hush: fix "var=val >file" not creating file

[oweals/busybox.git] / 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>
 *
 * 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.
 *      setup_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
 *      Here Documents ( << word )
 *      Functions
 *      Tilde Expansion
 *      Parameter Expansion for substring processing ${var#word} ${var%word}
 *
 * Bash stuff maybe optional enable:
 *      &> and >& redirection of stdout+stderr
 *      Brace expansion
 *      reserved words: [[ ]] function select
 *      substrings ${var:1:5}
 *
 * Major bugs:
 *      job handling woefully incomplete and buggy (improved --vda)
 * to-do:
 *      port selected bugfixes from post-0.49 busybox lash - done?
 *      change { and } from special chars to reserved words
 *      builtins: return, trap, ulimit
 *      test magic exec with redirection only
 *      follow IFS rules more precisely, including update semantics
 *      figure out what to do with backslash-newline
 *      propagate syntax errors, die on resource errors?
 *      continuation lines, both explicit and implicit - done?
 *
 * Licensed under the GPL v2 or later, see the file LICENSE in this tarball.
 */

#include "busybox.h" /* for APPLET_IS_NOFORK/NOEXEC */
//TODO: pull in some .h and find out whether we have SINGLE_APPLET_MAIN?
//#include "applet_tables.h" doesn't work
#include <glob.h>
/* #include <dmalloc.h> */
#if ENABLE_HUSH_CASE
#include <fnmatch.h>
#endif

#include "math.h"

#define HUSH_VER_STR "0.92"

#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 USE_FEATURE_SH_STANDALONE
#define SKIP_FEATURE_SH_STANDALONE(...) __VA_ARGS__
#define ENABLE_FEATURE_SH_STANDALONE 0
#define USE_FEATURE_SH_STANDALONE(...)
#define SKIP_FEATURE_SH_STANDALONE(...) __VA_ARGS__
#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

/* Keep unconditionally on for now */
#define HUSH_DEBUG 1
/* In progress... */
#define ENABLE_HUSH_FUNCTIONS 0


/* 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)

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

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

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

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

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

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

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

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

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

#ifndef debug_printf_clean
/* broken, of course, but OK for testing */
static const char *indenter(int i)
{
        static const char blanks[] ALIGN1 =
                "                                    ";
        return &blanks[sizeof(blanks) - i - 1];
}
#define debug_printf_clean(...) fprintf(stderr, __VA_ARGS__)
#define DEBUG_CLEAN 1
#endif

#if DEBUG_EXPAND
static void debug_print_strings(const char *prefix, char **vv)
{
        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.
 */
#ifdef FOR_HUSH_LEAKTOOL
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


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

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

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

#define SPECIAL_VAR_SYMBOL 3

typedef enum redir_type {
        REDIRECT_INPUT     = 1,
        REDIRECT_OVERWRITE = 2,
        REDIRECT_APPEND    = 3,
        REDIRECT_HEREIS    = 4,
        REDIRECT_IO        = 5
} redir_type;

/* 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[] = {
        { 0,                         0, "()" },
        { O_RDONLY,                  0, "<"  },
        { O_CREAT|O_TRUNC|O_WRONLY,  1, ">"  },
        { O_CREAT|O_APPEND|O_WRONLY, 1, ">>" },
        { O_RDONLY,                 -1, "<<" },
        { O_RDWR,                    1, "<>" }
};

typedef enum pipe_style {
        PIPE_SEQ = 1,
        PIPE_AND = 2,
        PIPE_OR  = 3,
        PIPE_BG  = 4,
} pipe_style;

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  ,
        /* two pseudo-keywords support contrived "case" syntax: */
        RES_MATCH , /* "word)" */
        RES_CASEI , /* "this command is inside CASE" */
        RES_ESAC  ,
#endif
        RES_XXXX  ,
        RES_SNTX
} reserved_style;

struct redir_struct {
        struct redir_struct *next;
        char *rd_filename;          /* filename */
        int fd;                     /* file descriptor being redirected */
        int dup;                    /* -1, or file descriptor being duplicated */
        smallint /*enum redir_type*/ rd_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 grp_type;          /* GRP_xxx */
        struct pipe *group;         /* if non-NULL, this "prog" is {} group,
                                     * subshell, or a compound statement */
        char **argv;                /* command name and arguments */
        struct redir_struct *redirects; /* I/O redirections */
};
/* 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.
 */
#define GRP_NORMAL   0
#define GRP_SUBSHELL 1
#if ENABLE_HUSH_FUNCTIONS
#define GRP_FUNCTION 2
#endif

struct pipe {
        struct pipe *next;
        int num_cmds;               /* total number of commands in job */
        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... */
};

/* 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 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 1: "{ { false; ..."
         * example 2: "if true; then { false; ..."
         * example 3: "if true; then if false; ..."
         * when we find closing "}" / "fi" / whatever, we move list_head
         * into stack->command->group and delete ourself.
         */
        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 */
        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;
};

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;
        smallint nonnull;
        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 *);
        int (*peek) (struct in_str *);
} in_str;
#define i_getch(input) ((input)->get(input))
#define i_peek(input) ((input)->peek(input))

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


/* "Globals" within this file */
/* Sorted roughly by size (smaller offsets == smaller code) */
struct globals {
#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;
        pid_t saved_tty_pgrp;
        int last_jobid;
        struct pipe *job_list;
        struct pipe *toplevel_list;
////    smallint ctrl_z_flag;
#endif
        smallint flag_SIGINT;
#if ENABLE_HUSH_LOOPS
        smallint flag_break_continue;
#endif
        smallint fake_mode;
        /* These four support $?, $#, and $1 */
        smalluint last_return_code;
        /* is 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 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;
        /* Signal and trap handling */
//      unsigned count_SIGCHLD;
//      unsigned handled_SIGCHLD;
        /* 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;
        char user_input_buf[ENABLE_FEATURE_EDITING ? BUFSIZ : 2];
#if ENABLE_FEATURE_SH_STANDALONE
        struct nofork_save_area nofork_save;
#endif
#if ENABLE_HUSH_JOB
        sigjmp_buf toplevel_jb;
#endif
};
#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);
static int builtin_echo(char **argv);
static int builtin_eval(char **argv);
static int builtin_exec(char **argv);
static int builtin_exit(char **argv);
static int builtin_export(char **argv);
#if ENABLE_HUSH_JOB
static int builtin_fg_bg(char **argv);
static int builtin_jobs(char **argv);
#endif
#if ENABLE_HUSH_HELP
static int builtin_help(char **argv);
#endif
static int builtin_pwd(char **argv);
static int builtin_read(char **argv);
static int builtin_test(char **argv);
static int builtin_trap(char **argv);
static int builtin_true(char **argv);
static int builtin_set(char **argv);
static int builtin_shift(char **argv);
static int builtin_source(char **argv);
static int builtin_umask(char **argv);
static int builtin_unset(char **argv);
static int builtin_wait(char **argv);
#if ENABLE_HUSH_LOOPS
static int builtin_break(char **argv);
static int builtin_continue(char **argv);
#endif
//static int builtin_not_written(char **argv);

/* 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);
#if ENABLE_HUSH_HELP
        const char *descr;
#define BLTIN(cmd, func, help) { cmd, func, help }
#else
#define BLTIN(cmd, func, help) { cmd, func }
#endif
};

/* For now, echo and test are unconditionally enabled.
 * Maybe make it configurable? */
static const struct built_in_command bltins[] = {
        BLTIN("."     , builtin_source, "Run commands in a file"),
        BLTIN(":"     , builtin_true, "No-op"),
        BLTIN("["     , builtin_test, "Test condition"),
#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("echo"  , builtin_echo, "Write to stdout"),
        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 variable"),
#if ENABLE_HUSH_JOB
        BLTIN("fg"    , builtin_fg_bg, "Bring job into the foreground"),
        BLTIN("jobs"  , builtin_jobs, "List active jobs"),
#endif
        BLTIN("pwd"   , builtin_pwd, "Print current directory"),
        BLTIN("read"  , builtin_read, "Input environment variable"),
//      BLTIN("return", builtin_not_written, "Return from a function"),
        BLTIN("set"   , builtin_set, "Set/unset shell local variables"),
        BLTIN("shift" , builtin_shift, "Shift positional parameters"),
        BLTIN("test"  , builtin_test, "Test condition"),
        BLTIN("trap"  , builtin_trap, "Trap signals"),
//      BLTIN("ulimit", builtin_not_written, "Control resource limits"),
        BLTIN("umask" , builtin_umask, "Set file creation mask"),
        BLTIN("unset" , builtin_unset, "Unset environment variable"),
        BLTIN("wait"  , builtin_wait, "Wait for process"),
#if ENABLE_HUSH_HELP
        BLTIN("help"  , builtin_help, "List shell built-in commands"),
#endif
};


static void maybe_die(const char *notice, const char *msg)
{
        /* Was using fancy stuff:
         * (G_interactive_fd ? bb_error_msg : bb_error_msg_and_die)(...params...)
         * but it SEGVs. ?! Oh well... explicit temp ptr works around that */
        void FAST_FUNC (*fp)(const char *s, ...) = bb_error_msg_and_die;
#if ENABLE_HUSH_INTERACTIVE
        if (G_interactive_fd)
                fp = bb_error_msg;
#endif
        fp(msg ? "%s: %s" : notice, notice, msg);
}
#if 1
#define syntax(msg) maybe_die("syntax error", msg);
#else
/* Debug -- trick gcc to expand __LINE__ and convert to string */
#define __syntax(msg, line) maybe_die("syntax error hush.c:" # line, msg)
#define _syntax(msg, line) __syntax(msg, line)
#define syntax(msg) _syntax(msg, __LINE__)
#endif


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

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

/* 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;
}

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);
}

static void putenv_all(char **strings)
{
        if (!strings)
                return;
        while (*strings) {
                debug_printf_env("putenv '%s'\n", *strings);
                putenv(*strings++);
        }
}

static char **putenv_all_and_save_old(char **strings)
{
        char **old = NULL;
        char **s = strings;

        if (!strings)
                return old;
        while (*strings) {
                char *v, *eq;

                eq = strchr(*strings, '=');
                if (eq) {
                        *eq = '\0';
                        v = getenv(*strings);
                        *eq = '=';
                        if (v) {
                                /* v points to VAL in VAR=VAL, go back to VAR */
                                v -= (eq - *strings) + 1;
                                old = add_string_to_strings(old, v);
                        }
                }
                strings++;
        }
        putenv_all(s);
        return old;
}

static void free_strings_and_unsetenv(char **strings, int unset)
{
        char **v;

        if (!strings)
                return;

        v = strings;
        while (*v) {
                if (unset) {
                        debug_printf_env("unsetenv '%s'\n", *v);
                        bb_unsetenv(*v);
                }
                free(*v++);
        }
        free(strings);
}

static void free_strings(char **strings)
{
        free_strings_and_unsetenv(strings, 0);
}


/* 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. [TODO]
 *
 * If job control is off, backgrounded commands ("cmd &")
 * have SIGINT, SIGQUIT set to SIG_IGN.
 *
 * Commands run in command substitution ("`cmd`")
 * have SIGTTIN, SIGTTOU, SIGTSTP set to SIG_IGN.
 *
 * Ordinary commands have signals set to SIG_IGN/DFL set as inherited
 * by the shell from its parent.
 *
 * Siganls 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) (right?)
 * 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).
 *    (check/expand this)
 *    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:
 *    nothing for {} child shell (say, "true | { true; true; } | true")
 *    unset all traps if () shell. [TODO]
 * 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 [disabled - bug somewhere, + bloat]
 * and to restore tty pgrp on signal-induced exit.
 *
 * TODO: check/fix wait builtin to be interruptible.
 */

//static void SIGCHLD_handler(int sig UNUSED_PARAM)
//{
//      G.count_SIGCHLD++;
//}

/* called once at shell init */
static void init_signal_mask(void)
{
        unsigned sig;
        unsigned mask = (1 << SIGQUIT);
        if (G_interactive_fd) {
                mask = 0
                        | (1 << SIGQUIT)
                        | (1 << SIGTERM)
                        | (1 << SIGHUP)
#if ENABLE_HUSH_JOB
                        | (1 << SIGTTIN) | (1 << SIGTTOU) | (1 << SIGTSTP)
#endif
                        | (1 << SIGINT)
                ;
        }
        G.non_DFL_mask = mask;

        sigprocmask(SIG_SETMASK, NULL, &G.blocked_set);
        sig = 0;
        while (mask) {
                if (mask & 1)
                        sigaddset(&G.blocked_set, sig);
                mask >>= 1;
                sig++;
        }
        sigdelset(&G.blocked_set, SIGCHLD);
        sigprocmask(SIG_SETMASK, &G.blocked_set, &G.inherited_set);
}

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_return_code;
                                builtin_eval(argv);
                                free(argv[1]);
                                G.last_return_code = save_rcode;
                        } /* else: "" trap, ignoring signal */
                        continue;
                }
                /* not a trap: special action */
                switch (sig) {
//              case SIGCHLD:
//                      G.count_SIGCHLD++;
//                      break;
                case SIGINT:
                        bb_putchar('\n');
                        G.flag_SIGINT = 1;
                        break;
//TODO
//              case SIGHUP: ...
//                      break;
                default: /* SIGTERM, SIGQUIT, SIGTTIN, SIGTTOU, SIGTSTP */
                        break;
                }
        }
        return last_sig;
}

#if ENABLE_HUSH_JOB

/* Restores tty foreground process group, and exits.
 * May be called as signal handler for fatal signal
 * (will faithfully 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_interactive_fd && 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 */
}

/* helper */
static void maybe_set_sighandler(int sig)
{
        void (*handler)(int);
        /* non_DFL_mask'ed signals are, well, masked,
         * no need to set handler for them.
         */
        if (!((G.non_DFL_mask >> sig) & 1)) {
                handler = signal(sig, sigexit);
                if (handler == SIG_IGN) /* oops... restore back to IGN! */
                        signal(sig, handler);
        }
}
/* Used only to set handler to restore pgrp on exit */
static void set_fatal_signals_to_sigexit(void)
{
        if (HUSH_DEBUG) {
                maybe_set_sighandler(SIGILL );
                maybe_set_sighandler(SIGFPE );
                maybe_set_sighandler(SIGBUS );
                maybe_set_sighandler(SIGSEGV);
                maybe_set_sighandler(SIGTRAP);
        } /* else: hush is perfect. what SEGV? */

        maybe_set_sighandler(SIGABRT);

        /* bash 3.2 seems to handle these just like 'fatal' ones */
        maybe_set_sighandler(SIGPIPE);
        maybe_set_sighandler(SIGALRM);
        maybe_set_sighandler(SIGHUP );

        /* if we aren't interactive... but in this case
         * we never want to restore pgrp on exit, and this fn is not called */
        /*maybe_set_sighandler(SIGTERM);*/
        /*maybe_set_sighandler(SIGINT );*/
}

#else /* !JOB */

#define set_fatal_signals_to_sigexit(handler) ((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.traps && G.traps[0] && G.traps[0][0]) {
                char *argv[] = { NULL, xstrdup(G.traps[0]), NULL };
                builtin_eval(argv);
                free(argv[1]);
        }

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


static const char *set_cwd(void)
{
        /* 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;
}


/* Get/check local shell variables */
static struct variable *get_local_var(const char *name)
{
        struct variable *cur;
        int len;

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

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

/* str holds "NAME=VAL" and is expected to be malloced.
 * We take ownership of it.
 * flg_export is used by:
 *  0: do not export
 *  1: export
 * -1: if NAME is set, leave export status alone
 *     if NAME is not set, do not export
 */
static int set_local_var(char *str, int flg_export)
{
        struct variable *cur;
        char *value;
        int name_len;

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

        name_len = value - str + 1; /* including '=' */
        cur = G.top_var; /* cannot be NULL (we have HUSH_VERSION and it's RO) */
        while (1) {
                if (strncmp(cur->varstr, str, name_len) != 0) {
                        if (!cur->next) {
                                /* Bail out. Note that now cur points
                                 * to last var in linked list */
                                break;
                        }
                        cur = cur->next;
                        continue;
                }
                /* We found an existing var with this name */
                *value = '\0';
                if (cur->flg_read_only) {
                        bb_error_msg("%s: readonly variable", str);
                        free(str);
                        return -1;
                }
                debug_printf_env("%s: unsetenv '%s'\n", __func__, str);
                unsetenv(str); /* just in case */
                *value = '=';
                if (strcmp(cur->varstr, str) == 0) {
 free_and_exp:
                        free(str);
                        goto exp;
                }
                if (cur->max_len >= strlen(str)) {
                        /* This one is from startup env, reuse space */
                        strcpy(cur->varstr, str);
                        goto free_and_exp;
                }
                /* max_len == 0 signifies "malloced" var, which we can
                 * (and has to) free */
                if (!cur->max_len)
                        free(cur->varstr);
                cur->max_len = 0;
                goto set_str_and_exp;
        }

