execute_cmd.c

/* execute_cmd.c -- Execute a COMMAND structure. */

/* Copyright (C) 1987-2022 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 (__GNUC__) && !defined (HAVE_ALLOCA_H) && defined (_AIX)
  #pragma alloca
#endif /* _AIX && RISC6000 && !__GNUC__ */

#include <stdio.h>
#include "chartypes.h"
#include "bashtypes.h"
#if !defined (_MINIX) && defined (HAVE_SYS_FILE_H)
#  include <sys/file.h>
#endif
#include "filecntl.h"
#include "posixstat.h"
#include <signal.h>
#if defined (HAVE_SYS_PARAM_H)
#  include <sys/param.h>
#endif

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

#include "posixtime.h"

#if defined (HAVE_SYS_RESOURCE_H) && !defined (RLIMTYPE)
#  include <sys/resource.h>
#endif

#if defined (HAVE_SYS_TIMES_H) && defined (HAVE_TIMES)
#  include <sys/times.h>
#endif

#include <errno.h>

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

#define NEED_FPURGE_DECL
#define NEED_SH_SETLINEBUF_DECL

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

#include "memalloc.h"
#include "shell.h"
#include <y.tab.h>	/* use <...> so we pick it up from the build directory */
#include "parser.h"
#include "flags.h"
#include "builtins.h"
#include "hashlib.h"
#include "jobs.h"
#include "execute_cmd.h"
#include "findcmd.h"
#include "redir.h"
#include "trap.h"
#include "pathexp.h"
#include "hashcmd.h"

#if defined (COND_COMMAND)
#  include "test.h"
#endif

#include "builtins/common.h"
#include "builtins/builtext.h"	/* list of builtins */

#include "builtins/getopt.h"

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

#if defined (BUFFERED_INPUT)
#  include "input.h"
#endif

#if defined (ALIAS)
#  include "alias.h"
#endif

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

#if defined (HAVE_MBSTR_H) && defined (HAVE_MBSCHR)
#  include <mbstr.h>		/* mbschr */
#endif

extern int command_string_index;
extern char *the_printed_command;
extern time_t shell_start_time;
#if defined (HAVE_GETTIMEOFDAY)
extern struct timeval shellstart;
#endif
#if 0
extern char *glob_argv_flags;
#endif

extern int close PARAMS((int));

/* Static functions defined and used in this file. */
static void close_pipes PARAMS((int, int));
static void do_piping PARAMS((int, int));
static void bind_lastarg PARAMS((char *));
static int shell_control_structure PARAMS((enum command_type));
static void cleanup_redirects PARAMS((REDIRECT *));

#if defined (JOB_CONTROL)
static int restore_signal_mask PARAMS((sigset_t *));
#endif

static int builtin_status PARAMS((int));

static int execute_for_command PARAMS((FOR_COM *));
#if defined (SELECT_COMMAND)
static int displen PARAMS((const char *));
static int print_index_and_element PARAMS((int, int, WORD_LIST *));
static void indent PARAMS((int, int));
static void print_select_list PARAMS((WORD_LIST *, int, int, int));
static char *select_query PARAMS((WORD_LIST *, int, char *, int));
static int execute_select_command PARAMS((SELECT_COM *));
#endif
#if defined (DPAREN_ARITHMETIC)
static int execute_arith_command PARAMS((ARITH_COM *));
#endif
#if defined (COND_COMMAND)
static int execute_cond_node PARAMS((COND_COM *));
static int execute_cond_command PARAMS((COND_COM *));
#endif
#if defined (COMMAND_TIMING)
static int mkfmt PARAMS((char *, int, int, time_t, int));
static void print_formatted_time PARAMS((FILE *, char *,
				      time_t, int, time_t, int,
				      time_t, int, int));
static int time_command PARAMS((COMMAND *, int, int, int, struct fd_bitmap *));
#endif
#if defined (ARITH_FOR_COMMAND)
static intmax_t eval_arith_for_expr PARAMS((WORD_LIST *, int *));
static int execute_arith_for_command PARAMS((ARITH_FOR_COM *));
#endif
static int execute_case_command PARAMS((CASE_COM *));
static int execute_while_command PARAMS((WHILE_COM *));
static int execute_until_command PARAMS((WHILE_COM *));
static int execute_while_or_until PARAMS((WHILE_COM *, int));
static int execute_if_command PARAMS((IF_COM *));
static int execute_null_command PARAMS((REDIRECT *, int, int, int));
static void fix_assignment_words PARAMS((WORD_LIST *));
static void fix_arrayref_words PARAMS((WORD_LIST *));
static int execute_simple_command PARAMS((SIMPLE_COM *, int, int, int, struct fd_bitmap *));
static int execute_builtin PARAMS((sh_builtin_func_t *, WORD_LIST *, int, int));
static int execute_function PARAMS((SHELL_VAR *, WORD_LIST *, int, struct fd_bitmap *, int, int));
static int execute_builtin_or_function PARAMS((WORD_LIST *, sh_builtin_func_t *,
					    SHELL_VAR *,
					    REDIRECT *, struct fd_bitmap *, int));
static void execute_subshell_builtin_or_function PARAMS((WORD_LIST *, REDIRECT *,
						      sh_builtin_func_t *,
						      SHELL_VAR *,
						      int, int, int,
						      struct fd_bitmap *,
						      int));
static int execute_disk_command PARAMS((WORD_LIST *, REDIRECT *, char *,
				      int, int, int, struct fd_bitmap *, int));

static char *getinterp PARAMS((char *, int, int *));
static void initialize_subshell PARAMS((void));
static int execute_in_subshell PARAMS((COMMAND *, int, int, int, struct fd_bitmap *));
#if defined (COPROCESS_SUPPORT)
static void coproc_setstatus PARAMS((struct coproc *, int));
static int execute_coproc PARAMS((COMMAND *, int, int, struct fd_bitmap *));
#endif

static int execute_pipeline PARAMS((COMMAND *, int, int, int, struct fd_bitmap *));

static int execute_connection PARAMS((COMMAND *, int, int, int, struct fd_bitmap *));

static int execute_intern_function PARAMS((WORD_DESC *, FUNCTION_DEF *));

/* Set to 1 if fd 0 was the subject of redirection to a subshell.  Global
   so that reader_loop can set it to zero before executing a command. */
int stdin_redir;

/* The name of the command that is currently being executed.
   `test' needs this, for example. */
char *this_command_name;

/* The printed representation of the currently-executing command (same as
   the_printed_command), except when a trap is being executed.  Useful for
   a debugger to know where exactly the program is currently executing. */
char *the_printed_command_except_trap;

/* For catching RETURN in a function. */
int return_catch_flag;
int return_catch_value;
procenv_t return_catch;

/* The value returned by the last synchronous command. */
volatile int last_command_exit_value;

/* Whether or not the last command (corresponding to last_command_exit_value)
   was terminated by a signal, and, if so, which one. */
int last_command_exit_signal;

/* Are we currently ignoring the -e option for the duration of a builtin's
   execution? */
int builtin_ignoring_errexit = 0;

/* The list of redirections to perform which will undo the redirections
   that I made in the shell. */
REDIRECT *redirection_undo_list = (REDIRECT *)NULL;

/* The list of redirections to perform which will undo the internal
   redirections performed by the `exec' builtin.  These are redirections
   that must be undone even when exec discards redirection_undo_list. */
REDIRECT *exec_redirection_undo_list = (REDIRECT *)NULL;

/* When greater than zero, value is the `level' of builtins we are
   currently executing (e.g. `eval echo a' would have it set to 2). */
int executing_builtin = 0;

/* Non-zero if we are executing a command list (a;b;c, etc.) */
int executing_list = 0;

/* Non-zero if failing commands in a command substitution should not exit the
   shell even if -e is set.  Used to pass the CMD_IGNORE_RETURN flag down to
   commands run in command substitutions by parse_and_execute. */
int comsub_ignore_return = 0;

/* Non-zero if we have just forked and are currently running in a subshell
   environment. */
int subshell_environment;

/* Count of nested subshells, like SHLVL.  Available via $BASH_SUBSHELL */
int subshell_level = 0;

/* Currently-executing shell function. */
SHELL_VAR *this_shell_function;

/* If non-zero, matches in case and [[ ... ]] are case-insensitive */
int match_ignore_case = 0;

int executing_command_builtin = 0;

struct stat SB;		/* used for debugging */

static int special_builtin_failed;

static COMMAND *currently_executing_command;

/* The line number that the currently executing function starts on. */
static int function_line_number;

/* XXX - set to 1 if we're running the DEBUG trap and we want to show the line
   number containing the function name.  Used by executing_line_number to
   report the correct line number.  Kind of a hack. */
static int showing_function_line;

static int connection_count;

/* $LINENO ($BASH_LINENO) for use by an ERR trap.  Global so parse_and_execute
   can save and restore it. */
int line_number_for_err_trap;

/* A convenience macro to avoid resetting line_number_for_err_trap while
   running the ERR trap. */
#define SET_LINE_NUMBER(v) \
do { \
  line_number = v; \
  if (signal_in_progress (ERROR_TRAP) == 0 && running_trap != (ERROR_TRAP + 1)) \
    line_number_for_err_trap = line_number; \
} while (0)

/* This can't be in executing_line_number() because that's used for LINENO
   and we want LINENO to reflect the line number of commands run during
   the ERR trap. Right now this is only used to push to BASH_LINENO. */
#define GET_LINE_NUMBER() \
  (signal_in_progress (ERROR_TRAP) && running_trap == ERROR_TRAP+1) \
    ? line_number_for_err_trap \
    : executing_line_number ()

/* A sort of function nesting level counter */
int funcnest = 0;
int funcnest_max = 0;

int evalnest = 0;
int evalnest_max = EVALNEST_MAX;

int sourcenest = 0;
int sourcenest_max = SOURCENEST_MAX;

volatile int from_return_trap = 0;

int lastpipe_opt = 0;

struct fd_bitmap *current_fds_to_close = (struct fd_bitmap *)NULL;

#define FD_BITMAP_DEFAULT_SIZE 32

/* Functions to allocate and deallocate the structures used to pass
   information from the shell to its children about file descriptors
   to close. */
struct fd_bitmap *
new_fd_bitmap (size)
     int size;
{
  struct fd_bitmap *ret;

  ret = (struct fd_bitmap *)xmalloc (sizeof (struct fd_bitmap));

  ret->size = size;

  if (size)
    {
      ret->bitmap = (char *)xmalloc (size);
      memset (ret->bitmap, '\0', size);
    }
  else
    ret->bitmap = (char *)NULL;
  return (ret);
}

void
dispose_fd_bitmap (fdbp)
     struct fd_bitmap *fdbp;
{
  FREE (fdbp->bitmap);
  free (fdbp);
}

void
close_fd_bitmap (fdbp)
     struct fd_bitmap *fdbp;
{
  register int i;

  if (fdbp)
    {
      for (i = 0; i < fdbp->size; i++)
	if (fdbp->bitmap[i])
	  {
	    close (i);
	    fdbp->bitmap[i] = 0;
	  }
    }
}

/* Return the line number of the currently executing command. */
int
executing_line_number ()
{
  if (executing && showing_function_line == 0 &&
      (variable_context == 0 || interactive_shell == 0) &&
      currently_executing_command)
    {
#if defined (COND_COMMAND)
      if (currently_executing_command->type == cm_cond)
	return currently_executing_command->value.Cond->line;
#endif
#if defined (DPAREN_ARITHMETIC)
      if (currently_executing_command->type == cm_arith)
	return currently_executing_command->value.Arith->line;
#endif
#if defined (ARITH_FOR_COMMAND)
      if (currently_executing_command->type == cm_arith_for)
	return currently_executing_command->value.ArithFor->line;
#endif

      return line_number;
    }
  else
    return line_number;
}

/* Execute the command passed in COMMAND.  COMMAND is exactly what
   read_command () places into GLOBAL_COMMAND.  See "command.h" for the
   details of the command structure.

   EXECUTION_SUCCESS or EXECUTION_FAILURE are the only possible
   return values.  Executing a command with nothing in it returns
   EXECUTION_SUCCESS. */
int
execute_command (command)
     COMMAND *command;
{
  struct fd_bitmap *bitmap;
  int result;

  current_fds_to_close = (struct fd_bitmap *)NULL;
  bitmap = new_fd_bitmap (FD_BITMAP_DEFAULT_SIZE);
  begin_unwind_frame ("execute-command");
  add_unwind_protect (dispose_fd_bitmap, (char *)bitmap);

  /* Just do the command, but not asynchronously. */
  result = execute_command_internal (command, 0, NO_PIPE, NO_PIPE, bitmap);

  dispose_fd_bitmap (bitmap);
  discard_unwind_frame ("execute-command");

#if defined (PROCESS_SUBSTITUTION)
  /* don't unlink fifos if we're in a shell function; wait until the function
     returns. */
  if (variable_context == 0 && executing_list == 0)
    unlink_fifo_list ();
#endif /* PROCESS_SUBSTITUTION */

  QUIT;
  return (result);
}

/* Return 1 if TYPE is a shell control structure type. */
static int
shell_control_structure (type)
     enum command_type type;
{
  switch (type)
    {
#if defined (ARITH_FOR_COMMAND)
    case cm_arith_for:
#endif
#if defined (SELECT_COMMAND)
    case cm_select:
#endif
#if defined (DPAREN_ARITHMETIC)
    case cm_arith:
#endif
#if defined (COND_COMMAND)
    case cm_cond:
#endif
    case cm_case:
    case cm_while:
    case cm_until:
    case cm_if:
    case cm_for:
    case cm_group:
    case cm_function_def:
      return (1);

    default:
      return (0);
    }
}

/* A function to use to unwind_protect the redirection undo list
   for loops. */
static void
cleanup_redirects (list)
     REDIRECT *list;
{
  do_redirections (list, RX_ACTIVE);
  dispose_redirects (list);
}

void
undo_partial_redirects ()
{
  if (redirection_undo_list)
    {
      cleanup_redirects (redirection_undo_list);
      redirection_undo_list = (REDIRECT *)NULL;
    }
}

#if 0
/* Function to unwind_protect the redirections for functions and builtins. */
static void
cleanup_func_redirects (list)
     REDIRECT *list;
{
  do_redirections (list, RX_ACTIVE);
}
#endif

void
dispose_exec_redirects ()
{
  if (exec_redirection_undo_list)
    {
      dispose_redirects (exec_redirection_undo_list);
      exec_redirection_undo_list = (REDIRECT *)NULL;
    }
}

void
dispose_partial_redirects ()
{
  if (redirection_undo_list)
    {
      dispose_redirects (redirection_undo_list);
      redirection_undo_list = (REDIRECT *)NULL;
    }
}

#if defined (JOB_CONTROL)
/* A function to restore the signal mask to its proper value when the shell
   is interrupted or errors occur while creating a pipeline. */
static int
restore_signal_mask (set)
     sigset_t *set;
{
  return (sigprocmask (SIG_SETMASK, set, (sigset_t *)NULL));
}
#endif /* JOB_CONTROL */

#ifdef DEBUG
/* A debugging function that can be called from gdb, for instance. */
void
open_files (void)
{
  register int i;
  int f, fd_table_size;

  fd_table_size = getdtablesize ();

  fprintf (stderr, "pid %ld open files:", (long)getpid ());
  for (i = 3; i < fd_table_size; i++)
    {
      if ((f = fcntl (i, F_GETFD, 0)) != -1)
	fprintf (stderr, " %d (%s)", i, f ? "close" : "open");
    }
  fprintf (stderr, "\n");
}
#endif

void
async_redirect_stdin ()
{
  int fd;

  fd = open ("/dev/null", O_RDONLY);
  if (fd > 0)
    {
      dup2 (fd, 0);
      close (fd);
    }
  else if (fd < 0)
    internal_error (_("cannot redirect standard input from /dev/null: %s"), strerror (errno));
}

#define DESCRIBE_PID(pid) do { if (interactive) describe_pid (pid); } while (0)

/* Execute the command passed in COMMAND, perhaps doing it asynchronously.
   COMMAND is exactly what read_command () places into GLOBAL_COMMAND.
   ASYNCHRONOUS, if non-zero, says to do this command in the background.
   PIPE_IN and PIPE_OUT are file descriptors saying where input comes
   from and where it goes.  They can have the value of NO_PIPE, which means
   I/O is stdin/stdout.
   FDS_TO_CLOSE is a list of file descriptors to close once the child has
   been forked.  This list often contains the unusable sides of pipes, etc.

   EXECUTION_SUCCESS or EXECUTION_FAILURE are the only possible
   return values.  Executing a command with nothing in it returns
   EXECUTION_SUCCESS. */
int
execute_command_internal (command, asynchronous, pipe_in, pipe_out,
			  fds_to_close)
     COMMAND *command;
     int asynchronous;
     int pipe_in, pipe_out;
     struct fd_bitmap *fds_to_close;
{
  int exec_result, user_subshell, invert, ignore_return, was_error_trap, fork_flags;
  REDIRECT *my_undo_list, *exec_undo_list;
  char *tcmd;
  volatile int save_line_number;
#if defined (PROCESS_SUBSTITUTION)
  volatile int ofifo, nfifo, osize, saved_fifo;
  volatile void *ofifo_list;
#endif

  if (breaking || continuing)
    return (last_command_exit_value);
  if (read_but_dont_execute)
    return (last_command_exit_value);
  if (command == 0)
    return (EXECUTION_SUCCESS);

  QUIT;
  run_pending_traps ();

#if 0
  if (running_trap == 0)
#endif
    currently_executing_command = command;

  invert = (command->flags & CMD_INVERT_RETURN) != 0;

  /* If we're inverting the return value and `set -e' has been executed,
     we don't want a failing command to inadvertently cause the shell
     to exit. */
  if (exit_immediately_on_error && invert)	/* XXX */
    command->flags |= CMD_IGNORE_RETURN;	/* XXX */

  exec_result = EXECUTION_SUCCESS;

  /* If a command was being explicitly run in a subshell, or if it is
     a shell control-structure, and it has a pipe, then we do the command
     in a subshell. */
  if (command->type == cm_subshell && (command->flags & CMD_NO_FORK))
    return (execute_in_subshell (command, asynchronous, pipe_in, pipe_out, fds_to_close));

#if defined (COPROCESS_SUPPORT)
  if (command->type == cm_coproc)
    return (last_command_exit_value = execute_coproc (command, pipe_in, pipe_out, fds_to_close));
#endif

  user_subshell = command->type == cm_subshell || ((command->flags & CMD_WANT_SUBSHELL) != 0);

#if defined (TIME_BEFORE_SUBSHELL)
  if ((command->flags & CMD_TIME_PIPELINE) && user_subshell && asynchronous == 0)
    {
      command->flags |= CMD_FORCE_SUBSHELL;
      exec_result = time_command (command, asynchronous, pipe_in, pipe_out, fds_to_close);
      currently_executing_command = (COMMAND *)NULL;
      return (exec_result);
    }
#endif

  if (command->type == cm_subshell ||
      (command->flags & (CMD_WANT_SUBSHELL|CMD_FORCE_SUBSHELL)) ||
      (shell_control_structure (command->type) &&
       (pipe_out != NO_PIPE || pipe_in != NO_PIPE || asynchronous)))
    {
      pid_t paren_pid;
      int s;
      char *p;

      /* Fork a subshell, turn off the subshell bit, turn off job
	 control and call execute_command () on the command again. */
      save_line_number = line_number;
      if (command->type == cm_subshell)
	SET_LINE_NUMBER (command->value.Subshell->line);	/* XXX - save value? */
	/* Otherwise we defer setting line_number */
      tcmd = make_command_string (command);
      fork_flags = asynchronous ? FORK_ASYNC : 0;
      paren_pid = make_child (p = savestring (tcmd), fork_flags);

      if (user_subshell && signal_is_trapped (ERROR_TRAP) && 
	  signal_in_progress (DEBUG_TRAP) == 0 && running_trap == 0)
	{
	  FREE (the_printed_command_except_trap);
	  the_printed_command_except_trap = savestring (the_printed_command);
	}

      if (paren_pid == 0)
        {
#if defined (JOB_CONTROL)
	  FREE (p);		/* child doesn't use pointer */
#endif
	  /* We want to run the exit trap for forced {} subshells, and we
	     want to note this before execute_in_subshell modifies the
	     COMMAND struct.  Need to keep in mind that execute_in_subshell
	     runs the exit trap for () subshells itself. */
	  /* This handles { command; } & */
	  s = user_subshell == 0 && command->type == cm_group && pipe_in == NO_PIPE && pipe_out == NO_PIPE && asynchronous;
	  /* run exit trap for : | { ...; } and { ...; } | : */
	  /* run exit trap for : | ( ...; ) and ( ...; ) | : */
	  s += user_subshell == 0 && command->type == cm_group && (pipe_in != NO_PIPE || pipe_out != NO_PIPE) && asynchronous == 0;

	  last_command_exit_value = execute_in_subshell (command, asynchronous, pipe_in, pipe_out, fds_to_close);
	  if (s)
	    subshell_exit (last_command_exit_value);
	  else
	    sh_exit (last_command_exit_value);
	  /* NOTREACHED */
        }
      else
	{
	  close_pipes (pipe_in, pipe_out);

#if defined (PROCESS_SUBSTITUTION) && defined (HAVE_DEV_FD)
	  if (variable_context == 0)	/* wait until shell function completes */
	    unlink_fifo_list ();
#endif
	  /* If we are part of a pipeline, and not the end of the pipeline,
	     then we should simply return and let the last command in the
	     pipe be waited for.  If we are not in a pipeline, or are the
	     last command in the pipeline, then we wait for the subshell
	     and return its exit status as usual. */
	  if (pipe_out != NO_PIPE)
	    return (EXECUTION_SUCCESS);

	  stop_pipeline (asynchronous, (COMMAND *)NULL);

	  line_number = save_line_number;

	  if (asynchronous == 0)
	    {
	      was_error_trap = signal_is_trapped (ERROR_TRAP) && signal_is_ignored (ERROR_TRAP) == 0;
	      invert = (command->flags & CMD_INVERT_RETURN) != 0;
	      ignore_return = (command->flags & CMD_IGNORE_RETURN) != 0;

	      exec_result = wait_for (paren_pid, 0);

	      /* If we have to, invert the return value. */
	      if (invert)
		exec_result = ((exec_result == EXECUTION_SUCCESS)
				? EXECUTION_FAILURE
				: EXECUTION_SUCCESS);

	      last_command_exit_value = exec_result;
	      if (user_subshell && was_error_trap && ignore_return == 0 && invert == 0 && exec_result != EXECUTION_SUCCESS)
		{
		  save_line_number = line_number;
		  line_number = line_number_for_err_trap;
		  run_error_trap ();
		  line_number = save_line_number;
		}

	      if (user_subshell && ignore_return == 0 && invert == 0 && exit_immediately_on_error && exec_result != EXECUTION_SUCCESS)
		{
		  run_pending_traps ();
		  jump_to_top_level (ERREXIT);
		}

	      return (last_command_exit_value);
	    }
	  else
	    {
	      DESCRIBE_PID (paren_pid);

	      run_pending_traps ();

	      /* Posix 2013 2.9.3.1: "the exit status of an asynchronous list
		 shall be zero." */
	      last_command_exit_value = 0;
	      return (EXECUTION_SUCCESS);
	    }
	}
    }

#if defined (COMMAND_TIMING)
  if (command->flags & CMD_TIME_PIPELINE)
    {
      if (asynchronous)
	{
	  command->flags |= CMD_FORCE_SUBSHELL;
	  exec_result = execute_command_internal (command, 1, pipe_in, pipe_out, fds_to_close);
	}
      else
	{
	  exec_result = time_command (command, asynchronous, pipe_in, pipe_out, fds_to_close);
#if 0
	  if (running_trap == 0)
#endif
	    currently_executing_command = (COMMAND *)NULL;
	}
      return (exec_result);
    }
#endif /* COMMAND_TIMING */

  if (shell_control_structure (command->type) && command->redirects)
    stdin_redir = stdin_redirects (command->redirects);

#if defined (PROCESS_SUBSTITUTION)
#  if !defined (HAVE_DEV_FD)
  reap_procsubs ();
#  endif

