hush: small fix for repeated continue and fix for wrong loop depth count

[oweals/busybox.git] / shell / hush.c

/* vi: set sw=4 ts=4: */
/*
 * sh.c -- 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.
 *
 * Bash grammar not implemented: (how many of these were in original sh?)
 *      $_
 *      &> and >& redirection of stdout+stderr
 *      Brace Expansion
 *      Tilde Expansion
 *      fancy forms of Parameter Expansion
 *      aliases
 *      Arithmetic Expansion
 *      <(list) and >(list) Process Substitution
 *      reserved words: case, esac, select, function
 *      Here Documents ( << word )
 *      Functions
 * Major bugs:
 *      job handling woefully incomplete and buggy (improved --vda)
 *      reserved word execution woefully incomplete and buggy
 * 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
 *      check setting of global_argc and global_argv
 *      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?
 *      memory leak finding and plugging - done?
 *      maybe change charmap[] to use 2-bit entries
 *
 * Licensed under the GPL v2 or later, see the file LICENSE in this tarball.
 */

#include "busybox.h" /* for APPLET_IS_NOFORK/NOEXEC */
#include <glob.h>
/* #include <dmalloc.h> */
#if ENABLE_HUSH_CASE
#include <fnmatch.h>
#endif

#define HUSH_VER_STR "0.9"

#if !BB_MMU && ENABLE_HUSH_TICK
//#undef ENABLE_HUSH_TICK
//#define ENABLE_HUSH_TICK 0
#warning On NOMMU, hush command substitution is dangerous.
#warning Dont use it for commands which produce lots of output.
#warning For more info see shell/hush.c, generate_stream_from_list().
#endif

#if !BB_MMU && ENABLE_HUSH_JOB
#undef ENABLE_HUSH_JOB
#define ENABLE_HUSH_JOB 0
#endif

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


/* 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_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_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
/* suppress "warning: no previous prototype..." */
void *xxmalloc(int lineno, size_t size);
void *xxrealloc(int lineno, void *ptr, size_t size);
char *xxstrdup(int lineno, const char *str);
void xxfree(void *ptr);
void *xxmalloc(int lineno, size_t size)
{
        void *ptr = xmalloc((size + 0xff) & ~0xff);
        fprintf(stderr, "line %d: malloc %p\n", lineno, ptr);
        return ptr;
}
void *xxrealloc(int lineno, void *ptr, size_t size)
{
        ptr = xrealloc(ptr, (size + 0xff) & ~0xff);
        fprintf(stderr, "line %d: realloc %p\n", lineno, ptr);
        return ptr;
}
char *xxstrdup(int lineno, const char *str)
{
        char *ptr = xstrdup(str);
        fprintf(stderr, "line %d: strdup %p\n", lineno, ptr);
        return ptr;
}
void xxfree(void *ptr)
{
        fprintf(stderr, "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


/* Keep unconditionally on for now */
#define HUSH_DEBUG 1
/* 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


#define SPECIAL_VAR_SYMBOL       3
#define PARSEFLAG_EXIT_FROM_LOOP 1

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;

/* This holds pointers to the various results of parsing */
struct p_context {
        struct child_prog *child;
        struct pipe *list_head;
        struct pipe *pipe;
        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
        int old_flag; /* bitmask of FLAG_xxx, for figuring out valid reserved words */
        struct p_context *stack;
#endif
};

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 child_prog {
        pid_t pid;                  /* 0 if exited */
        smallint is_stopped;        /* is the program currently running? */
        smallint subshell;          /* flag, non-zero if group must be forked */
        char **argv;                /* program name and arguments */
        struct pipe *group;         /* if non-NULL, first in group or subshell */
        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.
 */

struct pipe {
        struct pipe *next;
        int num_progs;              /* total number of programs in job */
        int alive_progs;            /* number of programs running (not exited) */
        int stopped_progs;          /* number of programs 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 child_prog *progs;   /* 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... */
};

/* 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;
        /* Misnomer! it's not "quoting", it's "protection against globbing"!
         * (by prepending \ to *, ?, [ and to \ too) */
        smallint o_quote;
        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,
};
/* 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 {
        CHAR_ORDINARY           = 0,
        CHAR_ORDINARY_IF_QUOTED = 1, /* example: *, # */
        CHAR_IFS                = 2, /* treated as ordinary if quoted */
        CHAR_SPECIAL            = 3, /* example: $ */
};

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;
#endif
#if ENABLE_FEATURE_EDITING
        line_input_t *line_input_state;
#endif
        pid_t root_pid;
#if ENABLE_HUSH_JOB
        int run_list_level;
        pid_t saved_task_pgrp;
        pid_t saved_tty_pgrp;
        int last_jobid;
        struct pipe *job_list;
        struct pipe *toplevel_list;
        smallint ctrl_z_flag;
#endif
#if ENABLE_HUSH_LOOPS
        smallint flag_break_continue;
#endif
        smallint fake_mode;
        /* these three support $?, $#, and $1 */
        smalluint last_return_code;
        char **global_argv;
        int global_argc;
#if ENABLE_HUSH_LOOPS
        unsigned depth_break_continue;
        unsigned depth_of_loop;
#endif
        pid_t last_bg_pid;
        const char *ifs;
        const char *cwd;
        struct variable *top_var; /* = &shell_ver (set in main()) */
        struct variable shell_ver;
#if ENABLE_FEATURE_SH_STANDALONE
        struct nofork_save_area nofork_save;
#endif
#if ENABLE_HUSH_JOB
        sigjmp_buf toplevel_jb;
#endif
        unsigned char charmap[256];
        char user_input_buf[ENABLE_FEATURE_EDITING ? BUFSIZ : 2];
};

#define G (*ptr_to_globals)

#if !ENABLE_HUSH_INTERACTIVE
enum { interactive_fd = 0 };
#endif
#if !ENABLE_HUSH_JOB
enum { run_list_level = 0 };
#endif

#if ENABLE_HUSH_INTERACTIVE
#define interactive_fd   (G.interactive_fd  )
#define PS1              (G.PS1             )
#define PS2              (G.PS2             )
#endif
#if ENABLE_FEATURE_EDITING
#define line_input_state (G.line_input_state)
#endif
#define root_pid         (G.root_pid        )
#if ENABLE_HUSH_JOB
#define run_list_level   (G.run_list_level  )
#define saved_task_pgrp  (G.saved_task_pgrp )
#define saved_tty_pgrp   (G.saved_tty_pgrp  )
#define last_jobid       (G.last_jobid      )
#define job_list         (G.job_list        )
#define toplevel_list    (G.toplevel_list   )
#define toplevel_jb      (G.toplevel_jb     )
#define ctrl_z_flag      (G.ctrl_z_flag     )
#endif /* JOB */
#define global_argv      (G.global_argv     )
#define global_argc      (G.global_argc     )
#define last_return_code (G.last_return_code)
#define ifs              (G.ifs             )
#define flag_break_continue  (G.flag_break_continue )
#define depth_break_continue (G.depth_break_continue)
#define depth_of_loop    (G.depth_of_loop   )
#define fake_mode        (G.fake_mode       )
#define cwd              (G.cwd             )
#define last_bg_pid      (G.last_bg_pid     )
#define top_var          (G.top_var         )
#define shell_ver        (G.shell_ver       )
#if ENABLE_FEATURE_SH_STANDALONE
#define nofork_save      (G.nofork_save     )
#endif
#if ENABLE_HUSH_JOB
#define toplevel_jb      (G.toplevel_jb     )
#endif
#define charmap          (G.charmap         )
#define user_input_buf   (G.user_input_buf  )
#define INIT_G() do { \
        SET_PTR_TO_GLOBALS(xzalloc(sizeof(G))); \
} while (0)


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

#if 1
/* Normal */
static void syntax(const char *msg)
{
        /* Was using fancy stuff:
         * (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, ...);

        fp = (interactive_fd ? bb_error_msg : bb_error_msg_and_die);
        fp(msg ? "%s: %s" : "syntax error", "syntax error", msg);
}

#else
/* Debug */
static void syntax_lineno(int line)
{
        void FAST_FUNC (*fp)(const char *s, ...);

        fp = (interactive_fd ? bb_error_msg : bb_error_msg_and_die);
        fp("syntax error hush.c:%d", line);
}
#define syntax(str) syntax_lineno(__LINE__)
#endif