        /* Not found - create next variable struct */
        cur->next = xzalloc(sizeof(*cur));
        cur = cur->next;

 set_str_and_exp:
        cur->varstr = str;
 exp:
        if (flg_export == 1)
                cur->flg_export = 1;
        if (cur->flg_export) {
                debug_printf_env("%s: putenv '%s'\n", __func__, cur->varstr);
                return putenv(cur->varstr);
        }
        return 0;
}

static int unset_local_var(const char *name)
{
        struct variable *cur;
        struct variable *prev = prev; /* for gcc */
        int name_len;

        if (!name)
                return EXIT_SUCCESS;
        name_len = strlen(name);
        cur = G.top_var;
        while (cur) {
                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;
                        }
                        /* prev is ok to use here because 1st variable, HUSH_VERSION,
                         * is ro, and we cannot reach this code on the 1st pass */
                        prev->next = cur->next;
                        debug_printf_env("%s: unsetenv '%s'\n", __func__, cur->varstr);
                        bb_unsetenv(cur->varstr);
                        if (!cur->max_len)
                                free(cur->varstr);
                        free(cur);
                        return EXIT_SUCCESS;
                }
                prev = cur;
                cur = cur->next;
        }
        return EXIT_SUCCESS;
}

#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);
}
#endif


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

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

#if ENABLE_HUSH_INTERACTIVE

static void cmdedit_set_initial_prompt(void)
{
        if (ENABLE_FEATURE_EDITING_FANCY_PROMPT) {
                G.PS1 = getenv("PS1");
                if (G.PS1 == NULL)
                        G.PS1 = "\\w \\$ ";
        } else
                G.PS1 = NULL;
}

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 ", G.cwd, (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 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;
        } 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
                ch = fgetc(i->file);
        }
        debug_printf("file_get: got a '%c' %d\n", ch, ch);
#if ENABLE_HUSH_INTERACTIVE
        if (ch == '\n')
                i->promptme = 1;
#endif
        return ch;
}

/* All the callers guarantee this routine will never be
 * used right after a newline, so prompting is not needed.
 */
static int 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;
        }
        ch = fgetc(i->file);
        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 a '%c' %d\n", *i->p, *i->p);
        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(o_string *o)
{
        o->length = 0;
        o->nonnull = 0;
        if (o->data)
                o->data[0] = '\0';
}

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

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_addstr(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';
}

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

static void o_addstr_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_addstr(o, str, len);
                return;
        }
        while (len) {
                char ch;
                int sz;
                int ordinary_cnt = strcspn(str, "*?[\\");
                if (ordinary_cnt > len) /* paranoia */
                        ordinary_cnt = len;
                o_addstr(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;
        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) {
                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;
                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_addstrauto(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);
static int parse_stream_dquoted(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_addstr_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;
}

/* 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 first_ch, ored_ch;
        int i;
        const char *val;
        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) {
#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_addstr(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;

                val = NULL;
                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_return_code);
                        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++;
//TODO: can we just stuff it into "output" directly?
                        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);

                        /* Optional: skip expansion if expr is simple ("a + 3", "i++" etc) */
                        exp_str = arg;
                        while (1) {
                                unsigned char c = *exp_str++;
                                if (c == '\0') {
                                        exp_str = NULL;
                                        goto skip_expand;
                                }
                                if (isdigit(c))
                                        continue;
                                if (strchr(" \t+-*/%_", c) != NULL)
                                        continue;
                                c |= 0x20; /* tolower */
                                if (c >= 'a' && c <= 'z')
                                        continue;
                                break;
                        }
                        /* We need to expand. Example: "echo $(($a + 1)) $((1 + $((2)) ))" */
                        {
                                struct in_str input;
                                o_string dest = NULL_O_STRING;

                                setup_string_in_str(&input, arg);
                                parse_stream_dquoted(&dest, &input, EOF);
                                //bb_error_msg("'%s' -> '%s'", arg, dest.data);
                                exp_str = expand_string_to_string(dest.data);
                                //bb_error_msg("'%s' -> '%s'", dest.data, exp_str);
                                o_free(&dest);
                        }
 skip_expand:
                        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) {
                                switch (errcode) {
                                case -3: maybe_die("arith", "exponent less than 0"); break;
                                case -2: maybe_die("arith", "divide by zero"); break;
                                case -5: maybe_die("arith", "expression recursion loop detected"); break;
                                default: maybe_die("arith", "syntax error"); break;
                                }
                        }
                        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, exp_null = false;
                        char *var = arg, exp_save, exp_op, *exp_word;
                        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) {
                                /* 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 == '?')
                                                maybe_die(var, *exp_word ? exp_word : "parameter null or not set");
                                        else
                                                val = exp_word;

                                        if (exp_op == '=') {
                                                if (isdigit(var[0]) || var[0] == '#') {
                                                        maybe_die(var, "special vars cannot assign in this way");
                                                        val = NULL;
                                                } else {
                                                        char *new_var = xmalloc(strlen(var) + strlen(val) + 2);
                                                        sprintf(new_var, "%s=%s", var, val);
                                                        set_local_var(new_var, -1);
                                                }
                                        }
                                }
                                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));
                }
                /* 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_addstrauto(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, (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);
}

/* 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: make one-element 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]);
        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");
                        list[n][-1] = ' '; /* TODO: or to G.ifs[0]? */
                        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;
}


/* 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->dup == -1 && redir->rd_filename == NULL) {
                        /* something went wrong in the parse.  Pretend it didn't happen */
                        continue;
                }
                if (redir->dup == -1) {
                        char *p;
                        mode = redir_table[redir->rd_type].mode;
//TODO: check redir for names like '\\'
                        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!) */
                                return 1;
                        }
                } else {
                        openfd = redir->dup;
                }

                if (openfd != redir->fd) {
                        if (squirrel && redir->fd < 3) {
                                squirrel[redir->fd] = dup(redir->fd);
                        }
                        if (openfd == -3) {
                                //close(openfd); // close(-3) ??!
                        } else {
                                dup2(openfd, redir->fd);
                                if (redir->dup == -1)
                                        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);
                }
        }
}


#if !defined(DEBUG_CLEAN)
#define free_pipe_list(head, indent) free_pipe_list(head)
#define free_pipe(pi, indent)        free_pipe(pi)
#endif
static void free_pipe_list(struct pipe *head, int indent);

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

        if (pi->stopped_cmds > 0)
                return;
        debug_printf_clean("%s run pipe: (pid %d)\n", indenter(indent), getpid());
        for (i = 0; i < pi->num_cmds; i++) {
                command = &pi->cmds[i];
                debug_printf_clean("%s  command %d:\n", indenter(indent), i);
                if (command->argv) {
                        for (a = 0, p = command->argv; *p; a++, p++) {
                                debug_printf_clean("%s   argv[%d] = %s\n", indenter(indent), 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("%s   begin group (grp_type:%d)\n", indenter(indent), command->grp_type);
                        free_pipe_list(command->group, indent+3);
                        debug_printf_clean("%s   end group\n", indenter(indent));
                        command->group = NULL;
                }
                for (r = command->redirects; r; r = rnext) {
                        debug_printf_clean("%s   redirect %d%s", indenter(indent), r->fd, redir_table[r->rd_type].descrip);
                        if (r->dup == -1) {
                                /* guard against the case >$FOO, where foo is unset or blank */
                                if (r->rd_filename) {
                                        debug_printf_clean(" %s\n", r->rd_filename);
                                        free(r->rd_filename);
                                        r->rd_filename = NULL;
                                }
                        } else {
                                debug_printf_clean("&%d\n", r->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, int indent)
{
        struct pipe *pi, *next;

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


#if !BB_MMU
typedef struct nommu_save_t {
        char **new_env;
        char **old_env;
        char **argv;
} nommu_save_t;
#else
#define pseudo_exec_argv(nommu_save, argv, assignment_cnt, argv_expanded) \
        pseudo_exec_argv(argv, assignment_cnt, argv_expanded)
#define pseudo_exec(nommu_save, command, argv_expanded) \
        pseudo_exec(command, argv_expanded)
#endif

/* Called after [v]fork() in run_pipe(), or from builtin_exec().
 * Never returns.
 * XXX no exit() here.  If you don't exec, use _exit instead.
 * The at_exit handlers apparently confuse the calling process,
 * in particular stdin handling.  Not sure why? -- because of vfork! (vda) */
static void pseudo_exec_argv(nommu_save_t *nommu_save,
                char **argv, int assignment_cnt,
                char **argv_expanded) NORETURN;
static void pseudo_exec_argv(nommu_save_t *nommu_save,
                char **argv, int assignment_cnt,
                char **argv_expanded)
{
        int rcode;
        char **new_env;
        const struct built_in_command *x;

        /* If a variable is assigned in a forest, and nobody listens,
         * was it ever really set?
         */
        if (!argv[assignment_cnt])
                _exit(EXIT_SUCCESS);

        new_env = expand_assignments(argv, assignment_cnt);
#if BB_MMU
        putenv_all(new_env);
        free(new_env); /* optional */
#else
        nommu_save->new_env = new_env;
        nommu_save->old_env = putenv_all_and_save_old(new_env);
#endif
        if (argv_expanded) {
                argv = argv_expanded;
        } else {
                argv = expand_strvec_to_strvec(argv + assignment_cnt);
#if !BB_MMU
                nommu_save->argv = argv;
#endif
        }

        /*
         * Check if the command matches any of the builtins.
         * Depending on context, this might be redundant.  But it's
         * easier to waste a few CPU cycles than it is to figure out
         * if this is one of those cases.
         */
        for (x = bltins; x != &bltins[ARRAY_SIZE(bltins)]; x++) {
                if (strcmp(argv[0], x->cmd) == 0) {
                        debug_printf_exec("running builtin '%s'\n", argv[0]);
                        rcode = x->function(argv);
                        fflush(stdout);
                        _exit(rcode);
                }
        }

        /* Check if the command matches any busybox applets */
#if ENABLE_FEATURE_SH_STANDALONE
        if (strchr(argv[0], '/') == NULL) {
                int a = find_applet_by_name(argv[0]);
                if (a >= 0) {
                        if (APPLET_IS_NOEXEC(a)) {
                                debug_printf_exec("running applet '%s'\n", argv[0]);
// is it ok that run_applet_no_and_exit() does exit(), not _exit()?
                                run_applet_no_and_exit(a, argv);
                        }
                        /* re-exec ourselves with the new arguments */
                        debug_printf_exec("re-execing applet '%s'\n", argv[0]);
                        execvp(bb_busybox_exec_path, argv);
                        /* If they called chroot or otherwise made the binary no longer
                         * executable, fall through */
                }
        }
#endif

        sigprocmask(SIG_SETMASK, &G.inherited_set, NULL);

        debug_printf_exec("execing '%s'\n", argv[0]);
        execvp(argv[0], argv);
        bb_perror_msg("can't exec '%s'", argv[0]);
        _exit(EXIT_FAILURE);
}

static int run_list(struct pipe *pi);

/* Called after [v]fork() in run_pipe()
 */
static void pseudo_exec(nommu_save_t *nommu_save,
                struct command *command,
                char **argv_expanded) NORETURN;
static void pseudo_exec(nommu_save_t *nommu_save,
                struct command *command,
                char **argv_expanded)
{
        if (command->argv) {
                pseudo_exec_argv(nommu_save, command->argv,
                                command->assignment_cnt, argv_expanded);
        }

        if (command->group) {
                /* Cases when we are here:
                 * ( list )
                 * { list } &
                 * ... | ( list ) | ...
                 * ... | { list } | ...
                 */
#if BB_MMU
                int rcode;
                debug_printf_exec("pseudo_exec: run_list\n");
                rcode = run_list(command->group);
                /* OK to leak memory by not calling free_pipe_list,
                 * since this process is about to exit */
                _exit(rcode);
#else
//TODO: re-exec "hush -c command->group_as_a_string"
                bb_error_msg_and_die("nested lists are not supported on NOMMU");
#endif
        }

        /* Can happen.  See what bash does with ">foo" by itself. */
        debug_printf("pseudo_exec'ed null command\n");
        _exit(EXIT_SUCCESS);
}

#if ENABLE_HUSH_JOB
static const char *get_cmdtext(struct pipe *pi)
{
        char **argv;
        char *p;
        int len;

        /* This is subtle. ->cmdtext is created only on first backgrounding.
         * (Think "cat, <ctrl-z>, fg, <ctrl-z>, fg, <ctrl-z>...." here...)
         * On subsequent bg argv is trashed, but we won't use it */
        if (pi->cmdtext)
                return pi->cmdtext;
        argv = pi->cmds[0].argv;
        if (!argv || !argv[0]) {
                pi->cmdtext = xzalloc(1);
                return pi->cmdtext;
        }

        len = 0;
        do len += strlen(*argv) + 1; while (*++argv);
        pi->cmdtext = p = xmalloc(len);
        argv = pi->cmds[0].argv;
        do {
                len = strlen(*argv);
                memcpy(p, *argv, len);
                p += len;
                *p++ = ' ';
        } while (*++argv);
        p[-1] = '\0';
        return pi->cmdtext;
}

static void insert_bg_job(struct pipe *pi)
{
        struct pipe *thejob;
        int i;

        /* Linear search for the ID of the job to use */
        pi->jobid = 1;
        for (thejob = G.job_list; thejob; thejob = thejob->next)
                if (thejob->jobid >= pi->jobid)
                        pi->jobid = thejob->jobid + 1;

        /* Add thejob to the list of running jobs */
        if (!G.job_list) {
                thejob = G.job_list = xmalloc(sizeof(*thejob));
        } else {
                for (thejob = G.job_list; thejob->next; thejob = thejob->next)
                        continue;
                thejob->next = xmalloc(sizeof(*thejob));
                thejob = thejob->next;
        }

        /* Physically copy the struct job */
        memcpy(thejob, pi, sizeof(struct pipe));
        thejob->cmds = xzalloc(sizeof(pi->cmds[0]) * pi->num_cmds);
        /* We cannot copy entire pi->cmds[] vector! Double free()s will happen */
        for (i = 0; i < pi->num_cmds; i++) {
// TODO: do we really need to have so many fields which are just dead weight
// at execution stage?
                thejob->cmds[i].pid = pi->cmds[i].pid;
                /* all other fields are not used and stay zero */
        }
        thejob->next = NULL;
        thejob->cmdtext = xstrdup(get_cmdtext(pi));

        /* We don't wait for background thejobs to return -- append it
           to the list of backgrounded thejobs and leave it alone */
        if (G_interactive_fd)
                printf("[%d] %d %s\n", thejob->jobid, thejob->cmds[0].pid, thejob->cmdtext);
        G.last_bg_pid = thejob->cmds[0].pid;
        G.last_jobid = thejob->jobid;
}

static void remove_bg_job(struct pipe *pi)
{
        struct pipe *prev_pipe;

        if (pi == G.job_list) {
                G.job_list = pi->next;
        } else {
                prev_pipe = G.job_list;
                while (prev_pipe->next != pi)
                        prev_pipe = prev_pipe->next;
                prev_pipe->next = pi->next;
        }
        if (G.job_list)
                G.last_jobid = G.job_list->jobid;
        else
                G.last_jobid = 0;
}

/* Remove a backgrounded job */
static void delete_finished_bg_job(struct pipe *pi)
{
        remove_bg_job(pi);
        pi->stopped_cmds = 0;
        free_pipe(pi, 0);
        free(pi);
}
#endif /* JOB */

/* Check to see if any processes have exited -- if they
 * have, figure out why and see if a job has completed */
static int checkjobs(struct pipe* fg_pipe)
{
        int attributes;
        int status;
#if ENABLE_HUSH_JOB
        struct pipe *pi;
#endif
        pid_t childpid;
        int rcode = 0;

        debug_printf_jobs("checkjobs %p\n", fg_pipe);

        errno = 0;
//      if (G.handled_SIGCHLD == G.count_SIGCHLD)
//              /* avoid doing syscall, nothing there anyway */
//              return rcode;

        attributes = WUNTRACED;
        if (fg_pipe == NULL)
                attributes |= WNOHANG;

/* Do we do this right?
 * bash-3.00# sleep 20 | false
 * <ctrl-Z pressed>
 * [3]+  Stopped          sleep 20 | false
 * bash-3.00# echo $?
 * 1   <========== bg pipe is not fully done, but exitcode is already known!
 */

//FIXME: non-interactive bash does not continue even if all processes in fg pipe
//are stopped. Testcase: "cat | cat" in a script (not on command line)
// + killall -STOP cat

 wait_more:
        while (1) {
                int i;
                int dead;

//              i = G.count_SIGCHLD;
                childpid = waitpid(-1, &status, attributes);
                if (childpid <= 0) {
                        if (childpid && errno != ECHILD)
                                bb_perror_msg("waitpid");
//                      else /* Until next SIGCHLD, waitpid's are useless */
//                              G.handled_SIGCHLD = i;
                        break;
                }
                dead = WIFEXITED(status) || WIFSIGNALED(status);