  /* XXX - also if sourcelevel != 0? */
  if (variable_context != 0 || executing_list)
    {
      ofifo = num_fifos ();
      ofifo_list = copy_fifo_list ((int *)&osize);
      begin_unwind_frame ("internal_fifos");
      if (ofifo_list)
	add_unwind_protect (xfree, ofifo_list);
      saved_fifo = 1;
    }
  else
    saved_fifo = 0;
#endif

  /* Handle WHILE FOR CASE etc. with redirections.  (Also '&' input
     redirection.)  */
  was_error_trap = signal_is_trapped (ERROR_TRAP) && signal_is_ignored (ERROR_TRAP) == 0;
  ignore_return = (command->flags & CMD_IGNORE_RETURN) != 0;

  if (do_redirections (command->redirects, RX_ACTIVE|RX_UNDOABLE) != 0)
    {
      undo_partial_redirects ();
      dispose_exec_redirects ();
#if defined (PROCESS_SUBSTITUTION)
      if (saved_fifo)
	{
	  free ((void *)ofifo_list);
          discard_unwind_frame ("internal_fifos");
	}
#endif

      /* Handle redirection error as command failure if errexit set. */
      last_command_exit_value = EXECUTION_FAILURE;
      if (ignore_return == 0 && invert == 0 && pipe_in == NO_PIPE && pipe_out == NO_PIPE)
	{
	  if (was_error_trap)
	    {
	      save_line_number = line_number;
	      line_number = line_number_for_err_trap;
	      run_error_trap ();
	      line_number = save_line_number;
	    }
	  if (exit_immediately_on_error)
	    {	  
	      run_pending_traps ();
	      jump_to_top_level (ERREXIT);
	    }
	}
      return (last_command_exit_value);
    }

  my_undo_list = redirection_undo_list;
  redirection_undo_list = (REDIRECT *)NULL;

  exec_undo_list = exec_redirection_undo_list;
  exec_redirection_undo_list = (REDIRECT *)NULL;

  if (my_undo_list || exec_undo_list)
    begin_unwind_frame ("loop_redirections");

  if (my_undo_list)
    add_unwind_protect ((Function *)cleanup_redirects, my_undo_list);

  if (exec_undo_list)
    add_unwind_protect ((Function *)dispose_redirects, exec_undo_list);

  QUIT;

  switch (command->type)
    {
    case cm_simple:
      {
	save_line_number = line_number;
	/* We can't rely on variables retaining their values across a
	   call to execute_simple_command if a longjmp occurs as the
	   result of a `return' builtin.  This is true for sure with gcc. */
#if defined (RECYCLES_PIDS)
	last_made_pid = NO_PID;
#endif
	was_error_trap = signal_is_trapped (ERROR_TRAP) && signal_is_ignored (ERROR_TRAP) == 0;

	if (ignore_return && command->value.Simple)
	  command->value.Simple->flags |= CMD_IGNORE_RETURN;
	if (command->flags & CMD_STDIN_REDIR)
	  command->value.Simple->flags |= CMD_STDIN_REDIR;

	SET_LINE_NUMBER (command->value.Simple->line);
	exec_result =
	  execute_simple_command (command->value.Simple, pipe_in, pipe_out,
				  asynchronous, fds_to_close);
	line_number = save_line_number;

	/* The temporary environment should be used for only the simple
	   command immediately following its definition. */
	dispose_used_env_vars ();

#if (defined (ultrix) && defined (mips)) || defined (C_ALLOCA)
	/* Reclaim memory allocated with alloca () on machines which
	   may be using the alloca emulation code. */
	(void) alloca (0);
#endif /* (ultrix && mips) || C_ALLOCA */

	/* If we forked to do the command, then we must wait_for ()
	   the child. */

	/* XXX - this is something to watch out for if there are problems
	   when the shell is compiled without job control.  Don't worry about
	   whether or not last_made_pid == last_pid; already_making_children
	   tells us whether or not there are unwaited-for children to wait
	   for and reap. */
	if (already_making_children && pipe_out == NO_PIPE)
	  {
	    stop_pipeline (asynchronous, (COMMAND *)NULL);

	    if (asynchronous)
	      {
		DESCRIBE_PID (last_made_pid);
		exec_result = EXECUTION_SUCCESS;
		invert = 0;		/* async commands always succeed */
	      }
	    else
#if !defined (JOB_CONTROL)
	      /* Do not wait for asynchronous processes started from
		 startup files. */
	    if (last_made_pid != NO_PID && last_made_pid != last_asynchronous_pid)
#else
	    if (last_made_pid != NO_PID)
#endif
	    /* When executing a shell function that executes other
	       commands, this causes the last simple command in
	       the function to be waited for twice.  This also causes
	       subshells forked to execute builtin commands (e.g., in
	       pipelines) to be waited for twice. */
	      exec_result = wait_for (last_made_pid, 0);
	  }
      }

      /* 2009/02/13 -- pipeline failure is processed elsewhere.  This handles
	 only the failure of a simple command. We don't want to run the error
	 trap if the command run by the `command' builtin fails; we want to
	 defer that until the command builtin itself returns failure. */
      /* 2020/07/14 -- this changes with how the command builtin is handled */ 
      if (was_error_trap && ignore_return == 0 && invert == 0 &&
	    pipe_in == NO_PIPE && pipe_out == NO_PIPE &&
	    (command->value.Simple->flags & CMD_COMMAND_BUILTIN) == 0 &&
	    exec_result != EXECUTION_SUCCESS)
	{
	  last_command_exit_value = exec_result;
	  line_number = line_number_for_err_trap;
	  run_error_trap ();
	  line_number = save_line_number;
	}

      if (ignore_return == 0 && invert == 0 &&
	  ((posixly_correct && interactive == 0 && special_builtin_failed) ||
	   (exit_immediately_on_error && pipe_in == NO_PIPE && pipe_out == NO_PIPE && exec_result != EXECUTION_SUCCESS)))
	{
	  last_command_exit_value = exec_result;
	  run_pending_traps ();

	  /* Undo redirections before running exit trap on the way out of
	     set -e. Report by Mark Farrell 5/19/2014 */
	  if (exit_immediately_on_error && signal_is_trapped (0) &&
		unwind_protect_tag_on_stack ("saved-redirects"))
	    run_unwind_frame ("saved-redirects");

	  jump_to_top_level (ERREXIT);
	}

      break;

    case cm_for:
      if (ignore_return)
	command->value.For->flags |= CMD_IGNORE_RETURN;
      exec_result = execute_for_command (command->value.For);
      break;

#if defined (ARITH_FOR_COMMAND)
    case cm_arith_for:
      if (ignore_return)
	command->value.ArithFor->flags |= CMD_IGNORE_RETURN;
      exec_result = execute_arith_for_command (command->value.ArithFor);
      break;
#endif

#if defined (SELECT_COMMAND)
    case cm_select:
      if (ignore_return)
	command->value.Select->flags |= CMD_IGNORE_RETURN;
      exec_result = execute_select_command (command->value.Select);
      break;
#endif

    case cm_case:
      if (ignore_return)
	command->value.Case->flags |= CMD_IGNORE_RETURN;
      exec_result = execute_case_command (command->value.Case);
      break;

    case cm_while:
      if (ignore_return)
	command->value.While->flags |= CMD_IGNORE_RETURN;
      exec_result = execute_while_command (command->value.While);
      break;

    case cm_until:
      if (ignore_return)
	command->value.While->flags |= CMD_IGNORE_RETURN;
      exec_result = execute_until_command (command->value.While);
      break;

    case cm_if:
      if (ignore_return)
	command->value.If->flags |= CMD_IGNORE_RETURN;
      exec_result = execute_if_command (command->value.If);
      break;

    case cm_group:

      /* This code can be executed from either of two paths: an explicit
	 '{}' command, or via a function call.  If we are executed via a
	 function call, we have already taken care of the function being
	 executed in the background (down there in execute_simple_command ()),
	 and this command should *not* be marked as asynchronous.  If we
	 are executing a regular '{}' group command, and asynchronous == 1,
	 we must want to execute the whole command in the background, so we
	 need a subshell, and we want the stuff executed in that subshell
	 (this group command) to be executed in the foreground of that
	 subshell (i.e. there will not be *another* subshell forked).

	 What we do is to force a subshell if asynchronous, and then call
	 execute_command_internal again with asynchronous still set to 1,
	 but with the original group command, so the printed command will
	 look right.

	 The code above that handles forking off subshells will note that
	 both subshell and async are on, and turn off async in the child
	 after forking the subshell (but leave async set in the parent, so
	 the normal call to describe_pid is made).  This turning off
	 async is *crucial*; if it is not done, this will fall into an
	 infinite loop of executions through this spot in subshell after
	 subshell until the process limit is exhausted. */

      if (asynchronous)
	{
	  command->flags |= CMD_FORCE_SUBSHELL;
	  exec_result =
	    execute_command_internal (command, 1, pipe_in, pipe_out,
				      fds_to_close);
	}
      else
	{
	  if (ignore_return && command->value.Group->command)
	    command->value.Group->command->flags |= CMD_IGNORE_RETURN;
	  exec_result =
	    execute_command_internal (command->value.Group->command,
				      asynchronous, pipe_in, pipe_out,
				      fds_to_close);
	}
      break;

    case cm_connection:
      exec_result = execute_connection (command, asynchronous,
					pipe_in, pipe_out, fds_to_close);
      if (asynchronous)
	invert = 0;		/* XXX */

      break;

#if defined (DPAREN_ARITHMETIC)
    case cm_arith:
#endif
#if defined (COND_COMMAND)
    case cm_cond:
#endif
    case cm_function_def:
      was_error_trap = signal_is_trapped (ERROR_TRAP) && signal_is_ignored (ERROR_TRAP) == 0;
#if defined (DPAREN_ARITHMETIC)
      if (ignore_return && command->type == cm_arith)
	command->value.Arith->flags |= CMD_IGNORE_RETURN;
#endif
#if defined (COND_COMMAND)
      if (ignore_return && command->type == cm_cond)
	command->value.Cond->flags |= CMD_IGNORE_RETURN;
#endif

      line_number_for_err_trap = save_line_number = line_number;	/* XXX */
#if defined (DPAREN_ARITHMETIC)
      if (command->type == cm_arith)
	exec_result = execute_arith_command (command->value.Arith);
      else
#endif
#if defined (COND_COMMAND)
      if (command->type == cm_cond)
	exec_result = execute_cond_command (command->value.Cond);
      else
#endif
      if (command->type == cm_function_def)
	exec_result = execute_intern_function (command->value.Function_def->name,
					       command->value.Function_def);
      line_number = save_line_number;

      if (was_error_trap && ignore_return == 0 && invert == 0 && exec_result != EXECUTION_SUCCESS)
	{
	  last_command_exit_value = exec_result;
	  save_line_number = line_number;
	  line_number = line_number_for_err_trap;
	  run_error_trap ();
	  line_number = save_line_number;
	}

      if (ignore_return == 0 && invert == 0 && exit_immediately_on_error && exec_result != EXECUTION_SUCCESS)
	{
	  last_command_exit_value = exec_result;
	  run_pending_traps ();
	  jump_to_top_level (ERREXIT);
	}

      break;

    default:
      command_error ("execute_command", CMDERR_BADTYPE, command->type, 0);
    }

  if (my_undo_list)
    cleanup_redirects (my_undo_list);

  if (exec_undo_list)
    dispose_redirects (exec_undo_list);

  if (my_undo_list || exec_undo_list)
    discard_unwind_frame ("loop_redirections");

#if defined (PROCESS_SUBSTITUTION)
  if (saved_fifo)
    {
      nfifo = num_fifos ();
      if (nfifo > ofifo)
	close_new_fifos ((void *)ofifo_list, osize);
      free ((void *)ofifo_list);
      discard_unwind_frame ("internal_fifos");
    }
#endif

  /* Invert the return value if we have to */
  if (invert)
    exec_result = (exec_result == EXECUTION_SUCCESS)
		    ? EXECUTION_FAILURE
		    : EXECUTION_SUCCESS;

#if defined (DPAREN_ARITHMETIC) || defined (COND_COMMAND)
  /* This is where we set PIPESTATUS from the exit status of the appropriate
     compound commands (the ones that look enough like simple commands to
     cause confusion).  We might be able to optimize by not doing this if
     subshell_environment != 0. */
  switch (command->type)
    {
#  if defined (DPAREN_ARITHMETIC)
    case cm_arith:
#  endif
#  if defined (COND_COMMAND)
    case cm_cond:
#  endif
      set_pipestatus_from_exit (exec_result);
      break;
    default:
      break;
    }
#endif

  last_command_exit_value = exec_result;
  run_pending_traps ();
  currently_executing_command = (COMMAND *)NULL;

  return (last_command_exit_value);
}

#if defined (COMMAND_TIMING)

#if defined (HAVE_GETRUSAGE) && defined (HAVE_GETTIMEOFDAY)
extern struct timeval *difftimeval PARAMS((struct timeval *, struct timeval *, struct timeval *));
extern struct timeval *addtimeval PARAMS((struct timeval *, struct timeval *, struct timeval *));
extern int timeval_to_cpu PARAMS((struct timeval *, struct timeval *, struct timeval *));
#endif

#define POSIX_TIMEFORMAT "real %2R\nuser %2U\nsys %2S"
#define BASH_TIMEFORMAT  "\nreal\t%3lR\nuser\t%3lU\nsys\t%3lS"

static const int precs[] = { 0, 100, 10, 1 };

/* Expand one `%'-prefixed escape sequence from a time format string. */
static int
mkfmt (buf, prec, lng, sec, sec_fraction)
     char *buf;
     int prec, lng;
     time_t sec;
     int sec_fraction;
{
  time_t min;
  char abuf[INT_STRLEN_BOUND(time_t) + 1];
  int ind, aind;

  ind = 0;
  abuf[sizeof(abuf) - 1] = '\0';

  /* If LNG is non-zero, we want to decompose SEC into minutes and seconds. */
  if (lng)
    {
      min = sec / 60;
      sec %= 60;
      aind = sizeof(abuf) - 2;
      do
	abuf[aind--] = (min % 10) + '0';
      while (min /= 10);
      aind++;
      while (abuf[aind])
	buf[ind++] = abuf[aind++];
      buf[ind++] = 'm';
    }

  /* Now add the seconds. */
  aind = sizeof (abuf) - 2;
  do
    abuf[aind--] = (sec % 10) + '0';
  while (sec /= 10);
  aind++;
  while (abuf[aind])
    buf[ind++] = abuf[aind++];

  /* We want to add a decimal point and PREC places after it if PREC is
     nonzero.  PREC is not greater than 3.  SEC_FRACTION is between 0
     and 999. */
  if (prec != 0)
    {
      buf[ind++] = locale_decpoint ();
      for (aind = 1; aind <= prec; aind++)
	{
	  buf[ind++] = (sec_fraction / precs[aind]) + '0';
	  sec_fraction %= precs[aind];
	}
    }

  if (lng)
    buf[ind++] = 's';
  buf[ind] = '\0';

  return (ind);
}

/* Interpret the format string FORMAT, interpolating the following escape
   sequences:
		%[prec][l][RUS]

   where the optional `prec' is a precision, meaning the number of
   characters after the decimal point, the optional `l' means to format
   using minutes and seconds (MMmNN[.FF]s), like the `times' builtin',
   and the last character is one of
   
		R	number of seconds of `real' time
		U	number of seconds of `user' time
		S	number of seconds of `system' time

   An occurrence of `%%' in the format string is translated to a `%'.  The
   result is printed to FP, a pointer to a FILE.  The other variables are
   the seconds and thousandths of a second of real, user, and system time,
   resectively. */
static void
print_formatted_time (fp, format, rs, rsf, us, usf, ss, ssf, cpu)
     FILE *fp;
     char *format;
     time_t rs;
     int rsf;
     time_t us;
     int usf;
     time_t ss;
     int ssf, cpu;
{
  int prec, lng, len;
  char *str, *s, ts[INT_STRLEN_BOUND (time_t) + sizeof ("mSS.FFFF")];
  time_t sum;
  int sum_frac;
  int sindex, ssize;

  len = strlen (format);
  ssize = (len + 64) - (len % 64);
  str = (char *)xmalloc (ssize);
  sindex = 0;

  for (s = format; *s; s++)
    {
      if (*s != '%' || s[1] == '\0')
	{
	  RESIZE_MALLOCED_BUFFER (str, sindex, 1, ssize, 64);
	  str[sindex++] = *s;
	}
      else if (s[1] == '%')
	{
	  s++;
	  RESIZE_MALLOCED_BUFFER (str, sindex, 1, ssize, 64);
	  str[sindex++] = *s;
	}
      else if (s[1] == 'P')
	{
	  s++;
#if 0
	  /* clamp CPU usage at 100% */
	  if (cpu > 10000)
	    cpu = 10000;
#endif
	  sum = cpu / 100;
	  sum_frac = (cpu % 100) * 10;
	  len = mkfmt (ts, 2, 0, sum, sum_frac);
	  RESIZE_MALLOCED_BUFFER (str, sindex, len, ssize, 64);
	  strcpy (str + sindex, ts);
	  sindex += len;
	}
      else
	{
	  prec = 3;	/* default is three places past the decimal point. */
	  lng = 0;	/* default is to not use minutes or append `s' */
	  s++;
	  if (DIGIT (*s))		/* `precision' */
	    {
	      prec = *s++ - '0';
	      if (prec > 3) prec = 3;
	    }
	  if (*s == 'l')		/* `length extender' */
	    {
	      lng = 1;
	      s++;
	    }
	  if (*s == 'R' || *s == 'E')
	    len = mkfmt (ts, prec, lng, rs, rsf);
	  else if (*s == 'U')
	    len = mkfmt (ts, prec, lng, us, usf);
	  else if (*s == 'S')
	    len = mkfmt (ts, prec, lng, ss, ssf);
	  else
	    {
	      internal_error (_("TIMEFORMAT: `%c': invalid format character"), *s);
	      free (str);
	      return;
	    }
	  RESIZE_MALLOCED_BUFFER (str, sindex, len, ssize, 64);
	  strcpy (str + sindex, ts);
	  sindex += len;
	}
    }

  str[sindex] = '\0';
  fprintf (fp, "%s\n", str);
  fflush (fp);

  free (str);
}

static int
time_command (command, asynchronous, pipe_in, pipe_out, fds_to_close)
     COMMAND *command;
     int asynchronous, pipe_in, pipe_out;
     struct fd_bitmap *fds_to_close;
{
  int rv, posix_time, old_flags, nullcmd, code;
  time_t rs, us, ss;
  int rsf, usf, ssf;
  int cpu;
  char *time_format;
  volatile procenv_t save_top_level;
  volatile int old_subshell;

#if defined (HAVE_GETRUSAGE) && defined (HAVE_GETTIMEOFDAY)
  struct timeval real, user, sys;
  struct timeval before, after;
#  if defined (HAVE_STRUCT_TIMEZONE)
  struct timezone dtz;				/* posix doesn't define this */
#  endif
  struct rusage selfb, selfa, kidsb, kidsa;	/* a = after, b = before */
#else
#  if defined (HAVE_TIMES)
  clock_t tbefore, tafter, real, user, sys;
  struct tms before, after;
#  endif
#endif

#if defined (HAVE_GETRUSAGE) && defined (HAVE_GETTIMEOFDAY)
#  if defined (HAVE_STRUCT_TIMEZONE)
  gettimeofday (&before, &dtz);
#  else
  gettimeofday (&before, (void *)NULL);
#  endif /* !HAVE_STRUCT_TIMEZONE */
  getrusage (RUSAGE_SELF, &selfb);
  getrusage (RUSAGE_CHILDREN, &kidsb);
#else
#  if defined (HAVE_TIMES)
  tbefore = times (&before);
#  endif
#endif

  old_subshell = subshell_environment;
  posix_time = command && (command->flags & CMD_TIME_POSIX);

  nullcmd = (command == 0) || (command->type == cm_simple && command->value.Simple->words == 0 && command->value.Simple->redirects == 0);
  if (posixly_correct && nullcmd)
    {
#if defined (HAVE_GETRUSAGE)
      selfb.ru_utime.tv_sec = kidsb.ru_utime.tv_sec = selfb.ru_stime.tv_sec = kidsb.ru_stime.tv_sec = 0;
      selfb.ru_utime.tv_usec = kidsb.ru_utime.tv_usec = selfb.ru_stime.tv_usec = kidsb.ru_stime.tv_usec = 0;
      before = shellstart;
#else
      before.tms_utime = before.tms_stime = before.tms_cutime = before.tms_cstime = 0;
      tbefore = shell_start_time;
#endif
    }

  old_flags = command->flags;
  COPY_PROCENV (top_level, save_top_level);
  command->flags &= ~(CMD_TIME_PIPELINE|CMD_TIME_POSIX);
  code = setjmp_nosigs (top_level);
  if (code == NOT_JUMPED)
    rv = execute_command_internal (command, asynchronous, pipe_in, pipe_out, fds_to_close);
  COPY_PROCENV (save_top_level, top_level);

  command->flags = old_flags;

  /* If we're jumping in a different subshell environment than we started,
     don't bother printing timing stats, just keep longjmping back to the
     original top level. */
  if (code != NOT_JUMPED && subshell_environment && subshell_environment != old_subshell)
    sh_longjmp (top_level, code);

  rs = us = ss = 0;
  rsf = usf = ssf = cpu = 0;

#if defined (HAVE_GETRUSAGE) && defined (HAVE_GETTIMEOFDAY)
#  if defined (HAVE_STRUCT_TIMEZONE)
  gettimeofday (&after, &dtz);
#  else
  gettimeofday (&after, (void *)NULL);
#  endif /* !HAVE_STRUCT_TIMEZONE */
  getrusage (RUSAGE_SELF, &selfa);
  getrusage (RUSAGE_CHILDREN, &kidsa);

  difftimeval (&real, &before, &after);
  timeval_to_secs (&real, &rs, &rsf);

  addtimeval (&user, difftimeval(&after, &selfb.ru_utime, &selfa.ru_utime),
		     difftimeval(&before, &kidsb.ru_utime, &kidsa.ru_utime));
  timeval_to_secs (&user, &us, &usf);

  addtimeval (&sys, difftimeval(&after, &selfb.ru_stime, &selfa.ru_stime),
		    difftimeval(&before, &kidsb.ru_stime, &kidsa.ru_stime));
  timeval_to_secs (&sys, &ss, &ssf);

  cpu = timeval_to_cpu (&real, &user, &sys);
#else
#  if defined (HAVE_TIMES)
  tafter = times (&after);

  real = tafter - tbefore;
  clock_t_to_secs (real, &rs, &rsf);

  user = (after.tms_utime - before.tms_utime) + (after.tms_cutime - before.tms_cutime);
  clock_t_to_secs (user, &us, &usf);

  sys = (after.tms_stime - before.tms_stime) + (after.tms_cstime - before.tms_cstime);
  clock_t_to_secs (sys, &ss, &ssf);

  cpu = (real == 0) ? 0 : ((user + sys) * 10000) / real;

#  else
  rs = us = ss = 0;
  rsf = usf = ssf = cpu = 0;
#  endif
#endif

  if (posix_time)
    time_format = POSIX_TIMEFORMAT;
  else if ((time_format = get_string_value ("TIMEFORMAT")) == 0)
    {
      if (posixly_correct && nullcmd)
	time_format = "user\t%2lU\nsys\t%2lS";
      else
	time_format = BASH_TIMEFORMAT;
    }

  if (time_format && *time_format)
    print_formatted_time (stderr, time_format, rs, rsf, us, usf, ss, ssf, cpu);

  if (code)
    sh_longjmp (top_level, code);

  return rv;
}
#endif /* COMMAND_TIMING */

/* Execute a command that's supposed to be in a subshell.  This must be
   called after make_child and we must be running in the child process.
   The caller will return or exit() immediately with the value this returns. */
static int
execute_in_subshell (command, asynchronous, pipe_in, pipe_out, fds_to_close)
     COMMAND *command;
     int asynchronous;
     int pipe_in, pipe_out;
     struct fd_bitmap *fds_to_close;
{
  volatile int user_subshell, user_coproc, invert;
  int return_code, function_value, should_redir_stdin, ois, result;
  volatile COMMAND *tcom;

  USE_VAR(user_subshell);
  USE_VAR(user_coproc);
  USE_VAR(invert);
  USE_VAR(tcom);
  USE_VAR(asynchronous);

  subshell_level++;
  should_redir_stdin = (asynchronous && (command->flags & CMD_STDIN_REDIR) &&
			  pipe_in == NO_PIPE &&
			  stdin_redirects (command->redirects) == 0);

  invert = (command->flags & CMD_INVERT_RETURN) != 0;
  user_subshell = command->type == cm_subshell || ((command->flags & CMD_WANT_SUBSHELL) != 0);
  user_coproc = command->type == cm_coproc;

  command->flags &= ~(CMD_FORCE_SUBSHELL | CMD_WANT_SUBSHELL | CMD_INVERT_RETURN);

  /* If a command is asynchronous in a subshell (like ( foo ) & or
     the special case of an asynchronous GROUP command where the

     the subshell bit is turned on down in case cm_group: below),
     turn off `asynchronous', so that two subshells aren't spawned.
     XXX - asynchronous used to be set to 0 in this block, but that
     means that setup_async_signals was never run.  Now it's set to
     0 after subshell_environment is set appropriately and setup_async_signals
     is run.

