shell/hush.c

/* vi: set sw=4 ts=4: */
/*
 * A prototype Bourne shell grammar parser.
 * Intended to follow the original Thompson and Ritchie
 * "small and simple is beautiful" philosophy, which
 * incidentally is a good match to today's BusyBox.
 *
 * Copyright (C) 2000,2001  Larry Doolittle <larry@doolittle.boa.org>
 * Copyright (C) 2008,2009  Denys Vlasenko <vda.linux@googlemail.com>
 *
 * Credits:
 *      The parser routines proper are all original material, first
 *      written Dec 2000 and Jan 2001 by Larry Doolittle.  The
 *      execution engine, the builtins, and much of the underlying
 *      support has been adapted from busybox-0.49pre's lash, which is
 *      Copyright (C) 1999-2004 by Erik Andersen <andersen@codepoet.org>
 *      written by Erik Andersen <andersen@codepoet.org>.  That, in turn,
 *      is based in part on ladsh.c, by Michael K. Johnson and Erik W.
 *      Troan, which they placed in the public domain.  I don't know
 *      how much of the Johnson/Troan code has survived the repeated
 *      rewrites.
 *
 * Other credits:
 *      o_addchr derived from similar w_addchar function in glibc-2.2.
 *      parse_redirect, redirect_opt_num, and big chunks of main
 *      and many builtins derived from contributions by Erik Andersen.
 *      Miscellaneous bugfixes from Matt Kraai.
 *
 * There are two big (and related) architecture differences between
 * this parser and the lash parser.  One is that this version is
 * actually designed from the ground up to understand nearly all
 * of the Bourne grammar.  The second, consequential change is that
 * the parser and input reader have been turned inside out.  Now,
 * the parser is in control, and asks for input as needed.  The old
 * way had the input reader in control, and it asked for parsing to
 * take place as needed.  The new way makes it much easier to properly
 * handle the recursion implicit in the various substitutions, especially
 * across continuation lines.
 *
 * POSIX syntax not implemented:
 *      aliases
 *      <(list) and >(list) Process Substitution
 *      Tilde Expansion
 *
 * Bash stuff (optionally enabled):
 *      &> and >& redirection of stdout+stderr
 *      Brace Expansion
 *      reserved words: [[ ]] function select
 *      substrings ${var:1:5}
 *      let EXPR [EXPR...]
 *        Each EXPR is an arithmetic expression (ARITHMETIC EVALUATION)
 *        If the last arg evaluates to 0, let returns 1; 0 otherwise.
 *        NB: let `echo 'a=a + 1'` - error (IOW: multi-word expansion is used)
 *      ((EXPR))
 *        The EXPR is evaluated according to ARITHMETIC EVALUATION.
 *        This is exactly equivalent to let "expression".
 *
 * TODOs:
 *      grep for "TODO" and fix (some of them are easy)
 *      builtins: ulimit
 *      special variables (PWD etc)
 *      follow IFS rules more precisely, including update semantics
 *      export builtin should be special, its arguments are assignments
 *          and therefore expansion of them should be "one-word" expansion:
 *              $ export i=`echo 'a  b'` # export has one arg: "i=a  b"
 *          compare with:
 *              $ ls i=`echo 'a  b'`     # ls has two args: "i=a" and "b"
 *              ls: cannot access i=a: No such file or directory
 *              ls: cannot access b: No such file or directory
 *          Note1: same applies to local builtin.
 *          Note2: bash 3.2.33(1) does this only if export word itself
 *          is not quoted:
 *              $ export i=`echo 'aaa  bbb'`; echo "$i"
 *              aaa  bbb
 *              $ "export" i=`echo 'aaa  bbb'`; echo "$i"
 *              aaa
 *
 * Licensed under the GPL v2 or later, see the file LICENSE in this tarball.
 */
#include "busybox.h"  /* for APPLET_IS_NOFORK/NOEXEC */
#include <glob.h>
/* #include <dmalloc.h> */
#if ENABLE_HUSH_CASE
# include <fnmatch.h>
#endif
#include "math.h"
#include "match.h"
#ifndef PIPE_BUF
# define PIPE_BUF 4096  /* amount of buffering in a pipe */
#endif


/* Build knobs */
#define LEAK_HUNTING 0
#define BUILD_AS_NOMMU 0
/* Enable/disable sanity checks. Ok to enable in production,
 * only adds a bit of bloat. Set to >1 to get non-production level verbosity.
 * Keeping 1 for now even in released versions.
 */
#define HUSH_DEBUG 1
/* Slightly bigger (+200 bytes), but faster hush.
 * So far it only enables a trick with counting SIGCHLDs and forks,
 * which allows us to do fewer waitpid's.
 * (we can detect a case where neither forks were done nor SIGCHLDs happened
 * and therefore waitpid will return the same result as last time)
 */
#define ENABLE_HUSH_FAST 0


#if BUILD_AS_NOMMU
# undef BB_MMU
# undef USE_FOR_NOMMU
# undef USE_FOR_MMU
# define BB_MMU 0
# define USE_FOR_NOMMU(...) __VA_ARGS__
# define USE_FOR_MMU(...)
#endif

#if defined SINGLE_APPLET_MAIN
/* STANDALONE does not make sense, and won't compile */
# undef CONFIG_FEATURE_SH_STANDALONE
# undef ENABLE_FEATURE_SH_STANDALONE
# undef IF_FEATURE_SH_STANDALONE
# define IF_FEATURE_SH_STANDALONE(...)
# define IF_NOT_FEATURE_SH_STANDALONE(...) __VA_ARGS__
# define ENABLE_FEATURE_SH_STANDALONE 0
#endif

#if !ENABLE_HUSH_INTERACTIVE
# undef ENABLE_FEATURE_EDITING
# define ENABLE_FEATURE_EDITING 0
# undef ENABLE_FEATURE_EDITING_FANCY_PROMPT
# define ENABLE_FEATURE_EDITING_FANCY_PROMPT 0
#endif

/* Do we support ANY keywords? */
#if ENABLE_HUSH_IF || ENABLE_HUSH_LOOPS || ENABLE_HUSH_CASE
# define HAS_KEYWORDS 1
# define IF_HAS_KEYWORDS(...) __VA_ARGS__
# define IF_HAS_NO_KEYWORDS(...)
#else
# define HAS_KEYWORDS 0
# define IF_HAS_KEYWORDS(...)
# define IF_HAS_NO_KEYWORDS(...) __VA_ARGS__
#endif

/* If you comment out one of these below, it will be #defined later
 * to perform debug printfs to stderr: */
#define debug_printf(...)        do {} while (0)
/* Finer-grained debug switches */
#define debug_printf_parse(...)  do {} while (0)
#define debug_print_tree(a, b)   do {} while (0)
#define debug_printf_exec(...)   do {} while (0)
#define debug_printf_env(...)    do {} while (0)
#define debug_printf_jobs(...)   do {} while (0)
#define debug_printf_expand(...) do {} while (0)
#define debug_printf_glob(...)   do {} while (0)
#define debug_printf_list(...)   do {} while (0)
#define debug_printf_subst(...)  do {} while (0)
#define debug_printf_clean(...)  do {} while (0)

#define ERR_PTR ((void*)(long)1)

#define JOB_STATUS_FORMAT "[%d] %-22s %.40s\n"

#define SPECIAL_VAR_SYMBOL 3

struct variable;

static const char hush_version_str[] ALIGN1 = "HUSH_VERSION="BB_VER;

/* This supports saving pointers malloced in vfork child,
 * to be freed in the parent.
 */
#if !BB_MMU
typedef struct nommu_save_t {
	char **new_env;
	struct variable *old_vars;
	char **argv;
	char **argv_from_re_execing;
} nommu_save_t;
#endif

typedef enum reserved_style {
	RES_NONE  = 0,
#if ENABLE_HUSH_IF
	RES_IF    ,
	RES_THEN  ,
	RES_ELIF  ,
	RES_ELSE  ,
	RES_FI    ,
#endif
#if ENABLE_HUSH_LOOPS
	RES_FOR   ,
	RES_WHILE ,
	RES_UNTIL ,
	RES_DO    ,
	RES_DONE  ,
#endif
#if ENABLE_HUSH_LOOPS || ENABLE_HUSH_CASE
	RES_IN    ,
#endif
#if ENABLE_HUSH_CASE
	RES_CASE  ,
	/* three pseudo-keywords support contrived "case" syntax: */
	RES_CASE_IN,   /* "case ... IN", turns into RES_MATCH when IN is observed */
	RES_MATCH ,    /* "word)" */
	RES_CASE_BODY, /* "this command is inside CASE" */
	RES_ESAC  ,
#endif
	RES_XXXX  ,
	RES_SNTX
} reserved_style;

typedef struct o_string {
	char *data;
	int length; /* position where data is appended */
	int maxlen;
	/* Protect newly added chars against globbing
	 * (by prepending \ to *, ?, [, \) */
	smallint o_escape;
	smallint o_glob;
	/* At least some part of the string was inside '' or "",
	 * possibly empty one: word"", wo''rd etc. */
	smallint o_quoted;
	smallint has_empty_slot;
	smallint o_assignment; /* 0:maybe, 1:yes, 2:no */
} o_string;
enum {
	MAYBE_ASSIGNMENT = 0,
	DEFINITELY_ASSIGNMENT = 1,
	NOT_ASSIGNMENT = 2,
	WORD_IS_KEYWORD = 3, /* not assigment, but next word may be: "if v=xyz cmd;" */
};
/* Used for initialization: o_string foo = NULL_O_STRING; */
#define NULL_O_STRING { NULL }

/* I can almost use ordinary FILE*.  Is open_memstream() universally
 * available?  Where is it documented? */
typedef struct in_str {
	const char *p;
	/* eof_flag=1: last char in ->p is really an EOF */
	char eof_flag; /* meaningless if ->p == NULL */
	char peek_buf[2];
#if ENABLE_HUSH_INTERACTIVE
	smallint promptme;
	smallint promptmode; /* 0: PS1, 1: PS2 */
#endif
	FILE *file;
	int (*get) (struct in_str *) FAST_FUNC;
	int (*peek) (struct in_str *) FAST_FUNC;
} in_str;
#define i_getch(input) ((input)->get(input))
#define i_peek(input) ((input)->peek(input))

/* The descrip member of this structure is only used to make
 * debugging output pretty */
static const struct {
	int mode;
	signed char default_fd;
	char descrip[3];
} redir_table[] = {
	{ O_RDONLY,                  0, "<"  },
	{ O_CREAT|O_TRUNC|O_WRONLY,  1, ">"  },
	{ O_CREAT|O_APPEND|O_WRONLY, 1, ">>" },
	{ O_CREAT|O_RDWR,            1, "<>" },
	{ O_RDONLY,                  0, "<<" },
/* Should not be needed. Bogus default_fd helps in debugging */
/*	{ O_RDONLY,                 77, "<<" }, */
};

struct redir_struct {
	struct redir_struct *next;
	char *rd_filename;          /* filename */
	int rd_fd;                  /* fd to redirect */
	/* fd to redirect to, or -3 if rd_fd is to be closed (n>&-) */
	int rd_dup;
	smallint rd_type;           /* (enum redir_type) */
	/* note: for heredocs, rd_filename contains heredoc delimiter,
	 * and subsequently heredoc itself; and rd_dup is a bitmask:
	 * bit 0: do we need to trim leading tabs?
	 * bit 1: is heredoc quoted (<<'delim' syntax) ?
	 */
};
typedef enum redir_type {
	REDIRECT_INPUT     = 0,
	REDIRECT_OVERWRITE = 1,
	REDIRECT_APPEND    = 2,
	REDIRECT_IO        = 3,
	REDIRECT_HEREDOC   = 4,
	REDIRECT_HEREDOC2  = 5, /* REDIRECT_HEREDOC after heredoc is loaded */

	REDIRFD_CLOSE      = -3,
	REDIRFD_SYNTAX_ERR = -2,
	REDIRFD_TO_FILE    = -1,
	/* otherwise, rd_fd is redirected to rd_dup */

	HEREDOC_SKIPTABS = 1,
	HEREDOC_QUOTED   = 2,
} redir_type;


struct command {
	pid_t pid;                  /* 0 if exited */
	int assignment_cnt;         /* how many argv[i] are assignments? */
	smallint is_stopped;        /* is the command currently running? */
	smallint cmd_type;          /* CMD_xxx */
#define CMD_NORMAL   0
#define CMD_SUBSHELL 1

/* used for "[[ EXPR ]]" */
#if ENABLE_HUSH_BASH_COMPAT
# define CMD_SINGLEWORD_NOGLOB 2
#endif

/* used for "export noglob=* glob* a=`echo a b`" */
//#define CMD_SINGLEWORD_NOGLOB_COND 3
// It is hard to implement correctly, it adds significant amounts of tricky code,
// and all this is only useful for really obscure export statements
// almost nobody would use anyway. #ifdef CMD_SINGLEWORD_NOGLOB_COND
// guards the code which implements it, but I have doubts it works
// in all cases (especially with mixed globbed/non-globbed arguments)