#if DEBUG_JOBS
                if (WIFSTOPPED(status))
                        debug_printf_jobs("pid %d stopped by sig %d (exitcode %d)\n",
                                        childpid, WSTOPSIG(status), WEXITSTATUS(status));
                if (WIFSIGNALED(status))
                        debug_printf_jobs("pid %d killed by sig %d (exitcode %d)\n",
                                        childpid, WTERMSIG(status), WEXITSTATUS(status));
                if (WIFEXITED(status))
                        debug_printf_jobs("pid %d exited, exitcode %d\n",
                                        childpid, WEXITSTATUS(status));
#endif
                /* Were we asked to wait for fg pipe? */
                if (fg_pipe) {
                        for (i = 0; i < fg_pipe->num_cmds; i++) {
                                debug_printf_jobs("check pid %d\n", fg_pipe->cmds[i].pid);
                                if (fg_pipe->cmds[i].pid != childpid)
                                        continue;
                                /* printf("process %d exit %d\n", i, WEXITSTATUS(status)); */
                                if (dead) {
                                        fg_pipe->cmds[i].pid = 0;
                                        fg_pipe->alive_cmds--;
                                        if (i == fg_pipe->num_cmds - 1) {
                                                /* last process gives overall exitstatus */
                                                rcode = WEXITSTATUS(status);
                                                IF_HAS_KEYWORDS(if (fg_pipe->pi_inverted) rcode = !rcode;)
                                        }
                                } else {
                                        fg_pipe->cmds[i].is_stopped = 1;
                                        fg_pipe->stopped_cmds++;
                                }
                                debug_printf_jobs("fg_pipe: alive_cmds %d stopped_cmds %d\n",
                                                fg_pipe->alive_cmds, fg_pipe->stopped_cmds);
                                if (fg_pipe->alive_cmds - fg_pipe->stopped_cmds <= 0) {
                                        /* All processes in fg pipe have exited/stopped */
#if ENABLE_HUSH_JOB
                                        if (fg_pipe->alive_cmds)
                                                insert_bg_job(fg_pipe);
#endif
                                        return rcode;
                                }
                                /* There are still running processes in the fg pipe */
                                goto wait_more; /* do waitpid again */
                        }
                        /* it wasnt fg_pipe, look for process in bg pipes */
                }

#if ENABLE_HUSH_JOB
                /* We asked to wait for bg or orphaned children */
                /* No need to remember exitcode in this case */
                for (pi = G.job_list; pi; pi = pi->next) {
                        for (i = 0; i < pi->num_cmds; i++) {
                                if (pi->cmds[i].pid == childpid)
                                        goto found_pi_and_prognum;
                        }
                }
                /* Happens when shell is used as init process (init=/bin/sh) */
                debug_printf("checkjobs: pid %d was not in our list!\n", childpid);
                continue; /* do waitpid again */

 found_pi_and_prognum:
                if (dead) {
                        /* child exited */
                        pi->cmds[i].pid = 0;
                        pi->alive_cmds--;
                        if (!pi->alive_cmds) {
                                if (G_interactive_fd)
                                        printf(JOB_STATUS_FORMAT, pi->jobid,
                                                        "Done", pi->cmdtext);
                                delete_finished_bg_job(pi);
                        }
                } else {
                        /* child stopped */
                        pi->cmds[i].is_stopped = 1;
                        pi->stopped_cmds++;
                }
#endif
        } /* while (waitpid succeeds)... */

        return rcode;
}

#if ENABLE_HUSH_JOB
static int checkjobs_and_fg_shell(struct pipe* fg_pipe)
{
        pid_t p;
        int rcode = checkjobs(fg_pipe);
        /* Job finished, move the shell to the foreground */
        p = getpgid(0); /* pgid of our process */
        debug_printf_jobs("fg'ing ourself: getpgid(0)=%d\n", (int)p);
        tcsetpgrp(G_interactive_fd, p);
        return rcode;
}
#endif

/* run_pipe() starts all the jobs, but doesn't wait for anything
 * to finish.  See checkjobs().
 *
 * Return code is normally -1, when the caller has to wait for children
 * to finish to determine the exit status of the pipe.  If the pipe
 * is a simple builtin command, however, the action is done by the
 * time run_pipe returns, and the exit code is provided as the
 * return value.
 *
 * Returns -1 only if started some children. IOW: we have to
 * mask out retvals of builtins etc with 0xff!
 *
 * The only case when we do not need to [v]fork is when the pipe
 * is single, non-backgrounded, non-subshell command. Examples:
 * cmd ; ...   { list } ; ...
 * cmd && ...  { list } && ...
 * cmd || ...  { list } || ...
 * If it is, then we can run cmd as a builtin, NOFORK [do we do this?],
 * or (if SH_STANDALONE) an applet, and we can run the { list }
 * with run_list(). Otherwise, we fork and exec cmd.
 *
 * Cases when we must fork:
 * non-single:   cmd | cmd
 * backgrounded: cmd &     { list } &
 * subshell:     ( list ) [&]
 */
static int run_pipe(struct pipe *pi)
{
        static const char *const null_ptr = NULL;
        int i;
        int nextin;
        int pipefds[2];         /* pipefds[0] is for reading */
        struct command *command;
        char **argv_expanded;
        char **argv;
        char *p;
        /* it is not always needed, but we aim to smaller code */
        int squirrel[] = { -1, -1, -1 };
        int rcode;

        debug_printf_exec("run_pipe start: members:%d\n", pi->num_cmds);

        USE_HUSH_JOB(pi->pgrp = -1;)
        pi->stopped_cmds = 0;
        command = &(pi->cmds[0]);
        argv_expanded = NULL;

        if (pi->num_cmds != 1
         || pi->followup == PIPE_BG
         || command->grp_type == GRP_SUBSHELL
        ) {
                goto must_fork;
        }

        pi->alive_cmds = 1;

        debug_printf_exec(": group:%p argv:'%s'\n",
                command->group, command->argv ? command->argv[0] : "NONE");

        if (command->group) {
#if ENABLE_HUSH_FUNCTIONS
                if (command->grp_type == GRP_FUNCTION) {
                        /* func () { list } */
                        bb_error_msg("here we ought to remember function definition, and go on");
                        return EXIT_SUCCESS;
                }
#endif
                /* { list } */
                debug_printf("non-subshell group\n");
                setup_redirects(command, squirrel);
                debug_printf_exec(": run_list\n");
                rcode = run_list(command->group) & 0xff;
                restore_redirects(squirrel);
                debug_printf_exec("run_pipe return %d\n", rcode);
                IF_HAS_KEYWORDS(if (pi->pi_inverted) rcode = !rcode;)
                return rcode;
        }

        argv = command->argv ? command->argv : (char **) &null_ptr;
        {
                const struct built_in_command *x;
                char **new_env = NULL;
                char **old_env = NULL;

                if (argv[command->assignment_cnt] == NULL) {
                        /* Assignments, but no command */
                        /* Ensure redirects take effect. Try "a=t >file" */
                        setup_redirects(command, squirrel);
                        restore_redirects(squirrel);
                        /* Set shell variables */
                        while (*argv) {
                                p = expand_string_to_string(*argv);
                                debug_printf_exec("set shell var:'%s'->'%s'\n",
                                                *argv, p);
                                set_local_var(p, 0);
                                argv++;
                        }
                        /* Do we need to flag set_local_var() errors?
                         * "assignment to readonly var" and "putenv error"
                         */
                        return EXIT_SUCCESS;
                }

                /* Expand the rest into (possibly) many strings each */
                argv_expanded = expand_strvec_to_strvec(argv + command->assignment_cnt);

                for (x = bltins; x != &bltins[ARRAY_SIZE(bltins)]; x++) {
                        if (strcmp(argv_expanded[0], x->cmd) != 0)
                                continue;
                        if (x->function == builtin_exec && argv_expanded[1] == NULL) {
                                debug_printf("exec with redirects only\n");
                                setup_redirects(command, NULL);
                                rcode = EXIT_SUCCESS;
                                goto clean_up_and_ret1;
                        }
                        debug_printf("builtin inline %s\n", argv_expanded[0]);
                        /* XXX setup_redirects acts on file descriptors, not FILEs.
                         * This is perfect for work that comes after exec().
                         * Is it really safe for inline use?  Experimentally,
                         * things seem to work with glibc. */
                        setup_redirects(command, squirrel);
                        new_env = expand_assignments(argv, command->assignment_cnt);
                        old_env = putenv_all_and_save_old(new_env);
                        debug_printf_exec(": builtin '%s' '%s'...\n",
                                    x->cmd, argv_expanded[1]);
                        rcode = x->function(argv_expanded) & 0xff;
#if ENABLE_FEATURE_SH_STANDALONE
 clean_up_and_ret:
#endif
                        restore_redirects(squirrel);
                        free_strings_and_unsetenv(new_env, 1);
                        putenv_all(old_env);
                        free(old_env); /* not free_strings()! */
 clean_up_and_ret1:
                        free(argv_expanded);
                        IF_HAS_KEYWORDS(if (pi->pi_inverted) rcode = !rcode;)
                        debug_printf_exec("run_pipe return %d\n", rcode);
                        return rcode;
                }
#if ENABLE_FEATURE_SH_STANDALONE
                i = find_applet_by_name(argv_expanded[0]);
                if (i >= 0 && APPLET_IS_NOFORK(i)) {
                        setup_redirects(command, squirrel);
                        save_nofork_data(&G.nofork_save);
                        new_env = expand_assignments(argv, command->assignment_cnt);
                        old_env = putenv_all_and_save_old(new_env);
                        debug_printf_exec(": run_nofork_applet '%s' '%s'...\n",
                                        argv_expanded[0], argv_expanded[1]);
                        rcode = run_nofork_applet_prime(&G.nofork_save, i, argv_expanded);
                        goto clean_up_and_ret;
                }
#endif
                /* It is neither builtin nor applet. We must fork. */
        }

 must_fork:
        /* NB: argv_expanded may already be created, and that
         * might include `cmd` runs! Do not rerun it! We *must*
         * use argv_expanded if it's non-NULL */

        /* Going to fork a child per each pipe member */
        pi->alive_cmds = 0;
        nextin = 0;

        for (i = 0; i < pi->num_cmds; i++) {
#if !BB_MMU
                volatile nommu_save_t nommu_save;
                nommu_save.new_env = NULL;
                nommu_save.old_env = NULL;
                nommu_save.argv = NULL;
#endif
                command = &(pi->cmds[i]);
                if (command->argv) {
                        debug_printf_exec(": pipe member '%s' '%s'...\n",
                                        command->argv[0], command->argv[1]);
                } else {
                        debug_printf_exec(": pipe member with no argv\n");
                }

                /* pipes are inserted between pairs of commands */
                pipefds[0] = 0;
                pipefds[1] = 1;
                if ((i + 1) < pi->num_cmds)
                        xpipe(pipefds);

                command->pid = BB_MMU ? fork() : vfork();
                if (!command->pid) { /* child */
#if ENABLE_HUSH_JOB
                        die_sleep = 0; /* let nofork's xfuncs die */

                        /* Every child adds itself to new process group
                         * with pgid == pid_of_first_child_in_pipe */
                        if (G.run_list_level == 1 && G_interactive_fd) {
                                pid_t pgrp;
                                pgrp = pi->pgrp;
                                if (pgrp < 0) /* true for 1st process only */
                                        pgrp = getpid();
                                if (setpgid(0, pgrp) == 0 && pi->followup != PIPE_BG) {
                                        /* We do it in *every* child, not just first,
                                         * to avoid races */
                                        tcsetpgrp(G_interactive_fd, pgrp);
                                }
                        }
#endif
                        xmove_fd(nextin, 0);
                        xmove_fd(pipefds[1], 1); /* write end */
                        if (pipefds[0] > 1)
                                close(pipefds[0]); /* read end */
                        /* Like bash, explicit redirects override pipes,
                         * and the pipe fd is available for dup'ing. */
                        setup_redirects(command, NULL);

                        /* Restore default handlers just prior to exec */
                        /*signal(SIGCHLD, SIG_DFL); - so far we don't have any handlers */

                        /* Stores to nommu_save list of env vars putenv'ed
                         * (NOMMU, on MMU we don't need that) */
                        /* cast away volatility... */
                        pseudo_exec((nommu_save_t*) &nommu_save, command, argv_expanded);
                        /* pseudo_exec() does not return */
                }
                /* parent */
#if !BB_MMU
                /* Clean up after vforked child */
                free(nommu_save.argv);
                free_strings_and_unsetenv(nommu_save.new_env, 1);
                putenv_all(nommu_save.old_env);
#endif
                free(argv_expanded);
                argv_expanded = NULL;
                if (command->pid < 0) { /* [v]fork failed */
                        /* Clearly indicate, was it fork or vfork */
                        bb_perror_msg(BB_MMU ? "fork" : "vfork");
                } else {
                        pi->alive_cmds++;
#if ENABLE_HUSH_JOB
                        /* Second and next children need to know pid of first one */
                        if (pi->pgrp < 0)
                                pi->pgrp = command->pid;
#endif
                }

                if (i)
                        close(nextin);
                if ((i + 1) < pi->num_cmds)
                        close(pipefds[1]); /* write end */
                /* Pass read (output) pipe end to next iteration */
                nextin = pipefds[0];
        }

        if (!pi->alive_cmds) {
                debug_printf_exec("run_pipe return 1 (all forks failed, no children)\n");
                return 1;
        }

        debug_printf_exec("run_pipe return -1 (%u children started)\n", pi->alive_cmds);
        return -1;
}

#ifndef debug_print_tree
static void debug_print_tree(struct pipe *pi, int lvl)
{
        static const char *const PIPE[] = {
                [PIPE_SEQ] = "SEQ",
                [PIPE_AND] = "AND",
                [PIPE_OR ] = "OR" ,
                [PIPE_BG ] = "BG" ,
        };
        static const char *RES[] = {
                [RES_NONE ] = "NONE" ,
#if ENABLE_HUSH_IF
                [RES_IF   ] = "IF"   ,
                [RES_THEN ] = "THEN" ,
                [RES_ELIF ] = "ELIF" ,
                [RES_ELSE ] = "ELSE" ,
                [RES_FI   ] = "FI"   ,
#endif
#if ENABLE_HUSH_LOOPS
                [RES_FOR  ] = "FOR"  ,
                [RES_WHILE] = "WHILE",
                [RES_UNTIL] = "UNTIL",
                [RES_DO   ] = "DO"   ,
                [RES_DONE ] = "DONE" ,
#endif
#if ENABLE_HUSH_LOOPS || ENABLE_HUSH_CASE
                [RES_IN   ] = "IN"   ,
#endif
#if ENABLE_HUSH_CASE
                [RES_CASE ] = "CASE" ,
                [RES_MATCH] = "MATCH",
                [RES_CASEI] = "CASEI",
                [RES_ESAC ] = "ESAC" ,
#endif
                [RES_XXXX ] = "XXXX" ,
                [RES_SNTX ] = "SNTX" ,
        };
        static const char *const GRPTYPE[] = {
                "()",
                "{}",
#if ENABLE_HUSH_FUNCTIONS
                "func()",
#endif
        };

        int pin, prn;

        pin = 0;
        while (pi) {
                fprintf(stderr, "%*spipe %d res_word=%s followup=%d %s\n", lvl*2, "",
                                pin, RES[pi->res_word], pi->followup, PIPE[pi->followup]);
                prn = 0;
                while (prn < pi->num_cmds) {
                        struct command *command = &pi->cmds[prn];
                        char **argv = command->argv;

                        fprintf(stderr, "%*s prog %d assignment_cnt:%d",
                                        lvl*2, "", prn,
                                        command->assignment_cnt);
                        if (command->group) {
                                fprintf(stderr, " group %s: (argv=%p)\n",
                                                GRPTYPE[command->grp_type],
                                                argv);
                                debug_print_tree(command->group, lvl+1);
                                prn++;
                                continue;
                        }
                        if (argv) while (*argv) {
                                fprintf(stderr, " '%s'", *argv);
                                argv++;
                        }
                        fprintf(stderr, "\n");
                        prn++;
                }
                pi = pi->next;
                pin++;
        }
}
#endif

/* NB: called by pseudo_exec, and therefore must not modify any
 * global data until exec/_exit (we can be a child after vfork!) */
static int run_list(struct pipe *pi)
{
#if ENABLE_HUSH_CASE
        char *case_word = NULL;
#endif
#if ENABLE_HUSH_LOOPS
        struct pipe *loop_top = NULL;
        char *for_varname = NULL;
        char **for_lcur = NULL;
        char **for_list = NULL;
#endif
        smallint flag_skip = 1;
        smalluint rcode = 0; /* probably just for compiler */
#if ENABLE_HUSH_IF || ENABLE_HUSH_CASE
        smalluint cond_code = 0;
#else
        enum { cond_code = 0, };
#endif
        /*enum reserved_style*/ smallint rword = RES_NONE;
        /*enum reserved_style*/ smallint skip_more_for_this_rword = RES_XXXX;

        debug_printf_exec("run_list start lvl %d\n", G.run_list_level + 1);

#if ENABLE_HUSH_LOOPS
        /* Check syntax for "for" */
        for (struct pipe *cpipe = pi; cpipe; cpipe = cpipe->next) {
                if (cpipe->res_word != RES_FOR && cpipe->res_word != RES_IN)
                        continue;
                /* current word is FOR or IN (BOLD in comments below) */
                if (cpipe->next == NULL) {
                        syntax("malformed for");
                        debug_printf_exec("run_list lvl %d return 1\n", G.run_list_level);
                        return 1;
                }
                /* "FOR v; do ..." and "for v IN a b; do..." are ok */
                if (cpipe->next->res_word == RES_DO)
                        continue;
                /* next word is not "do". It must be "in" then ("FOR v in ...") */
                if (cpipe->res_word == RES_IN /* "for v IN a b; not_do..."? */
                 || cpipe->next->res_word != RES_IN /* FOR v not_do_and_not_in..."? */
                ) {
                        syntax("malformed for");
                        debug_printf_exec("run_list lvl %d return 1\n", G.run_list_level);
                        return 1;
                }
        }
#endif