     This seems semantically correct to me.  For example,
     ( foo ) & seems to say ``do the command `foo' in a subshell
     environment, but don't wait for that subshell to finish'',
     and "{ foo ; bar ; } &" seems to me to be like functions or
     builtins in the background, which executed in a subshell
     environment.  I just don't see the need to fork two subshells. */

  /* Don't fork again, we are already in a subshell.  A `doubly
     async' shell is not interactive, however. */
  if (asynchronous)
    {
#if defined (JOB_CONTROL)
      /* If a construct like ( exec xxx yyy ) & is given while job
	 control is active, we want to prevent exec from putting the
	 subshell back into the original process group, carefully
	 undoing all the work we just did in make_child. */
      original_pgrp = -1;
#endif /* JOB_CONTROL */
      ois = interactive_shell;
      interactive_shell = 0;
      /* This test is to prevent alias expansion by interactive shells that
	 run `(command) &' but to allow scripts that have enabled alias
	 expansion with `shopt -s expand_alias' to continue to expand
	 aliases. */
      if (ois != interactive_shell)
	expand_aliases = expaliases_flag = 0;
    }

  /* Subshells are neither login nor interactive. */
  login_shell = interactive = 0;

  /* And we're no longer in a loop. See Posix interp 842 (we are not in the
     "same execution environment"). */
  if (shell_compatibility_level > 44)
    loop_level = 0;

  if (user_subshell)
    {
      subshell_environment = SUBSHELL_PAREN;	/* XXX */
      if (asynchronous)
	subshell_environment |= SUBSHELL_ASYNC;
    }
  else
    {
      subshell_environment = 0;			/* XXX */
      if (asynchronous)
	subshell_environment |= SUBSHELL_ASYNC;
      if (pipe_in != NO_PIPE || pipe_out != NO_PIPE)
	subshell_environment |= SUBSHELL_PIPE;
      if (user_coproc)
	subshell_environment |= SUBSHELL_COPROC;
    }

  QUIT;
  CHECK_TERMSIG;

  reset_terminating_signals ();		/* in sig.c */
  /* Cancel traps, in trap.c. */
  /* Reset the signal handlers in the child, but don't free the
     trap strings.  Set a flag noting that we have to free the
     trap strings if we run trap to change a signal disposition. */
  clear_pending_traps ();
  reset_signal_handlers ();
  subshell_environment |= SUBSHELL_RESETTRAP;
  /* Note that signal handlers have been reset, so we should no longer
    reset the handler and resend trapped signals to ourselves. */
  subshell_environment &= ~SUBSHELL_IGNTRAP;

  /* We are in a subshell, so forget that we are running a trap handler or
     that the signal handler has changed (we haven't changed it!) */
  /* XXX - maybe do this for `real' signals and not ERR/DEBUG/RETURN/EXIT
     traps? */
  if (running_trap > 0)
    {
      run_trap_cleanup (running_trap - 1);
      running_trap = 0;		/* XXX - maybe leave this */
    }

  /* Make sure restore_original_signals doesn't undo the work done by
     make_child to ensure that asynchronous children are immune to SIGINT
     and SIGQUIT.  Turn off asynchronous to make sure more subshells are
     not spawned. */
  if (asynchronous)
    {
      setup_async_signals ();
      asynchronous = 0;
    }
  else
    set_sigint_handler ();

#if defined (JOB_CONTROL)
  set_sigchld_handler ();
#endif /* JOB_CONTROL */

  /* Delete all traces that there were any jobs running.  This is
     only for subshells. */
  without_job_control ();

  if (fds_to_close)
    close_fd_bitmap (fds_to_close);

  do_piping (pipe_in, pipe_out);

#if defined (COPROCESS_SUPPORT)
  coproc_closeall ();
#endif

#if defined (PROCESS_SUBSTITUTION)
  clear_fifo_list ();		/* XXX- we haven't created any FIFOs */
#endif

  /* If this is a user subshell, set a flag if stdin was redirected.
     This is used later to decide whether to redirect fd 0 to
     /dev/null for async commands in the subshell.  This adds more
     sh compatibility, but I'm not sure it's the right thing to do.
     Note that an input pipe to a compound command suffices to inhibit
     the implicit /dev/null redirection for asynchronous commands
     executed as part of that compound command. */
  if (user_subshell)
    {
      stdin_redir = stdin_redirects (command->redirects) || pipe_in != NO_PIPE;
#if 0
      restore_default_signal (EXIT_TRAP);	/* XXX - reset_signal_handlers above */
#endif
    }
  else if (shell_control_structure (command->type) && pipe_in != NO_PIPE)
    stdin_redir = 1;

  /* If this is an asynchronous command (command &), we want to
     redirect the standard input from /dev/null in the absence of
     any specific redirection involving stdin. */
  if (should_redir_stdin && stdin_redir == 0)
    async_redirect_stdin ();

#if defined (BUFFERED_INPUT)
  /* In any case, we are not reading our command input from stdin. */
  default_buffered_input = -1;
#endif

  /* We can't optimize away forks if one of the commands executed by the
     subshell sets an exit trap, so we set CMD_NO_FORK for simple commands
     and set CMD_TRY_OPTIMIZING for simple commands on the right side of an
     and-or or `;' list to test for optimizing forks when they are executed. */
  if (user_subshell && command->type == cm_subshell &&
      (command->flags & (CMD_TIME_PIPELINE|CMD_INVERT_RETURN)) == 0)
    optimize_subshell_command (command->value.Subshell->command);

  /* Do redirections, then dispose of them before recursive call. */
  if (command->redirects)
    {
      if (do_redirections (command->redirects, RX_ACTIVE) != 0)
	exit (invert ? EXECUTION_SUCCESS : EXECUTION_FAILURE);

      dispose_redirects (command->redirects);
      command->redirects = (REDIRECT *)NULL;
    }

  if (command->type == cm_subshell)
    tcom = command->value.Subshell->command;
  else if (user_coproc)
    tcom = command->value.Coproc->command;
  else
    tcom = command;

  if (command->flags & CMD_TIME_PIPELINE)
    tcom->flags |= CMD_TIME_PIPELINE;
  if (command->flags & CMD_TIME_POSIX)
    tcom->flags |= CMD_TIME_POSIX;
  
  /* Make sure the subshell inherits any CMD_IGNORE_RETURN flag. */
  if ((command->flags & CMD_IGNORE_RETURN) && tcom != command)
    tcom->flags |= CMD_IGNORE_RETURN;

  /* If this is a simple command, tell execute_disk_command that it
     might be able to get away without forking and simply exec.
     This means things like ( sleep 10 ) will only cause one fork.
     If we're timing the command or inverting its return value, however,
     we cannot do this optimization. */
  if ((user_subshell || user_coproc) && (tcom->type == cm_simple || tcom->type == cm_subshell) &&
      ((tcom->flags & CMD_TIME_PIPELINE) == 0) &&
      ((tcom->flags & CMD_INVERT_RETURN) == 0))
    {
      tcom->flags |= CMD_NO_FORK;
      if (tcom->type == cm_simple)
	tcom->value.Simple->flags |= CMD_NO_FORK;
    }

  invert = (tcom->flags & CMD_INVERT_RETURN) != 0;
  tcom->flags &= ~CMD_INVERT_RETURN;

  result = setjmp_nosigs (top_level);

  /* If we're inside a function while executing this subshell, we
     need to handle a possible `return'. */
  function_value = 0;
  if (return_catch_flag)
    function_value = setjmp_nosigs (return_catch);

  /* If we're going to exit the shell, we don't want to invert the return
     status. */
  if (result == EXITPROG || result == EXITBLTIN)
    invert = 0, return_code = last_command_exit_value;
  else if (result)
    return_code = (last_command_exit_value == EXECUTION_SUCCESS) ? EXECUTION_FAILURE : last_command_exit_value;
  else if (function_value)
    return_code = return_catch_value;
  else
    return_code = execute_command_internal ((COMMAND *)tcom, asynchronous, NO_PIPE, NO_PIPE, fds_to_close);

  /* If we are asked to, invert the return value. */
  if (invert)
    return_code = (return_code == EXECUTION_SUCCESS) ? EXECUTION_FAILURE
						     : EXECUTION_SUCCESS;

  /* Check for terminating signals before we return to our caller, which we
     expect to exit immediately anyway. */
  CHECK_TERMSIG;

  /* If we were explicitly placed in a subshell with (), we need
     to do the `shell cleanup' things, such as running traps[0]. */
  if (user_subshell && signal_is_trapped (0))
    {
      last_command_exit_value = return_code;
      return_code = run_exit_trap ();
    }

#if 0
  subshell_level--;		/* don't bother, caller will just exit */
#endif
  return (return_code);
  /* NOTREACHED */
}

#if defined (COPROCESS_SUPPORT)
#define COPROC_MAX	16

typedef struct cpelement
  {
    struct cpelement *next;
    struct coproc *coproc;
  }
cpelement_t;
    
typedef struct cplist
  {
    struct cpelement *head;
    struct cpelement *tail;
    int ncoproc;
    int lock;
  }
cplist_t;

static struct cpelement *cpe_alloc PARAMS((struct coproc *));
static void cpe_dispose PARAMS((struct cpelement *));
static struct cpelement *cpl_add PARAMS((struct coproc *));
static struct cpelement *cpl_delete PARAMS((pid_t));
static void cpl_reap PARAMS((void));
static void cpl_flush PARAMS((void));
static void cpl_closeall PARAMS((void));
static struct cpelement *cpl_search PARAMS((pid_t));
static struct cpelement *cpl_searchbyname PARAMS((const char *));
static void cpl_prune PARAMS((void));

static void coproc_free PARAMS((struct coproc *));

/* Will go away when there is fully-implemented support for multiple coprocs. */
Coproc sh_coproc = { 0, NO_PID, -1, -1, 0, 0, 0, 0, 0 };

cplist_t coproc_list = {0, 0, 0};

/* Functions to manage the list of coprocs */

static struct cpelement *
cpe_alloc (cp)
     Coproc *cp;
{
  struct cpelement *cpe;

  cpe = (struct cpelement *)xmalloc (sizeof (struct cpelement));
  cpe->coproc = cp;
  cpe->next = (struct cpelement *)0;
  return cpe;
}

static void
cpe_dispose (cpe)
      struct cpelement *cpe;
{
  free (cpe);
}

static struct cpelement *
cpl_add (cp)
     Coproc *cp;
{
  struct cpelement *cpe;

  cpe = cpe_alloc (cp);

  if (coproc_list.head == 0)
    {
      coproc_list.head = coproc_list.tail = cpe;
      coproc_list.ncoproc = 0;			/* just to make sure */
    }
  else
    {
      coproc_list.tail->next = cpe;
      coproc_list.tail = cpe;
    }
  coproc_list.ncoproc++;

  return cpe;
}

static struct cpelement *
cpl_delete (pid)
     pid_t pid;
{
  struct cpelement *prev, *p;

  for (prev = p = coproc_list.head; p; prev = p, p = p->next)
    if (p->coproc->c_pid == pid)
      {
        prev->next = p->next;	/* remove from list */
        break;
      }

  if (p == 0)
    return 0;		/* not found */

  INTERNAL_DEBUG (("cpl_delete: deleting %d", pid));

  /* Housekeeping in the border cases. */
  if (p == coproc_list.head)
    coproc_list.head = coproc_list.head->next;
  else if (p == coproc_list.tail)
    coproc_list.tail = prev;

  coproc_list.ncoproc--;
  if (coproc_list.ncoproc == 0)
    coproc_list.head = coproc_list.tail = 0;
  else if (coproc_list.ncoproc == 1)
    coproc_list.tail = coproc_list.head;		/* just to make sure */

  return (p);
}

static void
cpl_reap ()
{
  struct cpelement *p, *next, *nh, *nt;

  /* Build a new list by removing dead coprocs and fix up the coproc_list
     pointers when done. */
  nh = nt = next = (struct cpelement *)0;
  for (p = coproc_list.head; p; p = next)
    {
      next = p->next;
      if (p->coproc->c_flags & COPROC_DEAD)
	{
	  coproc_list.ncoproc--;	/* keep running count, fix up pointers later */
	  INTERNAL_DEBUG (("cpl_reap: deleting %d", p->coproc->c_pid));
	  coproc_dispose (p->coproc);
	  cpe_dispose (p);
	}
      else if (nh == 0)
	nh = nt = p;
      else
	{
	  nt->next = p;
	  nt = nt->next;
	}
    }

  if (coproc_list.ncoproc == 0)
    coproc_list.head = coproc_list.tail = 0;
  else
    {
      if (nt)
        nt->next = 0;
      coproc_list.head = nh;
      coproc_list.tail = nt;
      if (coproc_list.ncoproc == 1)
	coproc_list.tail = coproc_list.head;		/* just to make sure */  
    }
}

/* Clear out the list of saved statuses */
static void
cpl_flush ()
{
  struct cpelement *cpe, *p;

  for (cpe = coproc_list.head; cpe; )
    {
      p = cpe;
      cpe = cpe->next;

      coproc_dispose (p->coproc);
      cpe_dispose (p);
    }

  coproc_list.head = coproc_list.tail = 0;
  coproc_list.ncoproc = 0;
}

static void
cpl_closeall ()
{
  struct cpelement *cpe;

  for (cpe = coproc_list.head; cpe; cpe = cpe->next)
    coproc_close (cpe->coproc);
}

static void
cpl_fdchk (fd)
     int fd;
{
  struct cpelement *cpe;

  for (cpe = coproc_list.head; cpe; cpe = cpe->next)
    coproc_checkfd (cpe->coproc, fd);
}

/* Search for PID in the list of coprocs; return the cpelement struct if
   found.  If not found, return NULL. */
static struct cpelement *
cpl_search (pid)
     pid_t pid;
{
  struct cpelement *cpe;

  for (cpe = coproc_list.head ; cpe; cpe = cpe->next)
    if (cpe->coproc->c_pid == pid)
      return cpe;
  return (struct cpelement *)NULL;
}

/* Search for the coproc named NAME in the list of coprocs; return the
   cpelement struct if found.  If not found, return NULL. */
static struct cpelement *
cpl_searchbyname (name)
     const char *name;
{
  struct cpelement *cp;

  for (cp = coproc_list.head ; cp; cp = cp->next)
    if (STREQ (cp->coproc->c_name, name))
      return cp;
  return (struct cpelement *)NULL;
}

static pid_t
cpl_firstactive ()
{
  struct cpelement *cpe;

  for (cpe = coproc_list.head ; cpe; cpe = cpe->next)
    if ((cpe->coproc->c_flags & COPROC_DEAD) == 0)
      return cpe->coproc->c_pid;
  return (pid_t)NO_PID;
}

#if 0
static void
cpl_prune ()
{
  struct cpelement *cp;

  while (coproc_list.head && coproc_list.ncoproc > COPROC_MAX)
    {
      cp = coproc_list.head;
      coproc_list.head = coproc_list.head->next;
      coproc_dispose (cp->coproc);
      cpe_dispose (cp);
      coproc_list.ncoproc--;
    }
}
#endif

/* These currently use a single global "shell coproc" but are written in a
   way to not preclude additional coprocs later (using the list management
   package above). */

struct coproc *
getcoprocbypid (pid)
     pid_t pid;
{
#if MULTIPLE_COPROCS
  struct cpelement *p;

  p = cpl_search (pid);
  return (p ? p->coproc : 0);
#else
  return (pid == sh_coproc.c_pid ? &sh_coproc : 0);
#endif
}

struct coproc *
getcoprocbyname (name)
     const char *name;
{
#if MULTIPLE_COPROCS
  struct cpelement *p;

  p = cpl_searchbyname (name);
  return (p ? p->coproc : 0);
#else
  return ((sh_coproc.c_name && STREQ (sh_coproc.c_name, name)) ? &sh_coproc : 0);
#endif
}

void
coproc_init (cp)
     struct coproc *cp;
{
  cp->c_name = 0;
  cp->c_pid = NO_PID;
  cp->c_rfd = cp->c_wfd = -1;
  cp->c_rsave = cp->c_wsave = -1;
  cp->c_flags = cp->c_status = cp->c_lock = 0;
}

struct coproc *
coproc_alloc (name, pid)
     char *name;
     pid_t pid;
{
  struct coproc *cp;

#if MULTIPLE_COPROCS
  cp = (struct coproc *)xmalloc (sizeof (struct coproc));
#else
  cp = &sh_coproc;
#endif
  coproc_init (cp);
  cp->c_lock = 2;

  cp->c_pid = pid;
  cp->c_name = savestring (name);
#if MULTIPLE_COPROCS
  cpl_add (cp);
#endif
  cp->c_lock = 0;
  return (cp);
}

static void
coproc_free (cp)
     struct coproc *cp;
{
  free (cp);
}

void
coproc_dispose (cp)
     struct coproc *cp;
{
  sigset_t set, oset;

  if (cp == 0)
    return;

  BLOCK_SIGNAL (SIGCHLD, set, oset);
  cp->c_lock = 3;
  coproc_unsetvars (cp);
  FREE (cp->c_name);
  coproc_close (cp);
#if MULTIPLE_COPROCS
  coproc_free (cp);
#else
  coproc_init (cp);
  cp->c_lock = 0;
#endif
  UNBLOCK_SIGNAL (oset);
}

/* Placeholder for now.  Will require changes for multiple coprocs */
void
coproc_flush ()
{
#if MULTIPLE_COPROCS
  cpl_flush ();
#else
  coproc_dispose (&sh_coproc);
#endif
}

void
coproc_close (cp)
     struct coproc *cp;
{
  if (cp->c_rfd >= 0)
    {
      close (cp->c_rfd);
      cp->c_rfd = -1;
    }
  if (cp->c_wfd >= 0)
    {
      close (cp->c_wfd);
      cp->c_wfd = -1;
    }
  cp->c_rsave = cp->c_wsave = -1;
}

void
coproc_closeall ()
{
#if MULTIPLE_COPROCS
  cpl_closeall ();
#else
  coproc_close (&sh_coproc);	/* XXX - will require changes for multiple coprocs */
#endif
}

void
coproc_reap ()
{
#if MULTIPLE_COPROCS
  cpl_reap ();
#else
  struct coproc *cp;

  cp = &sh_coproc;		/* XXX - will require changes for multiple coprocs */
  if (cp && (cp->c_flags & COPROC_DEAD))
    coproc_dispose (cp);
#endif
}

void
coproc_rclose (cp, fd)
     struct coproc *cp;
     int fd;
{
  if (cp->c_rfd >= 0 && cp->c_rfd == fd)
    {
      close (cp->c_rfd);
      cp->c_rfd = -1;
    }
}

void
coproc_wclose (cp, fd)
     struct coproc *cp;
     int fd;
{
  if (cp->c_wfd >= 0 && cp->c_wfd == fd)
    {
      close (cp->c_wfd);
      cp->c_wfd = -1;
    }
}

void
coproc_checkfd (cp, fd)
     struct coproc *cp;
     int fd;
{
  int update;

  update = 0;
  if (cp->c_rfd >= 0 && cp->c_rfd == fd)
    update = cp->c_rfd = -1;
  if (cp->c_wfd >= 0 && cp->c_wfd == fd)
    update = cp->c_wfd = -1;
  if (update)
    coproc_setvars (cp);
}

void
coproc_fdchk (fd)
     int fd;
{
#if MULTIPLE_COPROCS
  cpl_fdchk (fd);
#else
  coproc_checkfd (&sh_coproc, fd);
#endif
}

void
coproc_fdclose (cp, fd)
     struct coproc *cp;
     int fd;
{
  coproc_rclose (cp, fd);
  coproc_wclose (cp, fd);
  coproc_setvars (cp);
}

void
coproc_fdsave (cp)
     struct coproc *cp;
{
  cp->c_rsave = cp->c_rfd;
  cp->c_wsave = cp->c_wfd;
}

void
coproc_fdrestore (cp)
     struct coproc *cp;
{
  cp->c_rfd = cp->c_rsave;
  cp->c_wfd = cp->c_wsave;
}

static void
coproc_setstatus (cp, status)
     struct coproc *cp;
     int status;
{
  cp->c_lock = 4;
  cp->c_status = status;
  cp->c_flags |= COPROC_DEAD;
  cp->c_flags &= ~COPROC_RUNNING;
  /* Don't dispose the coproc or unset the COPROC_XXX variables because
     this is executed in a signal handler context.  Wait until coproc_reap
     takes care of it. */
  cp->c_lock = 0;
}

void
coproc_pidchk (pid, status)
     pid_t pid;
     int status;
{
  struct coproc *cp;

#if MULTIPLE_COPROCS
  struct cpelement *cpe;

  /* We're not disposing the coproc because this is executed in a signal
     handler context */
  cpe = cpl_search (pid);
  cp = cpe ? cpe->coproc : 0;
#else
  cp = getcoprocbypid (pid);
#endif
  if (cp)
    coproc_setstatus (cp, status);
}

pid_t
coproc_active ()
{
#if MULTIPLE_COPROCS
  return (cpl_firstactive ());
#else
  return ((sh_coproc.c_flags & COPROC_DEAD) ? NO_PID : sh_coproc.c_pid);
#endif
}
void
coproc_setvars (cp)
     struct coproc *cp;
{
  SHELL_VAR *v;
  char *namevar, *t;
  size_t l;
  WORD_DESC w;
#if defined (ARRAY_VARS)
  arrayind_t ind;
#endif

  if (cp->c_name == 0)
    return;

  /* We could do more here but right now we only check the name, warn if it's
     not a valid identifier, and refuse to create variables with invalid names
     if a coproc with such a name is supplied. */
  w.word = cp->c_name;
  w.flags = 0;
  if (check_identifier (&w, 1) == 0)
    return;

  l = strlen (cp->c_name);
  namevar = xmalloc (l + 16);

#if defined (ARRAY_VARS)
  v = find_variable (cp->c_name);

  /* This is the same code as in find_or_make_array_variable */
  if (v == 0)
    {
      v = find_variable_nameref_for_create (cp->c_name, 1);
      if (v == INVALID_NAMEREF_VALUE)
	{
	  free (namevar);
	  return;
	}
      if (v && nameref_p (v))
	{
	  free (cp->c_name);
	  cp->c_name = savestring (nameref_cell (v));
	  v = make_new_array_variable (cp->c_name);	  
	}
    }

  if (v && (readonly_p (v) || noassign_p (v)))
    {
      if (readonly_p (v))
	err_readonly (cp->c_name);
      free (namevar);
      return;
    }
  if (v == 0)
    v = make_new_array_variable (cp->c_name);
  if (array_p (v) == 0)
    v = convert_var_to_array (v);

  t = itos (cp->c_rfd);
  ind = 0;
  v = bind_array_variable (cp->c_name, ind, t, 0);
  free (t);

  t = itos (cp->c_wfd);
  ind = 1;
  v = bind_array_variable (cp->c_name, ind, t, 0);
  free (t);
#else
  sprintf (namevar, "%s_READ", cp->c_name);
  t = itos (cp->c_rfd);
  bind_variable (namevar, t, 0);
  free (t);
  sprintf (namevar, "%s_WRITE", cp->c_name);
  t = itos (cp->c_wfd);
  bind_variable (namevar, t, 0);
  free (t);
#endif

  sprintf (namevar, "%s_PID", cp->c_name);
  t = itos (cp->c_pid);
  v = bind_variable (namevar, t, 0);
  free (t);

  free (namevar);
}

void
coproc_unsetvars (cp)
     struct coproc *cp;
{
  int l;
  char *namevar;

  if (cp->c_name == 0)
    return;

  l = strlen (cp->c_name);
  namevar = xmalloc (l + 16);

  sprintf (namevar, "%s_PID", cp->c_name);
  unbind_variable_noref (namevar);  