#if ENABLE_HUSH_FUNCTIONS
# define CMD_FUNCDEF 3
#endif

	/* if non-NULL, this "command" is { list }, ( list ), or a compound statement */
	struct pipe *group;
#if !BB_MMU
	char *group_as_string;
#endif
#if ENABLE_HUSH_FUNCTIONS
	struct function *child_func;
/* This field is used to prevent a bug here:
 * while...do f1() {a;}; f1; f1() {b;}; f1; done
 * When we execute "f1() {a;}" cmd, we create new function and clear
 * cmd->group, cmd->group_as_string, cmd->argv[0].
 * When we execute "f1() {b;}", we notice that f1 exists,
 * and that its "parent cmd" struct is still "alive",
 * we put those fields back into cmd->xxx
 * (struct function has ->parent_cmd ptr to facilitate that).
 * When we loop back, we can execute "f1() {a;}" again and set f1 correctly.
 * Without this trick, loop would execute a;b;b;b;...
 * instead of correct sequence a;b;a;b;...
 * When command is freed, it severs the link
 * (sets ->child_func->parent_cmd to NULL).
 */
#endif
	char **argv;                /* command name and arguments */
/* argv vector may contain variable references (^Cvar^C, ^C0^C etc)
 * and on execution these are substituted with their values.
 * Substitution can make _several_ words out of one argv[n]!
 * Example: argv[0]=='.^C*^C.' here: echo .$*.
 * References of the form ^C`cmd arg^C are `cmd arg` substitutions.
 */
	struct redir_struct *redirects; /* I/O redirections */
};
/* Is there anything in this command at all? */
#define IS_NULL_CMD(cmd) \
	(!(cmd)->group && !(cmd)->argv && !(cmd)->redirects)


struct pipe {
	struct pipe *next;
	int num_cmds;               /* total number of commands in pipe */
	int alive_cmds;             /* number of commands running (not exited) */
	int stopped_cmds;           /* number of commands alive, but stopped */
#if ENABLE_HUSH_JOB
	int jobid;                  /* job number */
	pid_t pgrp;                 /* process group ID for the job */
	char *cmdtext;              /* name of job */
#endif
	struct command *cmds;       /* array of commands in pipe */
	smallint followup;          /* PIPE_BG, PIPE_SEQ, PIPE_OR, PIPE_AND */
	IF_HAS_KEYWORDS(smallint pi_inverted;) /* "! cmd | cmd" */
	IF_HAS_KEYWORDS(smallint res_word;) /* needed for if, for, while, until... */
};
typedef enum pipe_style {
	PIPE_SEQ = 1,
	PIPE_AND = 2,
	PIPE_OR  = 3,
	PIPE_BG  = 4,
} pipe_style;
/* Is there anything in this pipe at all? */
#define IS_NULL_PIPE(pi) \
	((pi)->num_cmds == 0 IF_HAS_KEYWORDS( && (pi)->res_word == RES_NONE))

/* This holds pointers to the various results of parsing */
struct parse_context {
	/* linked list of pipes */
	struct pipe *list_head;
	/* last pipe (being constructed right now) */
	struct pipe *pipe;
	/* last command in pipe (being constructed right now) */
	struct command *command;
	/* last redirect in command->redirects list */
	struct redir_struct *pending_redirect;
#if !BB_MMU
	o_string as_string;
#endif
#if HAS_KEYWORDS
	smallint ctx_res_w;
	smallint ctx_inverted; /* "! cmd | cmd" */
#if ENABLE_HUSH_CASE
	smallint ctx_dsemicolon; /* ";;" seen */
#endif
	/* bitmask of FLAG_xxx, for figuring out valid reserved words */
	int old_flag;
	/* group we are enclosed in:
	 * example: "if pipe1; pipe2; then pipe3; fi"
	 * when we see "if" or "then", we malloc and copy current context,
	 * and make ->stack point to it. then we parse pipeN.
	 * when closing "then" / fi" / whatever is found,
	 * we move list_head into ->stack->command->group,
	 * copy ->stack into current context, and delete ->stack.
	 * (parsing of { list } and ( list ) doesn't use this method)
	 */
	struct parse_context *stack;
#endif
};

/* On program start, environ points to initial environment.
 * putenv adds new pointers into it, unsetenv removes them.
 * Neither of these (de)allocates the strings.
 * setenv allocates new strings in malloc space and does putenv,
 * and thus setenv is unusable (leaky) for shell's purposes */
#define setenv(...) setenv_is_leaky_dont_use()
struct variable {
	struct variable *next;
	char *varstr;        /* points to "name=" portion */
#if ENABLE_HUSH_LOCAL
	unsigned func_nest_level;
#endif
	int max_len;         /* if > 0, name is part of initial env; else name is malloced */
	smallint flg_export; /* putenv should be done on this var */
	smallint flg_read_only;
};

enum {
	BC_BREAK = 1,
	BC_CONTINUE = 2,
};

#if ENABLE_HUSH_FUNCTIONS
struct function {
	struct function *next;
	char *name;
	struct command *parent_cmd;
	struct pipe *body;
#if !BB_MMU
	char *body_as_string;
#endif
};
#endif


/* "Globals" within this file */
/* Sorted roughly by size (smaller offsets == smaller code) */
struct globals {
	/* interactive_fd != 0 means we are an interactive shell.
	 * If we are, then saved_tty_pgrp can also be != 0, meaning
	 * that controlling tty is available. With saved_tty_pgrp == 0,
	 * job control still works, but terminal signals
	 * (^C, ^Z, ^Y, ^\) won't work at all, and background
	 * process groups can only be created with "cmd &".
	 * With saved_tty_pgrp != 0, hush will use tcsetpgrp()
	 * to give tty to the foreground process group,
	 * and will take it back when the group is stopped (^Z)
	 * or killed (^C).
	 */
#if ENABLE_HUSH_INTERACTIVE
	/* 'interactive_fd' is a fd# open to ctty, if we have one
	 * _AND_ if we decided to act interactively */
	int interactive_fd;
	const char *PS1;
	const char *PS2;
# define G_interactive_fd (G.interactive_fd)
#else
# define G_interactive_fd 0
#endif
#if ENABLE_FEATURE_EDITING
	line_input_t *line_input_state;
#endif
	pid_t root_pid;
	pid_t last_bg_pid;
#if ENABLE_HUSH_JOB
	int run_list_level;
	int last_jobid;
	pid_t saved_tty_pgrp;
	struct pipe *job_list;
# define G_saved_tty_pgrp (G.saved_tty_pgrp)
#else
# define G_saved_tty_pgrp 0
#endif
	smallint flag_SIGINT;
#if ENABLE_HUSH_LOOPS
	smallint flag_break_continue;
#endif
#if ENABLE_HUSH_FUNCTIONS
	/* 0: outside of a function (or sourced file)
	 * -1: inside of a function, ok to use return builtin
	 * 1: return is invoked, skip all till end of func
	 */
	smallint flag_return_in_progress;
#endif
	smallint fake_mode;
	smallint exiting; /* used to prevent EXIT trap recursion */
	/* These four support $?, $#, and $1 */
	smalluint last_exitcode;
	/* are global_argv and global_argv[1..n] malloced? (note: not [0]) */
	smalluint global_args_malloced;
	/* how many non-NULL argv's we have. NB: $# + 1 */
	int global_argc;
	char **global_argv;
#if !BB_MMU
	char *argv0_for_re_execing;
#endif
#if ENABLE_HUSH_LOOPS
	unsigned depth_break_continue;
	unsigned depth_of_loop;
#endif
	const char *ifs;
	const char *cwd;
	struct variable *top_var; /* = &G.shell_ver (set in main()) */
	struct variable shell_ver;
#if ENABLE_HUSH_FUNCTIONS
	struct function *top_func;
# if ENABLE_HUSH_LOCAL
	struct variable **shadowed_vars_pp;
	unsigned func_nest_level;
# endif
#endif
	/* Signal and trap handling */
#if ENABLE_HUSH_FAST
	unsigned count_SIGCHLD;
	unsigned handled_SIGCHLD;
	smallint we_have_children;
#endif
	/* which signals have non-DFL handler (even with no traps set)? */
	unsigned non_DFL_mask;
	char **traps; /* char *traps[NSIG] */
	sigset_t blocked_set;
	sigset_t inherited_set;
#if HUSH_DEBUG
	unsigned long memleak_value;
	int debug_indent;
#endif
	char user_input_buf[ENABLE_FEATURE_EDITING ? BUFSIZ : 2];
};
#define G (*ptr_to_globals)
/* Not #defining name to G.name - this quickly gets unwieldy
 * (too many defines). Also, I actually prefer to see when a variable
 * is global, thus "G." prefix is a useful hint */
#define INIT_G() do { \
	SET_PTR_TO_GLOBALS(xzalloc(sizeof(G))); \
} while (0)


/* Function prototypes for builtins */
static int builtin_cd(char **argv) FAST_FUNC;
static int builtin_echo(char **argv) FAST_FUNC;
static int builtin_eval(char **argv) FAST_FUNC;
static int builtin_exec(char **argv) FAST_FUNC;
static int builtin_exit(char **argv) FAST_FUNC;
static int builtin_export(char **argv) FAST_FUNC;
#if ENABLE_HUSH_JOB
static int builtin_fg_bg(char **argv) FAST_FUNC;
static int builtin_jobs(char **argv) FAST_FUNC;
#endif
#if ENABLE_HUSH_HELP
static int builtin_help(char **argv) FAST_FUNC;
#endif
#if ENABLE_HUSH_LOCAL
static int builtin_local(char **argv) FAST_FUNC;
#endif
#if HUSH_DEBUG
static int builtin_memleak(char **argv) FAST_FUNC;
#endif
static int builtin_pwd(char **argv) FAST_FUNC;
static int builtin_read(char **argv) FAST_FUNC;
static int builtin_set(char **argv) FAST_FUNC;
static int builtin_shift(char **argv) FAST_FUNC;
static int builtin_source(char **argv) FAST_FUNC;
static int builtin_test(char **argv) FAST_FUNC;
static int builtin_trap(char **argv) FAST_FUNC;
static int builtin_type(char **argv) FAST_FUNC;
static int builtin_true(char **argv) FAST_FUNC;
static int builtin_umask(char **argv) FAST_FUNC;
static int builtin_unset(char **argv) FAST_FUNC;
static int builtin_wait(char **argv) FAST_FUNC;
#if ENABLE_HUSH_LOOPS
static int builtin_break(char **argv) FAST_FUNC;
static int builtin_continue(char **argv) FAST_FUNC;
#endif
#if ENABLE_HUSH_FUNCTIONS
static int builtin_return(char **argv) FAST_FUNC;
#endif

/* Table of built-in functions.  They can be forked or not, depending on
 * context: within pipes, they fork.  As simple commands, they do not.
 * When used in non-forking context, they can change global variables
 * in the parent shell process.  If forked, of course they cannot.
 * For example, 'unset foo | whatever' will parse and run, but foo will
 * still be set at the end. */
struct built_in_command {
	const char *cmd;
	int (*function)(char **argv) FAST_FUNC;
#if ENABLE_HUSH_HELP
	const char *descr;
# define BLTIN(cmd, func, help) { cmd, func, help }
#else
# define BLTIN(cmd, func, help) { cmd, func }
#endif
};

static const struct built_in_command bltins1[] = {
	BLTIN("."        , builtin_source  , "Run commands in a file"),
	BLTIN(":"        , builtin_true    , NULL),
#if ENABLE_HUSH_JOB
	BLTIN("bg"       , builtin_fg_bg   , "Resume a job in the background"),
#endif
#if ENABLE_HUSH_LOOPS
	BLTIN("break"    , builtin_break   , "Exit from a loop"),
#endif
	BLTIN("cd"       , builtin_cd      , "Change directory"),
#if ENABLE_HUSH_LOOPS
	BLTIN("continue" , builtin_continue, "Start new loop iteration"),
#endif
	BLTIN("eval"     , builtin_eval    , "Construct and run shell command"),
	BLTIN("exec"     , builtin_exec    , "Execute command, don't return to shell"),
	BLTIN("exit"     , builtin_exit    , "Exit"),
	BLTIN("export"   , builtin_export  , "Set environment variables"),
#if ENABLE_HUSH_JOB
	BLTIN("fg"       , builtin_fg_bg   , "Bring job into the foreground"),
#endif
#if ENABLE_HUSH_HELP
	BLTIN("help"     , builtin_help    , NULL),
#endif
#if ENABLE_HUSH_JOB
	BLTIN("jobs"     , builtin_jobs    , "List jobs"),
#endif
#if ENABLE_HUSH_LOCAL
	BLTIN("local"    , builtin_local   , "Set local variables"),
#endif
#if HUSH_DEBUG
	BLTIN("memleak"  , builtin_memleak , NULL),
#endif
	BLTIN("read"     , builtin_read    , "Input into variable"),
#if ENABLE_HUSH_FUNCTIONS
	BLTIN("return"   , builtin_return  , "Return from a function"),
#endif
	BLTIN("set"      , builtin_set     , "Set/unset positional parameters"),
	BLTIN("shift"    , builtin_shift   , "Shift positional parameters"),
	BLTIN("trap"     , builtin_trap    , "Trap signals"),
	BLTIN("type"     , builtin_type    , "Write a description of command type"),
//	BLTIN("ulimit"   , builtin_ulimit  , "Control resource limits"),
	BLTIN("umask"    , builtin_umask   , "Set file creation mask"),
	BLTIN("unset"    , builtin_unset   , "Unset variables"),
	BLTIN("wait"     , builtin_wait    , "Wait for process"),
};
/* For now, echo and test are unconditionally enabled.
 * Maybe make it configurable? */
static const struct built_in_command bltins2[] = {
	BLTIN("["        , builtin_test    , NULL),
	BLTIN("echo"     , builtin_echo    , NULL),
	BLTIN("pwd"      , builtin_pwd     , NULL),
	BLTIN("test"     , builtin_test    , NULL),
};