        /* Past this point, all code paths should jump to ret: label
         * in order to return, no direct "return" statements please.
         * This helps to ensure that no memory is leaked. */

////TODO: ctrl-Z handling needs re-thinking and re-testing

#if ENABLE_HUSH_JOB
        /* Example of nested list: "while true; do { sleep 1 | exit 2; } done".
         * We are saving state before entering outermost list ("while...done")
         * so that ctrl-Z will correctly background _entire_ outermost list,
         * not just a part of it (like "sleep 1 | exit 2") */
        if (++G.run_list_level == 1 && G_interactive_fd) {
                if (sigsetjmp(G.toplevel_jb, 1)) {
                        /* ctrl-Z forked and we are parent; or ctrl-C.
                         * Sighandler has longjmped us here */
                        signal(SIGINT, SIG_IGN);
                        signal(SIGTSTP, SIG_IGN);
                        /* Restore level (we can be coming from deep inside
                         * nested levels) */
                        G.run_list_level = 1;
#if ENABLE_FEATURE_SH_STANDALONE
                        if (G.nofork_save.saved) { /* if save area is valid */
                                debug_printf_jobs("exiting nofork early\n");
                                restore_nofork_data(&G.nofork_save);
                        }
#endif
////                    if (G.ctrl_z_flag) {
////                            /* ctrl-Z has forked and stored pid of the child in pi->pid.
////                             * Remember this child as background job */
////                            insert_bg_job(pi);
////                    } else {
                                /* ctrl-C. We just stop doing whatever we were doing */
                                bb_putchar('\n');
////                    }
                        USE_HUSH_LOOPS(loop_top = NULL;)
                        USE_HUSH_LOOPS(G.depth_of_loop = 0;)
                        rcode = 0;
                        goto ret;
                }
////            /* ctrl-Z handler will store pid etc in pi */
////            G.toplevel_list = pi;
////            G.ctrl_z_flag = 0;
////#if ENABLE_FEATURE_SH_STANDALONE
////            G.nofork_save.saved = 0; /* in case we will run a nofork later */
////#endif
////            signal_SA_RESTART_empty_mask(SIGTSTP, handler_ctrl_z);
////            signal(SIGINT, handler_ctrl_c);
        }
#endif /* JOB */

        /* Go through list of pipes, (maybe) executing them. */
        for (; pi; pi = USE_HUSH_LOOPS(rword == RES_DONE ? loop_top : ) pi->next) {
                if (G.flag_SIGINT)
                        break;

                IF_HAS_KEYWORDS(rword = pi->res_word;)
                IF_HAS_NO_KEYWORDS(rword = RES_NONE;)
                debug_printf_exec(": rword=%d cond_code=%d skip_more=%d\n",
                                rword, cond_code, skip_more_for_this_rword);
#if ENABLE_HUSH_LOOPS
                if ((rword == RES_WHILE || rword == RES_UNTIL || rword == RES_FOR)
                 && loop_top == NULL /* avoid bumping G.depth_of_loop twice */
                ) {
                        /* start of a loop: remember where loop starts */
                        loop_top = pi;
                        G.depth_of_loop++;
                }
#endif
                if (rword == skip_more_for_this_rword && flag_skip) {
                        if (pi->followup == PIPE_SEQ)
                                flag_skip = 0;
                        /* it is "<false> && CMD" or "<true> || CMD"
                         * and we should not execute CMD */
                        continue;
                }
                flag_skip = 1;
                skip_more_for_this_rword = RES_XXXX;
#if ENABLE_HUSH_IF
                if (cond_code) {
                        if (rword == RES_THEN) {
                                /* "if <false> THEN cmd": skip cmd */
                                continue;
                        }
                } else {
                        if (rword == RES_ELSE || rword == RES_ELIF) {
                                /* "if <true> then ... ELSE/ELIF cmd":
                                 * skip cmd and all following ones */
                                break;
                        }
                }
#endif
#if ENABLE_HUSH_LOOPS
                if (rword == RES_FOR) { /* && pi->num_cmds - always == 1 */
                        if (!for_lcur) {
                                /* first loop through for */

                                static const char encoded_dollar_at[] ALIGN1 = {
                                        SPECIAL_VAR_SYMBOL, '@' | 0x80, SPECIAL_VAR_SYMBOL, '\0'
                                }; /* encoded representation of "$@" */
                                static const char *const encoded_dollar_at_argv[] = {
                                        encoded_dollar_at, NULL
                                }; /* argv list with one element: "$@" */
                                char **vals;

                                vals = (char**)encoded_dollar_at_argv;
                                if (pi->next->res_word == RES_IN) {
                                        /* if no variable values after "in" we skip "for" */
                                        if (!pi->next->cmds[0].argv)
                                                break;
                                        vals = pi->next->cmds[0].argv;
                                } /* else: "for var; do..." -> assume "$@" list */
                                /* create list of variable values */
                                debug_print_strings("for_list made from", vals);
                                for_list = expand_strvec_to_strvec(vals);
                                for_lcur = for_list;
                                debug_print_strings("for_list", for_list);
                                for_varname = pi->cmds[0].argv[0];
                                pi->cmds[0].argv[0] = NULL;
                        }
                        free(pi->cmds[0].argv[0]);
                        if (!*for_lcur) {
                                /* "for" loop is over, clean up */
                                free(for_list);
                                for_list = NULL;
                                for_lcur = NULL;
                                pi->cmds[0].argv[0] = for_varname;
                                break;
                        }
                        /* insert next value from for_lcur */
//TODO: does it need escaping?
                        pi->cmds[0].argv[0] = xasprintf("%s=%s", for_varname, *for_lcur++);
                        pi->cmds[0].assignment_cnt = 1;
                }
                if (rword == RES_IN) {
                        continue; /* "for v IN list;..." - "in" has no cmds anyway */
                }
                if (rword == RES_DONE) {
                        continue; /* "done" has no cmds too */
                }
#endif
#if ENABLE_HUSH_CASE
                if (rword == RES_CASE) {
                        case_word = expand_strvec_to_string(pi->cmds->argv);
                        continue;
                }
                if (rword == RES_MATCH) {
                        char **argv;

                        if (!case_word) /* "case ... matched_word) ... WORD)": we executed selected branch, stop */
                                break;
                        /* all prev words didn't match, does this one match? */
                        argv = pi->cmds->argv;
                        while (*argv) {
                                char *pattern = expand_string_to_string(*argv);
                                /* TODO: which FNM_xxx flags to use? */
                                cond_code = (fnmatch(pattern, case_word, /*flags:*/ 0) != 0);
                                free(pattern);
                                if (cond_code == 0) { /* match! we will execute this branch */
                                        free(case_word); /* make future "word)" stop */
                                        case_word = NULL;
                                        break;
                                }
                                argv++;
                        }
                        continue;
                }
                if (rword == RES_CASEI) { /* inside of a case branch */
                        if (cond_code != 0)
                                continue; /* not matched yet, skip this pipe */
                }
#endif
                /* Just pressing <enter> in shell should check for jobs.
                 * OTOH, in non-interactive shell this is useless
                 * and only leads to extra job checks */
                if (pi->num_cmds == 0) {
                        if (G_interactive_fd)
                                goto check_jobs_and_continue;
                        continue;
                }

                /* After analyzing all keywords and conditions, we decided
                 * to execute this pipe. NB: have to do checkjobs(NULL)
                 * after run_pipe() to collect any background children,
                 * even if list execution is to be stopped. */
                debug_printf_exec(": run_pipe with %d members\n", pi->num_cmds);
                {
                        int r;
#if ENABLE_HUSH_LOOPS
                        G.flag_break_continue = 0;
#endif
                        rcode = r = run_pipe(pi); /* NB: rcode is a smallint */
                        if (r != -1) {
                                /* we only ran a builtin: rcode is already known
                                 * and we don't need to wait for anything. */
                                check_and_run_traps(0);
#if ENABLE_HUSH_LOOPS
                                /* was it "break" or "continue"? */
                                if (G.flag_break_continue) {
                                        smallint fbc = G.flag_break_continue;
                                        /* we might fall into outer *loop*,
                                         * don't want to break it too */
                                        if (loop_top) {
                                                G.depth_break_continue--;
                                                if (G.depth_break_continue == 0)
                                                        G.flag_break_continue = 0;
                                                /* else: e.g. "continue 2" should *break* once, *then* continue */
                                        } /* else: "while... do... { we are here (innermost list is not a loop!) };...done" */
                                        if (G.depth_break_continue != 0 || fbc == BC_BREAK)
                                                goto check_jobs_and_break;
                                        /* "continue": simulate end of loop */
                                        rword = RES_DONE;
                                        continue;
                                }
#endif
                        } else if (pi->followup == PIPE_BG) {
                                /* what does bash do with attempts to background builtins? */
                                /* even bash 3.2 doesn't do that well with nested bg:
                                 * try "{ { sleep 10; echo DEEP; } & echo HERE; } &".
                                 * I'm NOT treating inner &'s as jobs */
                                check_and_run_traps(0);
#if ENABLE_HUSH_JOB
                                if (G.run_list_level == 1)
                                        insert_bg_job(pi);
#endif
                                rcode = 0; /* EXIT_SUCCESS */
                        } else {
#if ENABLE_HUSH_JOB
                                if (G.run_list_level == 1 && G_interactive_fd) {
                                        /* waits for completion, then fg's main shell */
                                        rcode = checkjobs_and_fg_shell(pi);
                                        check_and_run_traps(0);
                                        debug_printf_exec(": checkjobs_and_fg_shell returned %d\n", rcode);
                                } else
#endif
                                { /* this one just waits for completion */
                                        rcode = checkjobs(pi);
                                        check_and_run_traps(0);
                                        debug_printf_exec(": checkjobs returned %d\n", rcode);
                                }
                        }
                }
                debug_printf_exec(": setting last_return_code=%d\n", rcode);
                G.last_return_code = rcode;

                /* Analyze how result affects subsequent commands */
#if ENABLE_HUSH_IF
                if (rword == RES_IF || rword == RES_ELIF)
                        cond_code = rcode;
#endif
#if ENABLE_HUSH_LOOPS
                if (rword == RES_WHILE) {
                        if (rcode) {
                                rcode = 0; /* "while false; do...done" - exitcode 0 */
                                goto check_jobs_and_break;
                        }
                }
                if (rword == RES_UNTIL) {
                        if (!rcode) {
 check_jobs_and_break:
                                checkjobs(NULL);
                                break;
                        }
                }
#endif
                if ((rcode == 0 && pi->followup == PIPE_OR)
                 || (rcode != 0 && pi->followup == PIPE_AND)
                ) {
                        skip_more_for_this_rword = rword;
                }

 check_jobs_and_continue:
                checkjobs(NULL);
        } /* for (pi) */

#if ENABLE_HUSH_JOB
////    if (G.ctrl_z_flag) {
////            /* ctrl-Z forked somewhere in the past, we are the child,
////             * and now we completed running the list. Exit. */
//////TODO: _exit?
////            exit(rcode);
////    }
 ret:
        G.run_list_level--;
////    if (!G.run_list_level && G_interactive_fd) {
////            signal(SIGTSTP, SIG_IGN);
////            signal(SIGINT, SIG_IGN);
////    }
#endif
        debug_printf_exec("run_list lvl %d return %d\n", G.run_list_level + 1, rcode);
#if ENABLE_HUSH_LOOPS
        if (loop_top)
                G.depth_of_loop--;
        free(for_list);
#endif
#if ENABLE_HUSH_CASE
        free(case_word);
#endif
        return rcode;
}

/* Select which version we will use */
static int run_and_free_list(struct pipe *pi)
{
        int rcode = 0;
        debug_printf_exec("run_and_free_list entered\n");
        if (!G.fake_mode) {
                debug_printf_exec(": run_list with %d members\n", pi->num_cmds);
                rcode = run_list(pi);
        }
        /* free_pipe_list has the side effect of clearing memory.
         * In the long run that function can be merged with run_list,
         * but doing that now would hobble the debugging effort. */
        free_pipe_list(pi, /* indent: */ 0);
        debug_printf_exec("run_and_free_list return %d\n", rcode);
        return rcode;
}


/* Peek ahead in the in_str to find out if we have a "&n" construct,
 * as in "2>&1", that represents duplicating a file descriptor.
 * Return either -2 (syntax error), -1 (no &), or the number found.
 */
static int redirect_dup_num(struct in_str *input)
{
        int ch, d = 0, ok = 0;
        ch = i_peek(input);
        if (ch != '&') return -1;

        i_getch(input);  /* get the & */
        ch = i_peek(input);
        if (ch == '-') {
                i_getch(input);
                return -3;  /* "-" represents "close me" */
        }
        while (isdigit(ch)) {
                d = d*10 + (ch-'0');
                ok = 1;
                i_getch(input);
                ch = i_peek(input);
        }
        if (ok) return d;

        bb_error_msg("ambiguous redirect");
        return -2;
}

/* The src parameter allows us to peek forward to a possible &n syntax
 * for file descriptor duplication, e.g., "2>&1".
 * Return code is 0 normally, 1 if a syntax error is detected in src.
 * Resource errors (in xmalloc) cause the process to exit */
static int setup_redirect(struct parse_context *ctx,
                int fd,
                redir_type style,
                struct in_str *input)
{
        struct command *command = ctx->command;
        struct redir_struct *redir;
        struct redir_struct **redirp;
        int dup_num;

        /* Check for a '2>&1' type redirect */
        dup_num = redirect_dup_num(input);
        if (dup_num == -2)
                return 1;  /* syntax error */

        /* Create a new redir_struct and drop it onto the end of the linked list */
        redirp = &command->redirects;
        while ((redir = *redirp) != NULL) {
                redirp = &(redir->next);
        }
        *redirp = redir = xzalloc(sizeof(*redir));
        /* redir->next = NULL; */
        /* redir->rd_filename = NULL; */
        redir->rd_type = style;
        redir->fd = (fd == -1) ? redir_table[style].default_fd : fd;

        debug_printf("Redirect type %d%s\n", redir->fd, redir_table[style].descrip);

        redir->dup = dup_num;
        if (dup_num != -1) {
                /* Erik had a check here that the file descriptor in question
                 * is legit; I postpone that to "run time"
                 * A "-" representation of "close me" shows up as a -3 here */
                debug_printf("Duplicating redirect '%d>&%d'\n", redir->fd, redir->dup);
        } else {
                /* We do _not_ try to open the file that src points to,
                 * since we need to return and let src be expanded first.
                 * Set ctx->pending_redirect, so we know what to do at the
                 * end of the next parsed word. */
                ctx->pending_redirect = redir;
        }
        return 0;
}


static struct pipe *new_pipe(void)
{
        struct pipe *pi;
        pi = xzalloc(sizeof(struct pipe));
        /*pi->followup = 0; - deliberately invalid value */
        /*pi->res_word = RES_NONE; - RES_NONE is 0 anyway */
        return pi;
}

/* Command (member of a pipe) is complete. The only possible error here
 * is out of memory, in which case xmalloc exits. */
static int done_command(struct parse_context *ctx)
{
        /* The command is really already in the pipe structure, so
         * advance the pipe counter and make a new, null command. */
        struct pipe *pi = ctx->pipe;
        struct command *command = ctx->command;

        if (command) {
                if (command->group == NULL
                 && command->argv == NULL
                 && command->redirects == NULL
                ) {
                        debug_printf_parse("done_command: skipping null cmd, num_cmds=%d\n", pi->num_cmds);
                        return pi->num_cmds;
                }
                pi->num_cmds++;
                debug_printf_parse("done_command: ++num_cmds=%d\n", pi->num_cmds);
        } else {
                debug_printf_parse("done_command: initializing, num_cmds=%d\n", pi->num_cmds);
        }

        /* Only real trickiness here is that the uncommitted
         * command structure is not counted in pi->num_cmds. */
        pi->cmds = xrealloc(pi->cmds, sizeof(*pi->cmds) * (pi->num_cmds+1));
        command = &pi->cmds[pi->num_cmds];
        memset(command, 0, sizeof(*command));

        ctx->command = command;
        /* but ctx->pipe and ctx->list_head remain unchanged */

        return pi->num_cmds; /* used only for 0/nonzero check */
}

static void done_pipe(struct parse_context *ctx, pipe_style type)
{
        int not_null;

        debug_printf_parse("done_pipe entered, followup %d\n", type);
        /* Close previous command */
        not_null = done_command(ctx);
        ctx->pipe->followup = type;
        IF_HAS_KEYWORDS(ctx->pipe->pi_inverted = ctx->ctx_inverted;)
        IF_HAS_KEYWORDS(ctx->ctx_inverted = 0;)
        IF_HAS_KEYWORDS(ctx->pipe->res_word = ctx->ctx_res_w;)