#if defined (ARRAY_VARS)
  check_unbind_variable (cp->c_name);
#else
  sprintf (namevar, "%s_READ", cp->c_name);
  unbind_variable (namevar);
  sprintf (namevar, "%s_WRITE", cp->c_name);
  unbind_variable (namevar);
#endif  

  free (namevar);
}

static int
execute_coproc (command, pipe_in, pipe_out, fds_to_close)
     COMMAND *command;
     int pipe_in, pipe_out;
     struct fd_bitmap *fds_to_close;
{
  int rpipe[2], wpipe[2], estat, invert;
  pid_t coproc_pid;
  Coproc *cp;
  char *tcmd, *p, *name;
  sigset_t set, oset;

  /* XXX -- can be removed after changes to handle multiple coprocs */
#if !MULTIPLE_COPROCS
  if (sh_coproc.c_pid != NO_PID && (sh_coproc.c_rfd >= 0 || sh_coproc.c_wfd >= 0))
    internal_warning (_("execute_coproc: coproc [%d:%s] still exists"), sh_coproc.c_pid, sh_coproc.c_name);
  coproc_init (&sh_coproc);
#endif

  invert = (command->flags & CMD_INVERT_RETURN) != 0;

  /* expand name without splitting - could make this dependent on a shopt option */
  name = expand_string_unsplit_to_string (command->value.Coproc->name, 0);
  /* Optional check -- could be relaxed */
  if (legal_identifier (name) == 0)
    {
      internal_error (_("`%s': not a valid identifier"), name);
      free (name);
      return (invert ? EXECUTION_SUCCESS : EXECUTION_FAILURE);
    }
  else
    {
      free (command->value.Coproc->name);
      command->value.Coproc->name = name;
    }

  command_string_index = 0;
  tcmd = make_command_string (command);

  sh_openpipe ((int *)&rpipe);	/* 0 = parent read, 1 = child write */
  sh_openpipe ((int *)&wpipe); /* 0 = child read, 1 = parent write */

  BLOCK_SIGNAL (SIGCHLD, set, oset);

  coproc_pid = make_child (p = savestring (tcmd), FORK_ASYNC);

  if (coproc_pid == 0)
    {
      close (rpipe[0]);
      close (wpipe[1]);

#if defined (JOB_CONTROL)
      FREE (p);
#endif

      UNBLOCK_SIGNAL (oset);
      estat = execute_in_subshell (command, 1, wpipe[0], rpipe[1], fds_to_close);

      fflush (stdout);
      fflush (stderr);

      exit (estat);
    }

  close (rpipe[1]);
  close (wpipe[0]);

  cp = coproc_alloc (command->value.Coproc->name, coproc_pid);
  cp->c_rfd = rpipe[0];
  cp->c_wfd = wpipe[1];

  cp->c_flags |= COPROC_RUNNING;

  SET_CLOSE_ON_EXEC (cp->c_rfd);
  SET_CLOSE_ON_EXEC (cp->c_wfd);

  coproc_setvars (cp);

  UNBLOCK_SIGNAL (oset);

#if 0
  itrace ("execute_coproc (%s): [%d] %s", command->value.Coproc->name, coproc_pid, the_printed_command);
#endif

  close_pipes (pipe_in, pipe_out);
#if defined (PROCESS_SUBSTITUTION) && defined (HAVE_DEV_FD)
  unlink_fifo_list ();
#endif
  stop_pipeline (1, (COMMAND *)NULL);
  DESCRIBE_PID (coproc_pid);
  run_pending_traps ();

  return (invert ? EXECUTION_FAILURE : EXECUTION_SUCCESS);
}
#endif

/* If S == -1, it's a special value saying to close stdin */
static void
restore_stdin (s)
     int s;
{
  if (s == -1)
    close (0);
  else
    {
      dup2 (s, 0);
      close (s);
    }
}

/* Catch-all cleanup function for lastpipe code for unwind-protects */
static void
lastpipe_cleanup (s)
     int s;
{
  set_jobs_list_frozen (s);
}

static int
execute_pipeline (command, asynchronous, pipe_in, pipe_out, fds_to_close)
     COMMAND *command;
     int asynchronous, pipe_in, pipe_out;
     struct fd_bitmap *fds_to_close;
{
  int prev, fildes[2], new_bitmap_size, dummyfd, ignore_return, exec_result;
  int lstdin, lastpipe_flag, lastpipe_jid, old_frozen, stdin_valid;
  COMMAND *cmd;
  struct fd_bitmap *fd_bitmap;
  pid_t lastpid;

#if defined (JOB_CONTROL)
  sigset_t set, oset;
  BLOCK_CHILD (set, oset);
#endif /* JOB_CONTROL */

  ignore_return = (command->flags & CMD_IGNORE_RETURN) != 0;

  stdin_valid = sh_validfd (0);

  prev = pipe_in;
  cmd = command;

  while (cmd && cmd->type == cm_connection &&
	 cmd->value.Connection && cmd->value.Connection->connector == '|')
    {
      /* Make a pipeline between the two commands. */
      if (pipe (fildes) < 0)
	{
	  sys_error (_("pipe error"));
#if defined (JOB_CONTROL)
	  terminate_current_pipeline ();
	  kill_current_pipeline ();
	  UNBLOCK_CHILD (oset);
#endif /* JOB_CONTROL */
	  last_command_exit_value = EXECUTION_FAILURE;
	  /* The unwind-protects installed below will take care
	     of closing all of the open file descriptors. */
	  throw_to_top_level ();
	  return (EXECUTION_FAILURE);	/* XXX */
	}

      /* Here is a problem: with the new file close-on-exec
	 code, the read end of the pipe (fildes[0]) stays open
	 in the first process, so that process will never get a
	 SIGPIPE.  There is no way to signal the first process
	 that it should close fildes[0] after forking, so it
	 remains open.  No SIGPIPE is ever sent because there
	 is still a file descriptor open for reading connected
	 to the pipe.  We take care of that here.  This passes
	 around a bitmap of file descriptors that must be
	 closed after making a child process in execute_simple_command. */

      /* We need fd_bitmap to be at least as big as fildes[0].
	 If fildes[0] is less than fds_to_close->size, then
	 use fds_to_close->size. */
      new_bitmap_size = (fildes[0] < fds_to_close->size)
				? fds_to_close->size
				: fildes[0] + 8;

      fd_bitmap = new_fd_bitmap (new_bitmap_size);

      /* Now copy the old information into the new bitmap. */
      xbcopy ((char *)fds_to_close->bitmap, (char *)fd_bitmap->bitmap, fds_to_close->size);

      /* And mark the pipe file descriptors to be closed. */
      fd_bitmap->bitmap[fildes[0]] = 1;

      /* In case there are pipe or out-of-processes errors, we
	 want all these file descriptors to be closed when
	 unwind-protects are run, and the storage used for the
	 bitmaps freed up. */
      begin_unwind_frame ("pipe-file-descriptors");
      add_unwind_protect (dispose_fd_bitmap, fd_bitmap);
      add_unwind_protect (close_fd_bitmap, fd_bitmap);
      if (prev >= 0)
	add_unwind_protect (close, prev);
      dummyfd = fildes[1];
      add_unwind_protect (close, dummyfd);

#if defined (JOB_CONTROL)
      add_unwind_protect (restore_signal_mask, &oset);
#endif /* JOB_CONTROL */

      if (ignore_return && cmd->value.Connection->first)
	cmd->value.Connection->first->flags |= CMD_IGNORE_RETURN;
      execute_command_internal (cmd->value.Connection->first, asynchronous,
				prev, fildes[1], fd_bitmap);

      if (prev >= 0)
	close (prev);

      prev = fildes[0];
      close (fildes[1]);

      dispose_fd_bitmap (fd_bitmap);
      discard_unwind_frame ("pipe-file-descriptors");

      cmd = cmd->value.Connection->second;
    }

  lastpid = last_made_pid;

  /* Now execute the rightmost command in the pipeline.  */
  if (ignore_return && cmd)
    cmd->flags |= CMD_IGNORE_RETURN;

  lastpipe_flag = 0;

  begin_unwind_frame ("lastpipe-exec");
  lstdin = -2;		/* -1 is special, meaning fd 0 is closed */
  /* If the `lastpipe' option is set with shopt, and job control is not
     enabled, execute the last element of non-async pipelines in the
     current shell environment. */
  /* prev can be 0 if fd 0 was closed when this function was executed. prev
     will never be 0 at this point if fd 0 was valid when this function was
     executed (though we check above). */
  if (lastpipe_opt && job_control == 0 && asynchronous == 0 && pipe_out == NO_PIPE && prev >= 0)
    {
      /* -1 is a special value meaning to close stdin */
      lstdin = (prev > 0 && stdin_valid) ? move_to_high_fd (0, 1, -1) : -1;
      if (lstdin > 0 || lstdin == -1)
	{
	  do_piping (prev, pipe_out);
	  prev = NO_PIPE;
	  add_unwind_protect (restore_stdin, lstdin);
	  lastpipe_flag = 1;
	  old_frozen = freeze_jobs_list ();
	  lastpipe_jid = stop_pipeline (0, (COMMAND *)NULL);	/* XXX */
	  add_unwind_protect (lastpipe_cleanup, old_frozen);
#if defined (JOB_CONTROL)
	  UNBLOCK_CHILD (oset);		/* XXX */
#endif
	}
      if (cmd)
	cmd->flags |= CMD_LASTPIPE;
    }	  
  if (prev >= 0)
    add_unwind_protect (close, prev);

  exec_result = execute_command_internal (cmd, asynchronous, prev, pipe_out, fds_to_close);

  if (prev >= 0)
    close (prev);

  if (lstdin > 0 || lstdin == -1)
    restore_stdin (lstdin);

#if defined (JOB_CONTROL)
  UNBLOCK_CHILD (oset);
#endif

  QUIT;

  if (lastpipe_flag)
    {
#if defined (JOB_CONTROL)
      if (INVALID_JOB (lastpipe_jid) == 0)
        {
          append_process (savestring (the_printed_command_except_trap), dollar_dollar_pid, exec_result, lastpipe_jid);
          lstdin = wait_for (lastpid, 0);
        }
      else
	{
	  lstdin = wait_for_single_pid (lastpid, 0);		/* checks bgpids list */
	  if (lstdin > 256)		/* error sentinel */
	    lstdin = 127;
	}
#else
      lstdin = wait_for (lastpid, 0);
#endif

#if defined (JOB_CONTROL)
      /* If wait_for removes the job from the jobs table, use result of last
	 command as pipeline's exit status as usual.  The jobs list can get
	 frozen and unfrozen at inconvenient times if there are multiple pipelines
	 running simultaneously. */
      if (INVALID_JOB (lastpipe_jid) == 0)
	exec_result = job_exit_status (lastpipe_jid);
      else if (pipefail_opt)
	exec_result = exec_result | lstdin;	/* XXX */
      /* otherwise we use exec_result */
#endif

      set_jobs_list_frozen (old_frozen);
    }

  discard_unwind_frame ("lastpipe-exec");

  return (exec_result);
}

static int
execute_connection (command, asynchronous, pipe_in, pipe_out, fds_to_close)
     COMMAND *command;
     int asynchronous, pipe_in, pipe_out;
     struct fd_bitmap *fds_to_close;
{
  COMMAND *tc, *second;
  int ignore_return, exec_result, was_error_trap, invert;
  volatile int save_line_number;

  ignore_return = (command->flags & CMD_IGNORE_RETURN) != 0;

  switch (command->value.Connection->connector)
    {
    /* Do the first command asynchronously. */
    case '&':
      tc = command->value.Connection->first;
      if (tc == 0)
	return (EXECUTION_SUCCESS);

      if (ignore_return)
	tc->flags |= CMD_IGNORE_RETURN;
      tc->flags |= CMD_AMPERSAND;

      /* If this shell was compiled without job control support,
	 if we are currently in a subshell via `( xxx )', or if job
	 control is not active then the standard input for an
	 asynchronous command is forced to /dev/null. */
#if defined (JOB_CONTROL)
      if ((subshell_environment || !job_control) && !stdin_redir)
#else
      if (!stdin_redir)
#endif /* JOB_CONTROL */
	tc->flags |= CMD_STDIN_REDIR;

      exec_result = execute_command_internal (tc, 1, pipe_in, pipe_out, fds_to_close);
      QUIT;

      if (tc->flags & CMD_STDIN_REDIR)
	tc->flags &= ~CMD_STDIN_REDIR;

      second = command->value.Connection->second;
      if (second)
	{
	  if (ignore_return)
	    second->flags |= CMD_IGNORE_RETURN;

	  exec_result = execute_command_internal (second, asynchronous, pipe_in, pipe_out, fds_to_close);
	}

      break;

    /* Just call execute command on both sides. */
    case ';':
    case '\n':		/* special case, happens in command substitutions */
      if (ignore_return)
	{
	  if (command->value.Connection->first)
	    command->value.Connection->first->flags |= CMD_IGNORE_RETURN;
	  if (command->value.Connection->second)
	    command->value.Connection->second->flags |= CMD_IGNORE_RETURN;
	}
      executing_list++;
      QUIT;

#if 1
      execute_command (command->value.Connection->first);
#else
      execute_command_internal (command->value.Connection->first,
				  asynchronous, pipe_in, pipe_out,
				  fds_to_close);
#endif

      QUIT;
      optimize_connection_fork (command);			/* XXX */
      exec_result = execute_command_internal (command->value.Connection->second,
				      asynchronous, pipe_in, pipe_out,
				      fds_to_close);
      executing_list--;
      break;

    case '|':
      was_error_trap = signal_is_trapped (ERROR_TRAP) && signal_is_ignored (ERROR_TRAP) == 0;
      invert = (command->flags & CMD_INVERT_RETURN) != 0;
      ignore_return = (command->flags & CMD_IGNORE_RETURN) != 0;

      SET_LINE_NUMBER (line_number);	/* XXX - save value? */
      exec_result = execute_pipeline (command, asynchronous, pipe_in, pipe_out, fds_to_close);

      if (asynchronous)
	{
	  exec_result = EXECUTION_SUCCESS;
	  invert = 0;
	}

      if (was_error_trap && ignore_return == 0 && invert == 0 && exec_result != EXECUTION_SUCCESS)
	{
	  last_command_exit_value = exec_result;
	  save_line_number = line_number;
	  line_number = line_number_for_err_trap;
	  run_error_trap ();
	  line_number = save_line_number;
	}

      if (ignore_return == 0 && invert == 0 && exit_immediately_on_error && exec_result != EXECUTION_SUCCESS)
	{
	  last_command_exit_value = exec_result;
	  run_pending_traps ();
	  jump_to_top_level (ERREXIT);
	}

      break;

    case AND_AND:
    case OR_OR:
      if (asynchronous)
	{
	  /* If we have something like `a && b &' or `a || b &', run the
	     && or || stuff in a subshell.  Force a subshell and just call
	     execute_command_internal again.  Leave asynchronous on
	     so that we get a report from the parent shell about the
	     background job. */
	  command->flags |= CMD_FORCE_SUBSHELL;
	  exec_result = execute_command_internal (command, 1, pipe_in, pipe_out, fds_to_close);
	  break;
	}

      /* Execute the first command.  If the result of that is successful
	 and the connector is AND_AND, or the result is not successful
	 and the connector is OR_OR, then execute the second command,
	 otherwise return. */

      executing_list++;
      if (command->value.Connection->first)
	command->value.Connection->first->flags |= CMD_IGNORE_RETURN;

#if 1
      exec_result = execute_command (command->value.Connection->first);
#else
      exec_result = execute_command_internal (command->value.Connection->first, 0, NO_PIPE, NO_PIPE, fds_to_close);
#endif
      QUIT;
      if (((command->value.Connection->connector == AND_AND) &&
	   (exec_result == EXECUTION_SUCCESS)) ||
	  ((command->value.Connection->connector == OR_OR) &&
	   (exec_result != EXECUTION_SUCCESS)))
	{
	  optimize_connection_fork (command);

	  second = command->value.Connection->second;
	  if (ignore_return && second)
	    second->flags |= CMD_IGNORE_RETURN;

	  exec_result = execute_command (second);
	}
      executing_list--;
      break;

    default:
      command_error ("execute_connection", CMDERR_BADCONN, command->value.Connection->connector, 0);
      jump_to_top_level (DISCARD);
      exec_result = EXECUTION_FAILURE;
    }

  return exec_result;
}

/* The test used to be only for interactive_shell, but we don't want to report
   job status when the shell is not interactive or when job control isn't
   enabled. */
#define REAP() \
  do \
    { \
      if (job_control == 0 || interactive_shell == 0) \
	reap_dead_jobs (); \
    } \
  while (0)

/* Execute a FOR command.  The syntax is: FOR word_desc IN word_list;
   DO command; DONE */
static int
execute_for_command (for_command)
     FOR_COM *for_command;
{
  register WORD_LIST *releaser, *list;
  SHELL_VAR *v;
  char *identifier;
  int retval, save_line_number;
#if 0
  SHELL_VAR *old_value = (SHELL_VAR *)NULL; /* Remember the old value of x. */
#endif

  save_line_number = line_number;
  if (check_identifier (for_command->name, 1) == 0)
    {
      if (posixly_correct && interactive_shell == 0)
	{
	  last_command_exit_value = EX_BADUSAGE;
	  jump_to_top_level (ERREXIT);
	}
      return (EXECUTION_FAILURE);
    }

  loop_level++;
  identifier = for_command->name->word;

  line_number = for_command->line;	/* for expansion error messages */
  list = releaser = expand_words_no_vars (for_command->map_list);

  begin_unwind_frame ("for");
  add_unwind_protect (dispose_words, releaser);

#if 0
  if (lexical_scoping)
    {
      old_value = copy_variable (find_variable (identifier));
      if (old_value)
	add_unwind_protect (dispose_variable, old_value);
    }
#endif

  if (for_command->flags & CMD_IGNORE_RETURN)
    for_command->action->flags |= CMD_IGNORE_RETURN;

  for (retval = EXECUTION_SUCCESS; list; list = list->next)
    {
      QUIT;

      line_number = for_command->line;

      /* Remember what this command looks like, for debugger. */
      command_string_index = 0;
      print_for_command_head (for_command);

      if (echo_command_at_execute)
	xtrace_print_for_command_head (for_command);

      /* Save this command unless it's a trap command and we're not running
	 a debug trap. */
      if (signal_in_progress (DEBUG_TRAP) == 0 && running_trap == 0)
	{
	  FREE (the_printed_command_except_trap);
	  the_printed_command_except_trap = savestring (the_printed_command);
	}

      retval = run_debug_trap ();
#if defined (DEBUGGER)
      /* In debugging mode, if the DEBUG trap returns a non-zero status, we
	 skip the command. */
      if (debugging_mode && retval != EXECUTION_SUCCESS)
        continue;
#endif

      this_command_name = (char *)NULL;
      /* XXX - special ksh93 for command index variable handling */
      v = find_variable_last_nameref (identifier, 1);
      if (v && nameref_p (v))
	{
	  if (valid_nameref_value (list->word->word, 1) == 0)
	    {
	      sh_invalidid (list->word->word);
	      v = 0;
	    }
	  else if (readonly_p (v))
	    err_readonly (name_cell (v));
	  else
	    v = bind_variable_value (v, list->word->word, ASS_NAMEREF);
	}
      else
	v = bind_variable (identifier, list->word->word, 0);

      if (v == 0 || readonly_p (v) || noassign_p (v))
	{
	  line_number = save_line_number;
	  if (v && readonly_p (v) && interactive_shell == 0 && posixly_correct)
	    {
	      last_command_exit_value = EXECUTION_FAILURE;
	      jump_to_top_level (FORCE_EOF);
	    }
	  else
	    {
	      dispose_words (releaser);
	      discard_unwind_frame ("for");
	      loop_level--;
	      return (EXECUTION_FAILURE);
	    }
	}

      if (ifsname (identifier))
	setifs (v);
      else
	stupidly_hack_special_variables (identifier);

      retval = execute_command (for_command->action);
      REAP ();
      QUIT;

      if (breaking)
	{
	  breaking--;
	  break;
	}

      if (continuing)
	{
	  continuing--;
	  if (continuing)
	    break;
	}
    }

  loop_level--;
  line_number = save_line_number;

#if 0
  if (lexical_scoping)
    {
      if (!old_value)
        unbind_variable (identifier);
      else
	{
	  SHELL_VAR *new_value;

	  new_value = bind_variable (identifier, value_cell (old_value), 0);
	  new_value->attributes = old_value->attributes;
	  dispose_variable (old_value);
	}
    }
#endif

  dispose_words (releaser);
  discard_unwind_frame ("for");
  return (retval);
}

#if defined (ARITH_FOR_COMMAND)
/* Execute an arithmetic for command.  The syntax is

	for (( init ; step ; test ))
	do
		body
	done

   The execution should be exactly equivalent to

	eval \(\( init \)\)
	while eval \(\( test \)\) ; do
		body;
		eval \(\( step \)\)
	done
*/
static intmax_t
eval_arith_for_expr (l, okp)
     WORD_LIST *l;
     int *okp;
{
  WORD_LIST *new;
  intmax_t expresult;
  int r, eflag;
  char *expr, *temp;

  expr = l->next ? string_list (l) : l->word->word;
  temp = expand_arith_string (expr, Q_DOUBLE_QUOTES|Q_ARITH);
  if (l->next)
    free (expr);
  new = make_word_list (make_word (temp ? temp : ""), (WORD_LIST *)NULL);
  free (temp);

  if (new)
    {
      if (echo_command_at_execute)
	xtrace_print_arith_cmd (new);

      command_string_index = 0;
      print_arith_command (new);
      if (signal_in_progress (DEBUG_TRAP) == 0 && running_trap == 0)
	{
	  FREE (the_printed_command_except_trap);
	  the_printed_command_except_trap = savestring (the_printed_command);
	}

      r = run_debug_trap ();
      /* In debugging mode, if the DEBUG trap returns a non-zero status, we
	 skip the command. */
      eflag = (shell_compatibility_level > 51) ? 0 : EXP_EXPANDED;
      this_command_name = "((";		/* )) for expression error messages */
      
#if defined (DEBUGGER)
      if (debugging_mode == 0 || r == EXECUTION_SUCCESS)
	expresult = evalexp (new->word->word, eflag, okp);
      else
	{
	  expresult = 0;
	  if (okp)
	    *okp = 1;
	}
#else
      expresult = evalexp (new->word->word, eflag, okp);
#endif
      dispose_words (new);
    }
  else
    {
      expresult = 0;
      if (okp)
	*okp = 1;
    }
  return (expresult);
}

static int
execute_arith_for_command (arith_for_command)
     ARITH_FOR_COM *arith_for_command;
{
  intmax_t expresult;
  int expok, body_status, arith_lineno, save_lineno;

  body_status = EXECUTION_SUCCESS;
  loop_level++;
  save_lineno = line_number;

  if (arith_for_command->flags & CMD_IGNORE_RETURN)
    arith_for_command->action->flags |= CMD_IGNORE_RETURN;

  this_command_name = "((";	/* )) for expression error messages */

  /* save the starting line number of the command so we can reset
     line_number before executing each expression -- for $LINENO
     and the DEBUG trap. */
  line_number = arith_lineno = arith_for_command->line;
  if (variable_context && interactive_shell && sourcelevel == 0)
    {
      /* line numbers in a function start at 1 */
      line_number -= function_line_number - 1;
      if (line_number <= 0)
	line_number = 1;
    }