/* Debug printouts.
 */
#if HUSH_DEBUG
/* prevent disasters with G.debug_indent < 0 */
# define indent() fprintf(stderr, "%*s", (G.debug_indent * 2) & 0xff, "")
# define debug_enter() (G.debug_indent++)
# define debug_leave() (G.debug_indent--)
#else
# define indent()      ((void)0)
# define debug_enter() ((void)0)
# define debug_leave() ((void)0)
#endif

#ifndef debug_printf
# define debug_printf(...) (indent(), fprintf(stderr, __VA_ARGS__))
#endif

#ifndef debug_printf_parse
# define debug_printf_parse(...) (indent(), fprintf(stderr, __VA_ARGS__))
#endif

#ifndef debug_printf_exec
#define debug_printf_exec(...) (indent(), fprintf(stderr, __VA_ARGS__))
#endif

#ifndef debug_printf_env
# define debug_printf_env(...) (indent(), fprintf(stderr, __VA_ARGS__))
#endif

#ifndef debug_printf_jobs
# define debug_printf_jobs(...) (indent(), fprintf(stderr, __VA_ARGS__))
# define DEBUG_JOBS 1
#else
# define DEBUG_JOBS 0
#endif

#ifndef debug_printf_expand
# define debug_printf_expand(...) (indent(), fprintf(stderr, __VA_ARGS__))
# define DEBUG_EXPAND 1
#else
# define DEBUG_EXPAND 0
#endif

#ifndef debug_printf_glob
# define debug_printf_glob(...) (indent(), fprintf(stderr, __VA_ARGS__))
# define DEBUG_GLOB 1
#else
# define DEBUG_GLOB 0
#endif

#ifndef debug_printf_list
# define debug_printf_list(...) (indent(), fprintf(stderr, __VA_ARGS__))
#endif

#ifndef debug_printf_subst
# define debug_printf_subst(...) (indent(), fprintf(stderr, __VA_ARGS__))
#endif

#ifndef debug_printf_clean
# define debug_printf_clean(...) (indent(), fprintf(stderr, __VA_ARGS__))
# define DEBUG_CLEAN 1
#else
# define DEBUG_CLEAN 0
#endif

#if DEBUG_EXPAND
static void debug_print_strings(const char *prefix, char **vv)
{
	indent();
	fprintf(stderr, "%s:\n", prefix);
	while (*vv)
		fprintf(stderr, " '%s'\n", *vv++);
}
#else
# define debug_print_strings(prefix, vv) ((void)0)
#endif


/* Leak hunting. Use hush_leaktool.sh for post-processing.
 */
#if LEAK_HUNTING
static void *xxmalloc(int lineno, size_t size)
{
	void *ptr = xmalloc((size + 0xff) & ~0xff);
	fdprintf(2, "line %d: malloc %p\n", lineno, ptr);
	return ptr;
}
static void *xxrealloc(int lineno, void *ptr, size_t size)
{
	ptr = xrealloc(ptr, (size + 0xff) & ~0xff);
	fdprintf(2, "line %d: realloc %p\n", lineno, ptr);
	return ptr;
}
static char *xxstrdup(int lineno, const char *str)
{
	char *ptr = xstrdup(str);
	fdprintf(2, "line %d: strdup %p\n", lineno, ptr);
	return ptr;
}
static void xxfree(void *ptr)
{
	fdprintf(2, "free %p\n", ptr);
	free(ptr);
}
#define xmalloc(s)     xxmalloc(__LINE__, s)
#define xrealloc(p, s) xxrealloc(__LINE__, p, s)
#define xstrdup(s)     xxstrdup(__LINE__, s)
#define free(p)        xxfree(p)
#endif


/* Syntax and runtime errors. They always abort scripts.
 * In interactive use they usually discard unparsed and/or unexecuted commands
 * and return to the prompt.
 * HUSH_DEBUG >= 2 prints line number in this file where it was detected.
 */
#if HUSH_DEBUG < 2
# define die_if_script(lineno, fmt...)          die_if_script(fmt)
# define syntax_error(lineno, msg)              syntax_error(msg)
# define syntax_error_at(lineno, msg)           syntax_error_at(msg)
# define syntax_error_unterm_ch(lineno, ch)     syntax_error_unterm_ch(ch)
# define syntax_error_unterm_str(lineno, s)     syntax_error_unterm_str(s)
# define syntax_error_unexpected_ch(lineno, ch) syntax_error_unexpected_ch(ch)
#endif

static void die_if_script(unsigned lineno, const char *fmt, ...)
{
	va_list p;

#if HUSH_DEBUG >= 2
	bb_error_msg("hush.c:%u", lineno);
#endif
	va_start(p, fmt);
	bb_verror_msg(fmt, p, NULL);
	va_end(p);
	if (!G_interactive_fd)
		xfunc_die();
}

static void syntax_error(unsigned lineno, const char *msg)
{
	if (msg)
		die_if_script(lineno, "syntax error: %s", msg);
	else
		die_if_script(lineno, "syntax error", NULL);
}

static void syntax_error_at(unsigned lineno, const char *msg)
{
	die_if_script(lineno, "syntax error at '%s'", msg);
}

static void syntax_error_unterm_str(unsigned lineno, const char *s)
{
	die_if_script(lineno, "syntax error: unterminated %s", s);
}

/* It so happens that all such cases are totally fatal
 * even if shell is interactive: EOF while looking for closing
 * delimiter. There is nowhere to read stuff from after that,
 * it's EOF! The only choice is to terminate.
 */
static void syntax_error_unterm_ch(unsigned lineno, char ch) NORETURN;
static void syntax_error_unterm_ch(unsigned lineno, char ch)
{
	char msg[2] = { ch, '\0' };
	syntax_error_unterm_str(lineno, msg);
	xfunc_die();
}

static void syntax_error_unexpected_ch(unsigned lineno, int ch)
{
	char msg[2];
	msg[0] = ch;
	msg[1] = '\0';
	die_if_script(lineno, "syntax error: unexpected %s", ch == EOF ? "EOF" : msg);
}

#if HUSH_DEBUG < 2
# undef die_if_script
# undef syntax_error
# undef syntax_error_at
# undef syntax_error_unterm_ch
# undef syntax_error_unterm_str
# undef syntax_error_unexpected_ch
#else
# define die_if_script(fmt...)          die_if_script(__LINE__, fmt)
# define syntax_error(msg)              syntax_error(__LINE__, msg)
# define syntax_error_at(msg)           syntax_error_at(__LINE__, msg)
# define syntax_error_unterm_ch(ch)     syntax_error_unterm_ch(__LINE__, ch)
# define syntax_error_unterm_str(s)     syntax_error_unterm_str(__LINE__, s)
# define syntax_error_unexpected_ch(ch) syntax_error_unexpected_ch(__LINE__, ch)
#endif


#if ENABLE_HUSH_INTERACTIVE
static void cmdedit_update_prompt(void);
#else
# define cmdedit_update_prompt() ((void)0)
#endif


/* Utility functions
 */
static int glob_needed(const char *s)
{
	while (*s) {
		if (*s == '\\')
			s++;
		if (*s == '*' || *s == '[' || *s == '?')
			return 1;
		s++;
	}
	return 0;
}

static int is_well_formed_var_name(const char *s, char terminator)
{
	if (!s || !(isalpha(*s) || *s == '_'))
		return 0;
	s++;
	while (isalnum(*s) || *s == '_')
		s++;
	return *s == terminator;
}

/* Replace each \x with x in place, return ptr past NUL. */
static char *unbackslash(char *src)
{
	char *dst = src;
	while (1) {
		if (*src == '\\')
			src++;
		if ((*dst++ = *src++) == '\0')
			break;
	}
	return dst;
}

static char **add_strings_to_strings(char **strings, char **add, int need_to_dup)
{
	int i;
	unsigned count1;
	unsigned count2;
	char **v;

	v = strings;
	count1 = 0;
	if (v) {
		while (*v) {
			count1++;
			v++;
		}
	}
	count2 = 0;
	v = add;
	while (*v) {
		count2++;
		v++;
	}
	v = xrealloc(strings, (count1 + count2 + 1) * sizeof(char*));
	v[count1 + count2] = NULL;
	i = count2;
	while (--i >= 0)
		v[count1 + i] = (need_to_dup ? xstrdup(add[i]) : add[i]);
	return v;
}
#if LEAK_HUNTING
static char **xx_add_strings_to_strings(int lineno, char **strings, char **add, int need_to_dup)
{
	char **ptr = add_strings_to_strings(strings, add, need_to_dup);
	fdprintf(2, "line %d: add_strings_to_strings %p\n", lineno, ptr);
	return ptr;
}
#define add_strings_to_strings(strings, add, need_to_dup) \
	xx_add_strings_to_strings(__LINE__, strings, add, need_to_dup)
#endif

/* Note: takes ownership of "add" ptr (it is not strdup'ed) */
static char **add_string_to_strings(char **strings, char *add)
{
	char *v[2];
	v[0] = add;
	v[1] = NULL;
	return add_strings_to_strings(strings, v, /*dup:*/ 0);
}
#if LEAK_HUNTING
static char **xx_add_string_to_strings(int lineno, char **strings, char *add)
{
	char **ptr = add_string_to_strings(strings, add);
	fdprintf(2, "line %d: add_string_to_strings %p\n", lineno, ptr);
	return ptr;
}
#define add_string_to_strings(strings, add) \
	xx_add_string_to_strings(__LINE__, strings, add)
#endif

static void free_strings(char **strings)
{
	char **v;

	if (!strings)
		return;
	v = strings;
	while (*v) {
		free(*v);
		v++;
	}
	free(strings);
}


/* Helpers for setting new $n and restoring them back
 */
typedef struct save_arg_t {
	char *sv_argv0;
	char **sv_g_argv;
	int sv_g_argc;
	smallint sv_g_malloced;
} save_arg_t;

static void save_and_replace_G_args(save_arg_t *sv, char **argv)
{
	int n;

	sv->sv_argv0 = argv[0];
	sv->sv_g_argv = G.global_argv;
	sv->sv_g_argc = G.global_argc;
	sv->sv_g_malloced = G.global_args_malloced;

	argv[0] = G.global_argv[0]; /* retain $0 */
	G.global_argv = argv;
	G.global_args_malloced = 0;

	n = 1;
	while (*++argv)
		n++;
	G.global_argc = n;
}

static void restore_G_args(save_arg_t *sv, char **argv)
{
	char **pp;

	if (G.global_args_malloced) {
		/* someone ran "set -- arg1 arg2 ...", undo */
		pp = G.global_argv;
		while (*++pp) /* note: does not free $0 */
			free(*pp);
		free(G.global_argv);
	}
	argv[0] = sv->sv_argv0;
	G.global_argv = sv->sv_g_argv;
	G.global_argc = sv->sv_g_argc;
	G.global_args_malloced = sv->sv_g_malloced;
}