/* Index of subroutines: */
/*  in_str manipulations: */
static int static_get(struct in_str *i);
static int static_peek(struct in_str *i);
static int file_get(struct in_str *i);
static int file_peek(struct in_str *i);
static void setup_file_in_str(struct in_str *i, FILE *f);
static void setup_string_in_str(struct in_str *i, const char *s);
/*  "run" the final data structures: */
#if !defined(DEBUG_CLEAN)
#define free_pipe_list(head, indent) free_pipe_list(head)
#define free_pipe(pi, indent)        free_pipe(pi)
#endif
static int free_pipe_list(struct pipe *head, int indent);
static int free_pipe(struct pipe *pi, int indent);
/*  really run the final data structures: */
static int setup_redirects(struct child_prog *prog, int squirrel[]);
static int run_list(struct pipe *pi);
#if BB_MMU
#define pseudo_exec_argv(ptrs2free, argv, argv_expanded) pseudo_exec_argv(argv, argv_expanded)
#define      pseudo_exec(ptrs2free, child, argv_expanded)     pseudo_exec(child, argv_expanded)
#endif
static void pseudo_exec_argv(char **ptrs2free, char **argv, char **argv_expanded) NORETURN;
static void pseudo_exec(char **ptrs2free, struct child_prog *child, char **argv_expanded) NORETURN;
static int run_pipe(struct pipe *pi);
/*   data structure manipulation: */
static int setup_redirect(struct p_context *ctx, int fd, redir_type style, struct in_str *input);
static void initialize_context(struct p_context *ctx);
static int done_word(o_string *dest, struct p_context *ctx);
static int done_command(struct p_context *ctx);
static void done_pipe(struct p_context *ctx, pipe_style type);
/*   primary string parsing: */
static int redirect_dup_num(struct in_str *input);
static int redirect_opt_num(o_string *o);
#if ENABLE_HUSH_TICK
static int process_command_subs(o_string *dest,
                struct in_str *input, const char *subst_end);
#endif
static int parse_group(o_string *dest, struct p_context *ctx, struct in_str *input, int ch);
static const char *lookup_param(const char *src);
static int handle_dollar(o_string *dest,
                struct in_str *input);
static int parse_stream(o_string *dest, struct p_context *ctx, struct in_str *input0, const char *end_trigger);
/*   setup: */
static int parse_and_run_stream(struct in_str *inp, int parse_flag);
static int parse_and_run_string(const char *s, int parse_flag);
static int parse_and_run_file(FILE *f);
/*   job management: */
static int checkjobs(struct pipe* fg_pipe);
#if ENABLE_HUSH_JOB
static int checkjobs_and_fg_shell(struct pipe* fg_pipe);
static void insert_bg_job(struct pipe *pi);
static void remove_bg_job(struct pipe *pi);
static void delete_finished_bg_job(struct pipe *pi);
#else
int checkjobs_and_fg_shell(struct pipe* fg_pipe); /* never called */
#endif
/*     local variable support */
static char **expand_strvec_to_strvec(char **argv);
/* used for eval */
static char *expand_strvec_to_string(char **argv);
/* used for expansion of right hand of assignments */
static char *expand_string_to_string(const char *str);
static struct variable *get_local_var(const char *name);
static int set_local_var(char *str, int flg_export);
static void unset_local_var(const char *name);


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))
                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_malloced_strings_to_strings(char **strings, char **add)
{
        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] = add[i];
        return v;
}

static char **add_malloced_string_to_strings(char **strings, char *add)
{
        char *v[2];

        v[0] = add;
        v[1] = NULL;

        return add_malloced_strings_to_strings(strings, v);
}

static void free_strings(char **strings)
{
        if (strings) {
                char **v = strings;
                while (*v)
                        free(*v++);
                free(strings);
        }
}

#if !BB_MMU
#define EXTRA_PTRS 5 /* 1 for NULL, 1 for args, 3 for paranoid reasons */
static char **alloc_ptrs(char **argv)
{
        char **v = argv;
        while (*v)
                v++;
        return xzalloc((v - argv + EXTRA_PTRS) * sizeof(v[0]));
}
#endif


/* 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_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);
#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"),
        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("trap"  , builtin_not_written, "Trap signals"),
        BLTIN("test"  , builtin_test, "Test condition"),
//      BLTIN("ulimit", builtin_not_written, "Control resource limits"),
        BLTIN("umask" , builtin_umask, "Set file creation mask"),
        BLTIN("unset" , builtin_unset, "Unset environment variable"),
#if ENABLE_HUSH_HELP
        BLTIN("help"  , builtin_help, "List shell built-in commands"),
#endif
};


/* Signals are grouped, we handle them in batches */
static void set_misc_sighandler(void (*handler)(int))
{
        bb_signals(0
                + (1 << SIGINT)
                + (1 << SIGQUIT)
                + (1 << SIGTERM)
                , handler);
}

#if ENABLE_HUSH_JOB

static void set_fatal_sighandler(void (*handler)(int))
{
        bb_signals(0
                + (1 << SIGILL)
                + (1 << SIGTRAP)
                + (1 << SIGABRT)
                + (1 << SIGFPE)
                + (1 << SIGBUS)
                + (1 << SIGSEGV)
        /* bash 3.2 seems to handle these just like 'fatal' ones */
                + (1 << SIGHUP)
                + (1 << SIGPIPE)
                + (1 << SIGALRM)
                , handler);
}
static void set_jobctrl_sighandler(void (*handler)(int))
{
        bb_signals(0
                + (1 << SIGTSTP)
                + (1 << SIGTTIN)
                + (1 << SIGTTOU)
                , handler);
}
/* SIGCHLD is special and handled separately */

static void set_every_sighandler(void (*handler)(int))
{
        set_fatal_sighandler(handler);
        set_jobctrl_sighandler(handler);
        set_misc_sighandler(handler);
        signal(SIGCHLD, handler);
}

static void handler_ctrl_c(int sig UNUSED_PARAM)
{
        debug_printf_jobs("got sig %d\n", sig);
// as usual we can have all kinds of nasty problems with leaked malloc data here
        siglongjmp(toplevel_jb, 1);
}

static void handler_ctrl_z(int sig UNUSED_PARAM)
{
        pid_t pid;

        debug_printf_jobs("got tty sig %d in pid %d\n", sig, getpid());
        pid = fork();
        if (pid < 0) /* can't fork. Pretend there was no ctrl-Z */
                return;
        ctrl_z_flag = 1;
        if (!pid) { /* child */
                if (ENABLE_HUSH_JOB)
                        die_sleep = 0; /* let nofork's xfuncs die */
                setpgrp();
                debug_printf_jobs("set pgrp for child %d ok\n", getpid());
                set_every_sighandler(SIG_DFL);
                raise(SIGTSTP); /* resend TSTP so that child will be stopped */
                debug_printf_jobs("returning in child\n");
                /* return to nofork, it will eventually exit now,
                 * not return back to shell */
                return;
        }
        /* parent */
        /* finish filling up pipe info */
        toplevel_list->pgrp = pid; /* child is in its own pgrp */
        toplevel_list->progs[0].pid = pid;
        /* parent needs to longjmp out of running nofork.
         * we will "return" exitcode 0, with child put in background */
// as usual we can have all kinds of nasty problems with leaked malloc data here
        debug_printf_jobs("siglongjmp in parent\n");
        siglongjmp(toplevel_jb, 1);
}

/* 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);

        if (interactive_fd)
                tcsetpgrp(interactive_fd, saved_tty_pgrp);

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

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

/* Restores tty foreground process group, and exits. */
static void hush_exit(int exitcode) NORETURN;
static void hush_exit(int exitcode)
{
        fflush(NULL); /* flush all streams */
        sigexit(- (exitcode & 0xff));
}

#else /* !JOB */

#define set_fatal_sighandler(handler)   ((void)0)
#define set_jobctrl_sighandler(handler) ((void)0)
#define hush_exit(e)                    exit(e)

#endif /* JOB */


static const char *set_cwd(void)
{
        if (cwd == bb_msg_unknown)
                cwd = NULL;     /* xrealloc_getcwd_or_warn(arg) calls free(arg)! */
        cwd = xrealloc_getcwd_or_warn((char *)cwd);
        if (!cwd)
                cwd = bb_msg_unknown;
        return cwd;
}


/*
 * 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_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;
        if (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_addQchr(o_string *o, int ch)
{
        int sz = 1;
        if (o->o_quote && 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_quote) {
                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:%d\n", (p + strlen(p) + 1) - o->data);
        }
}
#else
#define debug_print_list(prefix, o, n) ((void)0)
#endif