  /* Evaluate the initialization expression. */
  expresult = eval_arith_for_expr (arith_for_command->init, &expok);
  if (expok == 0)
    {
      line_number = save_lineno;
      return (EXECUTION_FAILURE);
    }

  while (1)
    {
      /* Evaluate the test expression. */
      line_number = arith_lineno;
      expresult = eval_arith_for_expr (arith_for_command->test, &expok);
      line_number = save_lineno;

      if (expok == 0)
	{
	  body_status = EXECUTION_FAILURE;
	  break;
	}
      REAP ();
      if (expresult == 0)
	break;

      /* Execute the body of the arithmetic for command. */
      QUIT;
      body_status = execute_command (arith_for_command->action);
      QUIT;

      /* Handle any `break' or `continue' commands executed by the body. */
      if (breaking)
	{
	  breaking--;
	  break;
	}

      if (continuing)
	{
	  continuing--;
	  if (continuing)
	    break;
	}

      /* Evaluate the step expression. */
      line_number = arith_lineno;
      expresult = eval_arith_for_expr (arith_for_command->step, &expok);
      line_number = save_lineno;

      if (expok == 0)
	{
	  body_status = EXECUTION_FAILURE;
	  break;
	}
    }

  loop_level--;
  line_number = save_lineno;

  return (body_status);
}
#endif

#if defined (SELECT_COMMAND)
static int LINES, COLS, tabsize;

#define RP_SPACE ") "
#define RP_SPACE_LEN 2

/* XXX - does not handle numbers > 1000000 at all. */
#define NUMBER_LEN(s) \
((s < 10) ? 1 \
	  : ((s < 100) ? 2 \
		      : ((s < 1000) ? 3 \
				   : ((s < 10000) ? 4 \
						 : ((s < 100000) ? 5 \
								: 6)))))

static int
displen (s)
     const char *s;
{
#if defined (HANDLE_MULTIBYTE)
  wchar_t *wcstr;
  size_t slen;
  int wclen;

  wcstr = 0;
  slen = mbstowcs (wcstr, s, 0);
  if (slen == -1)
    slen = 0;
  wcstr = (wchar_t *)xmalloc (sizeof (wchar_t) * (slen + 1));
  mbstowcs (wcstr, s, slen + 1);
  wclen = wcswidth (wcstr, slen);
  free (wcstr);
  return (wclen < 0 ? STRLEN(s) : wclen);
#else
  return (STRLEN (s));
#endif
}

static int
print_index_and_element (len, ind, list)
      int len, ind;
      WORD_LIST *list;
{
  register WORD_LIST *l;
  register int i;

  if (list == 0)
    return (0);
  for (i = ind, l = list; l && --i; l = l->next)
    ;
  if (l == 0)		/* don't think this can happen */
    return (0);
  fprintf (stderr, "%*d%s%s", len, ind, RP_SPACE, l->word->word);
  return (displen (l->word->word));
}

static void
indent (from, to)
     int from, to;
{
  while (from < to)
    {
      if ((to / tabsize) > (from / tabsize))
	{
	  putc ('\t', stderr);
	  from += tabsize - from % tabsize;
	}
      else
	{
	  putc (' ', stderr);
	  from++;
	}
    }
}

static void
print_select_list (list, list_len, max_elem_len, indices_len)
     WORD_LIST *list;
     int list_len, max_elem_len, indices_len;
{
  int ind, row, elem_len, pos, cols, rows;
  int first_column_indices_len, other_indices_len;

  if (list == 0)
    {
      putc ('\n', stderr);
      return;
    }

  cols = max_elem_len ? COLS / max_elem_len : 1;
  if (cols == 0)
    cols = 1;
  rows = list_len ? list_len / cols + (list_len % cols != 0) : 1;
  cols = list_len ? list_len / rows + (list_len % rows != 0) : 1;

  if (rows == 1)
    {
      rows = cols;
      cols = 1;
    }

  first_column_indices_len = NUMBER_LEN (rows);
  other_indices_len = indices_len;

  for (row = 0; row < rows; row++)
    {
      ind = row;
      pos = 0;
      while (1)
	{
	  indices_len = (pos == 0) ? first_column_indices_len : other_indices_len;
	  elem_len = print_index_and_element (indices_len, ind + 1, list);
	  elem_len += indices_len + RP_SPACE_LEN;
	  ind += rows;
	  if (ind >= list_len)
	    break;
	  indent (pos + elem_len, pos + max_elem_len);
	  pos += max_elem_len;
	}
      putc ('\n', stderr);
    }
}

/* Print the elements of LIST, one per line, preceded by an index from 1 to
   LIST_LEN.  Then display PROMPT and wait for the user to enter a number.
   If the number is between 1 and LIST_LEN, return that selection.  If EOF
   is read, return a null string.  If a blank line is entered, or an invalid
   number is entered, the loop is executed again. */
static char *
select_query (list, list_len, prompt, print_menu)
     WORD_LIST *list;
     int list_len;
     char *prompt;
     int print_menu;
{
  int max_elem_len, indices_len, len, r, oe;
  intmax_t reply;
  WORD_LIST *l;
  char *repl_string, *t;

  COLS = default_columns ();

#if 0
  t = get_string_value ("TABSIZE");
  tabsize = (t && *t) ? atoi (t) : 8;
  if (tabsize <= 0)
    tabsize = 8;
#else
  tabsize = 8;
#endif

  max_elem_len = 0;
  for (l = list; l; l = l->next)
    {
      len = displen (l->word->word);
      if (len > max_elem_len)
	max_elem_len = len;
    }
  indices_len = NUMBER_LEN (list_len);
  max_elem_len += indices_len + RP_SPACE_LEN + 2;

  while (1)
    {
      if (print_menu)
	print_select_list (list, list_len, max_elem_len, indices_len);
      fprintf (stderr, "%s", prompt);
      fflush (stderr);
      QUIT;

      oe = executing_builtin;
      executing_builtin = 1;
      r = read_builtin ((WORD_LIST *)NULL);
      executing_builtin = oe;
      if (r != EXECUTION_SUCCESS)
	{
	  putchar ('\n');
	  return ((char *)NULL);
	}
      repl_string = get_string_value ("REPLY");
      if (repl_string == 0)
	return ((char *)NULL);
      if (*repl_string == 0)
	{
	  print_menu = 1;
	  continue;
	}
      if (legal_number (repl_string, &reply) == 0)
	return "";
      if (reply < 1 || reply > list_len)
	return "";

      for (l = list; l && --reply; l = l->next)
	;
      return (l->word->word);		/* XXX - can't be null? */
    }
}

/* Execute a SELECT command.  The syntax is:
   SELECT word IN list DO command_list DONE
   Only `break' or `return' in command_list will terminate
   the command. */
static int
execute_select_command (select_command)
     SELECT_COM *select_command;
{
  WORD_LIST *releaser, *list;
  SHELL_VAR *v;
  char *identifier, *ps3_prompt, *selection;
  int retval, list_len, show_menu, save_line_number;

  if (check_identifier (select_command->name, 1) == 0)
    return (EXECUTION_FAILURE);

  save_line_number = line_number;
  line_number = select_command->line;

  command_string_index = 0;
  print_select_command_head (select_command);

  if (echo_command_at_execute)
    xtrace_print_select_command_head (select_command);

#if 0
  if (signal_in_progress (DEBUG_TRAP) == 0 && (this_command_name == 0 || (STREQ (this_command_name, "trap") == 0)))
#else
  if (signal_in_progress (DEBUG_TRAP) == 0 && running_trap == 0)
#endif
    {
      FREE (the_printed_command_except_trap);
      the_printed_command_except_trap = savestring (the_printed_command);
    }

  retval = run_debug_trap ();
#if defined (DEBUGGER)
  /* In debugging mode, if the DEBUG trap returns a non-zero status, we
     skip the command. */
  if (debugging_mode && retval != EXECUTION_SUCCESS)
    return (EXECUTION_SUCCESS);
#endif

  this_command_name = (char *)0;

  loop_level++;
  identifier = select_command->name->word;

  /* command and arithmetic substitution, parameter and variable expansion,
     word splitting, pathname expansion, and quote removal. */
  list = releaser = expand_words_no_vars (select_command->map_list);
  list_len = list_length (list);
  if (list == 0 || list_len == 0)
    {
      if (list)
	dispose_words (list);
      line_number = save_line_number;
      return (EXECUTION_SUCCESS);
    }

  begin_unwind_frame ("select");
  add_unwind_protect (dispose_words, releaser);

  if (select_command->flags & CMD_IGNORE_RETURN)
    select_command->action->flags |= CMD_IGNORE_RETURN;

  retval = EXECUTION_SUCCESS;
  show_menu = 1;

  while (1)
    {
      line_number = select_command->line;
      ps3_prompt = get_string_value ("PS3");
      if (ps3_prompt == 0)
	ps3_prompt = "#? ";

      QUIT;
      selection = select_query (list, list_len, ps3_prompt, show_menu);
      QUIT;
      if (selection == 0)
	{
	  /* select_query returns EXECUTION_FAILURE if the read builtin
	     fails, so we want to return failure in this case. */
	  retval = EXECUTION_FAILURE;
	  break;
	}

      v = bind_variable (identifier, selection, 0);
      if (v == 0 || readonly_p (v) || noassign_p (v))
	{
	  if (v && readonly_p (v) && interactive_shell == 0 && posixly_correct)
	    {
	      last_command_exit_value = EXECUTION_FAILURE;
	      jump_to_top_level (FORCE_EOF);
	    }
	  else
	    {
	      dispose_words (releaser);
	      discard_unwind_frame ("select");
	      loop_level--;
	      line_number = save_line_number;
	      return (EXECUTION_FAILURE);
	    }
	}

      stupidly_hack_special_variables (identifier);

      retval = execute_command (select_command->action);

      REAP ();
      QUIT;

      if (breaking)
	{
	  breaking--;
	  break;
	}

      if (continuing)
	{
	  continuing--;
	  if (continuing)
	    break;
	}

#if defined (KSH_COMPATIBLE_SELECT)
      show_menu = 0;
      selection = get_string_value ("REPLY");
      if (selection && *selection == '\0')
        show_menu = 1;
#endif
    }

  loop_level--;
  line_number = save_line_number;

  dispose_words (releaser);
  discard_unwind_frame ("select");
  return (retval);
}
#endif /* SELECT_COMMAND */

/* Execute a CASE command.  The syntax is: CASE word_desc IN pattern_list ESAC.
   The pattern_list is a linked list of pattern clauses; each clause contains
   some patterns to compare word_desc against, and an associated command to
   execute. */
static int
execute_case_command (case_command)
     CASE_COM *case_command;
{
  register WORD_LIST *list;
  WORD_LIST *wlist, *es;
  PATTERN_LIST *clauses;
  char *word, *pattern;
  int retval, match, ignore_return, save_line_number, qflags;

  save_line_number = line_number;
  line_number = case_command->line;

  command_string_index = 0;
  print_case_command_head (case_command);

  if (echo_command_at_execute)
    xtrace_print_case_command_head (case_command);

#if 0
  if (signal_in_progress (DEBUG_TRAP) == 0 && (this_command_name == 0 || (STREQ (this_command_name, "trap") == 0)))
#else
  if (signal_in_progress (DEBUG_TRAP) == 0 && running_trap == 0)
#endif
    {
      FREE (the_printed_command_except_trap);
      the_printed_command_except_trap = savestring (the_printed_command);
    }

  retval = run_debug_trap();
#if defined (DEBUGGER)
  /* In debugging mode, if the DEBUG trap returns a non-zero status, we
     skip the command. */
  if (debugging_mode && retval != EXECUTION_SUCCESS)
    {
      line_number = save_line_number;
      return (EXECUTION_SUCCESS);
    }
#endif

  /* Use the same expansions (the ones POSIX specifies) as the patterns;
     dequote the resulting string (as POSIX specifies) since the quotes in
     patterns are handled specially below. We have to do it in this order
     because we're not supposed to perform word splitting. */
  wlist = expand_word_leave_quoted (case_command->word, 0);
  if (wlist)
    {
      char *t;
      t = string_list (wlist);
      word = dequote_string (t);
      free (t);
    }
  else
    word = savestring ("");
  dispose_words (wlist);

  retval = EXECUTION_SUCCESS;
  ignore_return = case_command->flags & CMD_IGNORE_RETURN;

  begin_unwind_frame ("case");
  add_unwind_protect (xfree, word);

#define EXIT_CASE()  goto exit_case_command

  for (clauses = case_command->clauses; clauses; clauses = clauses->next)
    {
      QUIT;
      for (list = clauses->patterns; list; list = list->next)
	{
	  es = expand_word_leave_quoted (list->word, 0);

	  if (es && es->word && es->word->word && *(es->word->word))
	    {
	      /* Convert quoted null strings into empty strings. */
	      qflags = QGLOB_CVTNULL;

	      /* We left CTLESC in place quoting CTLESC and CTLNUL after the
	      	 call to expand_word_leave_quoted; tell quote_string_for_globbing
	      	 to remove those here. This works for both unquoted portions of
		 the word (which call quote_escapes) and quoted portions
		 (which call quote_string). */
	      qflags |= QGLOB_CTLESC;
	      pattern = quote_string_for_globbing (es->word->word, qflags);
	    }
	  else
	    {
	      pattern = (char *)xmalloc (1);
	      pattern[0] = '\0';
	    }

	  /* Since the pattern does not undergo quote removal (as per
	     Posix.2, section 3.9.4.3), the strmatch () call must be able
	     to recognize backslashes as escape characters. */
	  match = strmatch (pattern, word, FNMATCH_EXTFLAG|FNMATCH_IGNCASE) != FNM_NOMATCH;
	  free (pattern);

	  dispose_words (es);
	  QUIT;

	  if (match)
	    {
	      do
		{
		  if (clauses->action && ignore_return)
		    clauses->action->flags |= CMD_IGNORE_RETURN;
		  retval = execute_command (clauses->action);
		}
	      while ((clauses->flags & CASEPAT_FALLTHROUGH) && (clauses = clauses->next));
	      if (clauses == 0 || (clauses->flags & CASEPAT_TESTNEXT) == 0)
		EXIT_CASE ();
	      else
		break;
	    }

	  QUIT;
	}
    }

exit_case_command:
  free (word);
  discard_unwind_frame ("case");
  line_number = save_line_number;
  return (retval);
}

#define CMD_WHILE 0
#define CMD_UNTIL 1

/* The WHILE command.  Syntax: WHILE test DO action; DONE.
   Repeatedly execute action while executing test produces
   EXECUTION_SUCCESS. */
static int
execute_while_command (while_command)
     WHILE_COM *while_command;
{
  return (execute_while_or_until (while_command, CMD_WHILE));
}

/* UNTIL is just like WHILE except that the test result is negated. */
static int
execute_until_command (while_command)
     WHILE_COM *while_command;
{
  return (execute_while_or_until (while_command, CMD_UNTIL));
}

/* The body for both while and until.  The only difference between the
   two is that the test value is treated differently.  TYPE is
   CMD_WHILE or CMD_UNTIL.  The return value for both commands should
   be EXECUTION_SUCCESS if no commands in the body are executed, and
   the status of the last command executed in the body otherwise. */
static int
execute_while_or_until (while_command, type)
     WHILE_COM *while_command;
     int type;
{
  int return_value, body_status;

  body_status = EXECUTION_SUCCESS;
  loop_level++;

  while_command->test->flags |= CMD_IGNORE_RETURN;
  if (while_command->flags & CMD_IGNORE_RETURN)
    while_command->action->flags |= CMD_IGNORE_RETURN;

  while (1)
    {
      return_value = execute_command (while_command->test);
      REAP ();

      /* Need to handle `break' in the test when we would break out of the
         loop.  The job control code will set `breaking' to loop_level
         when a job in a loop is stopped with SIGTSTP.  If the stopped job
         is in the loop test, `breaking' will not be reset unless we do
         this, and the shell will cease to execute commands.  The same holds
         true for `continue'. */
      if (type == CMD_WHILE && return_value != EXECUTION_SUCCESS)
	{
	  if (breaking)
	    breaking--;
	  if (continuing)
	    continuing--;
	  break;
	}
      if (type == CMD_UNTIL && return_value == EXECUTION_SUCCESS)
	{
	  if (breaking)
	    breaking--;
	  if (continuing)
	    continuing--;
	  break;
	}

      QUIT;
      body_status = execute_command (while_command->action);
      QUIT;

      if (breaking)
	{
	  breaking--;
	  break;
	}

      if (continuing)
	{
	  continuing--;
	  if (continuing)
	    break;
	}
    }
  loop_level--;

  return (body_status);
}

/* IF test THEN command [ELSE command].
   IF also allows ELIF in the place of ELSE IF, but
   the parser makes *that* stupidity transparent. */
static int
execute_if_command (if_command)
     IF_COM *if_command;
{
  int return_value, save_line_number;

  save_line_number = line_number;
  if_command->test->flags |= CMD_IGNORE_RETURN;
  return_value = execute_command (if_command->test);
  line_number = save_line_number;

  if (return_value == EXECUTION_SUCCESS)
    {
      QUIT;

      if (if_command->true_case && (if_command->flags & CMD_IGNORE_RETURN))
	if_command->true_case->flags |= CMD_IGNORE_RETURN;

      return (execute_command (if_command->true_case));
    }
  else
    {
      QUIT;

      if (if_command->false_case && (if_command->flags & CMD_IGNORE_RETURN))
	if_command->false_case->flags |= CMD_IGNORE_RETURN;

      return (execute_command (if_command->false_case));
    }
}

#if defined (DPAREN_ARITHMETIC)
static int
execute_arith_command (arith_command)
     ARITH_COM *arith_command;
{
  int expok, save_line_number, retval, eflag;
  intmax_t expresult;
  WORD_LIST *new;
  char *exp, *t;

  expresult = 0;

  save_line_number = line_number;
  this_command_name = "((";	/* )) */
  SET_LINE_NUMBER (arith_command->line);
  /* If we're in a function, update the line number information. */
  if (variable_context && interactive_shell && sourcelevel == 0)
    {
      /* line numbers in a function start at 1 */
      line_number -= function_line_number - 1;
      if (line_number <= 0)
	line_number = 1;
    }      

  command_string_index = 0;
  print_arith_command (arith_command->exp);

  if (signal_in_progress (DEBUG_TRAP) == 0 && running_trap == 0)
    {
      FREE (the_printed_command_except_trap);
      the_printed_command_except_trap = savestring (the_printed_command);
    }

  /* Run the debug trap before each arithmetic command, but do it after we
     update the line number information and before we expand the various
     words in the expression. */
  retval = run_debug_trap ();
#if defined (DEBUGGER)
  /* In debugging mode, if the DEBUG trap returns a non-zero status, we
     skip the command. */
  if (debugging_mode && retval != EXECUTION_SUCCESS)
    {
      line_number = save_line_number;
      return (EXECUTION_SUCCESS);
    }
#endif

  this_command_name = "((";	/* )) */
  t = (char *)NULL;
  new = arith_command->exp;
  exp = (new->next) ? (t = string_list (new)) : new->word->word;

  exp = expand_arith_string (exp, Q_DOUBLE_QUOTES|Q_ARITH);
  FREE (t);

  /* If we're tracing, make a new word list with `((' at the front and `))'
     at the back and print it. Change xtrace_print_arith_cmd to take a string
     when I change eval_arith_for_expr to use expand_arith_string(). */
  if (echo_command_at_execute)
    {
      new = make_word_list (make_word (exp ? exp : ""), (WORD_LIST *)NULL);
      xtrace_print_arith_cmd (new);
      dispose_words (new);
    }

  if (exp)
    {
      eflag = (shell_compatibility_level > 51) ? 0 : EXP_EXPANDED;
      expresult = evalexp (exp, eflag, &expok);
      line_number = save_line_number;
      free (exp);
    }
  else
    {
      expresult = 0;
      expok = 1;
    }

  if (expok == 0)
    return (EXECUTION_FAILURE);

  return (expresult == 0 ? EXECUTION_FAILURE : EXECUTION_SUCCESS);
}
#endif /* DPAREN_ARITHMETIC */

#if defined (COND_COMMAND)

static char * const nullstr = "";

/* XXX - can COND ever be NULL when this is called? */
static int
execute_cond_node (cond)
     COND_COM *cond;
{
  int result, invert, patmatch, rmatch, arith, mode, mflags, ignore;
  char *arg1, *arg2, *op;
#if 0
  char *t1, *t2;
#endif

  invert = (cond->flags & CMD_INVERT_RETURN);
  ignore = (cond->flags & CMD_IGNORE_RETURN);
  if (ignore)
    {
      if (cond->left)
	cond->left->flags |= CMD_IGNORE_RETURN;
      if (cond->right)
	cond->right->flags |= CMD_IGNORE_RETURN;
    }
      
  if (cond->type == COND_EXPR)
    result = execute_cond_node (cond->left);
  else if (cond->type == COND_OR)
    {
      result = execute_cond_node (cond->left);
      if (result != EXECUTION_SUCCESS)
	result = execute_cond_node (cond->right);
    }
  else if (cond->type == COND_AND)
    {
      result = execute_cond_node (cond->left);
      if (result == EXECUTION_SUCCESS)
	result = execute_cond_node (cond->right);
    }
  else if (cond->type == COND_UNARY)
    {
      int oa, varop, varflag;

      if (ignore)
	comsub_ignore_return++;
      varop = STREQ (cond->op->word, "-v");
#if defined (ARRAY_VARS)
      varflag = (varop && valid_array_reference (cond->left->op->word, VA_NOEXPAND)) ? TEST_ARRAYEXP : 0;
#else
      varflag = 0;
#endif
      arg1 = cond_expand_word (cond->left->op, varop ? 3 : 0);
      if (ignore)
	comsub_ignore_return--;
      if (arg1 == 0)
	arg1 = nullstr;
      if (echo_command_at_execute)
	xtrace_print_cond_term (cond->type, invert, cond->op, arg1, (char *)NULL);
#if defined (ARRAY_VARS)
      if (varop)
	oa = set_expand_once (0, 0);	/* no-op for compatibility levels <= 51 */
#endif
      result = unary_test (cond->op->word, arg1, varflag) ? EXECUTION_SUCCESS : EXECUTION_FAILURE;
#if defined (ARRAY_VARS)
      if (varop)
	assoc_expand_once = oa;
#endif
      if (arg1 != nullstr)
	free (arg1);
    }
  else if (cond->type == COND_BINARY)
    {
      rmatch = 0;
      op = cond->op->word;
      mode = 0;
      patmatch = (((op[1] == '=') && (op[2] == '\0') &&
		   (op[0] == '!' || op[0] == '=')) ||
		  (op[0] == '=' && op[1] == '\0'));
#if defined (COND_REGEXP)
      rmatch = (op[0] == '=' && op[1] == '~' && op[2] == '\0');
#endif
      arith = STREQ (op, "-eq") || STREQ (op, "-ne") || STREQ (op, "-lt") ||
	      STREQ (op, "-le") || STREQ (op, "-gt") || STREQ (op, "-ge");

      if (arith)
	mode = 3;
      else if (rmatch && shell_compatibility_level > 31)
	mode = 2;
      else if (patmatch)
	mode = 1;

      if (ignore)
	comsub_ignore_return++;
      arg1 = cond_expand_word (cond->left->op, arith ? mode : 0);
      if (ignore)
	comsub_ignore_return--;
      if (arg1 == 0)
	arg1 = nullstr;
      if (ignore)
	comsub_ignore_return++;
      arg2 = cond_expand_word (cond->right->op, mode);
      if (ignore)
	comsub_ignore_return--;
      if (arg2 == 0)
	arg2 = nullstr;

      if (echo_command_at_execute)
	xtrace_print_cond_term (cond->type, invert, cond->op, arg1, arg2);

#if defined (COND_REGEXP)
      if (rmatch)
	{
	  mflags = SHMAT_PWARN;
#if defined (ARRAY_VARS)
	  mflags |= SHMAT_SUBEXP;
#endif

