/* variables.c -- Functions for hacking shell variables. */

/* Copyright (C) 1987,1989 Free Software Foundation, Inc.

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

   Bash is free software; you can redistribute it and/or modify it
   under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 1, or (at your option)
   any later version.

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

   You should have received a copy of the GNU General Public License
   along with Bash; see the file COPYING.  If not, write to the Free
   Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. */

#include <stdio.h>
#include <ctype.h>
#include <pwd.h>
#include <sys/types.h>

#include "shell.h"
#include "hash.h"
#include "flags.h"

#if defined (USG) && !defined (isc386) && !defined (sgi)
struct passwd *getpwuid (), *getpwent ();
#endif

/* The list of shell variables that the user has created, or that came from
   the environment. */
HASH_TABLE *shell_variables = (HASH_TABLE *)NULL;

/* The list of shell functions that the user has created, or that came from
   the environment. */
HASH_TABLE *shell_functions = (HASH_TABLE *)NULL;

/* The current variable context.  This is really a count of how deep into
   executing functions we are. */
int variable_context = 0;

/* The array of shell assignments which are made only in the environment
   for a single command. */
char **temporary_env = (char **)NULL;

/* Some funky variables which are known about specially.  Here is where
   "$*", "$1", and all the cruft is kept. */
char *dollar_vars[10];
WORD_LIST *rest_of_args = (WORD_LIST *)NULL;

/* The value of $$. */
int dollar_dollar_pid;

/* An array which is passed to commands as their environment.  It is
   manufactured from the overlap of the initial environment and the
   shell variables that are marked for export. */
char **export_env = (char **)NULL;

/* Non-zero means that we have to remake EXPORT_ENV. */
int array_needs_making = 1;

/* The list of variables that may not be unset in this shell. */
char **non_unsettable_vars = (char **)NULL;

#if defined (USG)
#define DEFAULT_MAIL_PATH "/usr/mail/"
#else
#define DEFAULT_MAIL_PATH "/usr/spool/mail/"
#endif

/* Some forward declarations. */
SHELL_VAR *set_if_not ();	/* returns new or existing entry */
static void sbrand ();		/* set bash random number generator */

/* Make VAR be auto-exported.  VAR is a pointer to a SHELL_VAR. */
#define set_auto_export(var) \
{ var->attributes |= att_exported; array_needs_making = 1; }

/* Initialize the shell variables from the current environment. */
initialize_shell_variables (env)
     char *env[];
{
  extern char *primary_prompt, *secondary_prompt;
  char *name, *string;
  int c, char_index;
  int string_index = 0;
  SHELL_VAR *temp_var;

  if (!shell_variables)
    shell_variables = make_hash_table (0);

  if (!shell_functions)
    shell_functions = make_hash_table (0);

  while (string = env[string_index++])
    {
      char_index = 0;

      name = (char *)alloca (1 + strlen (string));

      while ((c = *string++) && c != '=')
	name[char_index++] = c;

      name[char_index] = '\0';

      /* If exported function, define it now. */
      /* Posix.2 style exported function: name()=value */
      if (strncmp ("() {", string, 4) == 0 ||
	  ((name[char_index - 1] == ')' &&
	    name[char_index - 2] == '(' &&
	    string[0] == '{')))
	{
	  char *eval_string;

	  eval_string = (char *)xmalloc (3 + strlen (string) + strlen (name));
	  sprintf (eval_string, "%s %s", name, string);
	  parse_and_execute (eval_string, name);

	  if (name[char_index - 1] == ')')
	    name[char_index - 2] = '\0';
	  set_func_auto_export (name);
	}
      else
	{
	  SHELL_VAR *v;

	  v = bind_variable (name, string);
	  set_auto_export (v);
	}
    }

  /* Remember this pid. */
  dollar_dollar_pid = (int)getpid ();

  /* Now make our own defaults in case the vars that we think are
     important are missing. */
  temp_var = set_if_not ("PATH", DEFAULT_PATH_VALUE);
  set_auto_export (temp_var);

  temp_var = set_if_not ("TERM", "dumb");
  set_auto_export (temp_var);

  set_if_not ("PS1", primary_prompt);
  set_if_not ("PS2", secondary_prompt);
  set_if_not ("IFS", " \t\n");

  /* Magic machine types.  Pretty convenient. */
  temp_var = set_if_not ("HOSTTYPE", HOSTTYPE);
  set_auto_export (temp_var);

  /* Default MAILPATH, and MAILCHECK. */
  set_if_not ("MAILCHECK", "60");
  if ((get_string_value ("MAIL") == (char *)NULL) &&
      (get_string_value ("MAILPATH") == (char *)NULL))
    {
      extern char *current_user_name;
      char *tem;

      tem = (char *)xmalloc (1 + sizeof (DEFAULT_MAIL_PATH)
			   + strlen (current_user_name));
      strcpy (tem, DEFAULT_MAIL_PATH);
      strcat (tem, current_user_name);

      bind_variable ("MAILPATH", tem);
      free (tem);
    }

  /* Set up $PWD. */
  {
    char *get_working_directory (), *cd;

    cd = get_working_directory ("shell-init");
    if (cd)
      {
	bind_variable ("PWD", cd);
	free (cd);
      }
  }