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

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

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

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

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

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

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


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

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

#if ENABLE_HUSH_INTERACTIVE

#if ENABLE_FEATURE_EDITING
static void cmdedit_set_initial_prompt(void)
{
#if !ENABLE_FEATURE_EDITING_FANCY_PROMPT
        PS1 = NULL;
#else
        PS1 = getenv("PS1");
        if (PS1 == NULL)
                PS1 = "\\w \\$ ";
#endif
}
#endif /* EDITING */

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*)PS1);
                PS1 = xasprintf("%s %c ", cwd, (geteuid() != 0) ? '$' : '#');
                prompt_str = PS1;
        } else {
                prompt_str = PS2;
        }
#else
        prompt_str = (promptmode == 0) ? PS1 : PS2;
#endif
        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 {
                r = read_line_input(prompt_str, user_input_buf, BUFSIZ-1, line_input_state);
        } while (r == 0); /* repeat if Ctrl-C */
        i->eof_flag = (r < 0);
        if (i->eof_flag) { /* EOF/error detected */
                user_input_buf[0] = EOF; /* yes, it will be truncated, it's ok */
                user_input_buf[1] = '\0';
        }
#else
        fputs(prompt_str, stdout);
        fflush(stdout);
        user_input_buf[0] = r = fgetc(i->file);
        /*user_input_buf[1] = '\0'; - already is and never changed */
        i->eof_flag = (r == EOF);
#endif
        i->p = 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 (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;
}


/* squirrel != NULL means we squirrel away copies of stdin, stdout,
 * and stderr if they are redirected. */
static int setup_redirects(struct child_prog *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);
                }
        }
}


/* 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(char **ptrs2free, char **argv, char **argv_expanded)
{
        int i, rcode;
        char *p;
        const struct built_in_command *x;

        for (i = 0; is_assignment(argv[i]); i++) {
                debug_printf_exec("pid %d environment modification: %s\n",
                                getpid(), argv[i]);
                p = expand_string_to_string(argv[i]);
#if !BB_MMU
                *ptrs2free++ = p;
#endif
                putenv(p);
        }
        argv += i;
        /* If a variable is assigned in a forest, and nobody listens,
         * was it ever really set?
         */
        if (!argv[0])
                _exit(EXIT_SUCCESS);

        if (argv_expanded) {
                argv = argv_expanded;
        } else {
                argv = expand_strvec_to_strvec(argv);
#if !BB_MMU
                *ptrs2free++ = (char*) 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

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

/* Called after [v]fork() in run_pipe()
 */
static void pseudo_exec(char **ptrs2free, struct child_prog *child, char **argv_expanded)
{
        if (child->argv)
                pseudo_exec_argv(ptrs2free, child->argv, argv_expanded);

        if (child->group) {
#if !BB_MMU
                bb_error_msg_and_die("nested lists are not supported on NOMMU");
#else
                int rcode;
                debug_printf_exec("pseudo_exec: run_list\n");
                rcode = run_list(child->group);
                /* OK to leak memory by not calling free_pipe_list,
                 * since this process is about to exit */
                _exit(rcode);
#endif
        }

        /* Can happen.  See what bash does with ">foo" by itself. */
        debug_printf("trying to pseudo_exec 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->progs[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->progs[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 = 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 (!job_list) {
                thejob = job_list = xmalloc(sizeof(*thejob));
        } else {
                for (thejob = 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->progs = xzalloc(sizeof(pi->progs[0]) * pi->num_progs);
        /* We cannot copy entire pi->progs[] vector! Double free()s will happen */
        for (i = 0; i < pi->num_progs; i++) {
// TODO: do we really need to have so many fields which are just dead weight
// at execution stage?
                thejob->progs[i].pid = pi->progs[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 */
        printf("[%d] %d %s\n", thejob->jobid, thejob->progs[0].pid, thejob->cmdtext);
        last_bg_pid = thejob->progs[0].pid;
        last_jobid = thejob->jobid;
}

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

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

/* Remove a backgrounded job */
static void delete_finished_bg_job(struct pipe *pi)
{
        remove_bg_job(pi);
        pi->stopped_progs = 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;

        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:
// TODO: safe_waitpid?
        while ((childpid = waitpid(-1, &status, attributes)) > 0) {
                int i;
                const int 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_progs; i++) {
                                debug_printf_jobs("check pid %d\n", fg_pipe->progs[i].pid);
                                if (fg_pipe->progs[i].pid != childpid)
                                        continue;
                                /* printf("process %d exit %d\n", i, WEXITSTATUS(status)); */
                                if (dead) {
                                        fg_pipe->progs[i].pid = 0;
                                        fg_pipe->alive_progs--;
                                        if (i == fg_pipe->num_progs - 1) {
                                                /* last process gives overall exitstatus */
                                                rcode = WEXITSTATUS(status);
                                                IF_HAS_KEYWORDS(if (fg_pipe->pi_inverted) rcode = !rcode;)
                                        }
                                } else {
                                        fg_pipe->progs[i].is_stopped = 1;
                                        fg_pipe->stopped_progs++;
                                }
                                debug_printf_jobs("fg_pipe: alive_progs %d stopped_progs %d\n",
                                                fg_pipe->alive_progs, fg_pipe->stopped_progs);
                                if (fg_pipe->alive_progs - fg_pipe->stopped_progs <= 0) {
                                        /* All processes in fg pipe have exited/stopped */
#if ENABLE_HUSH_JOB
                                        if (fg_pipe->alive_progs)
                                                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 = job_list; pi; pi = pi->next) {
                        for (i = 0; i < pi->num_progs; i++) {
                                if (pi->progs[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->progs[i].pid = 0;
                        pi->alive_progs--;
                        if (!pi->alive_progs) {
                                printf(JOB_STATUS_FORMAT, pi->jobid,
                                                "Done", pi->cmdtext);
                                delete_finished_bg_job(pi);
                        }
                } else {
                        /* child stopped */
                        pi->progs[i].is_stopped = 1;
                        pi->stopped_progs++;
                }
#endif
        } /* while (waitpid succeeds)... */

        /* wait found no children or failed */

        if (childpid && errno != ECHILD)
                bb_perror_msg("waitpid");
        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(interactive_fd, p);
//      if (tcsetpgrp(interactive_fd, p) && errno != ENOTTY)
//              bb_perror_msg("tcsetpgrp-4a");
        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.
 *
 * The input of the pipe is always stdin, the output is always
 * stdout.  The outpipe[] mechanism in BusyBox-0.48 lash is bogus,
 * because it tries to avoid running the command substitution in
 * subshell, when that is in fact necessary.  The subshell process
 * now has its stdout directed to the input of the appropriate pipe,
 * so this routine is noticeably simpler.
 *
 * Returns -1 only if started some children. IOW: we have to
 * mask out retvals of builtins etc with 0xff!
 */
static int run_pipe(struct pipe *pi)
{
        int i;
        int nextin;
        int pipefds[2];         /* pipefds[0] is for reading */
        struct child_prog *child;
        char **argv_expanded = NULL;
        char **argv;
        const struct built_in_command *x;
        char *p;
        /* it is not always needed, but we aim to smaller code */
        int squirrel[] = { -1, -1, -1 };
        int rcode;
        const int single_and_fg = (pi->num_progs == 1 && pi->followup != PIPE_BG);

        debug_printf_exec("run_pipe start: single_and_fg=%d\n", single_and_fg);

#if ENABLE_HUSH_JOB
        pi->pgrp = -1;
#endif
        pi->alive_progs = 1;
        pi->stopped_progs = 0;

        /* Check if this is a simple builtin (not part of a pipe).
         * Builtins within pipes have to fork anyway, and are handled in
         * pseudo_exec.  "echo foo | read bar" doesn't work on bash, either.
         */
        child = &(pi->progs[0]);
        if (single_and_fg && child->group && child->subshell == 0) {
                debug_printf("non-subshell grouping\n");
                setup_redirects(child, squirrel);
                debug_printf_exec(": run_list\n");
                rcode = run_list(child->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 = child->argv;

        if (single_and_fg && argv != NULL) {
                for (i = 0; is_assignment(argv[i]); i++)
                        continue;
                if (i != 0 && argv[i] == NULL) {
                        /* assignments, but no command: set local environment */
                        for (i = 0; argv[i] != NULL; i++) {
                                debug_printf("local environment set: %s\n", argv[i]);
                                p = expand_string_to_string(argv[i]);
                                set_local_var(p, 0);
                        }
                        return EXIT_SUCCESS; /* don't worry about errors in set_local_var() yet */
                }