#if 0
	  t1 = strescape(arg1);
	  t2 = strescape(arg2);
	  itrace("execute_cond_node: sh_regmatch on `%s' and `%s'", t1, t2);
	  free(t1);
	  free(t2);
#endif

	  result = sh_regmatch (arg1, arg2, mflags);
	}
      else
#endif /* COND_REGEXP */
	{
	  extended_glob = 1;
	  result = binary_test (cond->op->word, arg1, arg2, TEST_PATMATCH|TEST_ARITHEXP|TEST_LOCALE)
				  ? EXECUTION_SUCCESS
				  : EXECUTION_FAILURE;
	  extended_glob = extglob_flag;
	}
      if (arg1 != nullstr)
	free (arg1);
      if (arg2 != nullstr)
	free (arg2);
    }
  else
    {
      command_error ("execute_cond_node", CMDERR_BADTYPE, cond->type, 0);
      jump_to_top_level (DISCARD);
      result = EXECUTION_FAILURE;
    }

  if (invert)
    result = (result == EXECUTION_SUCCESS) ? EXECUTION_FAILURE : EXECUTION_SUCCESS;

  return result;
}

static int
execute_cond_command (cond_command)
     COND_COM *cond_command;
{
  int retval, save_line_number;

  save_line_number = line_number;

  SET_LINE_NUMBER (cond_command->line);
  /* If we're in a function, update the line number information. */
  if (variable_context && interactive_shell && sourcelevel == 0)
    {
      /* line numbers in a function start at 1 */
      line_number -= function_line_number - 1;
      if (line_number <= 0)
	line_number = 1;
    }
  command_string_index = 0;
  print_cond_command (cond_command);

  if (signal_in_progress (DEBUG_TRAP) == 0 && running_trap == 0)
    {
      FREE (the_printed_command_except_trap);
      the_printed_command_except_trap = savestring (the_printed_command);
    }

  /* Run the debug trap before each conditional command, but do it after we
     update the line number information. */
  retval = run_debug_trap ();
#if defined (DEBUGGER)
  /* In debugging mode, if the DEBUG trap returns a non-zero status, we
     skip the command. */
  if (debugging_mode && retval != EXECUTION_SUCCESS)
    {
      line_number = save_line_number;
      return (EXECUTION_SUCCESS);
    }
#endif

  this_command_name = "[[";	/* ]] */

#if 0
  debug_print_cond_command (cond_command);
#endif

  last_command_exit_value = retval = execute_cond_node (cond_command);
  line_number = save_line_number;
  return (retval);
}
#endif /* COND_COMMAND */

static void
bind_lastarg (arg)
     char *arg;
{
  SHELL_VAR *var;

  if (arg == 0)
    arg = "";
  var = bind_variable ("_", arg, 0);
  if (var)
    VUNSETATTR (var, att_exported);
}

/* Execute a null command.  Fork a subshell if the command uses pipes or is
   to be run asynchronously.  This handles all the side effects that are
   supposed to take place. */
static int
execute_null_command (redirects, pipe_in, pipe_out, async)
     REDIRECT *redirects;
     int pipe_in, pipe_out, async;
{
  int r;
  int forcefork, fork_flags;
  REDIRECT *rd;

  for (forcefork = 0, rd = redirects; rd; rd = rd->next)
    {
      forcefork += rd->rflags & REDIR_VARASSIGN;
      /* Safety */
      forcefork += (rd->redirector.dest == 0 || fd_is_bash_input (rd->redirector.dest)) && (INPUT_REDIRECT (rd->instruction) || TRANSLATE_REDIRECT (rd->instruction) || rd->instruction == r_close_this);
    }

  if (forcefork || pipe_in != NO_PIPE || pipe_out != NO_PIPE || async)
    {
      /* We have a null command, but we really want a subshell to take
	 care of it.  Just fork, do piping and redirections, and exit. */
      fork_flags = async ? FORK_ASYNC : 0;
      if (make_child ((char *)NULL, fork_flags) == 0)
	{
	  /* Cancel traps, in trap.c. */
	  restore_original_signals ();		/* XXX */

	  do_piping (pipe_in, pipe_out);

#if defined (COPROCESS_SUPPORT)
	  coproc_closeall ();
#endif

	  interactive = 0;			/* XXX */

	  subshell_environment = 0;
	  if (async)
	    subshell_environment |= SUBSHELL_ASYNC;
	  if (pipe_in != NO_PIPE || pipe_out != NO_PIPE)
	    subshell_environment |= SUBSHELL_PIPE;

	  if (do_redirections (redirects, RX_ACTIVE) == 0)
	    exit (EXECUTION_SUCCESS);
	  else
	    exit (EXECUTION_FAILURE);
	}
      else
	{
	  close_pipes (pipe_in, pipe_out);
#if defined (PROCESS_SUBSTITUTION) && defined (HAVE_DEV_FD)
	  if (pipe_out == NO_PIPE)
	    unlink_fifo_list ();
#endif
	  return (EXECUTION_SUCCESS);
	}
    }
  else
    {
      /* Even if there aren't any command names, pretend to do the
	 redirections that are specified.  The user expects the side
	 effects to take place.  If the redirections fail, then return
	 failure.  Otherwise, if a command substitution took place while
	 expanding the command or a redirection, return the value of that
	 substitution.  Otherwise, return EXECUTION_SUCCESS. */

      r = do_redirections (redirects, RX_ACTIVE|RX_UNDOABLE);
      cleanup_redirects (redirection_undo_list);
      redirection_undo_list = (REDIRECT *)NULL;

      if (r != 0)
	return (EXECUTION_FAILURE);
      else if (last_command_subst_pid != NO_PID)
	return (last_command_exit_value);
      else
	return (EXECUTION_SUCCESS);
    }
}

/* This is a hack to suppress word splitting for assignment statements
   given as arguments to builtins with the ASSIGNMENT_BUILTIN flag set. */
static void
fix_assignment_words (words)
     WORD_LIST *words;
{
  WORD_LIST *w, *wcmd;
  struct builtin *b;
  int assoc, global, array, integer;

  if (words == 0)
    return;

  b = 0;
  assoc = global = array = integer = 0;

  /* Skip over assignment statements preceding a command name */
  wcmd = words;
  for (wcmd = words; wcmd; wcmd = wcmd->next)
    if ((wcmd->word->flags & W_ASSIGNMENT) == 0)
      break;
  /* Posix (post-2008) says that `command' doesn't change whether
     or not the builtin it shadows is a `declaration command', even
     though it removes other special builtin properties.  In Posix
     mode, we skip over one or more instances of `command' and
     deal with the next word as the assignment builtin. */
  while (posixly_correct && wcmd && wcmd->word && wcmd->word->word && STREQ (wcmd->word->word, "command"))
    wcmd = wcmd->next;

  for (w = wcmd; w; w = w->next)
    if (w->word->flags & W_ASSIGNMENT)
      {
      	/* Lazy builtin lookup, only do it if we find an assignment */
	if (b == 0)
	  {
	    b = builtin_address_internal (wcmd->word->word, 0);
	    if (b == 0 || (b->flags & ASSIGNMENT_BUILTIN) == 0)
	      return;
	    else if (b && (b->flags & ASSIGNMENT_BUILTIN))
	      wcmd->word->flags |= W_ASSNBLTIN;
	  }
	w->word->flags |= (W_NOSPLIT|W_NOGLOB|W_TILDEEXP|W_ASSIGNARG);
#if defined (ARRAY_VARS)
	if (assoc)
	  w->word->flags |= W_ASSIGNASSOC;
	if (array)
	  w->word->flags |= W_ASSIGNARRAY;
#endif
	if (global)
	  w->word->flags |= W_ASSNGLOBAL;

	/* If we have an assignment builtin that does not create local variables,
	   make sure we create global variables even if we internally call
	   `declare'.  The CHKLOCAL flag means to set attributes or values on
	   an existing local variable, if there is one. */
	if (b && ((b->flags & (ASSIGNMENT_BUILTIN|LOCALVAR_BUILTIN)) == ASSIGNMENT_BUILTIN))
	  w->word->flags |= W_ASSNGLOBAL|W_CHKLOCAL;
	else if (b && (b->flags & ASSIGNMENT_BUILTIN) && (b->flags & LOCALVAR_BUILTIN) && variable_context)
	  w->word->flags |= W_FORCELOCAL;
      }
#if defined (ARRAY_VARS)
    /* Note that we saw an associative array option to a builtin that takes
       assignment statements.  This is a bit of a kludge. */
    else if (w->word->word[0] == '-' && (strpbrk (w->word->word+1, "Aag") != 0))
#else
    else if (w->word->word[0] == '-' && strchr (w->word->word+1, 'g'))
#endif
      {
	if (b == 0)
	  {
	    b = builtin_address_internal (wcmd->word->word, 0);
	    if (b == 0 || (b->flags & ASSIGNMENT_BUILTIN) == 0)
	      return;
	    else if (b && (b->flags & ASSIGNMENT_BUILTIN))
	      wcmd->word->flags |= W_ASSNBLTIN;
	  }
	if ((wcmd->word->flags & W_ASSNBLTIN) && strchr (w->word->word+1, 'A'))
	  assoc = 1;
	else if ((wcmd->word->flags & W_ASSNBLTIN) && strchr (w->word->word+1, 'a'))
	  array = 1;
	if ((wcmd->word->flags & W_ASSNBLTIN) && strchr (w->word->word+1, 'g'))
	  global = 1;
      }
}

#if defined (ARRAY_VARS)
/* Set W_ARRAYREF on words that are valid array references to a builtin that
   accepts them. This is intended to completely replace assoc_expand_once in
   time. */
static void
fix_arrayref_words (words)
     WORD_LIST *words;
{
  WORD_LIST *w, *wcmd;
  struct builtin *b;

  if (words == 0)
    return;

  b = 0;

  /* Skip over assignment statements preceding a command name */
  wcmd = words;
  for (wcmd = words; wcmd; wcmd = wcmd->next)
    if ((wcmd->word->flags & W_ASSIGNMENT) == 0)
      break;

  /* Skip over `command' */
  while (wcmd && wcmd->word && wcmd->word->word && STREQ (wcmd->word->word, "command"))
    wcmd = wcmd->next;

  if (wcmd == 0)
    return;

  /* If it's not an array reference builtin, we have nothing to do. */
  b = builtin_address_internal (wcmd->word->word, 0);
  if (b == 0 || (b->flags & ARRAYREF_BUILTIN) == 0)
    return;

  for (w = wcmd->next; w; w = w->next)
    {
      if (w->word && w->word->word && valid_array_reference (w->word->word, 0))
	w->word->flags |= W_ARRAYREF;
    }
}
#endif

#ifndef ISOPTION
#  define ISOPTION(s, c)  (s[0] == '-' && s[1] == c && s[2] == 0)
#endif

#define RETURN_NOT_COMMAND() \
  do { if (typep) *typep = 0; return words; } while (0)

/* Make sure we have `command [-p] command_name [args]', and handle skipping
   over the usual `--' that ends the options.  Returns the updated WORDS with
   the command and options stripped and sets *TYPEP to a non-zero value. If
   any other options are supplied, or there is not a command_name, we punt
   and return a zero value in *TYPEP without updating WORDS. */
static WORD_LIST *
check_command_builtin (words, typep)
     WORD_LIST *words;
     int *typep;
{
  int type;
  WORD_LIST *w;

  w = words->next;
  type = 1;

  if (w && ISOPTION (w->word->word, 'p'))	/* command -p */
    {
#if defined (RESTRICTED_SHELL)
      if (restricted)
        RETURN_NOT_COMMAND();
#endif
      w = w->next;
      type = 2;
    }

  if (w && ISOPTION (w->word->word, '-'))	/* command [-p] -- */
    w = w->next;
  else if (w && w->word->word[0] == '-')	/* any other option */
    RETURN_NOT_COMMAND();

  if (w == 0 || w->word->word == 0)		/* must have a command_name */
    RETURN_NOT_COMMAND();

  if (typep)
    *typep = type;
  return w;
}

/* Return 1 if the file found by searching $PATH for PATHNAME, defaulting
   to PATHNAME, is a directory.  Used by the autocd code below. */
static int
is_dirname (pathname)
     char *pathname;
{
  char *temp;
  int ret;

  temp = search_for_command (pathname, 0);
  ret = temp ? file_isdir (temp) : file_isdir (pathname);
  free (temp);
  return ret;
}

/* The meaty part of all the executions.  We have to start hacking the
   real execution of commands here.  Fork a process, set things up,
   execute the command. */
static int
execute_simple_command (simple_command, pipe_in, pipe_out, async, fds_to_close)
     SIMPLE_COM *simple_command;
     int pipe_in, pipe_out, async;
     struct fd_bitmap *fds_to_close;
{
  WORD_LIST *words, *lastword;
  char *command_line, *lastarg, *temp;
  int first_word_quoted, result, builtin_is_special, already_forked, dofork;
  int fork_flags, cmdflags;
  pid_t old_last_async_pid;
  sh_builtin_func_t *builtin;
  SHELL_VAR *func;
  volatile int old_builtin, old_command_builtin;

  result = EXECUTION_SUCCESS;
  special_builtin_failed = builtin_is_special = 0;
  command_line = (char *)0;

  QUIT;

  /* If we're in a function, update the line number information. */
  if (variable_context && interactive_shell && sourcelevel == 0)
    {
      /* line numbers in a function start at 1 */
      line_number -= function_line_number - 1;
      if (line_number <= 0)
	line_number = 1;
    }

  /* Remember what this command line looks like at invocation. */
  command_string_index = 0;
  print_simple_command (simple_command);

#if 0
  if (signal_in_progress (DEBUG_TRAP) == 0 && (this_command_name == 0 || (STREQ (this_command_name, "trap") == 0)))
#else
  if (signal_in_progress (DEBUG_TRAP) == 0 && running_trap == 0)
#endif
    {
      FREE (the_printed_command_except_trap);
      the_printed_command_except_trap = the_printed_command ? savestring (the_printed_command) : (char *)0;
    }

  /* Run the debug trap before each simple command, but do it after we
     update the line number information. */
  result = run_debug_trap ();
#if defined (DEBUGGER)
  /* In debugging mode, if the DEBUG trap returns a non-zero status, we
     skip the command. */
  if (debugging_mode && result != EXECUTION_SUCCESS)
    return (EXECUTION_SUCCESS);
#endif

  cmdflags = simple_command->flags;

  first_word_quoted =
    simple_command->words ? (simple_command->words->word->flags & W_QUOTED) : 0;

  last_command_subst_pid = NO_PID;
  old_last_async_pid = last_asynchronous_pid;

  already_forked = 0;

  /* If we're in a pipeline or run in the background, set DOFORK so we
     make the child early, before word expansion.  This keeps assignment
     statements from affecting the parent shell's environment when they
     should not. */
  dofork = pipe_in != NO_PIPE || pipe_out != NO_PIPE || async;

  /* Something like `%2 &' should restart job 2 in the background, not cause
     the shell to fork here. */
  if (dofork && pipe_in == NO_PIPE && pipe_out == NO_PIPE &&
	simple_command->words && simple_command->words->word &&
	simple_command->words->word->word &&
	(simple_command->words->word->word[0] == '%'))
    dofork = 0;

  if (dofork)
    {
      char *p;

      /* Do this now, because execute_disk_command will do it anyway in the
	 vast majority of cases. */
      maybe_make_export_env ();

      /* Don't let a DEBUG trap overwrite the command string to be saved with
	 the process/job associated with this child. */
      fork_flags = async ? FORK_ASYNC : 0;
      if (make_child (p = savestring (the_printed_command_except_trap), fork_flags) == 0)
	{
	  already_forked = 1;
	  cmdflags |= CMD_NO_FORK;

	  /* We redo some of what make_child() does with SUBSHELL_IGNTRAP */
	  subshell_environment = SUBSHELL_FORK|SUBSHELL_IGNTRAP;	/* XXX */
	  if (pipe_in != NO_PIPE || pipe_out != NO_PIPE)
	    subshell_environment |= SUBSHELL_PIPE;
	  if (async)
	    subshell_environment |= SUBSHELL_ASYNC;

	  /* We need to do this before piping to handle some really
	     pathological cases where one of the pipe file descriptors
	     is < 2. */
	  if (fds_to_close)
	    close_fd_bitmap (fds_to_close);

	  /* If we fork because of an input pipe, note input pipe for later to
	     inhibit async commands from redirecting stdin from /dev/null */
	  stdin_redir |= pipe_in != NO_PIPE;

	  do_piping (pipe_in, pipe_out);
	  pipe_in = pipe_out = NO_PIPE;
#if defined (COPROCESS_SUPPORT)
	  coproc_closeall ();
#endif

	  last_asynchronous_pid = old_last_async_pid;

	  if (async)
	    subshell_level++;		/* not for pipes yet */

#if defined (JOB_CONTROL)
	  FREE (p);			/* child doesn't use pointer */
#endif
	}
      else
	{
	  /* Don't let simple commands that aren't the last command in a
	     pipeline change $? for the rest of the pipeline (or at all). */
	  if (pipe_out != NO_PIPE)
	    result = last_command_exit_value;
	  close_pipes (pipe_in, pipe_out);
	  command_line = (char *)NULL;      /* don't free this. */
	  return (result);
	}
    }

  QUIT;		/* XXX */

  /* If we are re-running this as the result of executing the `command'
     builtin, do not expand the command words a second time. */
  if ((cmdflags & CMD_INHIBIT_EXPANSION) == 0)
    {
      current_fds_to_close = fds_to_close;
      fix_assignment_words (simple_command->words);
#if defined (ARRAY_VARS)
      fix_arrayref_words (simple_command->words);
#endif
      /* Pass the ignore return flag down to command substitutions */
      if (cmdflags & CMD_IGNORE_RETURN)	/* XXX */
	comsub_ignore_return++;
      words = expand_words (simple_command->words);
      if (cmdflags & CMD_IGNORE_RETURN)
	comsub_ignore_return--;
      current_fds_to_close = (struct fd_bitmap *)NULL;
    }
  else
    words = copy_word_list (simple_command->words);

  /* It is possible for WORDS not to have anything left in it.
     Perhaps all the words consisted of `$foo', and there was
     no variable `$foo'. */
  if (words == 0)
    {
      this_command_name = 0;
      result = execute_null_command (simple_command->redirects,
				     pipe_in, pipe_out,
				     already_forked ? 0 : async);
      if (already_forked)
	sh_exit (result);
      else
	{
	  bind_lastarg ((char *)NULL);
	  set_pipestatus_from_exit (result);
	  return (result);
	}
    }

  lastarg = (char *)NULL;

  begin_unwind_frame ("simple-command");

  if (echo_command_at_execute && (cmdflags & CMD_COMMAND_BUILTIN) == 0)
    xtrace_print_word_list (words, 1);

  builtin = (sh_builtin_func_t *)NULL;
  func = (SHELL_VAR *)NULL;

  /* This test is still here in case we want to change the command builtin
     handler code below to recursively call execute_simple_command (after
     modifying the simple_command struct). */
  if ((cmdflags & CMD_NO_FUNCTIONS) == 0)
    {
      /* Posix.2 says special builtins are found before functions.  We
	 don't set builtin_is_special anywhere other than here, because
	 this path is followed only when the `command' builtin is *not*
	 being used, and we don't want to exit the shell if a special
	 builtin executed with `command builtin' fails.  `command' is not
	 a special builtin. */
      if (posixly_correct)
	{
	  builtin = find_special_builtin (words->word->word);
	  if (builtin)
	    builtin_is_special = 1;
	}
      if (builtin == 0)
	func = find_function (words->word->word);
    }

  /* What happens in posix mode when an assignment preceding a command name
     fails.  This should agree with the code in execute_cmd.c:
     do_assignment_statements(), even though I don't think it's executed any
     more. */
  if (posixly_correct && tempenv_assign_error)
    {
#if defined (DEBUG)
      /* I don't know if this clause is ever executed, so let's check */
itrace("execute_simple_command: posix mode tempenv assignment error");
#endif
      last_command_exit_value = EXECUTION_FAILURE;
#if defined (STRICT_POSIX)
      jump_to_top_level ((interactive_shell == 0) ? FORCE_EOF : DISCARD);
#else
      if (interactive_shell == 0 && builtin_is_special)
	jump_to_top_level (FORCE_EOF);
      else if (interactive_shell == 0)
	jump_to_top_level (DISCARD);	/* XXX - maybe change later */
      else
	jump_to_top_level (DISCARD);
#endif
    }
  tempenv_assign_error = 0;	/* don't care about this any more */

  /* This is where we handle the command builtin as a pseudo-reserved word
     prefix. This allows us to optimize away forks if we can. */
  old_command_builtin = -1;
  if (builtin == 0 && func == 0)
    {
      WORD_LIST *disposer, *l;
      int cmdtype;

      builtin = find_shell_builtin (words->word->word);
      while (builtin == command_builtin)
	{
	  disposer = words;
	  cmdtype = 0;
	  words = check_command_builtin (words, &cmdtype);
	  if (cmdtype > 0)	/* command -p [--] words */
	    {
	      for (l = disposer; l->next != words; l = l->next)
		;
	      l->next = 0;
	      dispose_words (disposer);
	      cmdflags |= CMD_COMMAND_BUILTIN | CMD_NO_FUNCTIONS;
	      if (cmdtype == 2)
		cmdflags |= CMD_STDPATH;
	      builtin = find_shell_builtin (words->word->word);
	    }
	  else
	    break;
	}
      if (cmdflags & CMD_COMMAND_BUILTIN)
	{
	  old_command_builtin = executing_command_builtin;
	  unwind_protect_int (executing_command_builtin);
	  executing_command_builtin |= 1;
	}        
      builtin = 0;
    }

  add_unwind_protect (dispose_words, words);
  QUIT;

  /* Bind the last word in this command to "$_" after execution. */
  for (lastword = words; lastword->next; lastword = lastword->next)
    ;
  lastarg = lastword->word->word;

#if defined (JOB_CONTROL)
  /* Is this command a job control related thing? */
  if (words->word->word[0] == '%' && already_forked == 0)
    {
      this_command_name = async ? "bg" : "fg";
      last_shell_builtin = this_shell_builtin;
      this_shell_builtin = builtin_address (this_command_name);
      result = (*this_shell_builtin) (words);
      goto return_result;
    }

  /* One other possibililty.  The user may want to resume an existing job.
     If they do, find out whether this word is a candidate for a running
     job. */
  if (job_control && already_forked == 0 && async == 0 &&
	!first_word_quoted &&
	!words->next &&
	words->word->word[0] &&
	!simple_command->redirects &&
	pipe_in == NO_PIPE &&
	pipe_out == NO_PIPE &&
	(temp = get_string_value ("auto_resume")))
    {
      int job, jflags, started_status;

      jflags = JM_STOPPED|JM_FIRSTMATCH;
      if (STREQ (temp, "exact"))
	jflags |= JM_EXACT;
      else if (STREQ (temp, "substring"))
	jflags |= JM_SUBSTRING;
      else
	jflags |= JM_PREFIX;
      job = get_job_by_name (words->word->word, jflags);
      if (job != NO_JOB)
	{
	  run_unwind_frame ("simple-command");
	  this_command_name = "fg";
	  last_shell_builtin = this_shell_builtin;
	  this_shell_builtin = builtin_address ("fg");

	  started_status = start_job (job, 1);
	  return ((started_status < 0) ? EXECUTION_FAILURE : started_status);
	}
    }
#endif /* JOB_CONTROL */

run_builtin:
  /* Remember the name of this command globally. */
  this_command_name = words->word->word;

  QUIT;