  /* Do some things with shell level. */
  temp_var = set_if_not ("SHLVL", "0");
  set_auto_export (temp_var);
  adjust_shell_level (1);

  /* Make a variable $PPID, which holds the pid of the shell's parent.  */
  {
    char *ppid;
    SHELL_VAR *v;
    extern char *itos ();

    ppid = itos ((int) getppid ());
    v = find_variable ("PPID");

    if (v)
      v->attributes &= ~att_readonly;

    v = bind_variable ("PPID", ppid);
    v->attributes |= (att_readonly | att_integer);

    non_unsettable ("PPID");
    free (ppid);
  }

#if defined (GETOPTS_BUILTIN)
  /* Initialize the `getopts' stuff. */
  bind_variable ("OPTIND", "1");
  bind_variable ("OPTERR", "1");
#endif /* GETOPTS_BUILTIN */

  /* Get the full pathname to THIS shell, and set the BASH variable
     to it. */
  {
    extern char *shell_name, *find_user_command (), *full_pathname ();
    extern int login_shell;
    char *tname = find_user_command (shell_name);

    if ((login_shell == 1) && (*shell_name != '/'))
      {
	struct passwd *entry = getpwuid (getuid ());

	if (entry)
	  {
	    /* If HOME doesn't exist, set it. */
	    temp_var = (SHELL_VAR *)find_variable ("HOME");
	    if (!temp_var)
	      {
		temp_var = bind_variable ("HOME", entry->pw_dir);
		temp_var->attributes |= att_exported;
	      }
	    name = savestring (entry->pw_shell);
	  }
	else
	  name = savestring ("a.out");
	endpwent ();
      }
    else
      {
	if (!tname)
	  {
	    char *make_absolute ();
	    name = make_absolute (shell_name, get_string_value ("PWD"));
	  }
	else
	  {
	    name = full_pathname (tname);
	    free (tname);
	  }
      }

    /* Make the exported environment variable SHELL be whatever the name of
       this shell is.  Note that the `tset' command looks at this variable
       to determine what style of commands to output; if it ends in "csh",
       then C-shell commands are output, else Bourne shell commands. */
    temp_var = set_if_not ("SHELL", name);
    set_auto_export (temp_var);

    /* Make a variable called BASH, which is the name of THIS shell. */
    temp_var = bind_variable ("BASH", name);
    temp_var->attributes |= att_exported;

    free (name);
  }

  /* Make a variable called BASH_VERSION which contains the version info. */
  {
    char tt[12];
    extern char *dist_version;
    extern int build_version;

    sprintf (tt, "%s.%d", dist_version, build_version);
    bind_variable ("BASH_VERSION", tt);
  }

  /* Set history variables to defaults, and then do whatever we would
     do if the variable had just been set. */
  {
    char *tilde_expand ();
    char *tem = tilde_expand ("~/.bash_history");

    set_if_not ("HISTFILE", tem);
    free (tem);

    set_if_not ("HISTSIZE", "500");
    sv_histsize ("HISTSIZE");
  }

  /* seed the random number generator */

  sbrand (dollar_dollar_pid);

  /* If we have inherited `noclobber' from a previous shell, then set
     noclobbering on. */
  {
    extern int noclobber;

    noclobber = find_variable ("noclobber") != NULL;
  }

  /* Initialize the dynamic variables, and seed their values */
  initialize_dynamic_variables ();

  non_unsettable ("PATH");
  non_unsettable ("PS1");
  non_unsettable ("PS2");
  non_unsettable ("IFS");

  /* Get the users real user id, and save that in an readonly variable.
     To make the variable *really* readonly, we have added it to a special
     list of vars. */

  sv_uids ();
  set_var_read_only ("UID");
  set_var_read_only ("EUID");

  non_unsettable ("EUID");
  non_unsettable ("UID");
}

adjust_shell_level (change)
     int change;
{
  extern int shell_level;
  extern char *itos ();
  char *new_level;
  int old_level;


  old_level = atoi (get_string_value ("SHLVL"));
  shell_level = old_level + change;
  new_level = itos (shell_level);
  bind_variable ("SHLVL", new_level);
  free (new_level);
}

/* Add NAME to the list of variables that cannot be unset
   if it isn't already there. */
non_unsettable (name)
     char *name;
{
  register int i;

  if (!non_unsettable_vars)
    {
      non_unsettable_vars = (char **)xmalloc (1 * sizeof (char *));
      non_unsettable_vars[0] = (char *)NULL;
    }

  for (i = 0; non_unsettable_vars[i]; i++)
    if (strcmp (non_unsettable_vars[i], name) == 0)
      return;

  non_unsettable_vars = (char **)
    xrealloc (non_unsettable_vars, (2 + i) * sizeof (char *));
  non_unsettable_vars[i] = savestring (name);
  non_unsettable_vars[i + 1] = (char *)NULL;
}