        /* Without this check, even just <enter> on command line generates
         * tree of three NOPs (!). Which is harmless but annoying.
         * IOW: it is safe to do it unconditionally.
         * RES_NONE case is for "for a in; do ..." (empty IN set)
         * to work, possibly other cases too. */
        if (not_null IF_HAS_KEYWORDS(|| ctx->ctx_res_w != RES_NONE)) {
                struct pipe *new_p;
                debug_printf_parse("done_pipe: adding new pipe: "
                                "not_null:%d ctx->ctx_res_w:%d\n",
                                not_null, ctx->ctx_res_w);
                new_p = new_pipe();
                ctx->pipe->next = new_p;
                ctx->pipe = new_p;
                /* RES_THEN, RES_DO etc are "sticky" -
                 * they remain set for commands inside if/while.
                 * This is used to control execution.
                 * RES_FOR and RES_IN are NOT sticky (needed to support
                 * cases where variable or value happens to match a keyword):
                 */
#if ENABLE_HUSH_LOOPS
                if (ctx->ctx_res_w == RES_FOR
                 || ctx->ctx_res_w == RES_IN)
                        ctx->ctx_res_w = RES_NONE;
#endif
#if ENABLE_HUSH_CASE
                if (ctx->ctx_res_w == RES_MATCH)
                        ctx->ctx_res_w = RES_CASEI;
#endif
                ctx->command = NULL; /* trick done_command below */
                /* Create the memory for command, roughly:
                 * ctx->pipe->cmds = new struct command;
                 * ctx->command = &ctx->pipe->cmds[0];
                 */
                done_command(ctx);
        }
        debug_printf_parse("done_pipe return\n");
}

static void initialize_context(struct parse_context *ctx)
{
        memset(ctx, 0, sizeof(*ctx));
        ctx->pipe = ctx->list_head = new_pipe();
        /* Create the memory for command, roughly:
         * ctx->pipe->cmds = new struct command;
         * ctx->command = &ctx->pipe->cmds[0];
         */
        done_command(ctx);
}


/* If a reserved word is found and processed, parse context is modified
 * and 1 is returned.
 */
#if HAS_KEYWORDS
struct reserved_combo {
        char literal[6];
        unsigned char res;
        unsigned char assignment_flag;
        int flag;
};
enum {
        FLAG_END   = (1 << RES_NONE ),
#if ENABLE_HUSH_IF
        FLAG_IF    = (1 << RES_IF   ),
        FLAG_THEN  = (1 << RES_THEN ),
        FLAG_ELIF  = (1 << RES_ELIF ),
        FLAG_ELSE  = (1 << RES_ELSE ),
        FLAG_FI    = (1 << RES_FI   ),
#endif
#if ENABLE_HUSH_LOOPS
        FLAG_FOR   = (1 << RES_FOR  ),
        FLAG_WHILE = (1 << RES_WHILE),
        FLAG_UNTIL = (1 << RES_UNTIL),
        FLAG_DO    = (1 << RES_DO   ),
        FLAG_DONE  = (1 << RES_DONE ),
        FLAG_IN    = (1 << RES_IN   ),
#endif
#if ENABLE_HUSH_CASE
        FLAG_MATCH = (1 << RES_MATCH),
        FLAG_ESAC  = (1 << RES_ESAC ),
#endif
        FLAG_START = (1 << RES_XXXX ),
};

static const struct reserved_combo* match_reserved_word(o_string *word)
{
        /* Mostly a list of accepted follow-up reserved words.
         * FLAG_END means we are done with the sequence, and are ready
         * to turn the compound list into a command.
         * FLAG_START means the word must start a new compound list.
         */
        static const struct reserved_combo reserved_list[] = {
#if ENABLE_HUSH_IF
                { "!",     RES_NONE,  NOT_ASSIGNMENT , 0 },
                { "if",    RES_IF,    WORD_IS_KEYWORD, FLAG_THEN | FLAG_START },
                { "then",  RES_THEN,  WORD_IS_KEYWORD, FLAG_ELIF | FLAG_ELSE | FLAG_FI },
                { "elif",  RES_ELIF,  WORD_IS_KEYWORD, FLAG_THEN },
                { "else",  RES_ELSE,  WORD_IS_KEYWORD, FLAG_FI   },
                { "fi",    RES_FI,    NOT_ASSIGNMENT , FLAG_END  },
#endif
#if ENABLE_HUSH_LOOPS
                { "for",   RES_FOR,   NOT_ASSIGNMENT , FLAG_IN | FLAG_DO | FLAG_START },
                { "while", RES_WHILE, WORD_IS_KEYWORD, FLAG_DO | FLAG_START },
                { "until", RES_UNTIL, WORD_IS_KEYWORD, FLAG_DO | FLAG_START },
                { "in",    RES_IN,    NOT_ASSIGNMENT , FLAG_DO   },
                { "do",    RES_DO,    WORD_IS_KEYWORD, FLAG_DONE },
                { "done",  RES_DONE,  NOT_ASSIGNMENT , FLAG_END  },
#endif
#if ENABLE_HUSH_CASE
                { "case",  RES_CASE,  NOT_ASSIGNMENT , FLAG_MATCH | FLAG_START },
                { "esac",  RES_ESAC,  NOT_ASSIGNMENT , FLAG_END  },
#endif
        };
        const struct reserved_combo *r;

        for (r = reserved_list; r < reserved_list + ARRAY_SIZE(reserved_list); r++) {
                if (strcmp(word->data, r->literal) == 0)
                        return r;
        }
        return NULL;
}
static int reserved_word(o_string *word, struct parse_context *ctx)
{
#if ENABLE_HUSH_CASE
        static const struct reserved_combo reserved_match = {
                "",        RES_MATCH, NOT_ASSIGNMENT , FLAG_MATCH | FLAG_ESAC
        };
#endif
        const struct reserved_combo *r;

        r = match_reserved_word(word);
        if (!r)
                return 0;

        debug_printf("found reserved word %s, res %d\n", r->literal, r->res);
#if ENABLE_HUSH_CASE
        if (r->res == RES_IN && ctx->ctx_res_w == RES_CASE)
                /* "case word IN ..." - IN part starts first match part */
                r = &reserved_match;
        else
#endif
        if (r->flag == 0) { /* '!' */
                if (ctx->ctx_inverted) { /* bash doesn't accept '! ! true' */
                        syntax("! ! command");
                        IF_HAS_KEYWORDS(ctx->ctx_res_w = RES_SNTX;)
                }
                ctx->ctx_inverted = 1;
                return 1;
        }
        if (r->flag & FLAG_START) {
                struct parse_context *old;
                old = xmalloc(sizeof(*old));
                debug_printf_parse("push stack %p\n", old);
                *old = *ctx;   /* physical copy */
                initialize_context(ctx);
                ctx->stack = old;
        } else if (/*ctx->ctx_res_w == RES_NONE ||*/ !(ctx->old_flag & (1 << r->res))) {
                syntax(word->data);
                ctx->ctx_res_w = RES_SNTX;
                return 1;
        }
        ctx->ctx_res_w = r->res;
        ctx->old_flag = r->flag;
        if (ctx->old_flag & FLAG_END) {
                struct parse_context *old;
                done_pipe(ctx, PIPE_SEQ);
                debug_printf_parse("pop stack %p\n", ctx->stack);
                old = ctx->stack;
                old->command->group = ctx->list_head;
                old->command->grp_type = GRP_NORMAL;
                *ctx = *old;   /* physical copy */
                free(old);
        }
        word->o_assignment = r->assignment_flag;
        return 1;
}
#endif

/* Word is complete, look at it and update parsing context.
 * Normal return is 0. Syntax errors return 1.
 * Note: on return, word is reset, but not o_free'd!
 */
static int done_word(o_string *word, struct parse_context *ctx)
{
        struct command *command = ctx->command;

        debug_printf_parse("done_word entered: '%s' %p\n", word->data, command);
        if (word->length == 0 && word->nonnull == 0) {
                debug_printf_parse("done_word return 0: true null, ignored\n");
                return 0;
        }
        /* If this word wasn't an assignment, next ones definitely
         * can't be assignments. Even if they look like ones. */
        if (word->o_assignment != DEFINITELY_ASSIGNMENT
         && word->o_assignment != WORD_IS_KEYWORD
        ) {
                word->o_assignment = NOT_ASSIGNMENT;
        } else {
                if (word->o_assignment == DEFINITELY_ASSIGNMENT)
                        command->assignment_cnt++;
                word->o_assignment = MAYBE_ASSIGNMENT;
        }

        if (ctx->pending_redirect) {
                /* We do not glob in e.g. >*.tmp case. bash seems to glob here
                 * only if run as "bash", not "sh" */
                ctx->pending_redirect->rd_filename = xstrdup(word->data);
                word->o_assignment = NOT_ASSIGNMENT;
                debug_printf("word stored in rd_filename: '%s'\n", word->data);
        } else {
                /* "{ echo foo; } echo bar" - bad */
                /* NB: bash allows e.g.:
                 * if true; then { echo foo; } fi
                 * while if false; then false; fi do break; done
                 * TODO? */
                if (command->group) {
                        syntax(word->data);
                        debug_printf_parse("done_word return 1: syntax error, "
                                        "groups and arglists don't mix\n");
                        return 1;
                }
#if HAS_KEYWORDS
#if ENABLE_HUSH_CASE
                if (ctx->ctx_dsemicolon
                 && strcmp(word->data, "esac") != 0 /* not "... pattern) cmd;; esac" */
                ) {
                        /* already done when ctx_dsemicolon was set to 1: */
                        /* ctx->ctx_res_w = RES_MATCH; */
                        ctx->ctx_dsemicolon = 0;
                } else
#endif
                if (!command->argv /* if it's the first word... */
#if ENABLE_HUSH_LOOPS
                 && ctx->ctx_res_w != RES_FOR /* ...not after FOR or IN */
                 && ctx->ctx_res_w != RES_IN
#endif
                ) {
                        debug_printf_parse(": checking '%s' for reserved-ness\n", word->data);
                        if (reserved_word(word, ctx)) {
                                o_reset(word);
                                debug_printf_parse("done_word return %d\n",
                                                (ctx->ctx_res_w == RES_SNTX));
                                return (ctx->ctx_res_w == RES_SNTX);
                        }
                }
#endif
                if (word->nonnull /* word had "xx" or 'xx' at least as part of it. */
                 /* optimization: and if it's ("" or '') or ($v... or `cmd`...): */
                 && (word->data[0] == '\0' || word->data[0] == SPECIAL_VAR_SYMBOL)
                 /* (otherwise it's known to be not empty and is already safe) */
                ) {
                        /* exclude "$@" - it can expand to no word despite "" */
                        char *p = word->data;
                        while (p[0] == SPECIAL_VAR_SYMBOL
                            && (p[1] & 0x7f) == '@'
                            && p[2] == SPECIAL_VAR_SYMBOL
                        ) {
                                p += 3;
                        }
                        if (p == word->data || p[0] != '\0') {
                                /* saw no "$@", or not only "$@" but some
                                 * real text is there too */
                                /* insert "empty variable" reference, this makes
                                 * e.g. "", $empty"" etc to not disappear */
                                o_addchr(word, SPECIAL_VAR_SYMBOL);
                                o_addchr(word, SPECIAL_VAR_SYMBOL);
                        }
                }
                command->argv = add_string_to_strings(command->argv, xstrdup(word->data));
                debug_print_strings("word appended to argv", command->argv);
        }

        o_reset(word);
        ctx->pending_redirect = NULL;

#if ENABLE_HUSH_LOOPS
        /* Force FOR to have just one word (variable name) */
        /* NB: basically, this makes hush see "for v in ..." syntax as if
         * as it is "for v; in ...". FOR and IN become two pipe structs
         * in parse tree. */
        if (ctx->ctx_res_w == RES_FOR) {
//TODO: check that command->argv[0] is a valid variable name!
                done_pipe(ctx, PIPE_SEQ);
        }
#endif
#if ENABLE_HUSH_CASE
        /* Force CASE to have just one word */
        if (ctx->ctx_res_w == RES_CASE) {
                done_pipe(ctx, PIPE_SEQ);
        }
#endif
        debug_printf_parse("done_word return 0\n");
        return 0;
}

/* If a redirect is immediately preceded by a number, that number is
 * supposed to tell which file descriptor to redirect.  This routine
 * looks for such preceding numbers.  In an ideal world this routine
 * needs to handle all the following classes of redirects...
 *     echo 2>foo     # redirects fd  2 to file "foo", nothing passed to echo
 *     echo 49>foo    # redirects fd 49 to file "foo", nothing passed to echo
 *     echo -2>foo    # redirects fd  1 to file "foo",    "-2" passed to echo
 *     echo 49x>foo   # redirects fd  1 to file "foo",   "49x" passed to echo
 * A -1 output from this program means no valid number was found, so the
 * caller should use the appropriate default for this redirection.
 */
static int redirect_opt_num(o_string *o)
{
        int num;

        if (o->length == 0)
                return -1;
        for (num = 0; num < o->length; num++) {
                if (!isdigit(o->data[num])) {
                        return -1;
                }
        }
        num = atoi(o->data);
        o_reset(o);
        return num;
}

static struct pipe *parse_stream(struct in_str *input, int end_trigger);
static void parse_and_run_string(const char *s);

#if ENABLE_HUSH_TICK
static FILE *generate_stream_from_string(const char *s)
{
        FILE *pf;
        int pid, channel[2];

        xpipe(channel);
        pid = BB_MMU ? fork() : vfork();
        if (pid < 0)
                bb_perror_msg_and_die(BB_MMU ? "fork" : "vfork");

        if (pid == 0) { /* child */
                /* Process substitution is not considered to be usual
                 * 'command execution'.
                 * SUSv3 says ctrl-Z should be ignored, ctrl-C should not.
                 */
                bb_signals(0
                        + (1 << SIGTSTP)
                        + (1 << SIGTTIN)
                        + (1 << SIGTTOU)
                        , SIG_IGN);
                if (ENABLE_HUSH_JOB)
                        die_sleep = 0; /* let nofork's xfuncs die */
                close(channel[0]); /* NB: close _first_, then move fd! */
                xmove_fd(channel[1], 1);
                /* Prevent it from trying to handle ctrl-z etc */
                USE_HUSH_JOB(G.run_list_level = 1;)
#if BB_MMU
                parse_and_run_string(s);
                _exit(G.last_return_code);
#else
        /* We re-execute after vfork on NOMMU. This makes this script safe:
         * yes "0123456789012345678901234567890" | dd bs=32 count=64k >TESTFILE
         * huge=`cat TESTFILE` # was blocking here forever
         * echo OK
         */
//TODO: pass non-exported variables, traps, and functions
                execl(CONFIG_BUSYBOX_EXEC_PATH, "hush", "-c", s, NULL);
                _exit(127);
#endif
        }

        /* parent */
        close(channel[1]);
        pf = fdopen(channel[0], "r");
        return pf;
}

/* Return code is exit status of the process that is run. */
static int process_command_subs(o_string *dest, const char *s)
{
        FILE *pf;
        struct in_str pipe_str;
        int ch, eol_cnt;

        pf = generate_stream_from_string(s);
        if (pf == NULL)
                return 1;
        close_on_exec_on(fileno(pf));

        /* Now send results of command back into original context */
        setup_file_in_str(&pipe_str, pf);
        eol_cnt = 0;
        while ((ch = i_getch(&pipe_str)) != EOF) {
                if (ch == '\n') {
                        eol_cnt++;
                        continue;
                }
                while (eol_cnt) {
                        o_addchr(dest, '\n');
                        eol_cnt--;
                }
                o_addQchr(dest, ch);
        }

        debug_printf("done reading from pipe, pclose()ing\n");
        /* Note: we got EOF, and we just close the read end of the pipe.
         * We do not wait for the `cmd` child to terminate. bash and ash do.
         * Try these:
         * echo `echo Hi; exec 1>&-; sleep 2` - bash waits 2 sec
         * `false`; echo $? - bash outputs "1"
         */
        fclose(pf);
        debug_printf("closed FILE from child. return 0\n");
        return 0;
}
#endif

static int parse_group(o_string *dest, struct parse_context *ctx,
        struct in_str *input, int ch)
{
        /* dest contains characters seen prior to ( or {.
         * Typically it's empty, but for function defs,
         * it contains function name (without '()'). */
        struct pipe *pipe_list;
        int endch;
        struct command *command = ctx->command;

        debug_printf_parse("parse_group entered\n");
#if ENABLE_HUSH_FUNCTIONS
        if (ch == 'F') { /* function definition? */
                bb_error_msg("aha '%s' is a function, parsing it...", dest->data);
                //command->fname = dest->data;
                command->grp_type = GRP_FUNCTION;
//TODO: review every o_reset() location... do they handle all o_string fields correctly?
                memset(dest, 0, sizeof(*dest));
        }
#endif
        if (command->argv /* word [word](... */
         || dest->length /* word(... */
         || dest->nonnull /* ""(... */
        ) {
                syntax(NULL);
                debug_printf_parse("parse_group return 1: "
                        "syntax error, groups and arglists don't mix\n");
                return 1;
        }
        endch = '}';
        if (ch == '(') {
                endch = ')';
                command->grp_type = GRP_SUBSHELL;
        }
        pipe_list = parse_stream(input, endch);
        /* empty ()/{} or parse error? */
        if (!pipe_list || pipe_list == ERR_PTR) {
                syntax(NULL);
                debug_printf_parse("parse_group return 1: "
                        "parse_stream returned %p\n", pipe_list);
                return 1;
        }
        command->group = pipe_list;
        debug_printf_parse("parse_group return 0\n");
        return 0;
        /* command remains "open", available for possible redirects */
}