  /* This command could be a shell builtin or a user-defined function.
     We have already found special builtins by this time, so we do not
     set builtin_is_special.  If this is a function or builtin, and we
     have pipes, then fork a subshell in here.  Otherwise, just execute
     the command directly. */
  if (func == 0 && builtin == 0)
    builtin = find_shell_builtin (this_command_name);

  last_shell_builtin = this_shell_builtin;
  this_shell_builtin = builtin;

  if (builtin || func)
    {
      if (builtin)
        {
	  old_builtin = executing_builtin;
	  unwind_protect_int (executing_builtin);	/* modified in execute_builtin */
	  if (old_command_builtin == -1)	/* sentinel, can be set above */
	    {
	      old_command_builtin = executing_command_builtin;
	      unwind_protect_int (executing_command_builtin);	/* ditto and set above */
	    }
        }
      if (already_forked)
	{
	  /* reset_terminating_signals (); */	/* XXX */
	  /* Reset the signal handlers in the child, but don't free the
	     trap strings.  Set a flag noting that we have to free the
	     trap strings if we run trap to change a signal disposition. */
	  reset_signal_handlers ();
	  subshell_environment |= SUBSHELL_RESETTRAP;
	  subshell_environment &= ~SUBSHELL_IGNTRAP;

	  if (async)
	    {
	      if ((cmdflags & CMD_STDIN_REDIR) &&
		    pipe_in == NO_PIPE &&
		    (stdin_redirects (simple_command->redirects) == 0))
		async_redirect_stdin ();
	      setup_async_signals ();
	    }

	  if (async == 0)
	    subshell_level++;
	  execute_subshell_builtin_or_function
	    (words, simple_command->redirects, builtin, func,
	     pipe_in, pipe_out, async, fds_to_close,
	     cmdflags);
	  subshell_level--;
	}
      else
	{
	  result = execute_builtin_or_function
	    (words, builtin, func, simple_command->redirects, fds_to_close,
	     cmdflags);
	  if (builtin)
	    {
	      if (result > EX_SHERRBASE)
		{
		  switch (result)
		    {
		    case EX_REDIRFAIL:
		    case EX_BADASSIGN:
		    case EX_EXPFAIL:
		      /* These errors cause non-interactive posix mode shells to exit */
		      if (posixly_correct && builtin_is_special && interactive_shell == 0)
			{
			  last_command_exit_value = EXECUTION_FAILURE;
			  jump_to_top_level (ERREXIT);
			}
		      break;
		    case EX_DISKFALLBACK:
		      /* XXX - experimental */
		      executing_builtin = old_builtin;
		      executing_command_builtin = old_command_builtin;
		      builtin = 0;

		      /* The redirections have already been `undone', so this
			 will have to do them again. But piping is forever. */
		      pipe_in = pipe_out = -1;
		      goto execute_from_filesystem;
		    }
		  result = builtin_status (result);
		  if (builtin_is_special)
		    special_builtin_failed = 1;	/* XXX - take command builtin into account? */
		}
	      /* In POSIX mode, if there are assignment statements preceding
		 a special builtin, they persist after the builtin
		 completes. */
	      if (posixly_correct && builtin_is_special && temporary_env)
		merge_temporary_env ();
	    }
	  else		/* function */
	    {
	      if (result == EX_USAGE)
		result = EX_BADUSAGE;
	      else if (result > EX_SHERRBASE)
		result = builtin_status (result);
	    }

	  set_pipestatus_from_exit (result);

	  goto return_result;
	}
    }

  if (autocd && interactive && words->word && is_dirname (words->word->word))
    {
      words = make_word_list (make_word ("--"), words);
      words = make_word_list (make_word ("cd"), words);
      xtrace_print_word_list (words, 0);
      func = find_function ("cd");
      goto run_builtin;
    }

execute_from_filesystem:
  if (command_line == 0)
    command_line = savestring (the_printed_command_except_trap ? the_printed_command_except_trap : "");

#if defined (PROCESS_SUBSTITUTION)
  /* The old code did not test already_forked and only did this if
     subshell_environment&SUBSHELL_COMSUB != 0 (comsubs and procsubs). Other
     uses of the no-fork optimization left FIFOs in $TMPDIR */
  if (already_forked == 0 && (cmdflags & CMD_NO_FORK) && fifos_pending() > 0)
    cmdflags &= ~CMD_NO_FORK;
#endif
  result = execute_disk_command (words, simple_command->redirects, command_line,
			pipe_in, pipe_out, async, fds_to_close,
			cmdflags);

 return_result:
  bind_lastarg (lastarg);
  FREE (command_line);
  dispose_words (words);
  if (builtin)
    {
      executing_builtin = old_builtin;
      executing_command_builtin = old_command_builtin;
    }
  discard_unwind_frame ("simple-command");
  this_command_name = (char *)NULL;	/* points to freed memory now */
  return (result);
}

/* Translate the special builtin exit statuses.  We don't really need a
   function for this; it's a placeholder for future work. */
static int
builtin_status (result)
     int result;
{
  int r;

  switch (result)
    {
    case EX_USAGE:
    case EX_BADSYNTAX:
      r = EX_BADUSAGE;
      break;
    case EX_REDIRFAIL:
    case EX_BADASSIGN:
    case EX_EXPFAIL:
      r = EXECUTION_FAILURE;
      break;
    default:
      /* other special exit statuses not yet defined */
      r = (result > EX_SHERRBASE) ? EXECUTION_FAILURE : EXECUTION_SUCCESS;
      break;
    }
  return (r);
}

static int
execute_builtin (builtin, words, flags, subshell)
     sh_builtin_func_t *builtin;
     WORD_LIST *words;
     int flags, subshell;
{
  int result, eval_unwind, ignexit_flag;
  int isbltinenv, should_keep;
  char *error_trap;

  error_trap = 0;
  should_keep = 0;

  /* The eval builtin calls parse_and_execute, which does not know about
     the setting of flags, and always calls the execution functions with
     flags that will exit the shell on an error if -e is set.  If the
     eval builtin is being called, and we're supposed to ignore the exit
     value of the command, we turn the -e flag off ourselves and disable
     the ERR trap, then restore them when the command completes.  This is
     also a problem (as below) for the command and source/. builtins. */
  if (subshell == 0 && (flags & CMD_IGNORE_RETURN) &&
	(builtin == eval_builtin || (flags & CMD_COMMAND_BUILTIN) || builtin == source_builtin))
    {
      begin_unwind_frame ("eval_builtin");
      unwind_protect_int (exit_immediately_on_error);
      unwind_protect_int (builtin_ignoring_errexit);
      error_trap = TRAP_STRING (ERROR_TRAP);
      if (error_trap)
	{
	  error_trap = savestring (error_trap);
	  add_unwind_protect (xfree, error_trap);
	  add_unwind_protect (set_error_trap, error_trap);
	  restore_default_signal (ERROR_TRAP);
	}
      exit_immediately_on_error = 0;
      ignexit_flag = builtin_ignoring_errexit;
      builtin_ignoring_errexit = 1;
      eval_unwind = 1;
    }
  else
    eval_unwind = 0;

  /* The temporary environment for a builtin is supposed to apply to
     all commands executed by that builtin.  Currently, this is a
     problem only with the `unset', `source' and `eval' builtins.
     `mapfile' is a special case because it uses evalstring (same as
     eval or source) to run its callbacks. */
  /* SHOULD_KEEP is for the pop_scope call below; it only matters when
     posixly_correct is set, but we should propagate the temporary environment
     to the enclosing environment only for special builtins. */
  isbltinenv = (builtin == source_builtin || builtin == eval_builtin || builtin == unset_builtin || builtin == mapfile_builtin);
  should_keep = isbltinenv && builtin != mapfile_builtin;
#if defined (HISTORY) && defined (READLINE)
  if (builtin == fc_builtin || builtin == read_builtin)
    {
      isbltinenv = 1;
      should_keep = 0;
    }
#endif

  if (isbltinenv)
    {
      if (subshell == 0)
	begin_unwind_frame ("builtin_env");

      if (temporary_env)
	{
	  push_scope (VC_BLTNENV, temporary_env);
	  if (flags & CMD_COMMAND_BUILTIN)
	    should_keep = 0;
	  if (subshell == 0)
	    add_unwind_protect (pop_scope, should_keep ? "1" : 0);
          temporary_env = (HASH_TABLE *)NULL;	  
	}
    }

  if (subshell == 0 && builtin == eval_builtin)
    {
      if (evalnest_max > 0 && evalnest >= evalnest_max)
	{
	  internal_error (_("eval: maximum eval nesting level exceeded (%d)"), evalnest);
	  evalnest = 0;
	  jump_to_top_level (DISCARD);
	}
      unwind_protect_int (evalnest);
      /* The test for subshell == 0 above doesn't make a difference */
      evalnest++;	/* execute_subshell_builtin_or_function sets this to 0 */
    }
  else if (subshell == 0 && builtin == source_builtin)
    {
      if (sourcenest_max > 0 && sourcenest >= sourcenest_max)
	{
	  internal_error (_("%s: maximum source nesting level exceeded (%d)"), this_command_name, sourcenest);
	  sourcenest = 0;
	  jump_to_top_level (DISCARD);
	}
      unwind_protect_int (sourcenest);
      /* The test for subshell == 0 above doesn't make a difference */
      sourcenest++;	/* execute_subshell_builtin_or_function sets this to 0 */
    }

  /* `return' does a longjmp() back to a saved environment in execute_function.
     If a variable assignment list preceded the command, and the shell is
     running in POSIX mode, we need to merge that into the shell_variables
     table, since `return' is a POSIX special builtin. We don't do this if
     it's being run by the `command' builtin, since that's supposed to inhibit
     the special builtin properties. */
  if (posixly_correct && subshell == 0 && builtin == return_builtin && (flags & CMD_COMMAND_BUILTIN) == 0 && temporary_env)
    {
      begin_unwind_frame ("return_temp_env");
      add_unwind_protect (merge_temporary_env, (char *)NULL);
    }

  executing_builtin++;
  executing_command_builtin |= builtin == command_builtin;
  result = ((*builtin) (words->next));

  /* This shouldn't happen, but in case `return' comes back instead of
     longjmp'ing, we need to unwind. */
  if (posixly_correct && subshell == 0 && builtin == return_builtin && temporary_env)
    discard_unwind_frame ("return_temp_env");

  if (subshell == 0 && isbltinenv)
    run_unwind_frame ("builtin_env");

  if (eval_unwind)
    {
      builtin_ignoring_errexit = ignexit_flag;
      exit_immediately_on_error = builtin_ignoring_errexit ? 0 : errexit_flag;
      if (error_trap)
	{
	  set_error_trap (error_trap);
	  free (error_trap);
	}
      discard_unwind_frame ("eval_builtin");
    }

  return (result);
}

static void
maybe_restore_getopt_state (gs)
     sh_getopt_state_t *gs;
{
  /* If we have a local copy of OPTIND and it's at the right (current)
     context, then we restore getopt's internal state.  If not, we just
     let it go.  We know there is a local OPTIND if gs->gs_flags & 1.
     This is set below in execute_function() before the context is run. */
  if (gs->gs_flags & 1)
    sh_getopt_restore_istate (gs);
  else
    free (gs);
}

#if defined (ARRAY_VARS)
void
restore_funcarray_state (fa)
     struct func_array_state *fa;
{
  SHELL_VAR *nfv;
  ARRAY *funcname_a;

  array_pop (fa->source_a);
  array_pop (fa->lineno_a);

  GET_ARRAY_FROM_VAR ("FUNCNAME", nfv, funcname_a);
  if (nfv == fa->funcname_v)
    array_pop (funcname_a);

  free (fa);
}
#endif

static int
execute_function (var, words, flags, fds_to_close, async, subshell)
     SHELL_VAR *var;
     WORD_LIST *words;
     int flags;
     struct fd_bitmap *fds_to_close;
     int async, subshell;
{
  int return_val, result, lineno;
  COMMAND *tc, *fc, *save_current;
  char *debug_trap, *error_trap, *return_trap;
#if defined (ARRAY_VARS)
  SHELL_VAR *funcname_v, *bash_source_v, *bash_lineno_v;
  ARRAY *funcname_a;
  volatile ARRAY *bash_source_a;
  volatile ARRAY *bash_lineno_a;
  struct func_array_state *fa;
#endif
  FUNCTION_DEF *shell_fn;
  char *sfile, *t;
  sh_getopt_state_t *gs;
  SHELL_VAR *gv;

  USE_VAR(fc);

  if (funcnest_max > 0 && funcnest >= funcnest_max)
    {
      internal_error (_("%s: maximum function nesting level exceeded (%d)"), var->name, funcnest);
      funcnest = 0;	/* XXX - should we reset it somewhere else? */
      jump_to_top_level (DISCARD);
    }

#if defined (ARRAY_VARS)
  GET_ARRAY_FROM_VAR ("FUNCNAME", funcname_v, funcname_a);
  GET_ARRAY_FROM_VAR ("BASH_SOURCE", bash_source_v, bash_source_a);
  GET_ARRAY_FROM_VAR ("BASH_LINENO", bash_lineno_v, bash_lineno_a);
#endif

  tc = (COMMAND *)copy_command (function_cell (var));
  if (tc && (flags & CMD_IGNORE_RETURN))
    tc->flags |= CMD_IGNORE_RETURN;

  /* A limited attempt at optimization: shell functions at the end of command
     substitutions that are already marked NO_FORK. */
  if (tc && (flags & CMD_NO_FORK) && (subshell_environment & SUBSHELL_COMSUB))
    optimize_shell_function (tc);

  gs = sh_getopt_save_istate ();
  if (subshell == 0)
    {
      begin_unwind_frame ("function_calling");
      /* If the shell is in posix mode, this will push the variables in
	 the temporary environment to the "current shell environment" (the
	 global scope), and dispose the temporary env before setting it to
	 NULL later. This behavior has disappeared from the latest edition
	 of the standard, so I will eventually remove it from variables.c:
	 push_var_context. */
      push_context (var->name, subshell, temporary_env);
      /* This has to be before the pop_context(), because the unwinding of
	 local variables may cause the restore of a local declaration of
	 OPTIND to force a getopts state reset. */
      add_unwind_protect (maybe_restore_getopt_state, gs);
      add_unwind_protect (pop_context, (char *)NULL);
      unwind_protect_int (line_number);
      unwind_protect_int (line_number_for_err_trap);
      unwind_protect_int (function_line_number);
      unwind_protect_int (return_catch_flag);
      unwind_protect_jmp_buf (return_catch);
      add_unwind_protect (dispose_command, (char *)tc);
      unwind_protect_pointer (this_shell_function);
      unwind_protect_int (funcnest);
      unwind_protect_int (loop_level);
    }
  else
    push_context (var->name, subshell, temporary_env);	/* don't unwind-protect for subshells */

  temporary_env = (HASH_TABLE *)NULL;

  this_shell_function = var;
  make_funcname_visible (1);

  debug_trap = TRAP_STRING(DEBUG_TRAP);
  error_trap = TRAP_STRING(ERROR_TRAP);
  return_trap = TRAP_STRING(RETURN_TRAP);
  
  /* The order of the unwind protects for debug_trap, error_trap and
     return_trap is important here!  unwind-protect commands are run
     in reverse order of registration.  If this causes problems, take
     out the xfree unwind-protect calls and live with the small memory leak. */

  /* function_trace_mode != 0 means that all functions inherit the DEBUG trap.
     if the function has the trace attribute set, it inherits the DEBUG trap */
  if (debug_trap && ((trace_p (var) == 0) && function_trace_mode == 0))
    {
      if (subshell == 0)
	{
	  debug_trap = savestring (debug_trap);
	  add_unwind_protect (xfree, debug_trap);
	  add_unwind_protect (maybe_set_debug_trap, debug_trap);
	}
      restore_default_signal (DEBUG_TRAP);
    }

  /* error_trace_mode != 0 means that functions inherit the ERR trap. */
  if (error_trap && error_trace_mode == 0)
    {
      if (subshell == 0)
	{
	  error_trap = savestring (error_trap);
	  add_unwind_protect (xfree, error_trap);
	  add_unwind_protect (maybe_set_error_trap, error_trap);
	}
      restore_default_signal (ERROR_TRAP);
    }

  /* Shell functions inherit the RETURN trap if function tracing is on
     globally or on individually for this function. */
  if (return_trap && (signal_in_progress (DEBUG_TRAP) || ((trace_p (var) == 0) && function_trace_mode == 0)))
    {
      if (subshell == 0)
	{
	  return_trap = savestring (return_trap);
	  add_unwind_protect (xfree, return_trap);
	  add_unwind_protect (maybe_set_return_trap, return_trap);
	}
      restore_default_signal (RETURN_TRAP);
    }
  
  funcnest++;
#if defined (ARRAY_VARS)
  /* This is quite similar to the code in shell.c and elsewhere. */
  shell_fn = find_function_def (this_shell_function->name);
  sfile = shell_fn ? shell_fn->source_file : "";
  array_push ((ARRAY *)funcname_a, this_shell_function->name);

  array_push ((ARRAY *)bash_source_a, sfile);
  lineno = GET_LINE_NUMBER ();
  t = itos (lineno);
  array_push ((ARRAY *)bash_lineno_a, t);
  free (t);
#endif

#if defined (ARRAY_VARS)
  fa = (struct func_array_state *)xmalloc (sizeof (struct func_array_state));
  fa->source_a = (ARRAY *)bash_source_a;
  fa->source_v = bash_source_v;
  fa->lineno_a = (ARRAY *)bash_lineno_a;
  fa->lineno_v = bash_lineno_v;
  fa->funcname_a = (ARRAY *)funcname_a;
  fa->funcname_v = funcname_v;
  if (subshell == 0)
    add_unwind_protect (restore_funcarray_state, fa);
#endif

  /* The temporary environment for a function is supposed to apply to
     all commands executed within the function body. */

  /* Initialize BASH_ARGC and BASH_ARGV before we blow away the positional
     parameters */
  if (debugging_mode || shell_compatibility_level <= 44)
    init_bash_argv ();

  remember_args (words->next, 1);

  /* Update BASH_ARGV and BASH_ARGC */
  if (debugging_mode)
    {
      push_args (words->next);
      if (subshell == 0)
	add_unwind_protect (pop_args, 0);
    }

  /* Number of the line on which the function body starts. */
  line_number = function_line_number = tc->line;

#if defined (JOB_CONTROL)
  if (subshell)
    stop_pipeline (async, (COMMAND *)NULL);
#endif

  if (shell_compatibility_level > 43)
    loop_level = 0;

  fc = tc;

  from_return_trap = 0;

  return_catch_flag++;
  return_val = setjmp_nosigs (return_catch);

  if (return_val)
    {
      result = return_catch_value;
      /* Run the RETURN trap in the function's context. */
      save_current = currently_executing_command;
      if (from_return_trap == 0)
	run_return_trap ();
      currently_executing_command = save_current;
    }
  else
    {
      /* Run the debug trap here so we can trap at the start of a function's
	 execution rather than the execution of the body's first command. */
      showing_function_line = 1;
      save_current = currently_executing_command;
      result = run_debug_trap ();
#if defined (DEBUGGER)
      /* In debugging mode, if the DEBUG trap returns a non-zero status, we
	 skip the command. */
      if (debugging_mode == 0 || result == EXECUTION_SUCCESS)
	{
	  showing_function_line = 0;
	  currently_executing_command = save_current;
	  result = execute_command_internal (fc, 0, NO_PIPE, NO_PIPE, fds_to_close);

	  /* Run the RETURN trap in the function's context */
	  save_current = currently_executing_command;
	  run_return_trap ();
	  currently_executing_command = save_current;
	}
#else
      result = execute_command_internal (fc, 0, NO_PIPE, NO_PIPE, fds_to_close);

      save_current = currently_executing_command;
      run_return_trap ();
      currently_executing_command = save_current;
#endif
      showing_function_line = 0;
    }

  /* If we have a local copy of OPTIND, note it in the saved getopts state. */
  gv = find_variable ("OPTIND");
  if (gv && gv->context == variable_context)
    gs->gs_flags |= 1;

  if (subshell == 0)
    run_unwind_frame ("function_calling");
#if defined (ARRAY_VARS)
  else
    {
      restore_funcarray_state (fa);
      /* Restore BASH_ARGC and BASH_ARGV */
      if (debugging_mode)
	pop_args ();
    }
#endif

  if (variable_context == 0 || this_shell_function == 0)
    {
      make_funcname_visible (0);
#if defined (PROCESS_SUBSTITUTION)
      unlink_fifo_list ();
#endif
    }

  return (result);
}

/* A convenience routine for use by other parts of the shell to execute
   a particular shell function. */
int
execute_shell_function (var, words)
     SHELL_VAR *var;
     WORD_LIST *words;
{
  int ret;
  struct fd_bitmap *bitmap;

  bitmap = new_fd_bitmap (FD_BITMAP_DEFAULT_SIZE);
  begin_unwind_frame ("execute-shell-function");
  add_unwind_protect (dispose_fd_bitmap, (char *)bitmap);
      
  ret = execute_function (var, words, 0, bitmap, 0, 0);

  dispose_fd_bitmap (bitmap);
  discard_unwind_frame ("execute-shell-function");

  return ret;
}

/* Execute a shell builtin or function in a subshell environment.  This
   routine does not return; it only calls exit().  If BUILTIN is non-null,
   it points to a function to call to execute a shell builtin; otherwise
   VAR points at the body of a function to execute.  WORDS is the arguments
   to the command, REDIRECTS specifies redirections to perform before the
   command is executed. */
static void
execute_subshell_builtin_or_function (words, redirects, builtin, var,
				      pipe_in, pipe_out, async, fds_to_close,
				      flags)
     WORD_LIST *words;
     REDIRECT *redirects;
     sh_builtin_func_t *builtin;
     SHELL_VAR *var;
     int pipe_in, pipe_out, async;
     struct fd_bitmap *fds_to_close;
     int flags;
{
  int result, r, funcvalue;
#if defined (JOB_CONTROL)
  int jobs_hack;

  jobs_hack = (builtin == jobs_builtin) &&
		((subshell_environment & SUBSHELL_ASYNC) == 0 || pipe_out != NO_PIPE);
#endif

  /* A subshell is neither a login shell nor interactive. */
  login_shell = interactive = 0;
  if (builtin == eval_builtin)
    evalnest = 0;
  else if (builtin == source_builtin)
    sourcenest = 0;

  if (async)
    subshell_environment |= SUBSHELL_ASYNC;
  if (pipe_in != NO_PIPE || pipe_out != NO_PIPE)
    subshell_environment |= SUBSHELL_PIPE;

  maybe_make_export_env ();	/* XXX - is this needed? */

#if defined (JOB_CONTROL)
  /* Eradicate all traces of job control after we fork the subshell, so
     all jobs begun by this subshell are in the same process group as
     the shell itself. */

  /* Allow the output of `jobs' to be piped. */
  if (jobs_hack)
    kill_current_pipeline ();
  else
    without_job_control ();

  set_sigchld_handler ();
#else
  without_job_control ();
#endif /* JOB_CONTROL */

  set_sigint_handler ();

  if (fds_to_close)
    close_fd_bitmap (fds_to_close);

  do_piping (pipe_in, pipe_out);

  if (do_redirections (redirects, RX_ACTIVE) != 0)
    exit (EXECUTION_FAILURE);

  if (builtin)
    {
      /* Give builtins a place to jump back to on failure,
	 so we don't go back up to main(). */
      result = setjmp_nosigs (top_level);

      /* Give the return builtin a place to jump to when executed in a subshell
         or pipeline */
      funcvalue = 0;
      if (return_catch_flag && builtin == return_builtin)
        funcvalue = setjmp_nosigs (return_catch);

      if (result == EXITPROG || result == EXITBLTIN)
	subshell_exit (last_command_exit_value);
      else if (result)
	subshell_exit (EXECUTION_FAILURE);
      else if (funcvalue)
	subshell_exit (return_catch_value);
      else
	{
	  r = execute_builtin (builtin, words, flags, 1);
	  fflush (stdout);
	  if (r == EX_USAGE)
	    r = EX_BADUSAGE;
	  /* XXX - experimental */
	  else if (r == EX_DISKFALLBACK)
	    {
	      char *command_line;

	      command_line = savestring (the_printed_command_except_trap ? the_printed_command_except_trap : "");
	      r = execute_disk_command (words, (REDIRECT *)0, command_line,
		  -1, -1, async, (struct fd_bitmap *)0, flags|CMD_NO_FORK);
	    }
	  subshell_exit (r);
	}
    }
  else
    {
      r = execute_function (var, words, flags, fds_to_close, async, 1);
      fflush (stdout);
      subshell_exit (r);
    }
}

/* Execute a builtin or function in the current shell context.  If BUILTIN
   is non-null, it is the builtin command to execute, otherwise VAR points
   to the body of a function.  WORDS are the command's arguments, REDIRECTS
   are the redirections to perform.  FDS_TO_CLOSE is the usual bitmap of
   file descriptors to close.