/* Basic theory of signal handling in shell
 * ========================================
 * This does not describe what hush does, rather, it is current understanding
 * what it _should_ do. If it doesn't, it's a bug.
 * http://www.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#trap
 *
 * Signals are handled only after each pipe ("cmd | cmd | cmd" thing)
 * is finished or backgrounded. It is the same in interactive and
 * non-interactive shells, and is the same regardless of whether
 * a user trap handler is installed or a shell special one is in effect.
 * ^C or ^Z from keyboard seem to execute "at once" because it usually
 * backgrounds (i.e. stops) or kills all members of currently running
 * pipe.
 *
 * Wait builtin in interruptible by signals for which user trap is set
 * or by SIGINT in interactive shell.
 *
 * Trap handlers will execute even within trap handlers. (right?)
 *
 * User trap handlers are forgotten when subshell ("(cmd)") is entered.
 *
 * If job control is off, backgrounded commands ("cmd &")
 * have SIGINT, SIGQUIT set to SIG_IGN.
 *
 * Commands which are run in command substitution ("`cmd`")
 * have SIGTTIN, SIGTTOU, SIGTSTP set to SIG_IGN.
 *
 * Ordinary commands have signals set to SIG_IGN/DFL as inherited
 * by the shell from its parent.
 *
 * Signals which differ from SIG_DFL action
 * (note: child (i.e., [v]forked) shell is not an interactive shell):
 *
 * SIGQUIT: ignore
 * SIGTERM (interactive): ignore
 * SIGHUP (interactive):
 *    send SIGCONT to stopped jobs, send SIGHUP to all jobs and exit
 * SIGTTIN, SIGTTOU, SIGTSTP (if job control is on): ignore
 *    Note that ^Z is handled not by trapping SIGTSTP, but by seeing
 *    that all pipe members are stopped. Try this in bash:
 *    while :; do :; done - ^Z does not background it
 *    (while :; do :; done) - ^Z backgrounds it
 * SIGINT (interactive): wait for last pipe, ignore the rest
 *    of the command line, show prompt. NB: ^C does not send SIGINT
 *    to interactive shell while shell is waiting for a pipe,
 *    since shell is bg'ed (is not in foreground process group).
 *    Example 1: this waits 5 sec, but does not execute ls:
 *    "echo $$; sleep 5; ls -l" + "kill -INT <pid>"
 *    Example 2: this does not wait and does not execute ls:
 *    "echo $$; sleep 5 & wait; ls -l" + "kill -INT <pid>"
 *    Example 3: this does not wait 5 sec, but executes ls:
 *    "sleep 5; ls -l" + press ^C
 *
 * (What happens to signals which are IGN on shell start?)
 * (What happens with signal mask on shell start?)
 *
 * Implementation in hush
 * ======================
 * We use in-kernel pending signal mask to determine which signals were sent.
 * We block all signals which we don't want to take action immediately,
 * i.e. we block all signals which need to have special handling as described
 * above, and all signals which have traps set.
 * After each pipe execution, we extract any pending signals via sigtimedwait()
 * and act on them.
 *
 * unsigned non_DFL_mask: a mask of such "special" signals
 * sigset_t blocked_set:  current blocked signal set
 *
 * "trap - SIGxxx":
 *    clear bit in blocked_set unless it is also in non_DFL_mask
 * "trap 'cmd' SIGxxx":
 *    set bit in blocked_set (even if 'cmd' is '')
 * after [v]fork, if we plan to be a shell:
 *    unblock signals with special interactive handling
 *    (child shell is not interactive),
 *    unset all traps (note: regardless of child shell's type - {}, (), etc)
 * after [v]fork, if we plan to exec:
 *    POSIX says pending signal mask is cleared in child - no need to clear it.
 *    Restore blocked signal set to one inherited by shell just prior to exec.
 *
 * Note: as a result, we do not use signal handlers much. The only uses
 * are to count SIGCHLDs
 * and to restore tty pgrp on signal-induced exit.
 */
enum {
	SPECIAL_INTERACTIVE_SIGS = 0
		| (1 << SIGTERM)
		| (1 << SIGINT)
		| (1 << SIGHUP)
		,
	SPECIAL_JOB_SIGS = 0
#if ENABLE_HUSH_JOB
		| (1 << SIGTTIN)
		| (1 << SIGTTOU)
		| (1 << SIGTSTP)
#endif
};

#if ENABLE_HUSH_FAST
static void SIGCHLD_handler(int sig UNUSED_PARAM)
{
	G.count_SIGCHLD++;
//bb_error_msg("[%d] SIGCHLD_handler: G.count_SIGCHLD:%d G.handled_SIGCHLD:%d", getpid(), G.count_SIGCHLD, G.handled_SIGCHLD);
}
#endif

#if ENABLE_HUSH_JOB

/* After [v]fork, in child: do not restore tty pgrp on xfunc death */
#define disable_restore_tty_pgrp_on_exit() (die_sleep = 0)
/* After [v]fork, in parent: restore tty pgrp on xfunc death */
#define enable_restore_tty_pgrp_on_exit()  (die_sleep = -1)

/* Restores tty foreground process group, and exits.
 * May be called as signal handler for fatal signal
 * (will resend signal to itself, producing correct exit state)
 * or called directly with -EXITCODE.
 * We also call it if xfunc is exiting. */
static void sigexit(int sig) NORETURN;
static void sigexit(int sig)
{
	/* Disable all signals: job control, SIGPIPE, etc. */
	sigprocmask_allsigs(SIG_BLOCK);

	/* Careful: we can end up here after [v]fork. Do not restore
	 * tty pgrp then, only top-level shell process does that */
	if (G_saved_tty_pgrp && getpid() == G.root_pid)
		tcsetpgrp(G_interactive_fd, G_saved_tty_pgrp);

	/* Not a signal, just exit */
	if (sig <= 0)
		_exit(- sig);

	kill_myself_with_sig(sig); /* does not return */
}
#else

#define disable_restore_tty_pgrp_on_exit() ((void)0)
#define enable_restore_tty_pgrp_on_exit()  ((void)0)

#endif

/* Restores tty foreground process group, and exits. */
static void hush_exit(int exitcode) NORETURN;
static void hush_exit(int exitcode)
{
	if (G.exiting <= 0 && G.traps && G.traps[0] && G.traps[0][0]) {
		/* Prevent recursion:
		 * trap "echo Hi; exit" EXIT; exit
		 */
		char *argv[] = { NULL, G.traps[0], NULL };
		G.traps[0] = NULL;
		G.exiting = 1;
		builtin_eval(argv);
		free(argv[1]);
	}

#if ENABLE_HUSH_JOB
	fflush(NULL); /* flush all streams */
	sigexit(- (exitcode & 0xff));
#else
	exit(exitcode);
#endif
}

static int check_and_run_traps(int sig)
{
	static const struct timespec zero_timespec = { 0, 0 };
	smalluint save_rcode;
	int last_sig = 0;

	if (sig)
		goto jump_in;
	while (1) {
		sig = sigtimedwait(&G.blocked_set, NULL, &zero_timespec);
		if (sig <= 0)
			break;
 jump_in:
		last_sig = sig;
		if (G.traps && G.traps[sig]) {
			if (G.traps[sig][0]) {
				/* We have user-defined handler */
				char *argv[] = { NULL, xstrdup(G.traps[sig]), NULL };
				save_rcode = G.last_exitcode;
				builtin_eval(argv);
				free(argv[1]);
				G.last_exitcode = save_rcode;
			} /* else: "" trap, ignoring signal */
			continue;
		}
		/* not a trap: special action */
		switch (sig) {
#if ENABLE_HUSH_FAST
		case SIGCHLD:
			G.count_SIGCHLD++;
//bb_error_msg("[%d] check_and_run_traps: G.count_SIGCHLD:%d G.handled_SIGCHLD:%d", getpid(), G.count_SIGCHLD, G.handled_SIGCHLD);
			break;
#endif
		case SIGINT:
			/* Builtin was ^C'ed, make it look prettier: */
			bb_putchar('\n');
			G.flag_SIGINT = 1;
			break;
#if ENABLE_HUSH_JOB
		case SIGHUP: {
			struct pipe *job;
			/* bash is observed to signal whole process groups,
			 * not individual processes */
			for (job = G.job_list; job; job = job->next) {
				if (job->pgrp <= 0)
					continue;
				debug_printf_exec("HUPing pgrp %d\n", job->pgrp);
				if (kill(- job->pgrp, SIGHUP) == 0)
					kill(- job->pgrp, SIGCONT);
			}
			sigexit(SIGHUP);
		}
#endif
		default: /* ignored: */
			/* SIGTERM, SIGQUIT, SIGTTIN, SIGTTOU, SIGTSTP */
			break;
		}
	}
	return last_sig;
}


static const char *get_cwd(int force)
{
	if (force || G.cwd == NULL) {
		/* xrealloc_getcwd_or_warn(arg) calls free(arg),
		 * we must not try to free(bb_msg_unknown) */
		if (G.cwd == bb_msg_unknown)
			G.cwd = NULL;
		G.cwd = xrealloc_getcwd_or_warn((char *)G.cwd);
		if (!G.cwd)
			G.cwd = bb_msg_unknown;
	}
	return G.cwd;
}


/*
 * Shell and environment variable support
 */
static struct variable **get_ptr_to_local_var(const char *name)
{
	struct variable **pp;
	struct variable *cur;
	int len;

	len = strlen(name);
	pp = &G.top_var;
	while ((cur = *pp) != NULL) {
		if (strncmp(cur->varstr, name, len) == 0 && cur->varstr[len] == '=')
			return pp;
		pp = &cur->next;
	}
	return NULL;
}

static struct variable *get_local_var(const char *name)
{
	struct variable **pp = get_ptr_to_local_var(name);
	if (pp)
		return *pp;
	return NULL;
}

static const char *get_local_var_value(const char *name)
{
	struct variable **pp = get_ptr_to_local_var(name);
	if (pp)
		return strchr((*pp)->varstr, '=') + 1;
	return NULL;
}

/* str holds "NAME=VAL" and is expected to be malloced.
 * We take ownership of it.
 * flg_export:
 *  0: do not change export flag
 *     (if creating new variable, flag will be 0)
 *  1: set export flag and putenv the variable
 * -1: clear export flag and unsetenv the variable
 * flg_read_only is set only when we handle -R var=val
 */
#if !BB_MMU && ENABLE_HUSH_LOCAL
/* all params are used */
#elif BB_MMU && ENABLE_HUSH_LOCAL
#define set_local_var(str, flg_export, local_lvl, flg_read_only) \
	set_local_var(str, flg_export, local_lvl)
#elif BB_MMU && !ENABLE_HUSH_LOCAL
#define set_local_var(str, flg_export, local_lvl, flg_read_only) \
	set_local_var(str, flg_export)
#elif !BB_MMU && !ENABLE_HUSH_LOCAL
#define set_local_var(str, flg_export, local_lvl, flg_read_only) \
	set_local_var(str, flg_export, flg_read_only)
#endif
static int set_local_var(char *str, int flg_export, int local_lvl, int flg_read_only)
{
	struct variable **var_pp;
	struct variable *cur;
	char *eq_sign;
	int name_len;

	eq_sign = strchr(str, '=');
	if (!eq_sign) { /* not expected to ever happen? */
		free(str);
		return -1;
	}

	name_len = eq_sign - str + 1; /* including '=' */
	var_pp = &G.top_var;
	while ((cur = *var_pp) != NULL) {
		if (strncmp(cur->varstr, str, name_len) != 0) {
			var_pp = &cur->next;
			continue;
		}
		/* We found an existing var with this name */
		if (cur->flg_read_only) {
#if !BB_MMU
			if (!flg_read_only)
#endif
				bb_error_msg("%s: readonly variable", str);
			free(str);
			return -1;
		}
		if (flg_export == -1) { // "&& cur->flg_export" ?
			debug_printf_env("%s: unsetenv '%s'\n", __func__, str);
			*eq_sign = '\0';
			unsetenv(str);
			*eq_sign = '=';
		}
#if ENABLE_HUSH_LOCAL
		if (cur->func_nest_level < local_lvl) {
			/* New variable is declared as local,
			 * and existing one is global, or local
			 * from enclosing function.
			 * Remove and save old one: */
			*var_pp = cur->next;
			cur->next = *G.shadowed_vars_pp;
			*G.shadowed_vars_pp = cur;
			/* bash 3.2.33(1) and exported vars:
			 * # export z=z
			 * # f() { local z=a; env | grep ^z; }
			 * # f
			 * z=a
			 * # env | grep ^z
			 * z=z
			 */
			if (cur->flg_export)
				flg_export = 1;
			break;
		}
#endif
		if (strcmp(cur->varstr + name_len, eq_sign + 1) == 0) {
 free_and_exp:
			free(str);
			goto exp;
		}
		if (cur->max_len != 0) {
			if (cur->max_len >= strlen(str)) {
				/* This one is from startup env, reuse space */
				strcpy(cur->varstr, str);
				goto free_and_exp;
			}
		} else {
			/* max_len == 0 signifies "malloced" var, which we can
			 * (and has to) free */
			free(cur->varstr);
		}
		cur->max_len = 0;
		goto set_str_and_exp;
	}

	/* Not found - create new variable struct */
	cur = xzalloc(sizeof(*cur));
#if ENABLE_HUSH_LOCAL
	cur->func_nest_level = local_lvl;
#endif
	cur->next = *var_pp;
	*var_pp = cur;

 set_str_and_exp:
	cur->varstr = str;
#if !BB_MMU
	cur->flg_read_only = flg_read_only;
#endif
 exp:
	if (flg_export == 1)
		cur->flg_export = 1;
	if (name_len == 4 && cur->varstr[0] == 'P' && cur->varstr[1] == 'S')
		cmdedit_update_prompt();
	if (cur->flg_export) {
		if (flg_export == -1) {
			cur->flg_export = 0;
			/* unsetenv was already done */
		} else {
			debug_printf_env("%s: putenv '%s'\n", __func__, cur->varstr);
			return putenv(cur->varstr);
		}
	}
	return 0;
}

static int unset_local_var_len(const char *name, int name_len)
{
	struct variable *cur;
	struct variable **var_pp;

	if (!name)
		return EXIT_SUCCESS;
	var_pp = &G.top_var;
	while ((cur = *var_pp) != NULL) {
		if (strncmp(cur->varstr, name, name_len) == 0 && cur->varstr[name_len] == '=') {
			if (cur->flg_read_only) {
				bb_error_msg("%s: readonly variable", name);
				return EXIT_FAILURE;
			}
			*var_pp = cur->next;
			debug_printf_env("%s: unsetenv '%s'\n", __func__, cur->varstr);
			bb_unsetenv(cur->varstr);
			if (name_len == 3 && cur->varstr[0] == 'P' && cur->varstr[1] == 'S')
				cmdedit_update_prompt();
			if (!cur->max_len)
				free(cur->varstr);
			free(cur);
			return EXIT_SUCCESS;
		}
		var_pp = &cur->next;
	}
	return EXIT_SUCCESS;
}

static int unset_local_var(const char *name)
{
	return unset_local_var_len(name, strlen(name));
}

static void unset_vars(char **strings)
{
	char **v;

	if (!strings)
		return;
	v = strings;
	while (*v) {
		const char *eq = strchrnul(*v, '=');
		unset_local_var_len(*v, (int)(eq - *v));
		v++;
	}
	free(strings);
}