#if ENABLE_HUSH_TICK || ENABLE_SH_MATH_SUPPORT
/* Subroutines for copying $(...) and `...` things */
static void add_till_backquote(o_string *dest, struct in_str *input);
/* '...' */
static void add_till_single_quote(o_string *dest, struct in_str *input)
{
        while (1) {
                int ch = i_getch(input);
                if (ch == EOF)
                        break;
                if (ch == '\'')
                        break;
                o_addchr(dest, ch);
        }
}
/* "...\"...`..`...." - do we need to handle "...$(..)..." too? */
static void add_till_double_quote(o_string *dest, struct in_str *input)
{
        while (1) {
                int ch = i_getch(input);
                if (ch == '"')
                        break;
                if (ch == '\\') {  /* \x. Copy both chars. */
                        o_addchr(dest, ch);
                        ch = i_getch(input);
                }
                if (ch == EOF)
                        break;
                o_addchr(dest, ch);
                if (ch == '`') {
                        add_till_backquote(dest, input);
                        o_addchr(dest, ch);
                        continue;
                }
                //if (ch == '$') ...
        }
}
/* Process `cmd` - copy contents until "`" is seen. Complicated by
 * \` quoting.
 * "Within the backquoted style of command substitution, backslash
 * shall retain its literal meaning, except when followed by: '$', '`', or '\'.
 * The search for the matching backquote shall be satisfied by the first
 * backquote found without a preceding backslash; during this search,
 * if a non-escaped backquote is encountered within a shell comment,
 * a here-document, an embedded command substitution of the $(command)
 * form, or a quoted string, undefined results occur. A single-quoted
 * or double-quoted string that begins, but does not end, within the
 * "`...`" sequence produces undefined results."
 * Example                               Output
 * echo `echo '\'TEST\`echo ZZ\`BEST`    \TESTZZBEST
 */
static void add_till_backquote(o_string *dest, struct in_str *input)
{
        while (1) {
                int ch = i_getch(input);
                if (ch == '`')
                        break;
                if (ch == '\\') {  /* \x. Copy both chars unless it is \` */
                        int ch2 = i_getch(input);
                        if (ch2 != '`' && ch2 != '$' && ch2 != '\\')
                                o_addchr(dest, ch);
                        ch = ch2;
                }
                if (ch == EOF)
                        break;
                o_addchr(dest, ch);
        }
}
/* Process $(cmd) - copy contents until ")" is seen. Complicated by
 * quoting and nested ()s.
 * "With the $(command) style of command substitution, all characters
 * following the open parenthesis to the matching closing parenthesis
 * constitute the command. Any valid shell script can be used for command,
 * except a script consisting solely of redirections which produces
 * unspecified results."
 * Example                              Output
 * echo $(echo '(TEST)' BEST)           (TEST) BEST
 * echo $(echo 'TEST)' BEST)            TEST) BEST
 * echo $(echo \(\(TEST\) BEST)         ((TEST) BEST
 */
static void add_till_closing_paren(o_string *dest, struct in_str *input, bool dbl)
{
        int count = 0;
        while (1) {
                int ch = i_getch(input);
                if (ch == EOF)
                        break;
                if (ch == '(')
                        count++;
                if (ch == ')') {
                        if (--count < 0) {
                                if (!dbl)
                                        break;
                                if (i_peek(input) == ')') {
                                        i_getch(input);
                                        break;
                                }
                        }
                }
                o_addchr(dest, ch);
                if (ch == '\'') {
                        add_till_single_quote(dest, input);
                        o_addchr(dest, ch);
                        continue;
                }
                if (ch == '"') {
                        add_till_double_quote(dest, input);
                        o_addchr(dest, ch);
                        continue;
                }
                if (ch == '\\') { /* \x. Copy verbatim. Important for  \(, \) */
                        ch = i_getch(input);
                        if (ch == EOF)
                                break;
                        o_addchr(dest, ch);
                        continue;
                }
        }
}
#endif /* ENABLE_HUSH_TICK || ENABLE_SH_MATH_SUPPORT */

/* Return code: 0 for OK, 1 for syntax error */
static int handle_dollar(o_string *dest, struct in_str *input)
{
        int expansion;
        int ch = i_peek(input);  /* first character after the $ */
        unsigned char quote_mask = dest->o_escape ? 0x80 : 0;

        debug_printf_parse("handle_dollar entered: ch='%c'\n", ch);
        if (isalpha(ch)) {
                i_getch(input);
 make_var:
                o_addchr(dest, SPECIAL_VAR_SYMBOL);
                while (1) {
                        debug_printf_parse(": '%c'\n", ch);
                        o_addchr(dest, ch | quote_mask);
                        quote_mask = 0;
                        ch = i_peek(input);
                        if (!isalnum(ch) && ch != '_')
                                break;
                        i_getch(input);
                }
                o_addchr(dest, SPECIAL_VAR_SYMBOL);
        } else if (isdigit(ch)) {
 make_one_char_var:
                i_getch(input);
                o_addchr(dest, SPECIAL_VAR_SYMBOL);
                debug_printf_parse(": '%c'\n", ch);
                o_addchr(dest, ch | quote_mask);
                o_addchr(dest, SPECIAL_VAR_SYMBOL);
        } else switch (ch) {
        case '$': /* pid */
        case '!': /* last bg pid */
        case '?': /* last exit code */
        case '#': /* number of args */
        case '*': /* args */
        case '@': /* args */
                goto make_one_char_var;
        case '{': {
                bool first_char, all_digits;

                o_addchr(dest, SPECIAL_VAR_SYMBOL);
                i_getch(input);
                /* XXX maybe someone will try to escape the '}' */
                expansion = 0;
                first_char = true;
                all_digits = false;
                while (1) {
                        ch = i_getch(input);
                        if (ch == '}')
                                break;

                        if (first_char) {
                                if (ch == '#')
                                        /* ${#var}: length of var contents */
                                        goto char_ok;
                                else if (isdigit(ch)) {
                                        all_digits = true;
                                        goto char_ok;
                                }
                        }

                        if (expansion < 2
                         && (  (all_digits && !isdigit(ch))
                            || (!all_digits && !isalnum(ch) && ch != '_')
                            )
                        ) {
                                /* handle parameter expansions
                                 * http://www.opengroup.org/onlinepubs/009695399/utilities/xcu_chap02.html#tag_02_06_02
                                 */
                                if (first_char)
                                        goto case_default;
                                switch (ch) {
                                case ':': /* null modifier */
                                        if (expansion == 0) {
                                                debug_printf_parse(": null modifier\n");
                                                ++expansion;
                                                break;
                                        }
                                        goto case_default;
#if 0 /* not implemented yet :( */
                                case '#': /* remove prefix */
                                case '%': /* remove suffix */
                                        if (expansion == 0) {
                                                debug_printf_parse(": remove suffix/prefix\n");
                                                expansion = 2;
                                                break;
                                        }
                                        goto case_default;
#endif
                                case '-': /* default value */
                                case '=': /* assign default */
                                case '+': /* alternative */
                                case '?': /* error indicate */
                                        debug_printf_parse(": parameter expansion\n");
                                        expansion = 2;
                                        break;
                                default:
                                case_default:
                                        syntax("unterminated ${name}");
                                        debug_printf_parse("handle_dollar return 1: unterminated ${name}\n");
                                        return 1;
                                }
                        }
 char_ok:
                        debug_printf_parse(": '%c'\n", ch);
                        o_addchr(dest, ch | quote_mask);
                        quote_mask = 0;
                        first_char = false;
                }
                o_addchr(dest, SPECIAL_VAR_SYMBOL);
                break;
        }
        case '(': {
                i_getch(input);
#if ENABLE_SH_MATH_SUPPORT
                if (i_peek(input) == '(') {
                        i_getch(input);
                        o_addchr(dest, SPECIAL_VAR_SYMBOL);
                        o_addchr(dest, /*quote_mask |*/ '+');
                        add_till_closing_paren(dest, input, true);
                        o_addchr(dest, SPECIAL_VAR_SYMBOL);
                        break;
                }
#endif
#if ENABLE_HUSH_TICK
                //int pos = dest->length;
                o_addchr(dest, SPECIAL_VAR_SYMBOL);
                o_addchr(dest, quote_mask | '`');
                add_till_closing_paren(dest, input, false);
                //debug_printf_subst("SUBST RES2 '%s'\n", dest->data + pos);
                o_addchr(dest, SPECIAL_VAR_SYMBOL);
#endif
                break;
        }
        case '_':
                i_getch(input);
                ch = i_peek(input);
                if (isalnum(ch)) { /* it's $_name or $_123 */
                        ch = '_';
                        goto make_var;
                }
                /* else: it's $_ */
        /* TODO: */
        /* $_ Shell or shell script name; or last cmd name */
        /* $- Option flags set by set builtin or shell options (-i etc) */
        default:
                o_addQchr(dest, '$');
        }
        debug_printf_parse("handle_dollar return 0\n");
        return 0;
}

static int parse_stream_dquoted(o_string *dest,
                struct in_str *input, int dquote_end)
{
        int ch;
        int next;

 again:
        ch = i_getch(input);
        if (ch == dquote_end) { /* may be only '"' or EOF */
                dest->nonnull = 1;
                if (dest->o_assignment == NOT_ASSIGNMENT)
                        dest->o_escape ^= 1;
                debug_printf_parse("parse_stream_dquoted return 0\n");
                return 0;
        }
        if (ch == EOF) {
                syntax("unterminated \"");
                debug_printf_parse("parse_stream_dquoted return 1: unterminated \"\n");
                return 1;
        }
        next = '\0';
        if (ch != '\n') {
                next = i_peek(input);
        }
        debug_printf_parse(": ch=%c (%d) m=%d escape=%d\n",
                                        ch, ch, m, dest->o_escape);
        if (ch == '\\') {
                if (next == EOF) {
                        syntax("\\<eof>");
                        debug_printf_parse("parse_stream_dquoted return 1: \\<eof>\n");
                        return 1;
                }
                /* bash:
                 * "The backslash retains its special meaning [in "..."]
                 * only when followed by one of the following characters:
                 * $, `, ", \, or <newline>.  A double quote may be quoted
                 * within double quotes by preceding it with a backslash.
                 * If enabled, history expansion will be performed unless
                 * an ! appearing in double quotes is escaped using
                 * a backslash. The backslash preceding the ! is not removed."
                 */
                if (strchr("$`\"\\", next) != NULL) {
                        o_addqchr(dest, i_getch(input));
                } else {
                        o_addqchr(dest, '\\');
                }
                goto again;
        }
        if (ch == '$') {
                if (handle_dollar(dest, input) != 0) {
                        debug_printf_parse("parse_stream_dquoted return 1: "
                                        "handle_dollar returned non-0\n");
                        return 1;
                }
                goto again;
        }
#if ENABLE_HUSH_TICK
        if (ch == '`') {
                //int pos = dest->length;
                o_addchr(dest, SPECIAL_VAR_SYMBOL);
                o_addchr(dest, 0x80 | '`');
                add_till_backquote(dest, input);
                o_addchr(dest, SPECIAL_VAR_SYMBOL);
                //debug_printf_subst("SUBST RES3 '%s'\n", dest->data + pos);
                goto again;
        }
#endif
        o_addQchr(dest, ch);
        if (ch == '='
         && (dest->o_assignment == MAYBE_ASSIGNMENT
            || dest->o_assignment == WORD_IS_KEYWORD)
         && is_assignment(dest->data)
        ) {
                dest->o_assignment = DEFINITELY_ASSIGNMENT;
        }
        goto again;
}

/*
 * Scan input until EOF or end_trigger char.
 * Return a list of pipes to execute, or NULL on EOF
 * or if end_trigger character is met.
 * On syntax error, exit is shell is not interactive,
 * reset parsing machinery and start parsing anew,
 * or return ERR_PTR.
 */
static struct pipe *parse_stream(struct in_str *input, int end_trigger)
{
        struct parse_context ctx;
        o_string dest = NULL_O_STRING;
        int redir_fd;
        int next;
        int is_in_dquote;
        int ch;
        redir_type redir_style;

        /* Double-quote state is handled in the state variable is_in_dquote.
         * A single-quote triggers a bypass of the main loop until its mate is
         * found.  When recursing, quote state is passed in via dest->o_escape.
         */
        debug_printf_parse("parse_stream entered, end_trigger='%c'\n",
                        end_trigger ? : 'X');

        G.ifs = get_local_var_value("IFS");
        if (G.ifs == NULL)
                G.ifs = " \t\n";

 reset:
#if ENABLE_HUSH_INTERACTIVE
        input->promptmode = 0; /* PS1 */
#endif
        /* dest.o_assignment = MAYBE_ASSIGNMENT; - already is */
        initialize_context(&ctx);
        is_in_dquote = 0;
        while (1) {
                const char *is_ifs;
                const char *is_special;

                if (is_in_dquote) {
                        if (parse_stream_dquoted(&dest, input, '"')) {
                                goto parse_error;
                        }
                        /* We reached closing '"' */
                        is_in_dquote = 0;
                }
                next = '\0';
                ch = i_getch(input);
                debug_printf_parse(": ch=%c (%d) escape=%d\n",
                                                ch, ch, dest.o_escape);
                if (ch == EOF) {
                        struct pipe *pi;
                        if (done_word(&dest, &ctx)) {
                                goto parse_error;
                        }
                        o_free(&dest);
                        done_pipe(&ctx, PIPE_SEQ);
                        /* If we got nothing... */
                        pi = ctx.list_head;
                        if (pi->num_cmds == 0
                            IF_HAS_KEYWORDS( && pi->res_word == RES_NONE)
                        ) {
                                free_pipe_list(pi, 0);
                                pi = NULL;
                        }
                        debug_printf_parse("parse_stream return %p\n", pi);
                        return pi;
                }
                if (ch != '\n') {
                        next = i_peek(input);
                }

                is_ifs = strchr(G.ifs, ch);
                is_special = strchr("<>;&|(){}#'" /* special outside of "str" */
                                "\\$\"" USE_HUSH_TICK("`") /* always special */
                                , ch);

                if (!is_special && !is_ifs) { /* ordinary char */
                        o_addQchr(&dest, ch);
                        if ((dest.o_assignment == MAYBE_ASSIGNMENT
                            || dest.o_assignment == WORD_IS_KEYWORD)
                         && ch == '='
                         && is_assignment(dest.data)
                        ) {
                                dest.o_assignment = DEFINITELY_ASSIGNMENT;
                        }
                        continue;
                }

                if (is_ifs) {
                        if (done_word(&dest, &ctx)) {
                                goto parse_error;
                        }
                        if (ch == '\n') {
#if ENABLE_HUSH_CASE
                                /* "case ... in <newline> word) ..." -
                                 * newlines are ignored (but ';' wouldn't be) */
                                if (ctx.command->argv == NULL
                                 && ctx.ctx_res_w == RES_MATCH
                                ) {
                                        continue;
                                }
#endif
                                /* Treat newline as a command separator. */
                                done_pipe(&ctx, PIPE_SEQ);
                                dest.o_assignment = MAYBE_ASSIGNMENT;
                                ch = ';';
                                /* note: if (is_ifs) continue;
                                 * will still trigger for us */
                        }
                }
                if (end_trigger && end_trigger == ch) {
//TODO: disallow "{ cmd }" without semicolon
                        if (done_word(&dest, &ctx)) {
                                goto parse_error;
                        }
                        done_pipe(&ctx, PIPE_SEQ);
                        dest.o_assignment = MAYBE_ASSIGNMENT;
                        /* Do we sit outside of any if's, loops or case's? */
                        if (!HAS_KEYWORDS
                         IF_HAS_KEYWORDS(|| (ctx.ctx_res_w == RES_NONE && ctx.old_flag == 0))
                        ) {
                                debug_printf_parse("parse_stream return %p: "
                                                "end_trigger char found\n",
                                                ctx.list_head);
                                o_free(&dest);
                                return ctx.list_head;
                        }
                }
                if (is_ifs)
                        continue;

                if (dest.o_assignment == MAYBE_ASSIGNMENT) {
                        /* ch is a special char and thus this word
                         * cannot be an assignment */
                        dest.o_assignment = NOT_ASSIGNMENT;
                }