/* Set NAME to VALUE if NAME has no value. */
SHELL_VAR *
set_if_not (name, value)
     char *name, *value;
{
  SHELL_VAR *v = find_variable (name);

  if (!v)
    v = bind_variable (name, value);
  return (v);
}

/* Map FUNCTION over the variables in VARIABLES.  Return an array of the
   variables that satisfy FUNCTION.  Satisfy means that FUNCTION returns
   a non-zero value for.  A NULL value for FUNCTION means to use all
   variables. */
SHELL_VAR **
map_over (function, var_hash_table)
     Function *function;
     HASH_TABLE* var_hash_table;
{
  register int i;
  register BUCKET_CONTENTS *tlist;
  SHELL_VAR *var, **list = (SHELL_VAR **)NULL;
  int list_index = 0, list_size = 0;

  for (i = 0; i < var_hash_table->nbuckets; i++)
    {
      tlist = get_hash_bucket (i, var_hash_table);

      while (tlist)
	{
	  var = (SHELL_VAR *)tlist->data;

	  if (!function || (*function) (var))
	    {
	      if (list_index + 1 >= list_size)
		list = (SHELL_VAR **)
		  xrealloc (list, (list_size += 20) * sizeof (SHELL_VAR *));

	      list[list_index++] = var;
	      list[list_index] = (SHELL_VAR *)NULL;
	    }
	  tlist = tlist->next;
	}
    }
  return (list);
}

int
qsort_var_comp (var1, var2)
     SHELL_VAR **var1, **var2;
{
  return (strcmp ((*var1)->name, (*var2)->name));
}

sort_variables (array)
     SHELL_VAR **array;
{
  qsort (array, array_len (array), sizeof (SHELL_VAR *), qsort_var_comp);
}

/* Create a NULL terminated array of all the shell variables in TABLE. */
static SHELL_VAR **
all_vars (table)
     HASH_TABLE *table;
{
  SHELL_VAR **list;

  list = map_over ((Function *)NULL, table);
  if (list)
    sort_variables (list);
  return (list);
}

/* Create a NULL terminated array of all the shell variables. */
SHELL_VAR **
all_shell_variables ()
{
  return (all_vars (shell_variables));
}

/* Create a NULL terminated array of all the shell functions. */
SHELL_VAR **
all_shell_functions ()
{
  return (all_vars (shell_functions));
}

/* Print VARS to stdout in such a way that they can be read back in. */
print_var_list (list)
     register SHELL_VAR **list;
{
  register int i;
  register SHELL_VAR *var;

  for (i = 0; list && (var = list[i]); i++)
    if (!invisible_p (var))
      print_assignment (var);
}

#if defined (NOTDEF)
/* Print LIST (a linked list of shell variables) to stdout
   by printing the names, without the values.  Used to support the
   `set +' command. */
print_vars_no_values (list)
     register SHELL_VAR **list;
{
  register int i;
  register SHELL_VAR *var;

  for (i = 0; list && (var = list[i]); i++)
    if (!invisible_p (var))
      printf ("%s\n", var->name);
}
#endif

/* Print the value of a single SHELL_VAR.  No newline is
   output, but the variable is printed in such a way that
   it can be read back in. */
print_assignment (var)
     SHELL_VAR *var;
{
  if (function_p (var) && var->value)
    {
      printf ("%s=", var->name);
      print_var_function (var);
      printf ("\n");
    }
  else if (var->value)
    {
      printf ("%s=", var->name);
      print_var_value (var);
      printf ("\n");
    }
}

/* Print the value cell of VAR, a shell variable.  Do not print
   the name, nor leading/trailing newline. */
print_var_value (var)
     SHELL_VAR *var;
{
  if (var->value)
    printf ("%s", var->value);
}

/* Print the function cell of VAR, a shell variable.  Do not
   print the name, nor leading/trailing newline. */
print_var_function (var)
     SHELL_VAR *var;
{
  char *named_function_string ();

  if (function_p (var) && var->value)
    printf ("%s", named_function_string ((char *)NULL, var->value, 1));
}


/* **************************************************************** */
/*                                                                  */
/*                 Dynamic Variable Extension                       */
/*                                                                  */
/* **************************************************************** */

/* DYNAMIC VARIABLES
   
   These are variables whose values are generated anew each time they are
   referenced.  These are implemented using a pair of function pointers
   in the struct variable: assign_func, which is called from bind_variable,
   and dynamic_value, which is called from find_variable.
   
   assign_func is called from bind_variable, if bind_variable discovers
   that the variable being assigned to has such a function.  The function
   is called as
  	SHELL_VAR *temp = (*(entry->assign_func)) (entry, value)
   and the (SHELL_VAR *)temp is returned as the value of bind_variable.  It
   is usually ENTRY (self).
   
   dynamic_value is called from find_variable to return a `new' value for
   the specified dynamic varible.  If this function is NULL, the variable
   is treated as a `normal' shell variable.  If it is not, however, then
   this function is called like this:
  	tempvar = (*(var->dynamic_value)) (var);
   
   Sometimes `tempvar' will replace the value of `var'.  Other times, the
   shell will simply use the string value.  Pretty object-oriented, huh?
   
   Be warned, though: if you `unset' a special variable, it loses its
   special meaning, even if you subsequently set it.
   