#if ENABLE_SH_MATH_SUPPORT
#define is_name(c)      ((c) == '_' || isalpha((unsigned char)(c)))
#define is_in_name(c)   ((c) == '_' || isalnum((unsigned char)(c)))
static char *endofname(const char *name)
{
	char *p;

	p = (char *) name;
	if (!is_name(*p))
		return p;
	while (*++p) {
		if (!is_in_name(*p))
			break;
	}
	return p;
}

static void arith_set_local_var(const char *name, const char *val, int flags)
{
	/* arith code doesnt malloc space, so do it for it */
	char *var = xasprintf("%s=%s", name, val);
	set_local_var(var, flags, /*lvl:*/ 0, /*ro:*/ 0);
}
#endif


/*
 * Helpers for "var1=val1 var2=val2 cmd" feature
 */
static void add_vars(struct variable *var)
{
	struct variable *next;

	while (var) {
		next = var->next;
		var->next = G.top_var;
		G.top_var = var;
		if (var->flg_export) {
			debug_printf_env("%s: restoring exported '%s'\n", __func__, var->varstr);
			putenv(var->varstr);
		} else {
			debug_printf_env("%s: restoring variable '%s'\n", __func__, var->varstr);
		}
		var = next;
	}
}

static struct variable *set_vars_and_save_old(char **strings)
{
	char **s;
	struct variable *old = NULL;

	if (!strings)
		return old;
	s = strings;
	while (*s) {
		struct variable *var_p;
		struct variable **var_pp;
		char *eq;

		eq = strchr(*s, '=');
		if (eq) {
			*eq = '\0';
			var_pp = get_ptr_to_local_var(*s);
			*eq = '=';
			if (var_pp) {
				/* Remove variable from global linked list */
				var_p = *var_pp;
				debug_printf_env("%s: removing '%s'\n", __func__, var_p->varstr);
				*var_pp = var_p->next;
				/* Add it to returned list */
				var_p->next = old;
				old = var_p;
			}
			set_local_var(*s, /*exp:*/ 1, /*lvl:*/ 0, /*ro:*/ 0);
		}
		s++;
	}
	return old;
}


/*
 * in_str support
 */
static int FAST_FUNC static_get(struct in_str *i)
{
	int ch = *i->p++;
	if (ch != '\0')
		return ch;
	i->p--;
	return EOF;
}

static int FAST_FUNC static_peek(struct in_str *i)
{
	return *i->p;
}

#if ENABLE_HUSH_INTERACTIVE

static void cmdedit_update_prompt(void)
{
	if (ENABLE_FEATURE_EDITING_FANCY_PROMPT) {
		G.PS1 = get_local_var_value("PS1");
		if (G.PS1 == NULL)
			G.PS1 = "\\w \\$ ";
		G.PS2 = get_local_var_value("PS2");
	} else {
		G.PS1 = NULL;
	}
	if (G.PS2 == NULL)
		G.PS2 = "> ";
}

static const char* setup_prompt_string(int promptmode)
{
	const char *prompt_str;
	debug_printf("setup_prompt_string %d ", promptmode);
	if (!ENABLE_FEATURE_EDITING_FANCY_PROMPT) {
		/* Set up the prompt */
		if (promptmode == 0) { /* PS1 */
			free((char*)G.PS1);
			G.PS1 = xasprintf("%s %c ", get_cwd(0), (geteuid() != 0) ? '$' : '#');
			prompt_str = G.PS1;
		} else
			prompt_str = G.PS2;
	} else
		prompt_str = (promptmode == 0) ? G.PS1 : G.PS2;
	debug_printf("result '%s'\n", prompt_str);
	return prompt_str;
}

static void get_user_input(struct in_str *i)
{
	int r;
	const char *prompt_str;

	prompt_str = setup_prompt_string(i->promptmode);
#if ENABLE_FEATURE_EDITING
	/* Enable command line editing only while a command line
	 * is actually being read */
	do {
		G.flag_SIGINT = 0;
		/* buglet: SIGINT will not make new prompt to appear _at once_,
		 * only after <Enter>. (^C will work) */
		r = read_line_input(prompt_str, G.user_input_buf, BUFSIZ-1, G.line_input_state);
		/* catch *SIGINT* etc (^C is handled by read_line_input) */
		check_and_run_traps(0);
	} while (r == 0 || G.flag_SIGINT); /* repeat if ^C or SIGINT */
	i->eof_flag = (r < 0);
	if (i->eof_flag) { /* EOF/error detected */
		G.user_input_buf[0] = EOF; /* yes, it will be truncated, it's ok */
		G.user_input_buf[1] = '\0';
	}
#else
	do {
		G.flag_SIGINT = 0;
		fputs(prompt_str, stdout);
		fflush(stdout);
		G.user_input_buf[0] = r = fgetc(i->file);
		/*G.user_input_buf[1] = '\0'; - already is and never changed */
//do we need check_and_run_traps(0)? (maybe only if stdin)
	} while (G.flag_SIGINT);
	i->eof_flag = (r == EOF);
#endif
	i->p = G.user_input_buf;
}

#endif  /* INTERACTIVE */

/* This is the magic location that prints prompts
 * and gets data back from the user */
static int FAST_FUNC file_get(struct in_str *i)
{
	int ch;

	/* If there is data waiting, eat it up */
	if (i->p && *i->p) {
#if ENABLE_HUSH_INTERACTIVE
 take_cached:
#endif
		ch = *i->p++;
		if (i->eof_flag && !*i->p)
			ch = EOF;
		/* note: ch is never NUL */
	} else {
		/* need to double check i->file because we might be doing something
		 * more complicated by now, like sourcing or substituting. */
#if ENABLE_HUSH_INTERACTIVE
		if (G_interactive_fd && i->promptme && i->file == stdin) {
			do {
				get_user_input(i);
			} while (!*i->p); /* need non-empty line */
			i->promptmode = 1; /* PS2 */
			i->promptme = 0;
			goto take_cached;
		}
#endif
		do ch = fgetc(i->file); while (ch == '\0');
	}
	debug_printf("file_get: got '%c' %d\n", ch, ch);
#if ENABLE_HUSH_INTERACTIVE
	if (ch == '\n')
		i->promptme = 1;
#endif
	return ch;
}

/* All callers guarantee this routine will never
 * be used right after a newline, so prompting is not needed.
 */
static int FAST_FUNC file_peek(struct in_str *i)
{
	int ch;
	if (i->p && *i->p) {
		if (i->eof_flag && !i->p[1])
			return EOF;
		return *i->p;
		/* note: ch is never NUL */
	}
	do ch = fgetc(i->file); while (ch == '\0');
	i->eof_flag = (ch == EOF);
	i->peek_buf[0] = ch;
	i->peek_buf[1] = '\0';
	i->p = i->peek_buf;
	debug_printf("file_peek: got '%c' %d\n", ch, ch);
	return ch;
}

static void setup_file_in_str(struct in_str *i, FILE *f)
{
	i->peek = file_peek;
	i->get = file_get;
#if ENABLE_HUSH_INTERACTIVE
	i->promptme = 1;
	i->promptmode = 0; /* PS1 */
#endif
	i->file = f;
	i->p = NULL;
}

static void setup_string_in_str(struct in_str *i, const char *s)
{
	i->peek = static_peek;
	i->get = static_get;
#if ENABLE_HUSH_INTERACTIVE
	i->promptme = 1;
	i->promptmode = 0; /* PS1 */
#endif
	i->p = s;
	i->eof_flag = 0;
}


/*
 * o_string support
 */
#define B_CHUNK  (32 * sizeof(char*))

static void o_reset_to_empty_unquoted(o_string *o)
{
	o->length = 0;
	o->o_quoted = 0;
	if (o->data)
		o->data[0] = '\0';
}

static void o_free(o_string *o)
{
	free(o->data);
	memset(o, 0, sizeof(*o));
}

static ALWAYS_INLINE void o_free_unsafe(o_string *o)
{
	free(o->data);
}

static void o_grow_by(o_string *o, int len)
{
	if (o->length + len > o->maxlen) {
		o->maxlen += (2*len > B_CHUNK ? 2*len : B_CHUNK);
		o->data = xrealloc(o->data, 1 + o->maxlen);
	}
}

static void o_addchr(o_string *o, int ch)
{
	debug_printf("o_addchr: '%c' o->length=%d o=%p\n", ch, o->length, o);
	o_grow_by(o, 1);
	o->data[o->length] = ch;
	o->length++;
	o->data[o->length] = '\0';
}

static void o_addblock(o_string *o, const char *str, int len)
{
	o_grow_by(o, len);
	memcpy(&o->data[o->length], str, len);
	o->length += len;
	o->data[o->length] = '\0';
}

#if !BB_MMU
static void o_addstr(o_string *o, const char *str)
{
	o_addblock(o, str, strlen(str));
}
static void nommu_addchr(o_string *o, int ch)
{
	if (o)
		o_addchr(o, ch);
}
#else
# define nommu_addchr(o, str) ((void)0)
#endif

static void o_addstr_with_NUL(o_string *o, const char *str)
{
	o_addblock(o, str, strlen(str) + 1);
}

static void o_addblock_duplicate_backslash(o_string *o, const char *str, int len)
{
	while (len) {
		o_addchr(o, *str);
		if (*str++ == '\\'
		 && (*str != '*' && *str != '?' && *str != '[')
		) {
			o_addchr(o, '\\');
		}
		len--;
	}
}

/* My analysis of quoting semantics tells me that state information
 * is associated with a destination, not a source.
 */
static void o_addqchr(o_string *o, int ch)
{
	int sz = 1;
	char *found = strchr("*?[\\", ch);
	if (found)
		sz++;
	o_grow_by(o, sz);
	if (found) {
		o->data[o->length] = '\\';
		o->length++;
	}
	o->data[o->length] = ch;
	o->length++;
	o->data[o->length] = '\0';
}

static void o_addQchr(o_string *o, int ch)
{
	int sz = 1;
	if (o->o_escape && strchr("*?[\\", ch)) {
		sz++;
		o->data[o->length] = '\\';
		o->length++;
	}
	o_grow_by(o, sz);
	o->data[o->length] = ch;
	o->length++;
	o->data[o->length] = '\0';
}

static void o_addQstr(o_string *o, const char *str, int len)
{
	if (!o->o_escape) {
		o_addblock(o, str, len);
		return;
	}
	while (len) {
		char ch;
		int sz;
		int ordinary_cnt = strcspn(str, "*?[\\");
		if (ordinary_cnt > len) /* paranoia */
			ordinary_cnt = len;
		o_addblock(o, str, ordinary_cnt);
		if (ordinary_cnt == len)
			return;
		str += ordinary_cnt;
		len -= ordinary_cnt + 1; /* we are processing + 1 char below */

		ch = *str++;
		sz = 1;
		if (ch) { /* it is necessarily one of "*?[\\" */
			sz++;
			o->data[o->length] = '\\';
			o->length++;
		}
		o_grow_by(o, sz);
		o->data[o->length] = ch;
		o->length++;
		o->data[o->length] = '\0';
	}
}

/* A special kind of o_string for $VAR and `cmd` expansion.
 * It contains char* list[] at the beginning, which is grown in 16 element
 * increments. Actual string data starts at the next multiple of 16 * (char*).
 * list[i] contains an INDEX (int!) into this string data.
 * It means that if list[] needs to grow, data needs to be moved higher up
 * but list[i]'s need not be modified.
 * NB: remembering how many list[i]'s you have there is crucial.
 * o_finalize_list() operation post-processes this structure - calculates
 * and stores actual char* ptrs in list[]. Oh, it NULL terminates it as well.
 */
#if DEBUG_EXPAND || DEBUG_GLOB
static void debug_print_list(const char *prefix, o_string *o, int n)
{
	char **list = (char**)o->data;
	int string_start = ((n + 0xf) & ~0xf) * sizeof(list[0]);
	int i = 0;

	indent();
	fprintf(stderr, "%s: list:%p n:%d string_start:%d length:%d maxlen:%d\n",
			prefix, list, n, string_start, o->length, o->maxlen);
	while (i < n) {
		indent();
		fprintf(stderr, " list[%d]=%d '%s' %p\n", i, (int)list[i],
				o->data + (int)list[i] + string_start,
				o->data + (int)list[i] + string_start);
		i++;
	}
	if (n) {
		const char *p = o->data + (int)list[n - 1] + string_start;
		indent();
		fprintf(stderr, " total_sz:%ld\n", (long)((p + strlen(p) + 1) - o->data));
	}
}
#else
# define debug_print_list(prefix, o, n) ((void)0)
#endif