                /* Expand assignments into one string each */
                for (i = 0; is_assignment(argv[i]); i++) {
                        p = expand_string_to_string(argv[i]);
                        putenv(p);
//FIXME: do we leak p?!
                }

                /* Expand the rest into (possibly) many strings each */
                argv_expanded = expand_strvec_to_strvec(argv + i);

                for (x = bltins; x != &bltins[ARRAY_SIZE(bltins)]; x++) {
                        if (strcmp(argv_expanded[0], x->cmd) == 0) {
                                if (x->function == builtin_exec && argv_expanded[1] == NULL) {
                                        debug_printf("magic exec\n");
                                        setup_redirects(child, NULL);
                                        return EXIT_SUCCESS;
                                }
                                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(child, squirrel);
                                debug_printf_exec(": builtin '%s' '%s'...\n", x->cmd, argv_expanded[1]);
                                rcode = x->function(argv_expanded) & 0xff;
                                free(argv_expanded);
                                restore_redirects(squirrel);
                                debug_printf_exec("run_pipe return %d\n", rcode);
                                IF_HAS_KEYWORDS(if (pi->pi_inverted) rcode = !rcode;)
                                return rcode;
                        }
                }
#if ENABLE_FEATURE_SH_STANDALONE
                {
                        int a = find_applet_by_name(argv_expanded[0]);
                        if (a >= 0 && APPLET_IS_NOFORK(a)) {
                                setup_redirects(child, squirrel);
                                save_nofork_data(&nofork_save);
                                debug_printf_exec(": run_nofork_applet '%s' '%s'...\n", argv_expanded[0], argv_expanded[1]);
                                rcode = run_nofork_applet_prime(&nofork_save, a, argv_expanded);
                                free(argv_expanded);
                                restore_redirects(squirrel);
                                debug_printf_exec("run_pipe return %d\n", rcode);
                                IF_HAS_KEYWORDS(if (pi->pi_inverted) rcode = !rcode;)
                                return rcode;
                        }
                }
#endif
        }

        /* 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 */

        /* Disable job control signals for shell (parent) and
         * for initial child code after fork */
        set_jobctrl_sighandler(SIG_IGN);

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

        for (i = 0; i < pi->num_progs; i++) {
#if !BB_MMU
                char **ptrs2free = NULL;
#endif
                child = &(pi->progs[i]);
                if (child->argv) {
                        debug_printf_exec(": pipe member '%s' '%s'...\n", child->argv[0], child->argv[1]);
#if !BB_MMU
                        ptrs2free = alloc_ptrs(child->argv);
#endif
                } 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_progs)
                        xpipe(pipefds);

                child->pid = BB_MMU ? fork() : vfork();
                if (!child->pid) { /* child */
                        if (ENABLE_HUSH_JOB)
                                die_sleep = 0; /* let nofork's xfuncs die */
#if ENABLE_HUSH_JOB
                        /* Every child adds itself to new process group
                         * with pgid == pid_of_first_child_in_pipe */
                        if (run_list_level == 1 && interactive_fd) {
                                pid_t pgrp;
                                /* Don't do pgrp restore anymore on fatal signals */
                                set_fatal_sighandler(SIG_DFL);
                                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(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(child, NULL);

                        /* Restore default handlers just prior to exec */
                        set_jobctrl_sighandler(SIG_DFL);
                        set_misc_sighandler(SIG_DFL);
                        signal(SIGCHLD, SIG_DFL);
                        pseudo_exec(ptrs2free, child, argv_expanded); /* does not return */
                }
                free(argv_expanded);
                argv_expanded = NULL;
#if !BB_MMU
                free_strings(ptrs2free);
#endif
                if (child->pid < 0) { /* [v]fork failed */
                        /* Clearly indicate, was it fork or vfork */
                        bb_perror_msg(BB_MMU ? "fork" : "vfork");
                } else {
                        pi->alive_progs++;
#if ENABLE_HUSH_JOB
                        /* Second and next children need to know pid of first one */
                        if (pi->pgrp < 0)
                                pi->pgrp = child->pid;
#endif
                }

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

        if (!pi->alive_progs) {
                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_progs);
        return -1;
}

#ifndef debug_print_tree
static void debug_print_tree(struct pipe *pi, int lvl)
{
        static const char *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" ,
        };

        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_progs) {
                        struct child_prog *child = &pi->progs[prn];
                        char **argv = child->argv;

                        fprintf(stderr, "%*s prog %d", lvl*2, "", prn);
                        if (child->group) {
                                fprintf(stderr, " group %s: (argv=%p)\n",
                                                (child->subshell ? "()" : "{}"),
                                                argv);
                                debug_print_tree(child->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", 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", 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", 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. */

#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 (++run_list_level == 1 && interactive_fd) {
                if (sigsetjmp(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) */
                        run_list_level = 1;
#if ENABLE_FEATURE_SH_STANDALONE
                        if (nofork_save.saved) { /* if save area is valid */
                                debug_printf_jobs("exiting nofork early\n");
                                restore_nofork_data(&nofork_save);
                        }
#endif
                        if (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');
                        }
                        loop_top = NULL;
                        depth_of_loop = 0;
                        rcode = 0;
                        goto ret;
                }
                /* ctrl-Z handler will store pid etc in pi */
                toplevel_list = pi;
                ctrl_z_flag = 0;
#if ENABLE_FEATURE_SH_STANDALONE
                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_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 depth_of_loop twice */
                ) {
                        /* start of a loop: remember where loop starts */
                        loop_top = pi;
                        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_progs - 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->progs->argv)
                                                break;
                                        vals = pi->next->progs->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->progs->argv[0];
                                pi->progs->argv[0] = NULL;
                        }
                        free(pi->progs->argv[0]);
                        if (!*for_lcur) {
                                /* "for" loop is over, clean up */
                                free(for_list);
                                for_list = NULL;
                                for_lcur = NULL;
                                pi->progs->argv[0] = for_varname;
                                break;
                        }
                        /* insert next value from for_lcur */
//TODO: does it need escaping?
                        pi->progs->argv[0] = xasprintf("%s=%s", for_varname, *for_lcur++);
                }
                if (rword == RES_IN) /* "for v IN list;..." - "in" has no cmds anyway */
                        continue;
                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->progs->argv);
                        continue;
                }
                if (rword == RES_MATCH) {
                        char *pattern;
                        if (!case_word) /* "case ... matched_word) ... WORD)": we executed selected branch, stop */
                                break;
                        /* all prev words didn't match, does this one match? */
                        pattern = expand_strvec_to_string(pi->progs->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;
                        }
                        continue;
                }
                if (rword == RES_CASEI) { /* inside of a case branch */
                        if (cond_code != 0)
                                continue; /* not matched yet, skip this pipe */
                }
#endif
                if (pi->num_progs == 0)
                        continue;

                /* After analyzing all keywords and conditions, we decided
                 * to execute this pipe. NB: has 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_progs);
                {
                        int r;
#if ENABLE_HUSH_LOOPS
                        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. */
#if ENABLE_HUSH_LOOPS
                                /* was it "break" or "continue"? */
                                if (flag_break_continue) {
                                        smallint fbc = flag_break_continue;
                                        /* we might fall into outer *loop*,
                                         * don't want to break it too */
                                        if (loop_top) {
                                                depth_break_continue--;
                                                if (depth_break_continue == 0)
                                                        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 (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 */
#if ENABLE_HUSH_JOB
                                if (run_list_level == 1)
                                        insert_bg_job(pi);
#endif
                                rcode = 0; /* EXIT_SUCCESS */
                        } else {
#if ENABLE_HUSH_JOB
                                if (run_list_level == 1 && interactive_fd) {
                                        /* waits for completion, then fg's main shell */
                                        rcode = checkjobs_and_fg_shell(pi);
                                        debug_printf_exec(": checkjobs_and_fg_shell returned %d\n", rcode);
                                } else
#endif
                                { /* this one just waits for completion */
                                        rcode = checkjobs(pi);
                                        debug_printf_exec(": checkjobs returned %d\n", rcode);
                                }
                        }
                }
                debug_printf_exec(": setting last_return_code=%d\n", rcode);
                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;
                }
                checkjobs(NULL);
        } /* for (pi) */

#if ENABLE_HUSH_JOB
        if (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:
        if (!--run_list_level && interactive_fd) {
                signal(SIGTSTP, SIG_IGN);
                signal(SIGINT, SIG_IGN);
        }
#endif
        debug_printf_exec("run_list lvl %d return %d\n", run_list_level + 1, rcode);
#if ENABLE_HUSH_LOOPS
        if (loop_top)
                depth_of_loop--;
        free(for_list);
#endif
#if ENABLE_HUSH_CASE
        free(case_word);
#endif
        return rcode;
}