   The special assignment code would probably have been better put in
   subst.c: do_assignment, in the same style as
   stupidly_hack_special_variables, but I wanted the changes as
   localized as possible.  */

/* The value of $SECONDS.  This is the number of seconds since shell
   invocation, or, the number of seconds since the last assignment + the
   value of the last assignment. */
static long seconds_value_assigned = (long)0;

/* Originally defined in shell.c */
extern time_t shell_start_time;

SHELL_VAR *
assign_seconds (self, value)
     SHELL_VAR *self;
     char *value;
{
  seconds_value_assigned = atol (value);
  shell_start_time = NOW;
  return (self);
}

SHELL_VAR *
get_seconds (var)
     SHELL_VAR *var;
{
  extern char *itos ();
  time_t time_since_start;
  char *p;

  time_since_start = NOW - shell_start_time;
  p = itos((int) seconds_value_assigned + time_since_start);

  if (var->value)
    free (var->value);

  var->attributes |= att_integer;
  var->value = p;
  return (var);
}

/* The random number seed.  You can change this by setting RANDOM. */
static unsigned long rseed = 1;

/* A linear congruential random number generator based on the ANSI
   C standard.  A more complicated one is overkill.  */

/* Returns a pseudo-random number between 0 and 32767. */
static int
brand ()
{
  rseed = rseed * 1103515245 + 12345;
  return ((unsigned int)(rseed / 65536) % 32768);
}

/* Set the random number generator seed to SEED. */
static void
sbrand (seed)
     int seed;
{
  rseed = seed;
}

static SHELL_VAR *
assign_random (self, value)
     SHELL_VAR *self;
     char *value;
{
  int s = atoi (value);

  sbrand (s);
  return (self);
}

static SHELL_VAR *
get_random (var)
     SHELL_VAR *var;
{
  int rv;
  char *p;
  extern char *itos ();

  rv = brand ();
  p = itos ((int)rv);
  if (var->value)
    free (var->value);

  var->attributes |= att_integer;
  var->value = p;
  return (var);
}

/* Function which returns the current line number. */
static SHELL_VAR *
get_lineno (var)
     SHELL_VAR *var;
{
  extern int line_number;
  char *p;
  extern char *itos ();

  p = itos (line_number);
  if (var->value)
    free (var->value);
  var->value = p;
  return (var);
}

initialize_dynamic_variables ()
{
  SHELL_VAR *v;

  v = bind_variable ("SECONDS", (char *)NULL);
  v->dynamic_value = get_seconds;
  v->assign_func = assign_seconds;

  v = bind_variable ("RANDOM", (char *)NULL);
  v->dynamic_value = get_random;
  v->assign_func = assign_random;

  v = bind_variable ("LINENO", (char *)NULL);
  v->dynamic_value = get_lineno;
  v->assign_func = (DYNAMIC_FUNC *)NULL;
}

/* How to get a pointer to the shell variable or function named NAME.
   HASHED_VARS is a pointer to the hash table containing the list
   of interest (either variables or functions). */
SHELL_VAR *
var_lookup (name, hashed_vars)
     char *name;
     HASH_TABLE *hashed_vars;
{
  BUCKET_CONTENTS *bucket;

  bucket = find_hash_item (name, hashed_vars);

  if (bucket)
    return ((SHELL_VAR *)bucket->data);
  else
    return ((SHELL_VAR *)NULL);
}

/* Look up the variable entry whose name matches STRING.
   Returns the entry or NULL. */
SHELL_VAR *
find_variable (name)
     char *name;
{
  extern int variable_context;
  extern Function *this_shell_builtin;
  SHELL_VAR *find_tempenv_variable ();
  SHELL_VAR *var = (SHELL_VAR *)NULL;

  /* If we are executing a function or builtin, first look in the
     temporary environment for the variable.  This allows constructs
     such as "foo=x eval 'echo $foo'" to get the `exported' value
     of $foo. */
  if (variable_context || this_shell_builtin)
    var = find_tempenv_variable (name);

  if (!var)
    var = var_lookup (name, shell_variables);

  if (!var)
    return ((SHELL_VAR *)NULL);

  if (var->dynamic_value)
    return ((*(var->dynamic_value)) (var));
  else
    return (var);
}

/* Look up the function entry whose name matches STRING.
   Returns the entry or NULL. */
SHELL_VAR *
find_function (name)
     char *name;
{
  return (var_lookup (name, shell_functions));
}

/* Return the string value of a variable.  Return NULL if the variable
   doesn't exist, or only has a function as a value.  Don't cons a new
   string. */
char *
get_string_value (var_name)
     char *var_name;
{
  SHELL_VAR *var = find_variable (var_name);

  if (!var)
    return (char *)NULL;
  else
    return (var->value);
}

/* Create a local variable referenced by NAME. */
SHELL_VAR *
make_local_variable (name)
     char *name;
{
  SHELL_VAR *new_var, *old_var, *bind_variable ();
  BUCKET_CONTENTS *elt;

  /* local foo; local foo;  is a no-op. */
  old_var = find_variable (name);
  if (old_var && old_var->context == variable_context)
    return (old_var);

  elt = remove_hash_item (name, shell_variables);
  if (elt)
    {
      old_var = (SHELL_VAR *)elt->data;
      free (elt->key);
      free (elt);
    }
  else
    old_var = (SHELL_VAR *)NULL;