/* n = o_save_ptr_helper(str, n) "starts new string" by storing an index value
 * in list[n] so that it points past last stored byte so far.
 * It returns n+1. */
static int o_save_ptr_helper(o_string *o, int n)
{
	char **list = (char**)o->data;
	int string_start;
	int string_len;

	if (!o->has_empty_slot) {
		string_start = ((n + 0xf) & ~0xf) * sizeof(list[0]);
		string_len = o->length - string_start;
		if (!(n & 0xf)) { /* 0, 0x10, 0x20...? */
			debug_printf_list("list[%d]=%d string_start=%d (growing)\n", n, string_len, string_start);
			/* list[n] points to string_start, make space for 16 more pointers */
			o->maxlen += 0x10 * sizeof(list[0]);
			o->data = xrealloc(o->data, o->maxlen + 1);
			list = (char**)o->data;
			memmove(list + n + 0x10, list + n, string_len);
			o->length += 0x10 * sizeof(list[0]);
		} else {
			debug_printf_list("list[%d]=%d string_start=%d\n",
					n, string_len, string_start);
		}
	} else {
		/* We have empty slot at list[n], reuse without growth */
		string_start = ((n+1 + 0xf) & ~0xf) * sizeof(list[0]); /* NB: n+1! */
		string_len = o->length - string_start;
		debug_printf_list("list[%d]=%d string_start=%d (empty slot)\n",
				n, string_len, string_start);
		o->has_empty_slot = 0;
	}
	list[n] = (char*)(ptrdiff_t)string_len;
	return n + 1;
}

/* "What was our last o_save_ptr'ed position (byte offset relative o->data)?" */
static int o_get_last_ptr(o_string *o, int n)
{
	char **list = (char**)o->data;
	int string_start = ((n + 0xf) & ~0xf) * sizeof(list[0]);

	return ((int)(ptrdiff_t)list[n-1]) + string_start;
}

/* o_glob performs globbing on last list[], saving each result
 * as a new list[]. */
static int o_glob(o_string *o, int n)
{
	glob_t globdata;
	int gr;
	char *pattern;

	debug_printf_glob("start o_glob: n:%d o->data:%p\n", n, o->data);
	if (!o->data)
		return o_save_ptr_helper(o, n);
	pattern = o->data + o_get_last_ptr(o, n);
	debug_printf_glob("glob pattern '%s'\n", pattern);
	if (!glob_needed(pattern)) {
 literal:
		o->length = unbackslash(pattern) - o->data;
		debug_printf_glob("glob pattern '%s' is literal\n", pattern);
		return o_save_ptr_helper(o, n);
	}

	memset(&globdata, 0, sizeof(globdata));
	gr = glob(pattern, 0, NULL, &globdata);
	debug_printf_glob("glob('%s'):%d\n", pattern, gr);
	if (gr == GLOB_NOSPACE)
		bb_error_msg_and_die("out of memory during glob");
	if (gr == GLOB_NOMATCH) {
		globfree(&globdata);
		goto literal;
	}
	if (gr != 0) { /* GLOB_ABORTED ? */
		/* TODO: testcase for bad glob pattern behavior */
		bb_error_msg("glob(3) error %d on '%s'", gr, pattern);
	}
	if (globdata.gl_pathv && globdata.gl_pathv[0]) {
		char **argv = globdata.gl_pathv;
		o->length = pattern - o->data; /* "forget" pattern */
		while (1) {
			o_addstr_with_NUL(o, *argv);
			n = o_save_ptr_helper(o, n);
			argv++;
			if (!*argv)
				break;
		}
	}
	globfree(&globdata);
	if (DEBUG_GLOB)
		debug_print_list("o_glob returning", o, n);
	return n;
}

/* If o->o_glob == 1, glob the string so far remembered.
 * Otherwise, just finish current list[] and start new */
static int o_save_ptr(o_string *o, int n)
{
	if (o->o_glob) { /* if globbing is requested */
		/* If o->has_empty_slot, list[n] was already globbed
		 * (if it was requested back then when it was filled)
		 * so don't do that again! */
		if (!o->has_empty_slot)
			return o_glob(o, n); /* o_save_ptr_helper is inside */
	}
	return o_save_ptr_helper(o, n);
}

/* "Please convert list[n] to real char* ptrs, and NULL terminate it." */
static char **o_finalize_list(o_string *o, int n)
{
	char **list;
	int string_start;

	n = o_save_ptr(o, n); /* force growth for list[n] if necessary */
	if (DEBUG_EXPAND)
		debug_print_list("finalized", o, n);
	debug_printf_expand("finalized n:%d\n", n);
	list = (char**)o->data;
	string_start = ((n + 0xf) & ~0xf) * sizeof(list[0]);
	list[--n] = NULL;
	while (n) {
		n--;
		list[n] = o->data + (int)(ptrdiff_t)list[n] + string_start;
	}
	return list;
}


/* Expansion can recurse */
#if ENABLE_HUSH_TICK
static int process_command_subs(o_string *dest, const char *s);
#endif
static char *expand_string_to_string(const char *str);
#if BB_MMU
#define parse_stream_dquoted(as_string, dest, input, dquote_end) \
	parse_stream_dquoted(dest, input, dquote_end)
#endif
static int parse_stream_dquoted(o_string *as_string,
		o_string *dest,
		struct in_str *input,
		int dquote_end);

/* expand_strvec_to_strvec() takes a list of strings, expands
 * all variable references within and returns a pointer to
 * a list of expanded strings, possibly with larger number
 * of strings. (Think VAR="a b"; echo $VAR).
 * This new list is allocated as a single malloc block.
 * NULL-terminated list of char* pointers is at the beginning of it,
 * followed by strings themself.
 * Caller can deallocate entire list by single free(list). */

/* Store given string, finalizing the word and starting new one whenever
 * we encounter IFS char(s). This is used for expanding variable values.
 * End-of-string does NOT finalize word: think about 'echo -$VAR-' */
static int expand_on_ifs(o_string *output, int n, const char *str)
{
	while (1) {
		int word_len = strcspn(str, G.ifs);
		if (word_len) {
			if (output->o_escape || !output->o_glob)
				o_addQstr(output, str, word_len);
			else /* protect backslashes against globbing up :) */
				o_addblock_duplicate_backslash(output, str, word_len);
			str += word_len;
		}
		if (!*str)  /* EOL - do not finalize word */
			break;
		o_addchr(output, '\0');
		debug_print_list("expand_on_ifs", output, n);
		n = o_save_ptr(output, n);
		str += strspn(str, G.ifs); /* skip ifs chars */
	}
	debug_print_list("expand_on_ifs[1]", output, n);
	return n;
}

/* Helper to expand $((...)) and heredoc body. These act as if
 * they are in double quotes, with the exception that they are not :).
 * Just the rules are similar: "expand only $var and `cmd`"
 *
 * Returns malloced string.
 * As an optimization, we return NULL if expansion is not needed.
 */
static char *expand_pseudo_dquoted(const char *str)
{
	char *exp_str;
	struct in_str input;
	o_string dest = NULL_O_STRING;

	if (strchr(str, '$') == NULL
#if ENABLE_HUSH_TICK
	 && strchr(str, '`') == NULL
#endif
	) {
		return NULL;
	}

	/* We need to expand. Example:
	 * echo $(($a + `echo 1`)) $((1 + $((2)) ))
	 */
	setup_string_in_str(&input, str);
	parse_stream_dquoted(NULL, &dest, &input, EOF);
	//bb_error_msg("'%s' -> '%s'", str, dest.data);
	exp_str = expand_string_to_string(dest.data);
	//bb_error_msg("'%s' -> '%s'", dest.data, exp_str);
	o_free_unsafe(&dest);
	return exp_str;
}

/* Expand all variable references in given string, adding words to list[]
 * at n, n+1,... positions. Return updated n (so that list[n] is next one
 * to be filled). This routine is extremely tricky: has to deal with
 * variables/parameters with whitespace, $* and $@, and constructs like
 * 'echo -$*-'. If you play here, you must run testsuite afterwards! */
static int expand_vars_to_list(o_string *output, int n, char *arg, char or_mask)
{
	/* or_mask is either 0 (normal case) or 0x80 -
	 * expansion of right-hand side of assignment == 1-element expand.
	 * It will also do no globbing, and thus we must not backslash-quote!
	 */
	char ored_ch;
	char *p;

	ored_ch = 0;

	debug_printf_expand("expand_vars_to_list: arg '%s'\n", arg);
	debug_print_list("expand_vars_to_list", output, n);
	n = o_save_ptr(output, n);
	debug_print_list("expand_vars_to_list[0]", output, n);

	while ((p = strchr(arg, SPECIAL_VAR_SYMBOL)) != NULL) {
		char first_ch;
		int i;
		char *dyn_val = NULL;
		const char *val = NULL;
#if ENABLE_HUSH_TICK
		o_string subst_result = NULL_O_STRING;
#endif
#if ENABLE_SH_MATH_SUPPORT
		char arith_buf[sizeof(arith_t)*3 + 2];
#endif
		o_addblock(output, arg, p - arg);
		debug_print_list("expand_vars_to_list[1]", output, n);
		arg = ++p;
		p = strchr(p, SPECIAL_VAR_SYMBOL);

		first_ch = arg[0] | or_mask; /* forced to "quoted" if or_mask = 0x80 */
		/* "$@" is special. Even if quoted, it can still
		 * expand to nothing (not even an empty string) */
		if ((first_ch & 0x7f) != '@')
			ored_ch |= first_ch;

		switch (first_ch & 0x7f) {
		/* Highest bit in first_ch indicates that var is double-quoted */
		case '$': /* pid */
			val = utoa(G.root_pid);
			break;
		case '!': /* bg pid */
			val = G.last_bg_pid ? utoa(G.last_bg_pid) : (char*)"";
			break;
		case '?': /* exitcode */
			val = utoa(G.last_exitcode);
			break;
		case '#': /* argc */
			if (arg[1] != SPECIAL_VAR_SYMBOL)
				/* actually, it's a ${#var} */
				goto case_default;
			val = utoa(G.global_argc ? G.global_argc-1 : 0);
			break;
		case '*':
		case '@':
			i = 1;
			if (!G.global_argv[i])
				break;
			ored_ch |= first_ch; /* do it for "$@" _now_, when we know it's not empty */
			if (!(first_ch & 0x80)) { /* unquoted $* or $@ */
				smallint sv = output->o_escape;
				/* unquoted var's contents should be globbed, so don't escape */
				output->o_escape = 0;
				while (G.global_argv[i]) {
					n = expand_on_ifs(output, n, G.global_argv[i]);
					debug_printf_expand("expand_vars_to_list: argv %d (last %d)\n", i, G.global_argc - 1);
					if (G.global_argv[i++][0] && G.global_argv[i]) {
						/* this argv[] is not empty and not last:
						 * put terminating NUL, start new word */
						o_addchr(output, '\0');
						debug_print_list("expand_vars_to_list[2]", output, n);
						n = o_save_ptr(output, n);
						debug_print_list("expand_vars_to_list[3]", output, n);
					}
				}
				output->o_escape = sv;
			} else
			/* If or_mask is nonzero, we handle assignment 'a=....$@.....'
			 * and in this case should treat it like '$*' - see 'else...' below */
			if (first_ch == ('@'|0x80) && !or_mask) { /* quoted $@ */
				while (1) {
					o_addQstr(output, G.global_argv[i], strlen(G.global_argv[i]));
					if (++i >= G.global_argc)
						break;
					o_addchr(output, '\0');
					debug_print_list("expand_vars_to_list[4]", output, n);
					n = o_save_ptr(output, n);
				}
			} else { /* quoted $*: add as one word */
				while (1) {
					o_addQstr(output, G.global_argv[i], strlen(G.global_argv[i]));
					if (!G.global_argv[++i])
						break;
					if (G.ifs[0])
						o_addchr(output, G.ifs[0]);
				}
			}
			break;
		case SPECIAL_VAR_SYMBOL: /* <SPECIAL_VAR_SYMBOL><SPECIAL_VAR_SYMBOL> */
			/* "Empty variable", used to make "" etc to not disappear */
			arg++;
			ored_ch = 0x80;
			break;
#if ENABLE_HUSH_TICK
		case '`': /* <SPECIAL_VAR_SYMBOL>`cmd<SPECIAL_VAR_SYMBOL> */
			*p = '\0';
			arg++;
			/* Can't just stuff it into output o_string,
			 * expanded result may need to be globbed
			 * and $IFS-splitted */
			debug_printf_subst("SUBST '%s' first_ch %x\n", arg, first_ch);
			process_command_subs(&subst_result, arg);
			debug_printf_subst("SUBST RES '%s'\n", subst_result.data);
			val = subst_result.data;
			goto store_val;
#endif
#if ENABLE_SH_MATH_SUPPORT
		case '+': { /* <SPECIAL_VAR_SYMBOL>+cmd<SPECIAL_VAR_SYMBOL> */
			arith_eval_hooks_t hooks;
			arith_t res;
			int errcode;
			char *exp_str;

			arg++; /* skip '+' */
			*p = '\0'; /* replace trailing <SPECIAL_VAR_SYMBOL> */
			debug_printf_subst("ARITH '%s' first_ch %x\n", arg, first_ch);

			exp_str = expand_pseudo_dquoted(arg);
			hooks.lookupvar = get_local_var_value;
			hooks.setvar = arith_set_local_var;
			hooks.endofname = endofname;
			res = arith(exp_str ? exp_str : arg, &errcode, &hooks);
			free(exp_str);

			if (errcode < 0) {
				const char *msg = "error in arithmetic";
				switch (errcode) {
				case -3:
					msg = "exponent less than 0";
					break;
				case -2:
					msg = "divide by 0";
					break;
				case -5:
					msg = "expression recursion loop detected";
					break;
				}
				die_if_script(msg);
			}
			debug_printf_subst("ARITH RES '"arith_t_fmt"'\n", res);
			sprintf(arith_buf, arith_t_fmt, res);
			val = arith_buf;
			break;
		}
#endif
		default: /* <SPECIAL_VAR_SYMBOL>varname<SPECIAL_VAR_SYMBOL> */
		case_default: {
			bool exp_len = false;
			bool exp_null = false;
			char *var = arg;
			char exp_save = exp_save; /* for compiler */
			char exp_op = exp_op; /* for compiler */
			char *exp_word = exp_word; /* for compiler */
			size_t exp_off = 0;