/* return code is the exit status of the pipe */
static int free_pipe(struct pipe *pi, int indent)
{
        char **p;
        struct child_prog *child;
        struct redir_struct *r, *rnext;
        int a, i, ret_code = 0;

        if (pi->stopped_progs > 0)
                return ret_code;
        debug_printf_clean("%s run pipe: (pid %d)\n", indenter(indent), getpid());
        for (i = 0; i < pi->num_progs; i++) {
                child = &pi->progs[i];
                debug_printf_clean("%s  command %d:\n", indenter(indent), i);
                if (child->argv) {
                        for (a = 0, p = child->argv; *p; a++, p++) {
                                debug_printf_clean("%s   argv[%d] = %s\n", indenter(indent), a, *p);
                        }
                        free_strings(child->argv);
                        child->argv = NULL;
                } else if (child->group) {
                        debug_printf_clean("%s   begin group (subshell:%d)\n", indenter(indent), child->subshell);
                        ret_code = free_pipe_list(child->group, indent+3);
                        debug_printf_clean("%s   end group\n", indenter(indent));
                } else {
                        debug_printf_clean("%s   (nil)\n", indenter(indent));
                }
                for (r = child->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);
                }
                child->redirects = NULL;
        }
        free(pi->progs);   /* children are an array, they get freed all at once */
        pi->progs = NULL;
#if ENABLE_HUSH_JOB
        free(pi->cmdtext);
        pi->cmdtext = NULL;
#endif
        return ret_code;
}

static int free_pipe_list(struct pipe *head, int indent)
{
        int rcode = 0;   /* if list has no members */
        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
                rcode = 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);
        }
        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 (!fake_mode) {
                debug_printf_exec(": run_list with %d members\n", pi->num_progs);
                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;
}


/* 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, ifs);
                if (word_len) {
                        if (output->o_quote || !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, 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! */
/* NB: another bug is that we cannot detect empty strings yet:
 * "" or $empty"" expands to zero words, has to expand to empty word */
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

                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(root_pid);
                        break;
                case '!': /* bg pid */
                        val = last_bg_pid ? utoa(last_bg_pid) : (char*)"";
                        break;
                case '?': /* exitcode */
                        val = utoa(last_return_code);
                        break;
                case '#': /* argc */
                        val = utoa(global_argc ? global_argc-1 : 0);
                        break;
                case '*':
                case '@':
                        i = 1;
                        if (!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 $@ */
                                smallint sv = output->o_quote;
                                /* unquoted var's contents should be globbed, so don't quote */
                                output->o_quote = 0;
                                while (global_argv[i]) {
                                        n = expand_on_ifs(output, n, global_argv[i]);
                                        debug_printf_expand("expand_vars_to_list: argv %d (last %d)\n", i, global_argc-1);
                                        if (global_argv[i++][0] && global_argv[i]) {
                                                /* this argv[] is not empty and not last:
                                                 * put terminating NUL, start new word */
                                                o_addchr(output, '\0');
                                                debug_print_list("expand_vars_to_list[2]", output, n);
                                                n = o_save_ptr(output, n);
                                                debug_print_list("expand_vars_to_list[3]", output, n);
                                        }
                                }
                                output->o_quote = sv;
                        } else
                        /* If or_mask is nonzero, we handle assignment 'a=....$@.....'
                         * and in this case should treat it like '$*' - see 'else...' below */
                        if (first_ch == ('@'|0x80) && !or_mask) { /* quoted $@ */
                                while (1) {
                                        o_addQstr(output, global_argv[i], strlen(global_argv[i]));
                                        if (++i >= 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, global_argv[i], strlen(global_argv[i]));
                                        if (!global_argv[++i])
                                                break;
                                        if (ifs[0])
                                                o_addchr(output, 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> */
                        struct in_str input;
                        *p = '\0';
                        arg++;
//TODO: can we just stuff it into "output" directly?
                        debug_printf_subst("SUBST '%s' first_ch %x\n", arg, first_ch);
                        setup_string_in_str(&input, arg);
                        process_command_subs(&subst_result, &input, NULL);
                        debug_printf_subst("SUBST RES '%s'\n", subst_result.data);
                        val = subst_result.data;
                        goto store_val;
                }
#endif
                default: /* <SPECIAL_VAR_SYMBOL>varname<SPECIAL_VAR_SYMBOL> */
                        *p = '\0';
                        arg[0] = first_ch & 0x7f;
                        if (isdigit(arg[0])) {
                                i = xatoi_u(arg);
                                if (i < global_argc)
                                        val = global_argv[i];
                                /* else val remains NULL: $N with too big N */
                        } else
                                val = lookup_param(arg);
                        arg[0] = first_ch;
#if ENABLE_HUSH_TICK
 store_val:
#endif
                        *p = SPECIAL_VAR_SYMBOL;
                        if (!(first_ch & 0x80)) { /* unquoted $VAR */
                                debug_printf_expand("unquoted '%s', output->o_quote:%d\n", val, output->o_quote);
                                if (val) {
                                        /* unquoted var's contents should be globbed, so don't quote */
                                        smallint sv = output->o_quote;
                                        output->o_quote = 0;
                                        n = expand_on_ifs(output, n, val);
                                        val = NULL;
                                        output->o_quote = sv;
                                }
                        } else { /* quoted $VAR, val will be appended below */
                                debug_printf_expand("quoted '%s', output->o_quote:%d\n", val, output->o_quote);
                        }
                }
                if (val) {
                        o_addQstr(output, val, strlen(val));
                }

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

        if (arg[0]) {
                debug_print_list("expand_vars_to_list[a]", output, n);
                /* this part is literal, and it was already pre-quoted
                 * if needed (much earlier), do not use o_addQstr here! */
                o_addstr(output, arg, strlen(arg) + 1);
                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_quote = 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 */
        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 ifs[0]? */
                        n++;
                }
        }
        strcpy((char*)list, list[0]);
        debug_printf_expand("strvec_to_string='%s'\n", (char*)list);
        return (char*)list;
}


/* Used to 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 = top_var; cur; cur = cur->next) {
                if (strncmp(cur->varstr, name, len) == 0 && cur->varstr[len] == '=')
                        return cur;
        }
        return NULL;
}

/* str holds "NAME=VAL" and is expected to be malloced.
 * We take ownership of it. */
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 = 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;
                }
                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)
                cur->flg_export = 1;
        if (cur->flg_export)
                return putenv(cur->varstr);
        return 0;
}

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

        if (!name)
                return;
        name_len = strlen(name);
        cur = 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;
                        }
                /* 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;
                        unsetenv(cur->varstr);
                        if (!cur->max_len)
                                free(cur->varstr);
                        free(cur);
                        return;
                }
                prev = cur;
                cur = cur->next;
        }
}

/* 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 p_context *ctx, int fd, redir_type style,
        struct in_str *input)
{
        struct child_prog *child = ctx->child;
        struct redir_struct *redir = child->redirects;
        struct redir_struct *last_redir = NULL;

        /* Create a new redir_struct and drop it onto the end of the linked list */
        while (redir) {
                last_redir = redir;
                redir = redir->next;
        }
        redir = xzalloc(sizeof(struct redir_struct));
        /* redir->next = NULL; */
        /* redir->rd_filename = NULL; */
        if (last_redir) {
                last_redir->next = redir;
        } else {
                child->redirects = redir;
        }

        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);