  /* If a variable does not already exist with this name, then
     just make a new one. */
  if (!old_var)
    {
      new_var = bind_variable (name, "");
    }
  else
    {
      new_var = (SHELL_VAR *)xmalloc (sizeof (SHELL_VAR));

      new_var->name = savestring (name);
      new_var->value = savestring ("");

      new_var->dynamic_value = (DYNAMIC_FUNC *)NULL;
      new_var->assign_func = (DYNAMIC_FUNC *)NULL;

      new_var->attributes = 0;

      if (exported_p (old_var))
	new_var->attributes |= att_exported;

      new_var->prev_context = old_var;
      elt = add_hash_item (savestring (name), shell_variables);
      elt->data = (char *)new_var;
    }

  new_var->context = variable_context;
  return (new_var);
}

/* Bind a variable NAME to VALUE.  This conses up the name
   and value strings. */
SHELL_VAR *
bind_variable (name, value)
     char *name, *value;
{
  SHELL_VAR *entry = var_lookup (name, shell_variables);

  if (!entry)
    {
      /* Make a new entry for this variable.  Then do the binding. */
      entry = (SHELL_VAR *)xmalloc (sizeof (SHELL_VAR));

      entry->attributes = 0;
      entry->name = savestring (name);

      if (value)
	entry->value = savestring (value);
      else
	entry->value = (char *)NULL;

      entry->dynamic_value = (DYNAMIC_FUNC *)NULL;
      entry->assign_func = (DYNAMIC_FUNC *)NULL;

      /* Always assume variables are to be made at toplevel!
	 make_local_variable has the responsibilty of changing the
	 variable context. */
      entry->context = 0;
      entry->prev_context = (SHELL_VAR *)NULL;

      {
	BUCKET_CONTENTS *elt;

	elt = add_hash_item (savestring (name), shell_variables);
	elt->data = (char *)entry;
      }
    }
  else if (entry->assign_func)
    return ((*(entry->assign_func)) (entry, value));
  else
    {
      if (readonly_p (entry))
	{
	  report_error ("%s: read-only variable", name);
	  return (entry);
	}

      /* If this variable has had its type set to integer (via `declare -i'),
	 then do expression evaluation on it and store the result.  The
	 functions in expr.c (evalexp and bind_int_variable) are responsible
	 for turning off the integer flag if they don't want further
	 evaluation done. */
      if (integer_p (entry))
	{
	  long val, evalexp();
	  extern char *itos();

	  val = evalexp (value);
	  /* We cannot free () entry->value before this; what if the string
	     we are working is `even=even+2'?  We need the original value
	     around while we are doing the evaluation to handle any possible
	     recursion. */
	  if (entry->value)
	    free (entry->value);

	  entry->value = itos (val);
	}
      else
	{
	  if (entry->value)
	    free (entry->value);

	  if (value)
	    entry->value = savestring (value);
	  else
	    entry->value = (char *)NULL;
	}
    }

  if (mark_modified_vars)
    entry->attributes |= att_exported;

  if (exported_p (entry))
    array_needs_making = 1;

  return (entry);
}

/* Dispose of the information attached to VAR. */
dispose_variable (var)
     SHELL_VAR *var;
{
  if (!var)
    return;

  if (function_p (var))
    dispose_command (var->value);
  else if (var->value)
    free (var->value);

  free (var->name);

  if (exported_p (var))
    array_needs_making = 1;

  free (var);
}

/* Unset the variable referenced by NAME. */
unbind_variable (name)
     char *name;
{
  SHELL_VAR *var = find_variable (name);

  if (!var)
    return (-1);

  if (var->value)
    {
      free (var->value);
      var->value = (char *)NULL;
    }

  makunbound (name, shell_variables);

  return (0);
}

/* Make the variable associated with NAME go away.  HASH_LIST is the
   hash table from which this variable should be deleted (either
   shell_variables or shell_functions).
   Returns non-zero if the variable couldn't be found. */
makunbound (name, hash_list)
     char *name;
     HASH_TABLE *hash_list;
{
  BUCKET_CONTENTS *elt;
  SHELL_VAR *old_var, *new_var;

  elt = remove_hash_item (name, hash_list);

  if (!elt)
    return (-1);

  old_var = (SHELL_VAR *)elt->data;
  new_var = old_var->prev_context;

  if (old_var && exported_p (old_var))
    array_needs_making++;

  if (new_var)
    {
      /* Has to be a variable, functions don't have previous contexts. */
      BUCKET_CONTENTS *new_elt;

      new_elt = add_hash_item (savestring (new_var->name), hash_list);
      new_elt->data = (char *)new_var;

      if (exported_p (new_var))
	set_var_auto_export (new_var->name);
    }

  free (elt->key);
  free (elt);

  dispose_variable (old_var);
  stupidly_hack_special_variables (name);
  return (0);
}

/* Remove the variable with NAME if it is a local variable in the
   current context. */
kill_local_variable (name)
     char *name;
{
  SHELL_VAR *temp = find_variable (name);

  if (temp && (temp->context == variable_context))
    {
      makunbound (name, shell_variables);
      return (0);
    }
  return (-1);
}

