal name without
	     the `SIG' prefix. */
	  printf ("%s\n", (this_shell_builtin == kill_builtin && signum > 0) ? name + 3 : name);
	}
      else
	{
	  dflags = DSIG_NOCASE;
	  if (posixly_correct == 0 || this_shell_builtin != kill_builtin)
	    dflags |= DSIG_SIGPREFIX;
	  signum = decode_signal (list->word->word, dflags);
	  if (signum == NO_SIG)
	    {
	      sh_invalidsig (list->word->word);
	      result = EXECUTION_FAILURE;
	      list = list->next;
	      continue;
	    }
	  printf ("%d\n", signum);
	}
      list = list->next;
    }
  return (result);
}

/* **************************************************************** */
/*								    */
/*	    Finding builtin commands and their functions	    */
/*								    */
/* **************************************************************** */

/* Perform a binary search and return the address of the builtin function
   whose name is NAME.  If the function couldn't be found, or the builtin
   is disabled or has no function associated with it, return NULL.
   Return the address of the builtin.
   DISABLED_OKAY means find it even if the builtin is disabled. */
struct builtin *
builtin_address_internal (name, disabled_okay)
     char *name;
     int disabled_okay;
{
  int hi, lo, mid, j;

  hi = num_shell_builtins - 1;
  lo = 0;

  while (lo <= hi)
    {
      mid = (lo + hi) / 2;

      j = shell_builtins[mid].name[0] - name[0];

      if (j == 0)
	j = strcmp (shell_builtins[mid].name, name);

      if (j == 0)
	{
	  /* It must have a function pointer.  It must be enabled, or we
	     must have explicitly allowed disabled functions to be found,
	     and it must not have been deleted. */
	  if (shell_builtins[mid].function &&
	      ((shell_builtins[mid].flags & BUILTIN_DELETED) == 0) &&
	      ((shell_builtins[mid].flags & BUILTIN_ENABLED) || disabled_okay))
	    return (&shell_builtins[mid]);
	  else
	    return ((struct builtin *)NULL);
	}
      if (j > 0)
	hi = mid - 1;
      else
	lo = mid + 1;
    }
  return ((struct builtin *)NULL);
}

/* Return the pointer to the function implementing builtin command NAME. */
sh_builtin_func_t *
find_shell_builtin (name)
     char *name;
{
  current_builtin = builtin_address_internal (name, 0);
  return (current_builtin ? current_builtin->function : (sh_builtin_func_t *)NULL);
}

/* Return the address of builtin with NAME, whether it is enabled or not. */
sh_builtin_func_t *
builtin_address (name)
     char *name;
{
  current_builtin = builtin_address_internal (name, 1);
  return (current_builtin ? current_builtin->function : (sh_builtin_func_t *)NULL);
}

/* Return the function implementing the builtin NAME, but only if it is a
   POSIX.2 special builtin. */
sh_builtin_func_t *
find_special_builtin (name)
     char *name;
{
  current_builtin = builtin_address_internal (name, 0);
  return ((current_builtin && (current_builtin->flags & SPECIAL_BUILTIN)) ?
  			current_builtin->function :
  			(sh_builtin_func_t *)NULL);
}

static int
shell_builtin_compare (sbp1, sbp2)
     struct builtin *sbp1, *sbp2;
{
  int result;

  if ((result = sbp1->name[0] - sbp2->name[0]) == 0)
    result = strcmp (sbp1->name, sbp2->name);

  return (result);
}

/* Sort the table of shell builtins so that the binary search will work
   in find_shell_builtin. */
void
initialize_shell_builtins ()
{
  qsort (shell_builtins, num_shell_builtins, sizeof (struct builtin),
    (QSFUNC *)shell_builtin_compare);
}

#if !defined (HELP_BUILTIN)
void
builtin_help ()
{
  printf ("%s: %s\n", this_command_name, _("help not available in this version"));
}
#endif

/* **************************************************************** */
/*								    */
/*	    Variable assignments during builtin commands	    */
/*								    */
/* **************************************************************** */

/* Assign NAME=VALUE, passing FLAGS to the assignment functions. */
SHELL_VAR *
builtin_bind_variable (name, value, flags)
     char *name;
     char *value;
     int flags;
{
  SHELL_VAR *v;
  int vflags, bindflags;

#if defined (ARRAY_VARS)
  /* Callers are responsible for calling this with array references that have
     already undergone valid_array_reference checks (read, printf). */
  vflags = assoc_expand_once ? (VA_NOEXPAND|VA_ONEWORD) : 0;
  bindflags = flags | (assoc_expand_once ? ASS_NOEXPAND : 0) | ASS_ALLOWALLSUB;
  if (flags & ASS_NOEXPAND)
    vflags |= VA_NOEXPAND;
  if (flags & ASS_ONEWORD)
    vflags |= VA_ONEWORD;

  if (valid_array_reference (name, vflags) == 0)
    v = bind_variable (name, value, flags);
  else
    v = assign_array_element (name, value, bindflags, (array_eltstate_t *)0);
#else /* !ARRAY_VARS */
  v = bind_variable (name, value, flags);
#endif /* !ARRAY_VARS */

  if (v && readonly_p (v) == 0 && noassign_p (v) == 0)
    VUNSETATTR (v, att_invisible);

  return v;
}

SHELL_VAR *
builtin_bind_var_to_int (name, val, flags)
     char *name;
     intmax_t val;
     int flags;
{
  SHELL_VAR *v;

  v = bind_var_to_int (name, val, flags|ASS_ALLOWALLSUB);
  return v;
}

/* Like check_unbind_variable, but for use by builtins (only matters for
   error messages). */
int
builtin_unbind_variable (vname)
     const char *vname;
{
  SHELL_VAR *v;

  v = find_variable (vname);
  if (v && readonly_p (v))
    {
      builtin_error (_("%s: cannot unset: readonly %s"), vname, "variable");
      return -2;
    }
  else if (v && non_unsettable_p (v))
    {
      builtin_error (_("%s: cannot unset"), vname);
      return -2;
    }
  return (unbind_variable (vname));
}

int
builtin_arrayref_flags (w, baseflags)
     WORD_DESC *w;
     int baseflags;
{
  char *t;
  int vflags;

  vflags = baseflags;

  /* Don't require assoc_expand_once if we have an argument that's already
     passed through valid_array_reference and been expanded once. That
     doesn't protect it from normal expansions like word splitting, so
     proper quoting is still required. */
  if (w->flags & W_ARRAYREF)
    vflags |= VA_ONEWORD|VA_NOEXPAND;

#  if 0
  /* This is a little sketchier but handles quoted arguments. */
  if (assoc_expand_once && (t =  strchr (w->word, '[')) && t[strlen(t) - 1] == ']')
    vflags |= VA_ONEWORD|VA_NOEXPAND;
#  endif

  return vflags;
}

/* **************************************************************** */
/*								    */
/*	    External interface to manipulate shell options	    */
/*								    */
/* **************************************************************** */

#if defined (ARRAY_VARS)
int
set_expand_once (nval, uwp)
     int nval, uwp;
{
  int oa;

  oa = assoc_expand_once;
  if (shell_compatibility_level > 51)	/* XXX - internal */
    {
      if (uwp)
	unwind_protect_int (assoc_expand_once);
      assoc_expand_once = nval;
    }
  return oa;
}
#endif