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

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

/* If a reserved word is found and processed, parse context is modified
 * and 1 is returned.
 * Handles if, then, elif, else, fi, for, while, until, do, done.
 * case, function, and select are obnoxious, save those for later.
 */
#if HAS_KEYWORDS
static int reserved_word(const o_string *word, struct p_context *ctx)
{
        struct reserved_combo {
                char literal[7];
                unsigned char res;
                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 ),
        };
        /* 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,  0 },
                { "if",    RES_IF,    FLAG_THEN | FLAG_START },
                { "then",  RES_THEN,  FLAG_ELIF | FLAG_ELSE | FLAG_FI },
                { "elif",  RES_ELIF,  FLAG_THEN },
                { "else",  RES_ELSE,  FLAG_FI   },
                { "fi",    RES_FI,    FLAG_END  },
#endif
#if ENABLE_HUSH_LOOPS
                { "for",   RES_FOR,   FLAG_IN | FLAG_DO | FLAG_START },
                { "while", RES_WHILE, FLAG_DO | FLAG_START },
                { "until", RES_UNTIL, FLAG_DO | FLAG_START },
                { "in",    RES_IN,    FLAG_DO   },
                { "do",    RES_DO,    FLAG_DONE },
                { "done",  RES_DONE,  FLAG_END  },
#endif
#if ENABLE_HUSH_CASE
                { "case",  RES_CASE,  FLAG_MATCH | FLAG_START },
                { "esac",  RES_ESAC,  FLAG_END  },
#endif
        };
#if ENABLE_HUSH_CASE
        static const struct reserved_combo reserved_match = {
                "" /* "match" */, RES_MATCH, FLAG_MATCH | FLAG_ESAC
        };
#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)
                        continue;
                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(NULL);
                                IF_HAS_KEYWORDS(ctx->ctx_res_w = RES_SNTX;)
                        }
                        ctx->ctx_inverted = 1;
                        return 1;
                }
                if (r->flag & FLAG_START) {
                        struct p_context *new;
                        debug_printf("push stack\n");
                        new = xmalloc(sizeof(*new));
                        *new = *ctx;   /* physical copy */
                        initialize_context(ctx);
                        ctx->stack = new;
                } else if (/*ctx->ctx_res_w == RES_NONE ||*/ !(ctx->old_flag & (1 << r->res))) {
                        syntax(NULL);
                        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 p_context *old;
                        debug_printf("pop stack\n");
                        done_pipe(ctx, PIPE_SEQ);
                        old = ctx->stack;
                        old->child->group = ctx->list_head;
                        old->child->subshell = 0;
                        *ctx = *old;   /* physical copy */
                        free(old);
                }
                return 1;
        }
        return 0;
}
#endif

/* Word is complete, look at it and update parsing context.
 * Normal return is 0. Syntax errors return 1. */
static int done_word(o_string *word, struct p_context *ctx)
{
        struct child_prog *child = ctx->child;

        debug_printf_parse("done_word entered: '%s' %p\n", word->data, child);
        /* 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 = NOT_ASSIGNMENT;
        } else {
                word->o_assignment = MAYBE_ASSIGNMENT;
        }
        if (word->length == 0 && word->nonnull == 0) {
                debug_printf_parse("done_word return 0: true null, ignored\n");
                return 0;
        }
        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". TODO? */
                if (child->group) {
                        syntax(NULL);
                        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 (!child->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);
                                word->o_assignment = NOT_ASSIGNMENT;
                                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);
                        }
                }
                child->argv = add_malloced_string_to_strings(child->argv, xstrdup(word->data));
                debug_print_strings("word appended to argv", child->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 child->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;
}

/* 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 p_context *ctx)
{
        /* The child is really already in the pipe structure, so
         * advance the pipe counter and make a new, null child. */
        struct pipe *pi = ctx->pipe;
        struct child_prog *child = ctx->child;

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

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

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

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

static void done_pipe(struct p_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;
                ctx->child = NULL; /* needed! */
                /* 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
                /* Create the memory for child, roughly:
                 * ctx->pipe->progs = new struct child_prog;
                 * ctx->child = &ctx->pipe->progs[0];
                 */
                done_command(ctx);
        }
        debug_printf_parse("done_pipe return\n");
}

/* 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;
}

/* 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;
}

#if ENABLE_HUSH_TICK
static FILE *generate_stream_from_list(struct pipe *head)
{
        FILE *pf;
        int pid, channel[2];

        xpipe(channel);
/* *** NOMMU WARNING *** */
/* By using vfork here, we suspend parent till child exits or execs.
 * If child will not do it before it fills the pipe, it can block forever
 * in write(STDOUT_FILENO), and parent (shell) will be also stuck.
 * Try this script:
 * yes "0123456789012345678901234567890" | dd bs=32 count=64k >TESTFILE
 * huge=`cat TESTFILE` # will block here forever
 * echo OK
 */
        pid = BB_MMU ? fork() : vfork();
        if (pid < 0)
                bb_perror_msg_and_die(BB_MMU ? "fork" : "vfork");
        if (pid == 0) { /* child */
                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 */
#if ENABLE_HUSH_JOB
                run_list_level = 1;
#endif
                /* Process substitution is not considered to be usual
                 * 'command execution'.
                 * SUSv3 says ctrl-Z should be ignored, ctrl-C should not. */
                /* Not needed, we are relying on it being disabled
                 * everywhere outside actual command execution. */
                /*set_jobctrl_sighandler(SIG_IGN);*/
                set_misc_sighandler(SIG_DFL);
                /* Freeing 'head' here would break NOMMU. */
                _exit(run_list(head));
        }
        close(channel[1]);
        pf = fdopen(channel[0], "r");
        return pf;
        /* 'head' is freed by the caller */
}

/* Return code is exit status of the process that is run. */
static int process_command_subs(o_string *dest,
                struct in_str *input,
                const char *subst_end)
{
        int retcode, ch, eol_cnt;
        o_string result = NULL_O_STRING;
        struct p_context inner;
        FILE *p;
        struct in_str pipe_str;

        initialize_context(&inner);

        /* Recursion to generate command */
        retcode = parse_stream(&result, &inner, input, subst_end);
        if (retcode != 0)
                return retcode;  /* syntax error or EOF */
        done_word(&result, &inner);
        done_pipe(&inner, PIPE_SEQ);
        o_free(&result);

        p = generate_stream_from_list(inner.list_head);
        if (p == NULL)
                return 1;
        close_on_exec_on(fileno(p));
        setup_file_in_str(&pipe_str, p);

        /* Now send results of command back into original context */
        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--;
                }
//              /* Even unquoted `echo '\'` results in two backslashes
//               * (which are converted into one by globbing later) */
//              if (!dest->o_quote && ch == '\\') {
//                      o_addchr(dest, ch);
//              }
                o_addQchr(dest, ch);
        }

        debug_printf("done reading from pipe, pclose()ing\n");
        /* This is the step that wait()s for the child.  Should be pretty
         * safe, since we just read an EOF from its stdout.  We could try
         * to do better, by using wait(), and keeping track of background jobs
         * at the same time.  That would be a lot of work, and contrary
         * to the KISS philosophy of this program. */
        retcode = fclose(p);
        free_pipe_list(inner.list_head, /* indent: */ 0);
        debug_printf("closed FILE from child, retcode=%d\n", retcode);
        return retcode;
}
#endif

static int parse_group(o_string *dest, struct p_context *ctx,
        struct in_str *input, int ch)
{
        int rcode;
        const char *endch = NULL;
        struct p_context sub;
        struct child_prog *child = ctx->child;

        debug_printf_parse("parse_group entered\n");
        if (child->argv) {
                syntax(NULL);
                debug_printf_parse("parse_group return 1: syntax error, groups and arglists don't mix\n");
                return 1;
        }
        initialize_context(&sub);
        endch = "}";
        if (ch == '(') {
                endch = ")";
                child->subshell = 1;
        }
        rcode = parse_stream(dest, &sub, input, endch);
        if (rcode == 0) {
                done_word(dest, &sub); /* finish off the final word in the subcontext */
                done_pipe(&sub, PIPE_SEQ);  /* and the final command there, too */
                child->group = sub.list_head;
        }
        debug_printf_parse("parse_group return %d\n", rcode);
        return rcode;
        /* child remains "open", available for possible redirects */
}

/* Basically useful version until someone wants to get fancier,
 * see the bash man page under "Parameter Expansion" */
static const char *lookup_param(const char *src)
{
        struct variable *var = get_local_var(src);
        if (var)
                return strchr(var->varstr, '=') + 1;
        return NULL;
}

#if ENABLE_HUSH_TICK
/* 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_curly_brace(o_string *dest, struct in_str *input)
{
        int count = 0;
        while (1) {
                int ch = i_getch(input);
                if (ch == EOF)
                        break;
                if (ch == '(')
                        count++;
                if (ch == ')')
                        if (--count < 0)
                                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 */