/* Get rid of all of the variables in the current context. */
int
variable_in_context (var)
     SHELL_VAR *var;
{
  return (var && var->context == variable_context);
}

kill_all_local_variables ()
{
  register int i, pass;
  register SHELL_VAR *var, **list;
  HASH_TABLE *varlist;

  for (pass = 0; pass < 2; pass++)
    {
      varlist = pass ? shell_functions : shell_variables;

      list = map_over (variable_in_context, varlist);

      if (list)
	{
	  for (i = 0; var = list[i]; i++)
	    makunbound (var->name, varlist);

	  free (list);
	}
    }
}

/* Delete the entire contents of the hash table. */
delete_all_variables (hashed_vars)
     HASH_TABLE *hashed_vars;
{
  register int i;
  register BUCKET_CONTENTS *bucket;

  for (i = 0; i < hashed_vars->nbuckets; i++)
    {
      bucket = hashed_vars->bucket_array[i];

      while (bucket)
	{
	  BUCKET_CONTENTS *temp = bucket;
	  SHELL_VAR *var, *prev;

	  bucket = bucket->next;

	  var = (SHELL_VAR *)temp->data;

	  while (var)
	    {
	      prev = var->prev_context;
	      dispose_variable (var);

	      var = prev;
	    }

	  free (temp->key);
	  free (temp);
	}
      hashed_vars->bucket_array[i] = (BUCKET_CONTENTS *)NULL;
    }
}

SHELL_VAR *
new_shell_variable (name)
     char *name;
{
  SHELL_VAR *var;

  var = (SHELL_VAR *)xmalloc (sizeof (SHELL_VAR));

  bzero (var, sizeof (SHELL_VAR));
  var->name = savestring (name);
  return (var);
}

/* Do a function binding to a variable.  You pass the name and
   the command to bind to.  This conses the name and command. */
SHELL_VAR *
bind_function (name, value)
     char *name;
     COMMAND *value;
{
  SHELL_VAR *entry = find_function (name);

  if (!entry)
    {
      BUCKET_CONTENTS *elt;

      elt = add_hash_item (savestring (name), shell_functions);

      elt->data = (char *)new_shell_variable (name);
      entry = (SHELL_VAR *)elt->data;
      entry->dynamic_value = (DYNAMIC_FUNC *)NULL;
      entry->assign_func = (DYNAMIC_FUNC *)NULL;

      /* Functions are always made at the top level.  This allows a
	 function to define another function (like autoload). */
      entry->context = 0;
    }

  if (entry->value)
    dispose_command (entry->value);

  if (value)	/* I don't think this can happen anymore */
    entry->value = (char *)copy_command (value);
  else
    entry->value = (char *)NULL;

  entry->attributes |= att_function;

  if (mark_modified_vars)
    entry->attributes |= att_exported;

  entry->attributes &= ~att_invisible;	/* Just to be sure */

  array_needs_making = 1;

  return (entry);
}

/* Copy VAR to a new data structure and return that structure. */
SHELL_VAR *
copy_variable (var)
     SHELL_VAR *var;
{
  SHELL_VAR *copy = (SHELL_VAR *)NULL;

  if (var)
    {
      copy = (SHELL_VAR *)xmalloc (sizeof (SHELL_VAR));

      copy->attributes = var->attributes;
      copy->name = savestring (var->name);

      if (function_p (var))
	copy->value = (char *)copy_command (var->value);
      else if (var->value)
	copy->value = savestring (var->value);
      else
	copy->value = (char *)NULL;

      copy->dynamic_value = var->dynamic_value;
      copy->assign_func = var->assign_func;

      copy->context = var->context;

      /* Don't bother copying previous contexts along with this variable. */
      copy->prev_context = (SHELL_VAR *)NULL;
    }
  return (copy);
}

/* Make the variable associated with NAME be read-only.
   If NAME does not exist yet, create it. */
set_var_read_only (name)
     char *name;
{
  SHELL_VAR *entry = find_variable (name);

  if (!entry)
    {
      entry = bind_variable (name, "");
      if (!no_invisible_vars)
	entry->attributes |= att_invisible;
    }
  entry->attributes |= att_readonly;
}

/* Make the function associated with NAME be read-only.
   If NAME does not exist, we just punt, like auto_export code below. */
set_func_read_only (name)
     char *name;
{
  SHELL_VAR *entry = find_function (name);

  if (entry)
    entry->attributes |= att_readonly;
}

/* Make the variable associated with NAME be auto-exported.
   If NAME does not exist yet, create it. */
set_var_auto_export (name)
     char *name;
{
  SHELL_VAR *entry = find_variable (name);

  if (!entry)
    {
      entry = bind_variable (name, "");
      if (!no_invisible_vars)
	entry->attributes |= att_invisible;
    }

  set_auto_export (entry);
}

/* Make the function associated with NAME be auto-exported. */
set_func_auto_export (name)
     char *name;
{
  SHELL_VAR *entry = find_function (name);

  if (entry)
    {
      entry->attributes |= att_exported;
      array_needs_making = 1;
    }
}