                switch (ch) {
                case '#':
                        if (dest.length == 0) {
                                while (1) {
                                        ch = i_peek(input);
                                        if (ch == EOF || ch == '\n')
                                                break;
                                        i_getch(input);
                                }
                        } else {
                                o_addQchr(&dest, ch);
                        }
                        break;
                case '\\':
                        if (next == EOF) {
                                syntax("\\<eof>");
                                goto parse_error;
                        }
                        o_addchr(&dest, '\\');
                        o_addchr(&dest, i_getch(input));
                        break;
                case '$':
                        if (handle_dollar(&dest, input) != 0) {
                                debug_printf_parse("parse_stream parse error: "
                                        "handle_dollar returned non-0\n");
                                goto parse_error;
                        }
                        break;
                case '\'':
                        dest.nonnull = 1;
                        while (1) {
                                ch = i_getch(input);
                                if (ch == EOF) {
                                        syntax("unterminated '");
                                        goto parse_error;
                                }
                                if (ch == '\'')
                                        break;
                                if (dest.o_assignment == NOT_ASSIGNMENT)
                                        o_addqchr(&dest, ch);
                                else
                                        o_addchr(&dest, ch);
                        }
                        break;
                case '"':
                        dest.nonnull = 1;
                        is_in_dquote ^= 1; /* invert */
                        if (dest.o_assignment == NOT_ASSIGNMENT)
                                dest.o_escape ^= 1;
                        break;
#if ENABLE_HUSH_TICK
                case '`': {
                        //int pos = dest.length;
                        o_addchr(&dest, SPECIAL_VAR_SYMBOL);
                        o_addchr(&dest, '`');
                        add_till_backquote(&dest, input);
                        o_addchr(&dest, SPECIAL_VAR_SYMBOL);
                        //debug_printf_subst("SUBST RES3 '%s'\n", dest.data + pos);
                        break;
                }
#endif
                case '>':
                        redir_fd = redirect_opt_num(&dest);
                        if (done_word(&dest, &ctx)) {
                                goto parse_error;
                        }
                        redir_style = REDIRECT_OVERWRITE;
                        if (next == '>') {
                                redir_style = REDIRECT_APPEND;
                                i_getch(input);
                        }
#if 0
                        else if (next == '(') {
                                syntax(">(process) not supported");
                                goto parse_error;
                        }
#endif
                        setup_redirect(&ctx, redir_fd, redir_style, input);
                        break;
                case '<':
                        redir_fd = redirect_opt_num(&dest);
                        if (done_word(&dest, &ctx)) {
                                goto parse_error;
                        }
                        redir_style = REDIRECT_INPUT;
                        if (next == '<') {
                                redir_style = REDIRECT_HEREIS;
                                i_getch(input);
                        } else if (next == '>') {
                                redir_style = REDIRECT_IO;
                                i_getch(input);
                        }
#if 0
                        else if (next == '(') {
                                syntax("<(process) not supported");
                                goto parse_error;
                        }
#endif
                        setup_redirect(&ctx, redir_fd, redir_style, input);
                        break;
                case ';':
#if ENABLE_HUSH_CASE
 case_semi:
#endif
                        if (done_word(&dest, &ctx)) {
                                goto parse_error;
                        }
                        done_pipe(&ctx, PIPE_SEQ);
#if ENABLE_HUSH_CASE
                        /* Eat multiple semicolons, detect
                         * whether it means something special */
                        while (1) {
                                ch = i_peek(input);
                                if (ch != ';')
                                        break;
                                i_getch(input);
                                if (ctx.ctx_res_w == RES_CASEI) {
                                        ctx.ctx_dsemicolon = 1;
                                        ctx.ctx_res_w = RES_MATCH;
                                        break;
                                }
                        }
#endif
 new_cmd:
                        /* We just finished a cmd. New one may start
                         * with an assignment */
                        dest.o_assignment = MAYBE_ASSIGNMENT;
                        break;
                case '&':
                        if (done_word(&dest, &ctx)) {
                                goto parse_error;
                        }
                        if (next == '&') {
                                i_getch(input);
                                done_pipe(&ctx, PIPE_AND);
                        } else {
                                done_pipe(&ctx, PIPE_BG);
                        }
                        goto new_cmd;
                case '|':
                        if (done_word(&dest, &ctx)) {
                                goto parse_error;
                        }
#if ENABLE_HUSH_CASE
                        if (ctx.ctx_res_w == RES_MATCH)
                                break; /* we are in case's "word | word)" */
#endif
                        if (next == '|') { /* || */
                                i_getch(input);
                                done_pipe(&ctx, PIPE_OR);
                        } else {
                                /* we could pick up a file descriptor choice here
                                 * with redirect_opt_num(), but bash doesn't do it.
                                 * "echo foo 2| cat" yields "foo 2". */
                                done_command(&ctx);
                        }
                        goto new_cmd;
                case '(':
#if ENABLE_HUSH_CASE
                        /* "case... in [(]word)..." - skip '(' */
                        if (ctx.ctx_res_w == RES_MATCH
                         && ctx.command->argv == NULL /* not (word|(... */
                         && dest.length == 0 /* not word(... */
                         && dest.nonnull == 0 /* not ""(... */
                        ) {
                                continue;
                        }
#endif
#if ENABLE_HUSH_FUNCTIONS
                        if (dest.length != 0 /* not just () but word() */
                         && dest.nonnull == 0 /* not a"b"c() */
                         && ctx.command->argv == NULL /* it's the first word */
//TODO: "func ( ) {...}" - note spaces - is valid format too in bash
                         && i_peek(input) == ')'
                         && !match_reserved_word(&dest)
                        ) {
                                bb_error_msg("seems like a function definition");
                                i_getch(input);
                                do {
//TODO: do it properly.
                                        ch = i_getch(input);
                                } while (ch == ' ' || ch == '\n');
                                if (ch != '{') {
                                        syntax("was expecting {");
                                        goto parse_error;
                                }
                                ch = 'F'; /* magic value */
                        }
#endif
                case '{':
                        if (parse_group(&dest, &ctx, input, ch) != 0) {
                                goto parse_error;
                        }
                        goto new_cmd;
                case ')':
#if ENABLE_HUSH_CASE
                        if (ctx.ctx_res_w == RES_MATCH)
                                goto case_semi;
#endif
                case '}':
                        /* proper use of this character is caught by end_trigger:
                         * if we see {, we call parse_group(..., end_trigger='}')
                         * and it will match } earlier (not here). */
                        syntax("unexpected } or )");
                        goto parse_error;
                default:
                        if (HUSH_DEBUG)
                                bb_error_msg_and_die("BUG: unexpected %c\n", ch);
                }
        } /* while (1) */

 parse_error:
        {
                struct parse_context *pctx;
                IF_HAS_KEYWORDS(struct parse_context *p2;)

                /* Clean up allocated tree.
                 * Samples for finding leaks on syntax error recovery path.
                 * Run them from interactive shell, watch pmap `pidof hush`.
                 * while if false; then false; fi do break; done
                 * (bash accepts it)
                 * while if false; then false; fi; do break; fi
                 */
                pctx = &ctx;
                do {
                        /* Update pipe/command counts,
                         * otherwise freeing may miss some */
                        done_pipe(pctx, PIPE_SEQ);
                        debug_printf_clean("freeing list %p from ctx %p\n",
                                        pctx->list_head, pctx);
                        debug_print_tree(pctx->list_head, 0);
                        free_pipe_list(pctx->list_head, 0);
                        debug_printf_clean("freed list %p\n", pctx->list_head);
                        IF_HAS_KEYWORDS(p2 = pctx->stack;)
                        if (pctx != &ctx) {
                                free(pctx);
                        }
                        IF_HAS_KEYWORDS(pctx = p2;)
                } while (HAS_KEYWORDS && pctx);
                /* Free text, clear all dest fields */
                o_free(&dest);
                /* If we are not in top-level parse, we return,
                 * our caller will propagate error.
                 */
                if (end_trigger != ';')
                        return ERR_PTR;
                /* Discard cached input, force prompt */
                input->p = NULL;
                USE_HUSH_INTERACTIVE(input->promptme = 1;)
                goto reset;
        }
}

/* Execiting from string: eval, sh -c '...'
 *          or from file: /etc/profile, . file, sh <script>, sh (intereactive)
 * end_trigger controls how often we stop parsing
 * NUL: parse all, execute, return
 * ';': parse till ';' or newline, execute, repeat till EOF
 */
static void parse_and_run_stream(struct in_str *inp, int end_trigger)
{
        while (1) {
                struct pipe *pipe_list;

                pipe_list = parse_stream(inp, end_trigger);
                if (!pipe_list) /* EOF */
                        break;
                debug_print_tree(pipe_list, 0);
                debug_printf_exec("parse_and_run_stream: run_and_free_list\n");
                run_and_free_list(pipe_list);
        }
}

static void parse_and_run_string(const char *s)
{
        struct in_str input;
        setup_string_in_str(&input, s);
        parse_and_run_stream(&input, '\0');
}

static void parse_and_run_file(FILE *f)
{
        struct in_str input;
        setup_file_in_str(&input, f);
        parse_and_run_stream(&input, ';');
}

#if ENABLE_HUSH_JOB
/* Make sure we have a controlling tty.  If we get started under a job
 * aware app (like bash for example), make sure we are now in charge so
 * we don't fight over who gets the foreground */
static void setup_job_control(void)
{
        pid_t shell_pgrp;

        shell_pgrp = getpgrp();

        /* If we were ran as 'hush &',
         * sleep until we are in the foreground.  */
        while (tcgetpgrp(G_interactive_fd) != shell_pgrp) {
                /* Send TTIN to ourself (should stop us) */
                kill(- shell_pgrp, SIGTTIN);
                shell_pgrp = getpgrp();
        }

        /* We _must_ restore tty pgrp on fatal signals */
        set_fatal_signals_to_sigexit();

        /* Put ourselves in our own process group.  */
        bb_setpgrp(); /* is the same as setpgid(our_pid, our_pid); */
        /* Grab control of the terminal.  */
        tcsetpgrp(G_interactive_fd, getpid());
}
#endif

static int set_mode(const char cstate, const char mode)
{
        int state = (cstate == '-' ? 1 : 0);
        switch (mode) {
                case 'n': G.fake_mode = state; break;
                case 'x': /*G.debug_mode = state;*/ break;
                default:  return EXIT_FAILURE;
        }
        return EXIT_SUCCESS;
}

int hush_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int hush_main(int argc, char **argv)
{
        static const struct variable const_shell_ver = {
                .next = NULL,
                .varstr = (char*)hush_version_str,
                .max_len = 1, /* 0 can provoke free(name) */
                .flg_export = 1,
                .flg_read_only = 1,
        };

        int opt;
        FILE *input;
        char **e;
        struct variable *cur_var;

        INIT_G();

        G.root_pid = getpid();

        /* Deal with HUSH_VERSION */
        G.shell_ver = const_shell_ver; /* copying struct here */
        G.top_var = &G.shell_ver;
        debug_printf_env("unsetenv '%s'\n", "HUSH_VERSION");
        unsetenv("HUSH_VERSION"); /* in case it exists in initial env */
        /* Initialize our shell local variables with the values
         * currently living in the environment */
        cur_var = G.top_var;
        e = environ;
        if (e) while (*e) {
                char *value = strchr(*e, '=');
                if (value) { /* paranoia */
                        cur_var->next = xzalloc(sizeof(*cur_var));
                        cur_var = cur_var->next;
                        cur_var->varstr = *e;
                        cur_var->max_len = strlen(*e);
                        cur_var->flg_export = 1;
                }
                e++;
        }
        debug_printf_env("putenv '%s'\n", hush_version_str);
        putenv((char *)hush_version_str); /* reinstate HUSH_VERSION */

#if ENABLE_FEATURE_EDITING
        G.line_input_state = new_line_input_t(FOR_SHELL);
#endif
        /* XXX what should these be while sourcing /etc/profile? */
        G.global_argc = argc;
        G.global_argv = argv;
        /* Initialize some more globals to non-zero values */
        set_cwd();
#if ENABLE_HUSH_INTERACTIVE
        if (ENABLE_FEATURE_EDITING)
                cmdedit_set_initial_prompt();
        G.PS2 = "> ";
#endif

        if (EXIT_SUCCESS) /* otherwise is already done */
                G.last_return_code = EXIT_SUCCESS;

        if (argv[0] && argv[0][0] == '-') {
                debug_printf("sourcing /etc/profile\n");
                input = fopen_for_read("/etc/profile");
                if (input != NULL) {
                        close_on_exec_on(fileno(input));
                        parse_and_run_file(input);
                        fclose(input);
                }
        }
        input = stdin;

        /* http://www.opengroup.org/onlinepubs/9699919799/utilities/sh.html */
        while ((opt = getopt(argc, argv, "c:xins")) > 0) {
                switch (opt) {
                case 'c':
                        G.global_argv = argv + optind;
                        if (!argv[optind]) {
                                /* -c 'script' (no params): prevent empty $0 */
                                *--G.global_argv = argv[0];
                                optind--;
                        } /* else -c 'script' PAR0 PAR1: $0 is PAR0 */
                        G.global_argc = argc - optind;
                        parse_and_run_string(optarg);
                        goto final_return;
                case 'i':
                        /* Well, we cannot just declare interactiveness,
                         * we have to have some stuff (ctty, etc) */
                        /* G_interactive_fd++; */
                        break;
                case 's':
                        /* "-s" means "read from stdin", but this is how we always
                         * operate, so simply do nothing here. */
                        break;
                case 'n':
                case 'x':
                        if (!set_mode('-', opt))
                                break;
                default:
#ifndef BB_VER
                        fprintf(stderr, "Usage: sh [FILE]...\n"
                                        "   or: sh -c command [args]...\n\n");
                        exit(EXIT_FAILURE);
#else
                        bb_show_usage();
#endif
                }
        }
#if ENABLE_HUSH_JOB
        /* A shell is interactive if the '-i' flag was given, or if all of
         * the following conditions are met:
         *    no -c command
         *    no arguments remaining or the -s flag given
         *    standard input is a terminal
         *    standard output is a terminal
         *    Refer to Posix.2, the description of the 'sh' utility. */
        if (argv[optind] == NULL && input == stdin
         && isatty(STDIN_FILENO) && isatty(STDOUT_FILENO)
        ) {
                G.saved_tty_pgrp = tcgetpgrp(STDIN_FILENO);
                debug_printf("saved_tty_pgrp=%d\n", G.saved_tty_pgrp);
                if (G.saved_tty_pgrp >= 0) {
                        /* try to dup to high fd#, >= 255 */
                        G_interactive_fd = fcntl(STDIN_FILENO, F_DUPFD, 255);
                        if (G_interactive_fd < 0) {
                                /* try to dup to any fd */
                                G_interactive_fd = dup(STDIN_FILENO);
                                if (G_interactive_fd < 0)
                                        /* give up */
                                        G_interactive_fd = 0;
                        }
                        // TODO: track & disallow any attempts of user
                        // to (inadvertently) close/redirect it
                }
        }
        init_signal_mask(); /* note: ensures SIGCHLD is not masked */
        debug_printf("interactive_fd=%d\n", G_interactive_fd);
        if (G_interactive_fd) {
                fcntl(G_interactive_fd, F_SETFD, FD_CLOEXEC);
                /* Looks like they want an interactive shell */
                setup_job_control();
                /* -1 is special - makes xfuncs longjmp, not exit
                 * (we reset die_sleep = 0 whereever we [v]fork) */
                die_sleep = -1;
                if (setjmp(die_jmp)) {
                        /* xfunc has failed! die die die */
                        hush_exit(xfunc_error_retval);
                }
        }
#elif ENABLE_HUSH_INTERACTIVE
/* no job control compiled, only prompt/line editing */
        if (argv[optind] == NULL && input == stdin
         && isatty(STDIN_FILENO) && isatty(STDOUT_FILENO)
        ) {
                G_interactive_fd = fcntl(STDIN_FILENO, F_DUPFD, 255);
                if (G_interactive_fd < 0) {
                        /* try to dup to any fd */
                        G_interactive_fd = dup(STDIN_FILENO);
                        if (G_interactive_fd < 0)
                                /* give up */
                                G_interactive_fd = 0;
                }
                if (G_interactive_fd) {
                        fcntl(G_interactive_fd, F_SETFD, FD_CLOEXEC);
                }
        }
        init_signal_mask(); /* note: ensures SIGCHLD is not masked */
#else
        init_signal_mask();
#endif
        /* POSIX allows shell to re-enable SIGCHLD
         * even if it was SIG_IGN on entry */
//      G.count_SIGCHLD++; /* ensure it is != G.handled_SIGCHLD */
        signal(SIGCHLD, SIG_DFL); // SIGCHLD_handler);

#if ENABLE_HUSH_INTERACTIVE && !ENABLE_FEATURE_SH_EXTRA_QUIET
        if (G_interactive_fd) {
                printf("\n\n%s hush - the humble shell v"HUSH_VER_STR"\n", bb_banner);
                printf("Enter 'help' for a list of built-in commands.\n\n");
        }
#endif

        if (argv[optind] == NULL) {
                parse_and_run_file(stdin);
        } else {
                debug_printf("\nrunning script '%s'\n", argv[optind]);
                G.global_argv = argv + optind;
                G.global_argc = argc - optind;
                input = xfopen_for_read(argv[optind]);
                fcntl(fileno(input), F_SETFD, FD_CLOEXEC);
                parse_and_run_file(input);
        }

 final_return:

#if ENABLE_FEATURE_CLEAN_UP
        fclose(input);
        if (G.cwd != bb_msg_unknown)
                free((char*)G.cwd);
        cur_var = G.top_var->next;
        while (cur_var) {
                struct variable *tmp = cur_var;
                if (!cur_var->max_len)
                        free(cur_var->varstr);
                cur_var = cur_var->next;
                free(tmp);
        }
#endif
        hush_exit(G.last_return_code);
}


#if ENABLE_LASH
int lash_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int lash_main(int argc, char **argv)
{
        //bb_error_msg("lash is deprecated, please use hush instead");
        return hush_main(argc, argv);
}
#endif