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

        debug_printf_parse("handle_dollar entered: ch='%c'\n", ch);
        if (isalpha(ch)) {
                o_addchr(dest, SPECIAL_VAR_SYMBOL);
                while (1) {
                        debug_printf_parse(": '%c'\n", ch);
                        i_getch(input);
                        o_addchr(dest, ch | quote_mask);
                        quote_mask = 0;
                        ch = i_peek(input);
                        if (!isalnum(ch) && ch != '_')
                                break;
                }
                o_addchr(dest, SPECIAL_VAR_SYMBOL);
        } else if (isdigit(ch)) {
 make_one_char_var:
                o_addchr(dest, SPECIAL_VAR_SYMBOL);
                debug_printf_parse(": '%c'\n", ch);
                i_getch(input);
                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 '{':
                        o_addchr(dest, SPECIAL_VAR_SYMBOL);
                        i_getch(input);
                        /* XXX maybe someone will try to escape the '}' */
                        while (1) {
                                ch = i_getch(input);
                                if (ch == '}')
                                        break;
                                if (!isalnum(ch) && ch != '_') {
                                        syntax("unterminated ${name}");
                                        debug_printf_parse("handle_dollar return 1: unterminated ${name}\n");
                                        return 1;
                                }
                                debug_printf_parse(": '%c'\n", ch);
                                o_addchr(dest, ch | quote_mask);
                                quote_mask = 0;
                        }
                        o_addchr(dest, SPECIAL_VAR_SYMBOL);
                        break;
#if ENABLE_HUSH_TICK
                case '(': {
                        //int pos = dest->length;
                        i_getch(input);
                        o_addchr(dest, SPECIAL_VAR_SYMBOL);
                        o_addchr(dest, quote_mask | '`');
                        add_till_closing_curly_brace(dest, input);
                        //debug_printf_subst("SUBST RES2 '%s'\n", dest->data + pos);
                        o_addchr(dest, SPECIAL_VAR_SYMBOL);
                        break;
                }
#endif
                case '-':
                case '_':
                        /* still unhandled, but should be eventually */
                        bb_error_msg("unhandled syntax: $%c", ch);
                        return 1;
                        break;
                default:
                        o_addQchr(dest, '$');
        }
        debug_printf_parse("handle_dollar return 0\n");
        return 0;
}

/* Scan input, call done_word() whenever full IFS delimited word was seen.
 * Call done_pipe if '\n' was seen (and end_trigger != NULL).
 * Return code is 0 if end_trigger char is met,
 * -1 on EOF (but if end_trigger == NULL then return 0),
 * 1 for syntax error */
static int parse_stream(o_string *dest, struct p_context *ctx,
        struct in_str *input, const char *end_trigger)
{
        int ch, m;
        int redir_fd;
        redir_type redir_style;
        int shadow_quote = dest->o_quote;
        int next;

        /* Only double-quote state is handled in the state variable dest->o_quote.
         * 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_quote. */

        debug_printf_parse("parse_stream entered, end_trigger='%s'\n", end_trigger);

        while (1) {
                m = CHAR_IFS;
                next = '\0';
                ch = i_getch(input);
                if (ch != EOF) {
                        m = charmap[ch];
                        if (ch != '\n') {
                                next = i_peek(input);
                        }
                }
                debug_printf_parse(": ch=%c (%d) m=%d quote=%d\n",
                                                ch, ch, m, dest->o_quote);
                if (m == CHAR_ORDINARY
                 || (m != CHAR_SPECIAL && shadow_quote)
                ) {
                        if (ch == EOF) {
                                syntax("unterminated \"");
                                debug_printf_parse("parse_stream return 1: unterminated \"\n");
                                return 1;
                        }
                        o_addQchr(dest, ch);
                        if (dest->o_assignment == MAYBE_ASSIGNMENT
                         && ch == '='
                         && is_assignment(dest->data)
                        ) {
                                dest->o_assignment = DEFINITELY_ASSIGNMENT;
                        }
                        continue;
                }
                if (m == CHAR_IFS) {
                        if (done_word(dest, ctx)) {
                                debug_printf_parse("parse_stream return 1: done_word!=0\n");
                                return 1;
                        }
                        if (ch == EOF)
                                break;
                        /* If we aren't performing a substitution, treat
                         * a newline as a command separator.
                         * [why we don't handle it exactly like ';'? --vda] */
                        if (end_trigger && ch == '\n') {
                                done_pipe(ctx, PIPE_SEQ);
                        }
                }
                if (end_trigger) {
                        if (!shadow_quote && strchr(end_trigger, ch)) {
                                /* Special case: (...word) makes last word terminate,
                                 * as if ';' is seen */
                                if (ch == ')') {
                                        done_word(dest, ctx);
//err chk?
                                        done_pipe(ctx, PIPE_SEQ);
                                }
                                if (!HAS_KEYWORDS
                                 IF_HAS_KEYWORDS(|| (ctx->ctx_res_w == RES_NONE && ctx->old_flag == 0))
                                ) {
                                        debug_printf_parse("parse_stream return 0: end_trigger char found\n");
                                        return 0;
                                }
                        }
                }
                if (m == CHAR_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 && !shadow_quote) {
                                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>");
                                debug_printf_parse("parse_stream return 1: \\<eof>\n");
                                return 1;
                        }
                        /* bash:
                         * "The backslash retains its special meaning [in "..."]
                         * only when followed by one of the following characters:
                         * $, `, ", \, or <newline>.  A double quote may be quoted
                         * within double quotes by preceding it with a  backslash.
                         * If enabled, history expansion will be performed unless
                         * an ! appearing in double quotes is escaped using
                         * a backslash. The backslash preceding the ! is not removed."
                         */
                        if (shadow_quote) { //NOT SURE   dest->o_quote) {
                                if (strchr("$`\"\\", next) != NULL) {
                                        o_addqchr(dest, i_getch(input));
                                } else {
                                        o_addqchr(dest, '\\');
                                }
                        } else {
                                o_addchr(dest, '\\');
                                o_addchr(dest, i_getch(input));
                        }
                        break;
                case '$':
                        if (handle_dollar(dest, input) != 0) {
                                debug_printf_parse("parse_stream return 1: handle_dollar returned non-0\n");
                                return 1;
                        }
                        break;
                case '\'':
                        dest->nonnull = 1;
                        while (1) {
                                ch = i_getch(input);
                                if (ch == EOF) {
                                        syntax("unterminated '");
                                        debug_printf_parse("parse_stream return 1: unterminated '\n");
                                        return 1;
                                }
                                if (ch == '\'')
                                        break;
                                if (dest->o_assignment == NOT_ASSIGNMENT)
                                        o_addqchr(dest, ch);
                                else
                                        o_addchr(dest, ch);
                        }
                        break;
                case '"':
                        dest->nonnull = 1;
                        shadow_quote ^= 1; /* invert */
                        if (dest->o_assignment == NOT_ASSIGNMENT)
                                dest->o_quote ^= 1;
                        break;
#if ENABLE_HUSH_TICK
                case '`': {
                        //int pos = dest->length;
                        o_addchr(dest, SPECIAL_VAR_SYMBOL);
                        o_addchr(dest, shadow_quote /*or dest->o_quote??*/ ? 0x80 | '`' : '`');
                        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);
                        done_word(dest, ctx);
                        redir_style = REDIRECT_OVERWRITE;
                        if (next == '>') {
                                redir_style = REDIRECT_APPEND;
                                i_getch(input);
                        }
#if 0
                        else if (next == '(') {
                                syntax(">(process) not supported");
                                debug_printf_parse("parse_stream return 1: >(process) not supported\n");
                                return 1;
                        }
#endif
                        setup_redirect(ctx, redir_fd, redir_style, input);
                        break;
                case '<':
                        redir_fd = redirect_opt_num(dest);
                        done_word(dest, ctx);
                        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");
                                debug_printf_parse("parse_stream return 1: <(process) not supported\n");
                                return 1;
                        }
#endif
                        setup_redirect(ctx, redir_fd, redir_style, input);
                        break;
                case ';':
#if ENABLE_HUSH_CASE
 case_semi:
#endif
                        done_word(dest, ctx);
                        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
                        break;
                case '&':
                        done_word(dest, ctx);
                        if (next == '&') {
                                i_getch(input);
                                done_pipe(ctx, PIPE_AND);
                        } else {
                                done_pipe(ctx, PIPE_BG);
                        }
                        break;
                case '|':
                        done_word(dest, ctx);
                        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);
                        }
                        break;
                case '(':
#if ENABLE_HUSH_CASE
                        if (dest->length == 0 // && argv[0] == NULL
                         && ctx->ctx_res_w == RES_MATCH
                        ) {
                                continue;
                        }
#endif
                case '{':
                        if (parse_group(dest, ctx, input, ch) != 0) {
                                debug_printf_parse("parse_stream return 1: parse_group returned non-0\n");
                                return 1;
                        }
                        break;
                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 */
                        syntax("unexpected } or )");
                        debug_printf_parse("parse_stream return 1: unexpected '}'\n");
                        return 1;
                default:
                        if (HUSH_DEBUG)
                                bb_error_msg_and_die("BUG: unexpected %c\n", ch);
                }
        } /* while (1) */
        debug_printf_parse("parse_stream return %d\n", -(end_trigger != NULL));
        if (end_trigger)
                return -1;
        return 0;
}

static void set_in_charmap(const char *set, int code)
{
        while (*set)
                charmap[(unsigned char)*set++] = code;
}

static void update_charmap(void)
{
        /* char *ifs and char charmap[256] are both globals. */
        ifs = getenv("IFS");
        if (ifs == NULL)
                ifs = " \t\n";
        /* Precompute a list of 'flow through' behavior so it can be treated
         * quickly up front.  Computation is necessary because of IFS.
         * Special case handling of IFS == " \t\n" is not implemented.
         * The charmap[] array only really needs two bits each,
         * and on most machines that would be faster (reduced L1 cache use).
         */
        memset(charmap, CHAR_ORDINARY, sizeof(charmap));
#if ENABLE_HUSH_TICK
        set_in_charmap("\\$\"`", CHAR_SPECIAL);
#else
        set_in_charmap("\\$\"", CHAR_SPECIAL);
#endif
        set_in_charmap("<>;&|(){}#'", CHAR_ORDINARY_IF_QUOTED);
        set_in_charmap(ifs, CHAR_IFS);  /* are ordinary if quoted */
}