/* Returns non-zero if STRING is an assignment statement.  The returned value
   is the index of the `=' sign. */
assignment (string)
     char *string;
{
  register int c, index = 0;

  c = string[index];

  if (!isletter (c) && c != '_')
    return (0);

  while (c = string[index])
    {
      /* The following is safe.  Note that '=' at the start of a word
	 is not an assignment statement. */
      if (c == '=')
	return (index);

      if (!isletter (c) && !digit (c) && c != '_')
	return (0);

      index++;
    }
  return (0);
}

int
visible_var (var)
     SHELL_VAR *var;
{
  return (!invisible_p (var));
}

SHELL_VAR **
all_visible_variables ()
{
  SHELL_VAR **list;

  list = map_over (visible_var, shell_variables);

  if (list)
    sort_variables (list);

  return (list);
}

SHELL_VAR **
all_visible_functions ()
{
  SHELL_VAR **list;

  list = map_over (visible_var, shell_functions);

  if (list)
    sort_variables (list);

  return (list);
}

/* Return non-zero if the variable VAR is visible and exported. */
int
visible_and_exported (var)
     SHELL_VAR *var;
{
  return (!invisible_p (var) && exported_p (var));
}

/* Make an array of assignment statements from the hash table
   HASHED_VARS which contains SHELL_VARs.  Only visible, exported
   variables are eligible. */
char **
make_var_array (hashed_vars)
     HASH_TABLE *hashed_vars;
{
  register int i, list_index;
  register SHELL_VAR *var;
  char **list = (char **)NULL;
  SHELL_VAR **vars;

  vars = map_over (visible_and_exported, hashed_vars);

  if (!vars)
    return (char **)NULL;

  list = (char **)xmalloc ((1 + array_len ((char **)vars)) * sizeof (char *));

  for (i = 0, list_index = 0; var = vars[i]; i++)
    {
      char *value, *named_function_string ();

      if (function_p (var))
	{
	  value =
	    named_function_string ((char *)NULL,
				   (COMMAND *)function_cell (var), 0);
	}
      else
	value = value_cell (var);

      if (value)
	{
#if 0
	  list[list_index] =
	    (char *)xmalloc (2 + strlen (var->name) + strlen (value));

	  sprintf (list[list_index], "%s=%s", var->name, value);
#else
	  /* Let's see if this makes any kind of performance difference. */
	  int name_len = strlen (var->name);
	  int value_len = strlen (value);
	  char	*p;

	  p = list[list_index] =  (char *)xmalloc (2 + name_len + value_len);
	  strcpy (p, var->name);
	  p[name_len] = '=';
	  strcpy (&p[name_len + 1], value);
#endif
	  list_index++;
	}
    }

  free (vars);
  list[list_index] = (char *)NULL;
  return (list);
}

/* Add STRING to the array of foo=bar strings that we already
   have to add to the environment.  */
assign_in_env (string)
     char *string;
{
  int size;

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

  if (name[offset] == '=')
    {
      char *tilde_expand (), *string_list ();
      WORD_LIST *list, *expand_string_unsplit ();

      name[offset] = 0;
      temp = name + offset + 1;
      temp = tilde_expand (temp);

      list = expand_string_unsplit (temp, 0);
      value = string_list (list);

      if (list)
	dispose_words (list);

      free (temp);
    }

  if (!value) value = savestring ("");

  temp = (char *)xmalloc (2 + strlen (name) + strlen (value));
  sprintf (temp, "%s=%s", name, value);
  free (name);

  if (!temporary_env)
    {
      temporary_env = (char **)xmalloc (sizeof (char *));
      temporary_env [0] = (char *)NULL;
    }

  size = array_len (temporary_env);
  temporary_env = (char **)
    xrealloc (temporary_env, (size + 2) * (sizeof (char *)));

  temporary_env[size] = (temp);
  temporary_env[size + 1] = (char *)NULL;
  array_needs_making = 1;

  if (echo_command_at_execute)
    {
      /* The K*rn shell prints the `+ ' in front of assignment statements,
	 so we do too. */
      extern char *indirection_level_string ();
      fprintf (stderr, "%s%s\n", indirection_level_string (), temp);
      fflush (stderr);
    }
}

/* Find a variable in the temporary environment that is named NAME.
   Return a consed variable, or NULL if not found. */
SHELL_VAR *
find_tempenv_variable (name)
     char *name;
{
  register int i, l = strlen (name);

  if (!temporary_env)
    return ((SHELL_VAR *)NULL);

  for (i = 0; temporary_env[i]; i++)
    {
      if (strncmp (temporary_env[i], name, l) == 0 &&
	  temporary_env[i][l] == '=')
	{
	  SHELL_VAR *temp;

	  temp = new_shell_variable (name);

	  if (temporary_env[i][l + 1])
	    temp->value = savestring (&temporary_env[i][l + 1]);
	  else
	    temp->value = savestring ("");
	  temp->attributes = att_exported;
	  temp->context = 0;
	  temp->prev_context = (SHELL_VAR *)NULL;

	  temp->dynamic_value = (DYNAMIC_FUNC *)NULL;
	  temp->assign_func = (DYNAMIC_FUNC *)NULL;

	  return (temp);
	}
    }
  return ((SHELL_VAR *)NULL);
}

/* Free the storage used in the variable array for temporary
   environment variables. */
dispose_used_env_vars ()
{
  if (!temporary_env)
    return;

  free_array (temporary_env);
  temporary_env = (char **)NULL;
  array_needs_making = 1;
}