/*
 * Built-ins
 */
static int builtin_trap(char **argv)
{
        int i;
        int sig;
        char *new_cmd;

        if (!G.traps)
                G.traps = xzalloc(sizeof(G.traps[0]) * NSIG);

        if (!argv[1]) {
                /* No args: print all trapped.  This isn't 100% correct as we should
                 * be escaping the cmd so that it can be pasted back in ...
                 */
                for (i = 0; i < NSIG; ++i)
                        if (G.traps[i])
                                printf("trap -- '%s' %s\n", G.traps[i], get_signame(i));
                return EXIT_SUCCESS;
        }

        new_cmd = NULL;
        i = 0;
        /* if first arg is decimal: reset all specified */
        sig = bb_strtou(*++argv, NULL, 10);
        if (errno == 0) {
                int ret;
 set_all:
                ret = EXIT_SUCCESS;
                while (*argv) {
                        sig = get_signum(*argv++);
                        if (sig < 0 || sig >= NSIG) {
                                ret = EXIT_FAILURE;
                                /* mimic bash message exactly */
                                bb_perror_msg("trap: %s: invalid signal specification", argv[i]);
                                continue;
                        }

                        free(G.traps[sig]);
                        G.traps[sig] = xstrdup(new_cmd);

                        debug_printf("trap: setting SIG%s (%i) to '%s'",
                                get_signame(sig), sig, G.traps[sig]);

                        /* There is no signal for 0 (EXIT) */
                        if (sig == 0)
                                continue;

                        if (new_cmd) {
                                sigaddset(&G.blocked_set, sig);
                        } else {
                                /* there was a trap handler, we are removing it
                                 * (if sig has non-DFL handling,
                                 * we don't need to do anything) */
                                if (sig < 32 && (G.non_DFL_mask & (1 << sig)))
                                        continue;
                                sigdelset(&G.blocked_set, sig);
                        }
                        sigprocmask(SIG_SETMASK, &G.blocked_set, NULL);
                }
                return ret;
        }

        /* first arg is "-": reset all specified to default */
        /* first arg is "": ignore all specified */
        /* everything else: execute first arg upon signal */
        if (!argv[1]) {
                bb_error_msg("trap: invalid arguments");
                return EXIT_FAILURE;
        }
        if (LONE_DASH(*argv))
                /* nothing! */;
        else
                new_cmd = *argv;
        argv++;
        goto set_all;
}

static int builtin_true(char **argv UNUSED_PARAM)
{
        return 0;
}

static int builtin_test(char **argv)
{
        int argc = 0;
        while (*argv) {
                argc++;
                argv++;
        }
        return test_main(argc, argv - argc);
}

static int builtin_echo(char **argv)
{
        int argc = 0;
        while (*argv) {
                argc++;
                argv++;
        }
        return echo_main(argc, argv - argc);
}

static int builtin_eval(char **argv)
{
        int rcode = EXIT_SUCCESS;

        if (argv[1]) {
                char *str = expand_strvec_to_string(argv + 1);
                /* bash:
                 * eval "echo Hi; done" ("done" is syntax error):
                 * "echo Hi" will not execute too.
                 */
                parse_and_run_string(str);
                free(str);
                rcode = G.last_return_code;
        }
        return rcode;
}

static int builtin_cd(char **argv)
{
        const char *newdir;
        if (argv[1] == NULL) {
                /* bash does nothing (exitcode 0) if HOME is ""; if it's unset,
                 * bash says "bash: cd: HOME not set" and does nothing (exitcode 1)
                 */
                newdir = getenv("HOME") ? : "/";
        } else
                newdir = argv[1];
        if (chdir(newdir)) {
                printf("cd: %s: %s\n", newdir, strerror(errno));
                return EXIT_FAILURE;
        }
        set_cwd();
        return EXIT_SUCCESS;
}

static int builtin_exec(char **argv)
{
        if (argv[1] == NULL)
                return EXIT_SUCCESS; /* bash does this */
        {
#if !BB_MMU
                nommu_save_t dummy;
#endif
// FIXME: if exec fails, bash does NOT exit! We do...
                pseudo_exec_argv(&dummy, argv + 1, 0, NULL);
                /* never returns */
        }
}

static int builtin_exit(char **argv)
{
// TODO: bash does it ONLY on top-level sh exit (+interacive only?)
        //puts("exit"); /* bash does it */
// TODO: warn if we have background jobs: "There are stopped jobs"
// On second consecutive 'exit', exit anyway.
        if (argv[1] == NULL)
                hush_exit(G.last_return_code);
        /* mimic bash: exit 123abc == exit 255 + error msg */
        xfunc_error_retval = 255;
        /* bash: exit -2 == exit 254, no error msg */
        hush_exit(xatoi(argv[1]) & 0xff);
}

static int builtin_export(char **argv)
{
        const char *value;
        char *name = argv[1];

        if (name == NULL) {
                // TODO:
                // ash emits: export VAR='VAL'
                // bash: declare -x VAR="VAL"
                // (both also escape as needed (quotes, $, etc))
                char **e = environ;
                if (e)
                        while (*e)
                                puts(*e++);
                return EXIT_SUCCESS;
        }

        value = strchr(name, '=');
        if (!value) {
                /* They are exporting something without a =VALUE */
                struct variable *var;

                var = get_local_var(name);
                if (var) {
                        var->flg_export = 1;
                        debug_printf_env("%s: putenv '%s'\n", __func__, var->varstr);
                        putenv(var->varstr);
                }
                /* bash does not return an error when trying to export
                 * an undefined variable.  Do likewise. */
                return EXIT_SUCCESS;
        }

        set_local_var(xstrdup(name), 1);
        return EXIT_SUCCESS;
}

#if ENABLE_HUSH_JOB
/* built-in 'fg' and 'bg' handler */
static int builtin_fg_bg(char **argv)
{
        int i, jobnum;
        struct pipe *pi;

        if (!G_interactive_fd)
                return EXIT_FAILURE;
        /* If they gave us no args, assume they want the last backgrounded task */
        if (!argv[1]) {
                for (pi = G.job_list; pi; pi = pi->next) {
                        if (pi->jobid == G.last_jobid) {
                                goto found;
                        }
                }
                bb_error_msg("%s: no current job", argv[0]);
                return EXIT_FAILURE;
        }
        if (sscanf(argv[1], "%%%d", &jobnum) != 1) {
                bb_error_msg("%s: bad argument '%s'", argv[0], argv[1]);
                return EXIT_FAILURE;
        }
        for (pi = G.job_list; pi; pi = pi->next) {
                if (pi->jobid == jobnum) {
                        goto found;
                }
        }
        bb_error_msg("%s: %d: no such job", argv[0], jobnum);
        return EXIT_FAILURE;
 found:
        // TODO: bash prints a string representation
        // of job being foregrounded (like "sleep 1 | cat")
        if (*argv[0] == 'f') {
                /* Put the job into the foreground.  */
                tcsetpgrp(G_interactive_fd, pi->pgrp);
        }

        /* Restart the processes in the job */
        debug_printf_jobs("reviving %d procs, pgrp %d\n", pi->num_cmds, pi->pgrp);
        for (i = 0; i < pi->num_cmds; i++) {
                debug_printf_jobs("reviving pid %d\n", pi->cmds[i].pid);
                pi->cmds[i].is_stopped = 0;
        }
        pi->stopped_cmds = 0;

        i = kill(- pi->pgrp, SIGCONT);
        if (i < 0) {
                if (errno == ESRCH) {
                        delete_finished_bg_job(pi);
                        return EXIT_SUCCESS;
                } else {
                        bb_perror_msg("kill (SIGCONT)");
                }
        }

        if (*argv[0] == 'f') {
                remove_bg_job(pi);
                return checkjobs_and_fg_shell(pi);
        }
        return EXIT_SUCCESS;
}
#endif

#if ENABLE_HUSH_HELP
static int builtin_help(char **argv UNUSED_PARAM)
{
        const struct built_in_command *x;

        printf("\nBuilt-in commands:\n");
        printf("-------------------\n");
        for (x = bltins; x != &bltins[ARRAY_SIZE(bltins)]; x++) {
                printf("%s\t%s\n", x->cmd, x->descr);
        }
        printf("\n\n");
        return EXIT_SUCCESS;
}
#endif

#if ENABLE_HUSH_JOB
static int builtin_jobs(char **argv UNUSED_PARAM)
{
        struct pipe *job;
        const char *status_string;

        for (job = G.job_list; job; job = job->next) {
                if (job->alive_cmds == job->stopped_cmds)
                        status_string = "Stopped";
                else
                        status_string = "Running";

                printf(JOB_STATUS_FORMAT, job->jobid, status_string, job->cmdtext);
        }
        return EXIT_SUCCESS;
}
#endif

static int builtin_pwd(char **argv UNUSED_PARAM)
{
        puts(set_cwd());
        return EXIT_SUCCESS;
}

static int builtin_read(char **argv)
{
        char *string;
        const char *name = argv[1] ? argv[1] : "REPLY";

        string = xmalloc_reads(STDIN_FILENO, xasprintf("%s=", name), NULL);
        return set_local_var(string, 0);
}

/* http://www.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#set
 * built-in 'set' handler
 * SUSv3 says:
 * set [-abCefhmnuvx] [-o option] [argument...]
 * set [+abCefhmnuvx] [+o option] [argument...]
 * set -- [argument...]
 * set -o
 * set +o
 * Implementations shall support the options in both their hyphen and
 * plus-sign forms. These options can also be specified as options to sh.
 * Examples:
 * Write out all variables and their values: set
 * Set $1, $2, and $3 and set "$#" to 3: set c a b
 * Turn on the -x and -v options: set -xv
 * Unset all positional parameters: set --
 * Set $1 to the value of x, even if it begins with '-' or '+': set -- "$x"
 * Set the positional parameters to the expansion of x, even if x expands
 * with a leading '-' or '+': set -- $x
 *
 * So far, we only support "set -- [argument...]" and some of the short names.
 */
static int builtin_set(char **argv)
{
        int n;
        char **pp, **g_argv;
        char *arg = *++argv;

        if (arg == NULL) {
                struct variable *e;
                for (e = G.top_var; e; e = e->next)
                        puts(e->varstr);
                return EXIT_SUCCESS;
        }

        do {
                if (!strcmp(arg, "--")) {
                        ++argv;
                        goto set_argv;
                }

                if (arg[0] == '+' || arg[0] == '-') {
                        for (n = 1; arg[n]; ++n)
                                if (set_mode(arg[0], arg[n]))
                                        goto error;
                        continue;
                }

                break;
        } while ((arg = *++argv) != NULL);
        /* Now argv[0] is 1st argument */

        /* Only reset global_argv if we didn't process anything */
        if (arg == NULL)
                return EXIT_SUCCESS;
 set_argv:

        /* NB: G.global_argv[0] ($0) is never freed/changed */
        g_argv = G.global_argv;
        if (G.global_args_malloced) {
                pp = g_argv;
                while (*++pp)
                        free(*pp);
                g_argv[1] = NULL;
        } else {
                G.global_args_malloced = 1;
                pp = xzalloc(sizeof(pp[0]) * 2);
                pp[0] = g_argv[0]; /* retain $0 */
                g_argv = pp;
        }
        /* This realloc's G.global_argv */
        G.global_argv = pp = add_strings_to_strings(g_argv, argv, /*dup:*/ 1);

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

        return EXIT_SUCCESS;

        /* Nothing known, so abort */
 error:
        bb_error_msg("set: %s: invalid option", arg);
        return EXIT_FAILURE;
}

static int builtin_shift(char **argv)
{
        int n = 1;
        if (argv[1]) {
                n = atoi(argv[1]);
        }
        if (n >= 0 && n < G.global_argc) {
                if (G.global_args_malloced) {
                        int m = 1;
                        while (m <= n)
                                free(G.global_argv[m++]);
                }
                G.global_argc -= n;
                memmove(&G.global_argv[1], &G.global_argv[n+1],
                                G.global_argc * sizeof(G.global_argv[0]));
                return EXIT_SUCCESS;
        }
        return EXIT_FAILURE;
}

static int builtin_source(char **argv)
{
        FILE *input;

        if (argv[1] == NULL)
                return EXIT_FAILURE;

        /* XXX search through $PATH is missing */
        input = fopen_for_read(argv[1]);
        if (!input) {
                bb_error_msg("can't open '%s'", argv[1]);
                return EXIT_FAILURE;
        }
        close_on_exec_on(fileno(input));

        /* Now run the file */
        /* XXX argv and argc are broken; need to save old G.global_argv
         * (pointer only is OK!) on this stack frame,
         * set G.global_argv=argv+1, recurse, and restore. */
        parse_and_run_file(input);
        fclose(input);
        return G.last_return_code;
}

static int builtin_umask(char **argv)
{
        mode_t new_umask;
        const char *arg = argv[1];
        if (arg) {
                new_umask = bb_strtou(arg, NULL, 8);
                if (errno)
                        return EXIT_FAILURE;
        } else {
                new_umask = umask(0);
                printf("%.3o\n", (unsigned) new_umask);
        }
        umask(new_umask);
        return EXIT_SUCCESS;
}

/* http://www.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#unset */
static int builtin_unset(char **argv)
{
        size_t i;
        int ret;
        bool var = true;

        if (!argv[1])
                return EXIT_SUCCESS;

        i = 0;
        if (argv[1][0] == '-') {
                switch (argv[1][1]) {
                case 'v': break;
                case 'f': if (ENABLE_HUSH_FUNCTIONS) { var = false; break; }
                default:
                        bb_error_msg("unset: %s: invalid option", argv[1]);
                        return EXIT_FAILURE;
                }
                ++i;
        }

        ret = EXIT_SUCCESS;
        while (argv[++i]) {
                if (var) {
                        if (unset_local_var(argv[i]))
                                ret = EXIT_FAILURE;
                }
#if ENABLE_HUSH_FUNCTIONS
                else
                        unset_local_func(argv[i]);
#endif
        }
        return ret;
}

/* http://www.opengroup.org/onlinepubs/9699919799/utilities/wait.html */
static int builtin_wait(char **argv)
{
        int ret = EXIT_SUCCESS;
        int status, sig;

        if (*++argv == NULL) {
                /* Don't care about wait results */
                /* Note 1: must wait until there are no more children */
                /* Note 2: must be interruptible */
                /* Examples:
                 * $ sleep 3 & sleep 6 & wait
                 * [1] 30934 sleep 3
                 * [2] 30935 sleep 6
                 * [1] Done                   sleep 3
                 * [2] Done                   sleep 6
                 * $ sleep 3 & sleep 6 & wait
                 * [1] 30936 sleep 3
                 * [2] 30937 sleep 6
                 * [1] Done                   sleep 3
                 * ^C <-- after ~4 sec from keyboard
                 * $
                 */
                sigaddset(&G.blocked_set, SIGCHLD);
                sigprocmask(SIG_SETMASK, &G.blocked_set, NULL);
                while (1) {
                        checkjobs(NULL);
                        if (errno == ECHILD)
                                break;
                        /* Wait for SIGCHLD or any other signal of interest */
                        /* sigtimedwait with infinite timeout: */
                        sig = sigwaitinfo(&G.blocked_set, NULL);
                        if (sig > 0) {
                                sig = check_and_run_traps(sig);
                                if (sig && sig != SIGCHLD) { /* see note 2 */
                                        ret = 128 + sig;
                                        break;
                                }
                        }
                }
                sigdelset(&G.blocked_set, SIGCHLD);
                sigprocmask(SIG_SETMASK, &G.blocked_set, NULL);
                return ret;
        }

        /* This is probably buggy wrt interruptible-ness */
        while (*argv) {
                pid_t pid = bb_strtou(*argv, NULL, 10);
                if (errno) {
                        /* mimic bash message */
                        bb_error_msg("wait: '%s': not a pid or valid job spec", *argv);
                        return EXIT_FAILURE;
                }
                if (waitpid(pid, &status, 0) == pid) {
                        if (WIFSIGNALED(status))
                                ret = 128 + WTERMSIG(status);
                        else if (WIFEXITED(status))
                                ret = WEXITSTATUS(status);
                        else /* wtf? */
                                ret = EXIT_FAILURE;
                } else {
                        bb_perror_msg("wait %s", *argv);
                        ret = 127;
                }
                argv++;
        }

        return ret;
}

#if ENABLE_HUSH_LOOPS
static int builtin_break(char **argv)
{
        if (G.depth_of_loop == 0) {
                bb_error_msg("%s: only meaningful in a loop", argv[0]);
                return EXIT_SUCCESS; /* bash compat */
        }
        G.flag_break_continue++; /* BC_BREAK = 1 */
        G.depth_break_continue = 1;
        if (argv[1]) {
                G.depth_break_continue = bb_strtou(argv[1], NULL, 10);
                if (errno || !G.depth_break_continue || argv[2]) {
                        bb_error_msg("%s: bad arguments", argv[0]);
                        G.flag_break_continue = BC_BREAK;
                        G.depth_break_continue = UINT_MAX;
                }
        }
        if (G.depth_of_loop < G.depth_break_continue)
                G.depth_break_continue = G.depth_of_loop;
        return EXIT_SUCCESS;
}

static int builtin_continue(char **argv)
{
        G.flag_break_continue = 1; /* BC_CONTINUE = 2 = 1+1 */
        return builtin_break(argv);
}
#endif