   If BUILTIN is exec_builtin, the redirections specified in REDIRECTS are
   not undone before this function returns. */
static int
execute_builtin_or_function (words, builtin, var, redirects,
			     fds_to_close, flags)
     WORD_LIST *words;
     sh_builtin_func_t *builtin;
     SHELL_VAR *var;
     REDIRECT *redirects;
     struct fd_bitmap *fds_to_close;
     int flags;
{
  int result;
  REDIRECT *saved_undo_list;
#if defined (PROCESS_SUBSTITUTION)
  int ofifo, nfifo, osize;
  void *ofifo_list;
#endif

#if defined (PROCESS_SUBSTITUTION)
  begin_unwind_frame ("saved_fifos");
  /* If we return, we longjmp and don't get a chance to restore the old
     fifo list, so we add an unwind protect to free it */
  ofifo = num_fifos ();
  ofifo_list = copy_fifo_list (&osize);
  if (ofifo_list)
    add_unwind_protect (xfree, ofifo_list);
#endif

  if (do_redirections (redirects, RX_ACTIVE|RX_UNDOABLE) != 0)
    {
      undo_partial_redirects ();
      dispose_exec_redirects ();
#if defined (PROCESS_SUBSTITUTION)
      free (ofifo_list);
#endif
      return (EX_REDIRFAIL);	/* was EXECUTION_FAILURE */
    }

  saved_undo_list = redirection_undo_list;

  /* Calling the "exec" builtin changes redirections forever. */
  if (builtin == exec_builtin)
    {
      dispose_redirects (saved_undo_list);
      saved_undo_list = exec_redirection_undo_list;
      exec_redirection_undo_list = (REDIRECT *)NULL;
    }
  else
    dispose_exec_redirects ();

  if (saved_undo_list)
    {
      begin_unwind_frame ("saved-redirects");
      add_unwind_protect (cleanup_redirects, (char *)saved_undo_list);
    }

  redirection_undo_list = (REDIRECT *)NULL;

  if (builtin)
    result = execute_builtin (builtin, words, flags, 0);
  else
    result = execute_function (var, words, flags, fds_to_close, 0, 0);

  /* We do this before undoing the effects of any redirections. */
  fflush (stdout);
  fpurge (stdout);
  if (ferror (stdout))
    clearerr (stdout);  

  /* If we are executing the `command' builtin, but this_shell_builtin is
     set to `exec_builtin', we know that we have something like
     `command exec [redirection]', since otherwise `exec' would have
     overwritten the shell and we wouldn't get here.  In this case, we
     want to behave as if the `command' builtin had not been specified
     and preserve the redirections. */
  if (builtin == command_builtin && this_shell_builtin == exec_builtin)
    {
      int discard;

      discard = 0;
      if (saved_undo_list)
	{
	  dispose_redirects (saved_undo_list);
	  discard = 1;
	}
      redirection_undo_list = exec_redirection_undo_list;
      saved_undo_list = exec_redirection_undo_list = (REDIRECT *)NULL;      
      if (discard)
	discard_unwind_frame ("saved-redirects");
    }

  if (saved_undo_list)
    {
      redirection_undo_list = saved_undo_list;
      discard_unwind_frame ("saved-redirects");
    }

  undo_partial_redirects ();

#if defined (PROCESS_SUBSTITUTION)
  /* Close any FIFOs created by this builtin or function. */
  nfifo = num_fifos ();
  if (nfifo > ofifo)
    close_new_fifos (ofifo_list, osize);
  if (ofifo_list)
    free (ofifo_list);
  discard_unwind_frame ("saved_fifos");
#endif

  return (result);
}

void
setup_async_signals ()
{
#if defined (__BEOS__)
  set_signal_handler (SIGHUP, SIG_IGN);	/* they want csh-like behavior */
#endif

#if defined (JOB_CONTROL)
  if (job_control == 0)
#endif
    {
      /* Make sure we get the original signal dispositions now so we don't
	 confuse the trap builtin later if the subshell tries to use it to
	 reset SIGINT/SIGQUIT.  Don't call set_signal_ignored; that sets
	 the value of original_signals to SIG_IGN. Posix interpretation 751. */
      get_original_signal (SIGINT);
      set_signal_handler (SIGINT, SIG_IGN);

      get_original_signal (SIGQUIT);
      set_signal_handler (SIGQUIT, SIG_IGN);
    }
}

/* Execute a simple command that is hopefully defined in a disk file
   somewhere.

   1) fork ()
   2) connect pipes
   3) look up the command
   4) do redirections
   5) execve ()
   6) If the execve failed, see if the file has executable mode set.
   If so, and it isn't a directory, then execute its contents as
   a shell script.

   Note that the filename hashing stuff has to take place up here,
   in the parent.  This is probably why the Bourne style shells
   don't handle it, since that would require them to go through
   this gnarly hair, for no good reason.

   NOTE: callers expect this to fork or exit(). */

/* Name of a shell function to call when a command name is not found. */
#ifndef NOTFOUND_HOOK
#  define NOTFOUND_HOOK "command_not_found_handle"
#endif

static int
execute_disk_command (words, redirects, command_line, pipe_in, pipe_out,
		      async, fds_to_close, cmdflags)
     WORD_LIST *words;
     REDIRECT *redirects;
     char *command_line;
     int pipe_in, pipe_out, async;
     struct fd_bitmap *fds_to_close;
     int cmdflags;
{
  char *pathname, *command, **args, *p;
  int nofork, stdpath, result, fork_flags;
  pid_t pid;
  SHELL_VAR *hookf;
  WORD_LIST *wl;

  stdpath = (cmdflags & CMD_STDPATH);	/* use command -p path */
  nofork = (cmdflags & CMD_NO_FORK);	/* Don't fork, just exec, if no pipes */
  pathname = words->word->word;

  p = 0;
  result = EXECUTION_SUCCESS;
#if defined (RESTRICTED_SHELL)
  command = (char *)NULL;
  if (restricted && mbschr (pathname, '/'))
    {
      internal_error (_("%s: restricted: cannot specify `/' in command names"),
		    pathname);
      result = last_command_exit_value = EXECUTION_FAILURE;

      /* If we're not going to fork below, we must already be in a child
         process or a context in which it's safe to call exit(2).  */
      if (nofork && pipe_in == NO_PIPE && pipe_out == NO_PIPE)
	exit (last_command_exit_value);
      else
	goto parent_return;
    }
#endif /* RESTRICTED_SHELL */

  /* If we want to change this so `command -p' (CMD_STDPATH) does not insert
     any pathname it finds into the hash table, it should read
     command = search_for_command (pathname, stdpath ? CMDSRCH_STDPATH : CMDSRCH_HASH);
  */
  command = search_for_command (pathname, CMDSRCH_HASH|(stdpath ? CMDSRCH_STDPATH : 0));
  QUIT;

  if (command)
    {
      /* If we're optimizing out the fork (implicit `exec'), decrement the
	 shell level like `exec' would do. Don't do this if we are already
	 in a pipeline environment, assuming it's already been done. */
      if (nofork && pipe_in == NO_PIPE && pipe_out == NO_PIPE && (subshell_environment & SUBSHELL_PIPE) == 0)
	adjust_shell_level (-1);

      maybe_make_export_env ();
      put_command_name_into_env (command);
    }

  /* We have to make the child before we check for the non-existence
     of COMMAND, since we want the error messages to be redirected. */
  /* If we can get away without forking and there are no pipes to deal with,
     don't bother to fork, just directly exec the command. */
  if (nofork && pipe_in == NO_PIPE && pipe_out == NO_PIPE)
    pid = 0;
  else
    {
      fork_flags = async ? FORK_ASYNC : 0;
      pid = make_child (p = savestring (command_line), fork_flags);
    }

  if (pid == 0)
    {
      int old_interactive;

      reset_terminating_signals ();	/* XXX */
      /* Cancel traps, in trap.c. */
      restore_original_signals ();
      subshell_environment &= ~SUBSHELL_IGNTRAP;

#if defined (JOB_CONTROL)
      FREE (p);
#endif

      /* restore_original_signals may have undone the work done
	 by make_child to ensure that SIGINT and SIGQUIT are ignored
	 in asynchronous children. */
      if (async)
	{
	  if ((cmdflags & CMD_STDIN_REDIR) &&
		pipe_in == NO_PIPE &&
		(stdin_redirects (redirects) == 0))
	    async_redirect_stdin ();
	  setup_async_signals ();
	}

      /* This functionality is now provided by close-on-exec of the
	 file descriptors manipulated by redirection and piping.
	 Some file descriptors still need to be closed in all children
	 because of the way bash does pipes; fds_to_close is a
	 bitmap of all such file descriptors. */
      if (fds_to_close)
	close_fd_bitmap (fds_to_close);

      do_piping (pipe_in, pipe_out);

      old_interactive = interactive;
      if (async)
	interactive = 0;

      subshell_environment |= SUBSHELL_FORK;	/* XXX - was just = */

#if defined (PROCESS_SUBSTITUTION) && !defined (HAVE_DEV_FD)
      clear_fifo_list ();	/* XXX - we haven't created any FIFOs */
#endif

      /* reset shell_pgrp to pipeline_pgrp here for word expansions performed
         by the redirections here? */
      if (redirects && (do_redirections (redirects, RX_ACTIVE) != 0))
	{
#if defined (PROCESS_SUBSTITUTION)
	  /* Try to remove named pipes that may have been created as the
	     result of redirections. */
	  unlink_all_fifos ();
#endif /* PROCESS_SUBSTITUTION */
	  exit (EXECUTION_FAILURE);
	}

#if defined (PROCESS_SUBSTITUTION) && !defined (HAVE_DEV_FD)
      /* This should only contain FIFOs created as part of redirection
	 expansion. */
      unlink_all_fifos ();
#endif

      if (async)
	interactive = old_interactive;

      if (command == 0)
	{
	  hookf = find_function (NOTFOUND_HOOK);
	  if (hookf == 0)
	    {
	      /* Make sure filenames are displayed using printable characters */
	      pathname = printable_filename (pathname, 0);
	      internal_error (_("%s: command not found"), pathname);
	      exit (EX_NOTFOUND);	/* Posix.2 says the exit status is 127 */
	    }

	  /* We don't want to manage process groups for processes we start
	     from here, so we turn off job control and don't attempt to
	     manipulate the terminal's process group. */
	  without_job_control ();

#if defined (JOB_CONTROL)
	  set_sigchld_handler ();
#endif

	  wl = make_word_list (make_word (NOTFOUND_HOOK), words);
	  exit (execute_shell_function (hookf, wl));
	}

      /* Execve expects the command name to be in args[0].  So we
	 leave it there, in the same format that the user used to
	 type it in. */
      args = strvec_from_word_list (words, 0, 0, (int *)NULL);
      exit (shell_execve (command, args, export_env));
    }
  else
    {
parent_return:
      QUIT;

      /* Make sure that the pipes are closed in the parent. */
      close_pipes (pipe_in, pipe_out);
#if defined (PROCESS_SUBSTITUTION) && defined (HAVE_DEV_FD)
#if 0
      if (variable_context == 0)
        unlink_fifo_list ();
#endif
#endif
      FREE (command);
      return (result);
    }
}

/* CPP defines to decide whether a particular index into the #! line
   corresponds to a valid interpreter name or argument character, or
   whitespace.  The MSDOS define is to allow \r to be treated the same
   as \n. */

#if !defined (MSDOS)
#  define STRINGCHAR(ind) \
    (ind < sample_len && !whitespace (sample[ind]) && sample[ind] != '\n')
#  define WHITECHAR(ind) \
    (ind < sample_len && whitespace (sample[ind]))
#else	/* MSDOS */
#  define STRINGCHAR(ind) \
    (ind < sample_len && !whitespace (sample[ind]) && sample[ind] != '\n' && sample[ind] != '\r')
#  define WHITECHAR(ind) \
    (ind < sample_len && whitespace (sample[ind]))
#endif	/* MSDOS */

static char *
getinterp (sample, sample_len, endp)
     char *sample;
     int sample_len, *endp;
{
  register int i;
  char *execname;
  int start;

  /* Find the name of the interpreter to exec. */
  for (i = 2; i < sample_len && whitespace (sample[i]); i++)
    ;

  for (start = i; STRINGCHAR(i); i++)
    ;

  execname = substring (sample, start, i);

  if (endp)
    *endp = i;
  return execname;
}

#if !defined (HAVE_HASH_BANG_EXEC)
/* If the operating system on which we're running does not handle
   the #! executable format, then help out.  SAMPLE is the text read
   from the file, SAMPLE_LEN characters.  COMMAND is the name of
   the script; it and ARGS, the arguments given by the user, will
   become arguments to the specified interpreter.  ENV is the environment
   to pass to the interpreter.

   The word immediately following the #! is the interpreter to execute.
   A single argument to the interpreter is allowed. */

static int
execute_shell_script (sample, sample_len, command, args, env)
     char *sample;
     int sample_len;
     char *command;
     char **args, **env;
{
  char *execname, *firstarg;
  int i, start, size_increment, larry;

  /* Find the name of the interpreter to exec. */
  execname = getinterp (sample, sample_len, &i);
  size_increment = 1;

  /* Now the argument, if any. */
  for (firstarg = (char *)NULL, start = i; WHITECHAR(i); i++)
    ;

  /* If there is more text on the line, then it is an argument for the
     interpreter. */

  if (STRINGCHAR(i))  
    {
      for (start = i; STRINGCHAR(i); i++)
	;
      firstarg = substring ((char *)sample, start, i);
      size_increment = 2;
    }

  larry = strvec_len (args) + size_increment;
  args = strvec_resize (args, larry + 1);

  for (i = larry - 1; i; i--)
    args[i] = args[i - size_increment];

  args[0] = execname;
  if (firstarg)
    {
      args[1] = firstarg;
      args[2] = command;
    }
  else
    args[1] = command;

  args[larry] = (char *)NULL;

  return (shell_execve (execname, args, env));
}
#undef STRINGCHAR
#undef WHITECHAR

#endif /* !HAVE_HASH_BANG_EXEC */

static void
initialize_subshell ()
{
#if defined (ALIAS)
  /* Forget about any aliases that we knew of.  We are in a subshell. */
  delete_all_aliases ();
#endif /* ALIAS */

#if defined (HISTORY)
  /* Forget about the history lines we have read.  This is a non-interactive
     subshell. */
  history_lines_this_session = 0;
#endif

  /* Forget about the way job control was working. We are in a subshell. */
  without_job_control ();

#if defined (JOB_CONTROL)
  set_sigchld_handler ();
  init_job_stats ();
#endif /* JOB_CONTROL */

  /* Reset the values of the shell flags and options. */
  reset_shell_flags ();
  reset_shell_options ();
  reset_shopt_options ();

  /* Zero out builtin_env, since this could be a shell script run from a
     sourced file with a temporary environment supplied to the `source/.'
     builtin.  Such variables are not supposed to be exported (empirical
     testing with sh and ksh).  Just throw it away; don't worry about a
     memory leak. */
  if (vc_isbltnenv (shell_variables))
    shell_variables = shell_variables->down;

  clear_unwind_protect_list (0);
  /* XXX -- are there other things we should be resetting here? */
  parse_and_execute_level = 0;		/* nothing left to restore it */

  /* We're no longer inside a shell function. */
  variable_context = return_catch_flag = funcnest = evalnest = sourcenest = 0;

  executing_list = 0;		/* XXX */

  /* If we're not interactive, close the file descriptor from which we're
     reading the current shell script. */
  if (interactive_shell == 0)
    unset_bash_input (0);
}

#if defined (HAVE_SETOSTYPE) && defined (_POSIX_SOURCE)
#  define SETOSTYPE(x)	__setostype(x)
#else
#  define SETOSTYPE(x)
#endif

#define HASH_BANG_BUFSIZ	128

#define READ_SAMPLE_BUF(file, buf, len) \
  do \
    { \
      fd = open(file, O_RDONLY); \
      if (fd >= 0) \
	{ \
	  len = read (fd, buf, HASH_BANG_BUFSIZ); \
	  close (fd); \
	} \
      else \
	len = -1; \
    } \
  while (0)
      
/* Call execve (), handling interpreting shell scripts, and handling
   exec failures. */
int
shell_execve (command, args, env)
     char *command;
     char **args, **env;
{
  int larray, i, fd;
  char sample[HASH_BANG_BUFSIZ];
  int sample_len;

  SETOSTYPE (0);		/* Some systems use for USG/POSIX semantics */
  execve (command, args, env);
  i = errno;			/* error from execve() */
  CHECK_TERMSIG;
  SETOSTYPE (1);

  /* If we get to this point, then start checking out the file.
     Maybe it is something we can hack ourselves. */
  if (i != ENOEXEC)
    {
      /* make sure this is set correctly for file_error/report_error */
      last_command_exit_value = (i == ENOENT) ?  EX_NOTFOUND : EX_NOEXEC; /* XXX Posix.2 says that exit status is 126 */
      if (file_isdir (command))
#if defined (EISDIR)
	internal_error (_("%s: %s"), command, strerror (EISDIR));
#else
	internal_error (_("%s: is a directory"), command);
#endif
      else if (executable_file (command) == 0)
	{
	  errno = i;
	  file_error (command);
	}
      /* errors not involving the path argument to execve. */
      else if (i == E2BIG || i == ENOMEM)
	{
	  errno = i;
	  file_error (command);
	}
      else if (i == ENOENT)
	{
	  errno = i;
	  internal_error (_("%s: cannot execute: required file not found"), command);
	}
      else
	{
	  /* The file has the execute bits set, but the kernel refuses to
	     run it for some reason.  See why. */
#if defined (HAVE_HASH_BANG_EXEC)
	  READ_SAMPLE_BUF (command, sample, sample_len);
	  if (sample_len > 0)
	    sample[sample_len - 1] = '\0';
	  if (sample_len > 2 && sample[0] == '#' && sample[1] == '!')
	    {
	      char *interp;
	      int ilen;

	      interp = getinterp (sample, sample_len, (int *)NULL);
	      ilen = strlen (interp);
	      errno = i;
	      if (interp[ilen - 1] == '\r')
		{
		  interp = xrealloc (interp, ilen + 2);
		  interp[ilen - 1] = '^';
		  interp[ilen] = 'M';
		  interp[ilen + 1] = '\0';
		}
	      sys_error (_("%s: %s: bad interpreter"), command, interp ? interp : "");
	      FREE (interp);
	      return (EX_NOEXEC);
	    }
#endif
	  errno = i;
	  file_error (command);
	}
      return (last_command_exit_value);
    }

  /* This file is executable.
     If it begins with #!, then help out people with losing operating
     systems.  Otherwise, check to see if it is a binary file by seeing
     if the contents of the first line (or up to 80 characters) are in the
     ASCII set.  If it's a text file, execute the contents as shell commands,
     otherwise return 126 (EX_BINARY_FILE). */
  READ_SAMPLE_BUF (command, sample, sample_len);

  if (sample_len == 0)
    return (EXECUTION_SUCCESS);

  /* Is this supposed to be an executable script?
     If so, the format of the line is "#! interpreter [argument]".
     A single argument is allowed.  The BSD kernel restricts
     the length of the entire line to 32 characters (32 bytes
     being the size of the BSD exec header), but we allow up to 128
     characters. */
  if (sample_len > 0)
    {
#if !defined (HAVE_HASH_BANG_EXEC)
      if (sample_len > 2 && sample[0] == '#' && sample[1] == '!')
	return (execute_shell_script (sample, sample_len, command, args, env));
      else
#endif
      if (check_binary_file (sample, sample_len))
	{
	  internal_error (_("%s: cannot execute binary file: %s"), command, strerror (i));
	  errno = i;
	  return (EX_BINARY_FILE);
	}
    }

  /* We have committed to attempting to execute the contents of this file
     as shell commands. */

  reset_parser ();
  initialize_subshell ();

  set_sigint_handler ();

  /* Insert the name of this shell into the argument list. */
  larray = strvec_len (args) + 1;
  args = strvec_resize (args, larray + 1);

  for (i = larray - 1; i; i--)
    args[i] = args[i - 1];

  args[0] = shell_name;
  args[1] = command;
  args[larray] = (char *)NULL;

  if (args[0][0] == '-')
    args[0]++;

#if defined (RESTRICTED_SHELL)
  if (restricted)
    change_flag ('r', FLAG_OFF);
#endif

  if (subshell_argv)
    {
      /* Can't free subshell_argv[0]; that is shell_name. */
      for (i = 1; i < subshell_argc; i++)
	free (subshell_argv[i]);
      free (subshell_argv);
    }

  dispose_command (currently_executing_command);	/* XXX */
  currently_executing_command = (COMMAND *)NULL;

  subshell_argc = larray;
  subshell_argv = args;
  subshell_envp = env;

  unbind_args ();	/* remove the positional parameters */

#if defined (PROCESS_SUBSTITUTION) && defined (HAVE_DEV_FD)
  clear_fifo_list ();	/* pipe fds are what they are now */
#endif

  sh_longjmp (subshell_top_level, 1);
  /*NOTREACHED*/
}

static int
execute_intern_function (name, funcdef)
     WORD_DESC *name;
     FUNCTION_DEF *funcdef;
{
  SHELL_VAR *var;
  char *t;

  if (check_identifier (name, posixly_correct) == 0)
    {
      if (posixly_correct && interactive_shell == 0)
	{
	  last_command_exit_value = EX_BADUSAGE;
	  jump_to_top_level (ERREXIT);
	}
      return (EXECUTION_FAILURE);
    }

  if (strchr (name->word, CTLESC))	/* WHY? */
    {
      t = dequote_escapes (name->word);
      free (name->word);
      name->word = t;
    }

  /* Posix interpretation 383 */
  if (posixly_correct && find_special_builtin (name->word))
    {
      internal_error (_("`%s': is a special builtin"), name->word);
      last_command_exit_value = EX_BADUSAGE;
      jump_to_top_level (interactive_shell ? DISCARD : ERREXIT);
    }

  var = find_function (name->word);
  if (var && (readonly_p (var) || noassign_p (var)))
    {
      if (readonly_p (var))
	internal_error (_("%s: readonly function"), var->name);
      return (EXECUTION_FAILURE);
    }

#if defined (DEBUGGER)
  bind_function_def (name->word, funcdef, 1);
#endif

  bind_function (name->word, funcdef->command);
  return (EXECUTION_SUCCESS);
}

#if defined (INCLUDE_UNUSED)
#if defined (PROCESS_SUBSTITUTION)
void
close_all_files ()
{
  register int i, fd_table_size;

  fd_table_size = getdtablesize ();
  if (fd_table_size > 256)	/* clamp to a reasonable value */
    fd_table_size = 256;

  for (i = 3; i < fd_table_size; i++)
    close (i);
}
#endif /* PROCESS_SUBSTITUTION */
#endif

static void
close_pipes (in, out)
     int in, out;
{
  if (in >= 0)
    close (in);
  if (out >= 0)
    close (out);
}

static void
dup_error (oldd, newd)
     int oldd, newd;
{
  sys_error (_("cannot duplicate fd %d to fd %d"), oldd, newd);
}

/* Redirect input and output to be from and to the specified pipes.
   NO_PIPE and REDIRECT_BOTH are handled correctly. */
static void
do_piping (pipe_in, pipe_out)
     int pipe_in, pipe_out;
{
  if (pipe_in != NO_PIPE)
    {
      if (dup2 (pipe_in, 0) < 0)
	dup_error (pipe_in, 0);
      if (pipe_in > 0)
	close (pipe_in);
#ifdef __CYGWIN__
      /* Let stdio know the fd may have changed from text to binary mode. */
      freopen (NULL, "r", stdin);
#endif /* __CYGWIN__ */
    }
  if (pipe_out != NO_PIPE)
    {
      if (pipe_out != REDIRECT_BOTH)
	{
	  if (dup2 (pipe_out, 1) < 0)
	    dup_error (pipe_out, 1);
	  if (pipe_out == 0 || pipe_out > 1)
	    close (pipe_out);
	}
      else
	{
	  if (dup2 (1, 2) < 0)
	    dup_error (1, 2);
	}
#ifdef __CYGWIN__
      /* Let stdio know the fd may have changed from text to binary mode, and
	 make sure to preserve stdout line buffering. */
      freopen (NULL, "w", stdout);
      sh_setlinebuf (stdout);
#endif /* __CYGWIN__ */
    }
}