			*p = '\0';
			arg[0] = first_ch & 0x7f;

			/* prepare for expansions */
			if (var[0] == '#') {
				/* handle length expansion ${#var} */
				exp_len = true;
				++var;
			} else {
				/* maybe handle parameter expansion */
				exp_off = strcspn(var, ":-=+?%#");
				if (!var[exp_off])
					exp_off = 0;
				if (exp_off) {
					exp_save = var[exp_off];
					exp_null = exp_save == ':';
					exp_word = var + exp_off;
					if (exp_null)
						++exp_word;
					exp_op = *exp_word++;
					var[exp_off] = '\0';
				}
			}

			/* lookup the variable in question */
			if (isdigit(var[0])) {
				/* handle_dollar() should have vetted var for us */
				i = xatoi_u(var);
				if (i < G.global_argc)
					val = G.global_argv[i];
				/* else val remains NULL: $N with too big N */
			} else
				val = get_local_var_value(var);

			/* handle any expansions */
			if (exp_len) {
				debug_printf_expand("expand: length of '%s' = ", val);
				val = utoa(val ? strlen(val) : 0);
				debug_printf_expand("%s\n", val);
			} else if (exp_off) {
				if (exp_op == '%' || exp_op == '#') {
					if (val) {
						/* we need to do a pattern match */
						bool match_at_left;
						char *loc;
						scan_t scan = pick_scan(exp_op, *exp_word, &match_at_left);
						if (exp_op == *exp_word)	/* ## or %% */
							++exp_word;
						val = dyn_val = xstrdup(val);
						loc = scan(dyn_val, exp_word, match_at_left);
						if (match_at_left) /* # or ## */
							val = loc;
						else if (loc) /* % or %% and match was found */
							*loc = '\0';
					}
				} else {
					/* we need to do an expansion */
					int exp_test = (!val || (exp_null && !val[0]));
					if (exp_op == '+')
						exp_test = !exp_test;
					debug_printf_expand("expand: op:%c (null:%s) test:%i\n", exp_op,
						exp_null ? "true" : "false", exp_test);
					if (exp_test) {
						if (exp_op == '?') {
//TODO: how interactive bash aborts expansion mid-command?
							/* ${var?[error_msg_if_unset]} */
							/* ${var:?[error_msg_if_unset_or_null]} */
							/* mimic bash message */
							die_if_script("%s: %s",
								var,
								exp_word[0] ? exp_word : "parameter null or not set"
							);
						} else {
							val = exp_word;
						}

						if (exp_op == '=') {
							/* ${var=[word]} or ${var:=[word]} */
							if (isdigit(var[0]) || var[0] == '#') {
								/* mimic bash message */
								die_if_script("$%s: cannot assign in this way", var);
								val = NULL;
							} else {
								char *new_var = xasprintf("%s=%s", var, val);
								set_local_var(new_var, /*exp:*/ 0, /*lvl:*/ 0, /*ro:*/ 0);
							}
						}
					}
				}

				var[exp_off] = exp_save;
			}

			arg[0] = first_ch;
#if ENABLE_HUSH_TICK
 store_val:
#endif
			if (!(first_ch & 0x80)) { /* unquoted $VAR */
				debug_printf_expand("unquoted '%s', output->o_escape:%d\n", val, output->o_escape);
				if (val) {
					/* unquoted var's contents should be globbed, so don't escape */
					smallint sv = output->o_escape;
					output->o_escape = 0;
					n = expand_on_ifs(output, n, val);
					val = NULL;
					output->o_escape = sv;
				}
			} else { /* quoted $VAR, val will be appended below */
				debug_printf_expand("quoted '%s', output->o_escape:%d\n", val, output->o_escape);
			}
		} /* default: */
		} /* switch (char after <SPECIAL_VAR_SYMBOL>) */

		if (val) {
			o_addQstr(output, val, strlen(val));
		}
		free(dyn_val);
		/* Do the check to avoid writing to a const string */
		if (*p != SPECIAL_VAR_SYMBOL)
			*p = SPECIAL_VAR_SYMBOL;

#if ENABLE_HUSH_TICK
		o_free(&subst_result);
#endif
		arg = ++p;
	} /* end of "while (SPECIAL_VAR_SYMBOL is found) ..." */

	if (arg[0]) {
		debug_print_list("expand_vars_to_list[a]", output, n);
		/* this part is literal, and it was already pre-quoted
		 * if needed (much earlier), do not use o_addQstr here! */
		o_addstr_with_NUL(output, arg);
		debug_print_list("expand_vars_to_list[b]", output, n);
	} else if (output->length == o_get_last_ptr(output, n) /* expansion is empty */
	 && !(ored_ch & 0x80) /* and all vars were not quoted. */
	) {
		n--;
		/* allow to reuse list[n] later without re-growth */
		output->has_empty_slot = 1;
	} else {
		o_addchr(output, '\0');
	}
	return n;
}

static char **expand_variables(char **argv, int or_mask)
{
	int n;
	char **list;
	char **v;
	o_string output = NULL_O_STRING;

	if (or_mask & 0x100) {
		output.o_escape = 1; /* protect against globbing for "$var" */
		/* (unquoted $var will temporarily switch it off) */
		output.o_glob = 1;
	}

	n = 0;
	v = argv;
	while (*v) {
		n = expand_vars_to_list(&output, n, *v, (unsigned char)or_mask);
		v++;
	}
	debug_print_list("expand_variables", &output, n);

	/* output.data (malloced in one block) gets returned in "list" */
	list = o_finalize_list(&output, n);
	debug_print_strings("expand_variables[1]", list);
	return list;
}

static char **expand_strvec_to_strvec(char **argv)
{
	return expand_variables(argv, 0x100);
}

#if ENABLE_HUSH_BASH_COMPAT
static char **expand_strvec_to_strvec_singleword_noglob(char **argv)
{
	return expand_variables(argv, 0x80);
}
#endif

#ifdef CMD_SINGLEWORD_NOGLOB_COND
static char **expand_strvec_to_strvec_singleword_noglob_cond(char **argv)
{
	int n;
	char **list;
	char **v;
	o_string output = NULL_O_STRING;

	n = 0;
	v = argv;
	while (*v) {
		int is_var = is_well_formed_var_name(*v, '=');
		/* is_var * 0x80: singleword expansion for vars */
		n = expand_vars_to_list(&output, n, *v, is_var * 0x80);

		/* Subtle! expand_vars_to_list did not glob last word yet.
		 * It does this only when fed with further data.
		 * Therefore we set globbing flags AFTER it, not before:
		 */

		/* if it is not recognizably abc=...; then: */
		output.o_escape = !is_var; /* protect against globbing for "$var" */
		/* (unquoted $var will temporarily switch it off) */
		output.o_glob = !is_var; /* and indeed do globbing */
		v++;
	}
	debug_print_list("expand_cond", &output, n);

	/* output.data (malloced in one block) gets returned in "list" */
	list = o_finalize_list(&output, n);
	debug_print_strings("expand_cond[1]", list);
	return list;
}
#endif

/* Used for expansion of right hand of assignments */
/* NB: should NOT do globbing! "export v=/bin/c*; env | grep ^v=" outputs
 * "v=/bin/c*" */
static char *expand_string_to_string(const char *str)
{
	char *argv[2], **list;

	argv[0] = (char*)str;
	argv[1] = NULL;
	list = expand_variables(argv, 0x80); /* 0x80: singleword expansion */
	if (HUSH_DEBUG)
		if (!list[0] || list[1])
			bb_error_msg_and_die("BUG in varexp2");
	/* actually, just move string 2*sizeof(char*) bytes back */
	overlapping_strcpy((char*)list, list[0]);
	unbackslash((char*)list);
	debug_printf_expand("string_to_string='%s'\n", (char*)list);
	return (char*)list;
}

/* Used for "eval" builtin */
static char* expand_strvec_to_string(char **argv)
{
	char **list;

	list = expand_variables(argv, 0x80);
	/* Convert all NULs to spaces */
	if (list[0]) {
		int n = 1;
		while (list[n]) {
			if (HUSH_DEBUG)
				if (list[n-1] + strlen(list[n-1]) + 1 != list[n])
					bb_error_msg_and_die("BUG in varexp3");
			/* bash uses ' ' regardless of $IFS contents */
			list[n][-1] = ' ';
			n++;
		}
	}
	overlapping_strcpy((char*)list, list[0]);
	debug_printf_expand("strvec_to_string='%s'\n", (char*)list);
	return (char*)list;
}

static char **expand_assignments(char **argv, int count)
{
	int i;
	char **p = NULL;
	/* Expand assignments into one string each */
	for (i = 0; i < count; i++) {
		p = add_string_to_strings(p, expand_string_to_string(argv[i]));
	}
	return p;
}


#if BB_MMU
/* never called */
void re_execute_shell(char ***to_free, const char *s,
		char *g_argv0, char **g_argv,
		char **builtin_argv) NORETURN;

static void reset_traps_to_defaults(void)
{
	/* This function is always called in a child shell
	 * after fork (not vfork, NOMMU doesn't use this function).
	 * Child shells are not interactive.
	 * SIGTTIN/SIGTTOU/SIGTSTP should not have special handling.
	 * Testcase: (while :; do :; done) + ^Z should background.
	 * Same goes for SIGTERM, SIGHUP, SIGINT.
	 */
	unsigned sig;
	unsigned mask;

	if (!G.traps && !(G.non_DFL_mask & SPECIAL_INTERACTIVE_SIGS))
		return;

	/* Stupid. It can be done with *single* &= op, but we can't use
	 * the fact that G.blocked_set is implemented as a bitmask... */
	mask = (SPECIAL_INTERACTIVE_SIGS >> 1);
	sig = 1;
	while (1) {
		if (mask & 1)
			sigdelset(&G.blocked_set, sig);
		mask >>= 1;
		if (!mask)
			break;
		sig++;
	}

	G.non_DFL_mask &= ~SPECIAL_INTERACTIVE_SIGS;
	mask = G.non_DFL_mask;
	if (G.traps) for (sig = 0; sig < NSIG; sig++, mask >>= 1) {
		if (!G.traps[sig])
			continue;
		free(G.traps[sig]);
		G.traps[sig] = NULL;
		/* There is no signal for 0 (EXIT) */
		if (sig == 0)
			continue;
		/* There was a trap handler, we are removing it.
		 * But if sig still has non-DFL handling,
		 * we should not unblock it. */
		if (mask & 1)
			continue;
		sigdelset(&G.blocked_set, sig);
	}
	sigprocmask(SIG_SETMASK, &G.blocked_set, NULL);
}