/* Stupid comparison routine for qsort () ing strings. */
int
qsort_string_compare (s1, s2)
     register char **s1, **s2;
{
  return (strcmp (*s1, *s2));
}

/* Sort ARRAY, a null terminated array of pointers to strings. */
sort_char_array (array)
     char **array;
{
  qsort (array, array_len (array), sizeof (char *), qsort_string_compare);
}

#define ISFUNC(s, o) ((s[o + 1] == '(')  && (s[o + 2] == ')'))

/* Add ASSIGN to ARRAY, or supercede a previous assignment in the
   array with the same left-hand side.  Return the new array. */
char **
add_or_supercede (assign, array)
     char *assign;
     register char **array;
{
  register int i;
  int equal_offset = assignment (assign);

  if (!equal_offset)
    return (array);

  /* If this is a function, then only supercede the function definition.
     We do this by including the `=(' in the comparison.  */
  if (assign[equal_offset + 1] == '(')
    equal_offset++;

  for (i = 0; array[i]; i++)
    {
      if (STREQN (assign, array[i], equal_offset + 1))
	{
	  free (array[i]);
	  array[i] = savestring (assign);
	  return (array);
	}
    }
  array = (char **)xrealloc (array, ((2 + i) * sizeof (char *)));
  array[i++] = savestring (assign);
  array[i] = (char *)NULL;
  return (array);
}

/* Make the environment array for the command about to be executed.  If the
   array needs making.  Otherwise, do nothing.  If a shell action could
   change the array that commands receive for their environment, then the
   code should `array_needs_making++'. */
maybe_make_export_env ()
{
  register int i;
  register char **temp_array;

  if (array_needs_making)
    {
      if (export_env)
	free_array (export_env);

#ifdef SHADOWED_ENV
      export_env =
	(char **)xmalloc ((1 + array_len (shell_environment)) * sizeof (char *));

      for (i = 0; shell_environment[i]; i++)
	export_env[i] = savestring (shell_environment[i]);
      export_env[i] = (char *)NULL;

#else /* !SHADOWED_ENV */

      export_env = (char **)xmalloc (sizeof (char *));
      export_env[0] = (char *)NULL;

#endif /* SHADOWED_ENV */

      temp_array = make_var_array (shell_variables);
      for (i = 0; temp_array && temp_array[i]; i++)
	export_env = add_or_supercede (temp_array[i], export_env);
      free_array (temp_array);

      temp_array = make_var_array (shell_functions);
      for (i = 0; temp_array && temp_array[i]; i++)
	export_env = add_or_supercede (temp_array[i], export_env);
      free_array (temp_array);

      if (temporary_env)
	{
	  for (i = 0; temporary_env[i]; i++)
	    export_env = add_or_supercede (temporary_env[i], export_env);

	  /* Sort the array alphabetically. */
	  sort_char_array (export_env);
	}
      array_needs_making = 0;
    }
}

/* We always put _ in the environment as the name of this command. */
put_command_name_into_env (command_name)
     char *command_name;
{
  char *dummy;

  dummy = (char *)xmalloc (4 + strlen (command_name));

  /* These three statements replace a call to sprintf */
  dummy[0] = '_';
  dummy[1] = '=';
  strcpy (&dummy[2], command_name);
  export_env = add_or_supercede (dummy, export_env);
  free (dummy);
}

/* We supply our own version of getenv () because we want library
   routines to get the changed values of exported variables. */
char *last_tempenv_value = (char *)NULL;

/* The NeXT C library has getenv () defined and used in the same file.
   This screws our scheme.  However, Bash will run on the NeXT using
   the C library getenv (), since right now the only environment variable
   that we care about is HOME, and that is already defined.  */
#if defined (__STDC__)
#  define _CONST_HACK const
#else
#  define _CONST_HACK
#endif /* !__STDC__ */

#if !defined (NeXT)
char *
getenv (name)
     char _CONST_HACK *name;
{
  SHELL_VAR *var = find_tempenv_variable (name);

  if (var)
    {
      if (last_tempenv_value)
	free (last_tempenv_value);

      last_tempenv_value = savestring (value_cell (var));
      dispose_variable (var);
      return (last_tempenv_value);
    }
  else if (shell_variables)
    {
      var = find_variable (name);
      if (var && exported_p (var))
	return (value_cell (var));
    }
  else
    {
      register int i, len = strlen (name);
      extern char **environ;

      /* In some cases, s5r3 invokes getenv() before main(); BSD systems
         using gprof also exhibit this behavior.  This means that
         shell_variables will be 0 when this is invoked.  We look up the
	 variable in the real environment in that case. */

      for (i = 0; environ[i]; i++)
	{
	  if ((strncmp (environ[i], name, len) == 0) &&
	      (environ[i][len] == '='))
	    return (environ[i] + len + 1);
	}
    }

  return ((char *)NULL);
}
#endif /* NeXT */