#else /* !BB_MMU */

static void re_execute_shell(char ***to_free, const char *s,
		char *g_argv0, char **g_argv,
		char **builtin_argv) NORETURN;
static void re_execute_shell(char ***to_free, const char *s,
		char *g_argv0, char **g_argv,
		char **builtin_argv)
{
	char param_buf[sizeof("-$%x:%x:%x:%x:%x") + sizeof(unsigned) * 2];
	char *heredoc_argv[4];
	struct variable *cur;
#if ENABLE_HUSH_FUNCTIONS
	struct function *funcp;
#endif
	char **argv, **pp;
	unsigned cnt;

	if (!g_argv0) { /* heredoc */
		argv = heredoc_argv;
		argv[0] = (char *) G.argv0_for_re_execing;
		argv[1] = (char *) "-<";
		argv[2] = (char *) s;
		argv[3] = NULL;
		pp = &argv[3]; /* used as pointer to empty environment */
		goto do_exec;
	}

	cnt = 0;
	pp = builtin_argv;
	if (pp) while (*pp++)
		cnt++;

	sprintf(param_buf, "-$%x:%x:%x:%x" IF_HUSH_LOOPS(":%x")
			, (unsigned) G.root_pid
			, (unsigned) G.last_bg_pid
			, (unsigned) G.last_exitcode
			, cnt
			IF_HUSH_LOOPS(, G.depth_of_loop)
			);
	/* 1:hush 2:-$<pid>:<pid>:<exitcode>:<depth> <vars...> <funcs...>
	 * 3:-c 4:<cmd> 5:<arg0> <argN...> 6:NULL
	 */
	cnt += 6;
	for (cur = G.top_var; cur; cur = cur->next) {
		if (!cur->flg_export || cur->flg_read_only)
			cnt += 2;
	}
#if ENABLE_HUSH_FUNCTIONS
	for (funcp = G.top_func; funcp; funcp = funcp->next)
		cnt += 3;
#endif
	pp = g_argv;
	while (*pp++)
		cnt++;
	*to_free = argv = pp = xzalloc(sizeof(argv[0]) * cnt);
	*pp++ = (char *) G.argv0_for_re_execing;
	*pp++ = param_buf;
	for (cur = G.top_var; cur; cur = cur->next) {
		if (cur->varstr == hush_version_str)
			continue;
		if (cur->flg_read_only) {
			*pp++ = (char *) "-R";
			*pp++ = cur->varstr;
		} else if (!cur->flg_export) {
			*pp++ = (char *) "-V";
			*pp++ = cur->varstr;
		}
	}
#if ENABLE_HUSH_FUNCTIONS
	for (funcp = G.top_func; funcp; funcp = funcp->next) {
		*pp++ = (char *) "-F";
		*pp++ = funcp->name;
		*pp++ = funcp->body_as_string;
	}
#endif
	/* We can pass activated traps here. Say, -Tnn:trap_string
	 *
	 * However, POSIX says that subshells reset signals with traps
	 * to SIG_DFL.
	 * I tested bash-3.2 and it not only does that with true subshells
	 * of the form ( list ), but with any forked children shells.
	 * I set trap "echo W" WINCH; and then tried:
	 *
	 * { echo 1; sleep 20; echo 2; } &
	 * while true; do echo 1; sleep 20; echo 2; break; done &
	 * true | { echo 1; sleep 20; echo 2; } | cat
	 *
	 * In all these cases sending SIGWINCH to the child shell
	 * did not run the trap. If I add trap "echo V" WINCH;
	 * _inside_ group (just before echo 1), it works.
	 *
	 * I conclude it means we don't need to pass active traps here.
	 * exec syscall below resets them to SIG_DFL for us.
	 */
	*pp++ = (char *) "-c";
	*pp++ = (char *) s;
	if (builtin_argv) {
		while (*++builtin_argv)
			*pp++ = *builtin_argv;
		*pp++ = (char *) "";
	}
	*pp++ = g_argv0;
	while (*g_argv)
		*pp++ = *g_argv++;
	/* *pp = NULL; - is already there */
	pp = environ;

 do_exec:
	debug_printf_exec("re_execute_shell pid:%d cmd:'%s'\n", getpid(), s);
	sigprocmask(SIG_SETMASK, &G.inherited_set, NULL);
	execve(bb_busybox_exec_path, argv, pp);
	/* Fallback. Useful for init=/bin/hush usage etc */
	if (argv[0][0] == '/')
		execve(argv[0], argv, pp);
	xfunc_error_retval = 127;
	bb_error_msg_and_die("can't re-execute the shell");
}
#endif  /* !BB_MMU */


static void setup_heredoc(struct redir_struct *redir)
{
	struct fd_pair pair;
	pid_t pid;
	int len, written;
	/* the _body_ of heredoc (misleading field name) */
	const char *heredoc = redir->rd_filename;
	char *expanded;
#if !BB_MMU
	char **to_free;
#endif

	expanded = NULL;
	if (!(redir->rd_dup & HEREDOC_QUOTED)) {
		expanded = expand_pseudo_dquoted(heredoc);
		if (expanded)
			heredoc = expanded;
	}
	len = strlen(heredoc);

	close(redir->rd_fd); /* often saves dup2+close in xmove_fd */
	xpiped_pair(pair);
	xmove_fd(pair.rd, redir->rd_fd);

	/* Try writing without forking. Newer kernels have
	 * dynamically growing pipes. Must use non-blocking write! */
	ndelay_on(pair.wr);
	while (1) {
		written = write(pair.wr, heredoc, len);
		if (written <= 0)
			break;
		len -= written;
		if (len == 0) {
			close(pair.wr);
			free(expanded);
			return;
		}
		heredoc += written;
	}
	ndelay_off(pair.wr);

	/* Okay, pipe buffer was not big enough */
	/* Note: we must not create a stray child (bastard? :)
	 * for the unsuspecting parent process. Child creates a grandchild
	 * and exits before parent execs the process which consumes heredoc
	 * (that exec happens after we return from this function) */
#if !BB_MMU
	to_free = NULL;
#endif
	pid = vfork();
	if (pid < 0)
		bb_perror_msg_and_die("vfork");
	if (pid == 0) {
		/* child */
		disable_restore_tty_pgrp_on_exit();
		pid = BB_MMU ? fork() : vfork();
		if (pid < 0)
			bb_perror_msg_and_die(BB_MMU ? "fork" : "vfork");
		if (pid != 0)
			_exit(0);
		/* grandchild */
		close(redir->rd_fd); /* read side of the pipe */
#if BB_MMU
		full_write(pair.wr, heredoc, len); /* may loop or block */
		_exit(0);
#else
		/* Delegate blocking writes to another process */
		xmove_fd(pair.wr, STDOUT_FILENO);
		re_execute_shell(&to_free, heredoc, NULL, NULL, NULL);
#endif
	}
	/* parent */
#if ENABLE_HUSH_FAST
	G.count_SIGCHLD++;
//bb_error_msg("[%d] fork in setup_heredoc: G.count_SIGCHLD:%d G.handled_SIGCHLD:%d", getpid(), G.count_SIGCHLD, G.handled_SIGCHLD);
#endif
	enable_restore_tty_pgrp_on_exit();
#if !BB_MMU
	free(to_free);
#endif
	close(pair.wr);
	free(expanded);
	wait(NULL); /* wait till child has died */
}

/* squirrel != NULL means we squirrel away copies of stdin, stdout,
 * and stderr if they are redirected. */
static int setup_redirects(struct command *prog, int squirrel[])
{
	int openfd, mode;
	struct redir_struct *redir;

	for (redir = prog->redirects; redir; redir = redir->next) {
		if (redir->rd_type == REDIRECT_HEREDOC2) {
			/* rd_fd<<HERE case */
			if (squirrel && redir->rd_fd < 3
			 && squirrel[redir->rd_fd] < 0
			) {
				squirrel[redir->rd_fd] = dup(redir->rd_fd);
			}
			/* for REDIRECT_HEREDOC2, rd_filename holds _contents_
			 * of the heredoc */
			debug_printf_parse("set heredoc '%s'\n",
					redir->rd_filename);
			setup_heredoc(redir);
			continue;
		}

		if (redir->rd_dup == REDIRFD_TO_FILE) {
			/* rd_fd<*>file case (<*> is <,>,>>,<>) */
			char *p;
			if (redir->rd_filename == NULL) {
				/* Something went wrong in the parse.
				 * Pretend it didn't happen */
				bb_error_msg("bug in redirect parse");
				continue;
			}
			mode = redir_table[redir->rd_type].mode;
			p = expand_string_to_string(redir->rd_filename);
			openfd = open_or_warn(p, mode);
			free(p);
			if (openfd < 0) {
			/* this could get lost if stderr has been redirected, but
			 * bash and ash both lose it as well (though zsh doesn't!) */
//what the above comment tries to say?
				return 1;
			}
		} else {
			/* rd_fd<*>rd_dup or rd_fd<*>- cases */
			openfd = redir->rd_dup;
		}

		if (openfd != redir->rd_fd) {
			if (squirrel && redir->rd_fd < 3
			 && squirrel[redir->rd_fd] < 0
			) {
				squirrel[redir->rd_fd] = dup(redir->rd_fd);
			}
			if (openfd == REDIRFD_CLOSE) {
				/* "n>-" means "close me" */
				close(redir->rd_fd);
			} else {
				xdup2(openfd, redir->rd_fd);
				if (redir->rd_dup == REDIRFD_TO_FILE)
					close(openfd);
			}
		}
	}
	return 0;
}

static void restore_redirects(int squirrel[])
{
	int i, fd;
	for (i = 0; i < 3; i++) {
		fd = squirrel[i];
		if (fd != -1) {
			/* We simply die on error */
			xmove_fd(fd, i);
		}
	}
}


static void free_pipe_list(struct pipe *head);

/* Return code is the exit status of the pipe */
static void free_pipe(struct pipe *pi)
{
	char **p;
	struct command *command;
	struct redir_struct *r, *rnext;
	int a, i;

	if (pi->stopped_cmds > 0) /* why? */
		return;
	debug_printf_clean("run pipe: (pid %d)\n", getpid());
	for (i = 0; i < pi->num_cmds; i++) {
		command = &pi->cmds[i];
		debug_printf_clean("  command %d:\n", i);
		if (command->argv) {
			for (a = 0, p = command->argv; *p; a++, p++) {
				debug_printf_clean("   argv[%d] = %s\n", a, *p);
			}
			free_strings(command->argv);
			command->argv = NULL;
		}
		/* not "else if": on syntax error, we may have both! */
		if (command->group) {
			debug_printf_clean("   begin group (cmd_type:%d)\n",
					command->cmd_type);
			free_pipe_list(command->group);
			debug_printf_clean("   end group\n");
			command->group = NULL;
		}
		/* else is crucial here.
		 * If group != NULL, child_func is meaningless */
#if ENABLE_HUSH_FUNCTIONS
		else if (command->child_func) {
			debug_printf_exec("cmd %p releases child func at %p\n", command, command->child_func);
			command->child_func->parent_cmd = NULL;
		}
#endif
#if !BB_MMU
		free(command->group_as_string);
		command->group_as_string = NULL;
#endif
		for (r = command->redirects; r; r = rnext) {
			debug_printf_clean("   redirect %d%s",
					r->rd_fd, redir_table[r->rd_type].descrip);
			/* guard against the case >$FOO, where foo is unset or blank */
			if (r->rd_filename) {
				debug_printf_clean(" fname:'%s'\n", r->rd_filename);
				free(r->rd_filename);
				r->rd_filename = NULL;
			}
			debug_printf_clean(" rd_dup:%d\n", r->rd_dup);
			rnext = r->next;
			free(r);
		}
		command->redirects = NULL;
	}
	free(pi->cmds);   /* children are an array, they get freed all at once */
	pi->cmds = NULL;
#if ENABLE_HUSH_JOB
	free(pi->cmdtext);
	pi->cmdtext = NULL;
#endif
}

static void free_pipe_list(struct pipe *head)
{
	struct pipe *pi, *next;

	for (pi = head; pi; pi = next) {
#if HAS_KEYWORDS
		debug_printf_clean(" pipe reserved word %d\n", pi->res_word);
#endif
		free_pipe(pi);
		debug_printf_clean("pipe followup code %d\n", pi->followup);
		next = pi->next;
		/*pi->next = NULL;*/
		free(pi);
	}
}


static int run_list(struct pipe *pi);
#if BB_MMU
#define parse_stream(pstring, input, end_trigger) \
	parse_stream(input, end_trigger)
#endif
static struct pipe *parse_stream(char **pstring,
		struct in_str *input,
		int end_trigger);
static void parse_and_run_string(const char *s);


static char *find_in_path(const char *arg)
{
	char *ret = NULL;
	const char *PATH = get_local_var_value("PATH");

	if (!PATH)
		return NULL;

	while (1) {
		const char *end = strchrnul(PATH, ':');
		int sz = end - PATH; /* must be int! */

		free(ret);
		if (sz != 0) {
			ret = xasprintf("%.*s/%s", sz, PATH, arg);
		} else {
			/* We have xxx::yyyy in $PATH,
			 * it means "use current dir" */
			ret = xstrdup(arg);
		}
		if (access(ret, F_OK) == 0)
			break;

		if (*end == '\0') {
			free(ret);
			return NULL;
		}
		PATH = end + 1;
	}

	return ret;
}

static const struct built_in_command* find_builtin_helper(const char *name,
		const struct built_in_command *x,
		const struct built_in_command *end)
{
	while (x != end) {
		if (strcmp(name, x->cmd) != 0) {
			x++;
			continue;
		}
		debug_printf_exec("found builtin '%s'\n", name);
		return x;
	}
	return NULL;
}
static const struct built_in_command* find_builtin1(const char *name)
{
	return find_builtin_helper(name, bltins1, &bltins1[ARRAY_SIZE(bltins1)]);
}
static const struct built_in_command* find_builtin(const char *name)
{
	const struct built_in_command *x = find_builtin1(name);
	if (x)
		return x;
	return find_builtin_helper(name, bltins2, &bltins2[ARRAY_SIZE(bltins2)]);
}

#if ENABLE_HUSH_FUNCTIONS
static const struct function *find_function(const char *name)
{
	const struct function *funcp = G.top_func;
	while (funcp) {
		if (strcmp(name, funcp->name) == 0) {
			break;
		}
		funcp = funcp->next;
	}
	if (funcp)
		debug_printf_exec("found function '%s'\n", name);
	return funcp;
}

/* Note: takes ownership on name ptr */
static struct function *new_function(char *name)
{
	struct function *funcp;
	struct function **funcpp = &G.top_func;

	while ((funcp = *funcpp) != NULL) {
		struct command *cmd;

		if (strcmp(funcp->name, name) != 0) {
			funcpp = &funcp->next;
			continue;
		}

		cmd = funcp-><