/* Most recursion does not come through here, the exception is
 * from builtin_source() and builtin_eval() */
static int parse_and_run_stream(struct in_str *inp, int parse_flag)
{
        struct p_context ctx;
        o_string temp = NULL_O_STRING;
        int rcode;

        do {
                initialize_context(&ctx);
                update_charmap();
#if ENABLE_HUSH_INTERACTIVE
                inp->promptmode = 0; /* PS1 */
#endif
                /* We will stop & execute after each ';' or '\n'.
                 * Example: "sleep 9999; echo TEST" + ctrl-C:
                 * TEST should be printed */
                rcode = parse_stream(&temp, &ctx, inp, ";\n");
#if HAS_KEYWORDS
                if (rcode != 1 && ctx.old_flag != 0) {
                        syntax(NULL);
                }
#endif
                if (rcode != 1 IF_HAS_KEYWORDS(&& ctx.old_flag == 0)) {
                        done_word(&temp, &ctx);
                        done_pipe(&ctx, PIPE_SEQ);
                        debug_print_tree(ctx.list_head, 0);
                        debug_printf_exec("parse_stream_outer: run_and_free_list\n");
                        run_and_free_list(ctx.list_head);
                } else {
                        /* We arrive here also if rcode == 1 (error in parse_stream) */
#if HAS_KEYWORDS
                        if (ctx.old_flag != 0) {
                                free(ctx.stack);
                                o_reset(&temp);
                        }
#endif
                        /*temp.nonnull = 0; - o_free does it below */
                        /*temp.o_quote = 0; - o_free does it below */
                        free_pipe_list(ctx.list_head, /* indent: */ 0);
                        /* Discard all unprocessed line input, force prompt on */
                        inp->p = NULL;
#if ENABLE_HUSH_INTERACTIVE
                        inp->promptme = 1;
#endif
                }
                o_free(&temp);
                /* loop on syntax errors, return on EOF: */
        } while (rcode != -1 && !(parse_flag & PARSEFLAG_EXIT_FROM_LOOP));
        return 0;
}

static int parse_and_run_string(const char *s, int parse_flag)
{
        struct in_str input;
        setup_string_in_str(&input, s);
        return parse_and_run_stream(&input, parse_flag);
}

static int parse_and_run_file(FILE *f)
{
        int rcode;
        struct in_str input;
        setup_file_in_str(&input, f);
        rcode = parse_and_run_stream(&input, 0 /* parse_flag */);
        return rcode;
}

#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;

        saved_task_pgrp = shell_pgrp = getpgrp();
        debug_printf_jobs("saved_task_pgrp=%d\n", saved_task_pgrp);
        close_on_exec_on(interactive_fd);

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

        /* Ignore job-control and misc signals.  */
        set_jobctrl_sighandler(SIG_IGN);
        set_misc_sighandler(SIG_IGN);
//huh?  signal(SIGCHLD, SIG_IGN);

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

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


int hush_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int hush_main(int argc, char **argv)
{
        static const char version_str[] ALIGN1 = "HUSH_VERSION="HUSH_VER_STR;
        static const struct variable const_shell_ver = {
                .next = NULL,
                .varstr = (char*)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();

        root_pid = getpid();

        /* Deal with HUSH_VERSION */
        shell_ver = const_shell_ver; /* copying struct here */
        top_var = &shell_ver;
        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 = 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++;
        }
        putenv((char *)version_str); /* reinstate HUSH_VERSION */

#if ENABLE_FEATURE_EDITING
        line_input_state = new_line_input_t(FOR_SHELL);
#endif
        /* XXX what should these be while sourcing /etc/profile? */
        global_argc = argc;
        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();
#endif
        PS2 = "> ";
#endif

        if (EXIT_SUCCESS) /* otherwise is already done */
                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;

        while ((opt = getopt(argc, argv, "c:xif")) > 0) {
                switch (opt) {
                case 'c':
                        global_argv = argv + optind;
                        global_argc = argc - optind;
                        opt = parse_and_run_string(optarg, 0 /* parse_flag */);
                        goto final_return;
                case 'i':
                        /* Well, we cannot just declare interactiveness,
                         * we have to have some stuff (ctty, etc) */
                        /* interactive_fd++; */
                        break;
                case 'f':
                        fake_mode = 1;
                        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)
        ) {
                saved_tty_pgrp = tcgetpgrp(STDIN_FILENO);
                debug_printf("saved_tty_pgrp=%d\n", saved_tty_pgrp);
                if (saved_tty_pgrp >= 0) {
                        /* try to dup to high fd#, >= 255 */
                        interactive_fd = fcntl(STDIN_FILENO, F_DUPFD, 255);
                        if (interactive_fd < 0) {
                                /* try to dup to any fd */
                                interactive_fd = dup(STDIN_FILENO);
                                if (interactive_fd < 0)
                                        /* give up */
                                        interactive_fd = 0;
                        }
                        // TODO: track & disallow any attempts of user
                        // to (inadvertently) close/redirect it
                }
        }
        debug_printf("interactive_fd=%d\n", interactive_fd);
        if (interactive_fd) {
                fcntl(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);
                }
#if !ENABLE_FEATURE_SH_EXTRA_QUIET
                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
        }
#elif ENABLE_HUSH_INTERACTIVE
/* no job control compiled, only prompt/line editing */
        if (argv[optind] == NULL && input == stdin
         && isatty(STDIN_FILENO) && isatty(STDOUT_FILENO)
        ) {
                interactive_fd = fcntl(STDIN_FILENO, F_DUPFD, 255);
                if (interactive_fd < 0) {
                        /* try to dup to any fd */
                        interactive_fd = dup(STDIN_FILENO);
                        if (interactive_fd < 0)
                                /* give up */
                                interactive_fd = 0;
                }
                if (interactive_fd) {
                        fcntl(interactive_fd, F_SETFD, FD_CLOEXEC);
                        set_misc_sighandler(SIG_IGN);
                }
        }
#endif

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

 final_return:

#if ENABLE_FEATURE_CLEAN_UP
        fclose(input);
        if (cwd != bb_msg_unknown)
                free((char*)cwd);
        cur_var = 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(opt ? opt : 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_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);
                parse_and_run_string(str, PARSEFLAG_EXIT_FROM_LOOP);
                free(str);
                rcode = 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
                char **ptrs2free = alloc_ptrs(argv);
#endif
// FIXME: if exec fails, bash does NOT exit! We do...
                pseudo_exec_argv(ptrs2free, argv + 1, 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(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;
                        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 (!interactive_fd)
                return EXIT_FAILURE;
        /* If they gave us no args, assume they want the last backgrounded task */
        if (!argv[1]) {
                for (pi = job_list; pi; pi = pi->next) {
                        if (pi->jobid == 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 = 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(interactive_fd, pi->pgrp);
        }

        /* Restart the processes in the job */
        debug_printf_jobs("reviving %d procs, pgrp %d\n", pi->num_progs, pi->pgrp);
        for (i = 0; i < pi->num_progs; i++) {
                debug_printf_jobs("reviving pid %d\n", pi->progs[i].pid);
                pi->progs[i].is_stopped = 0;
        }
        pi->stopped_progs = 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 = job_list; job; job = job->next) {
                if (job->alive_progs == job->stopped_progs)
                        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);
}

/* built-in 'set [VAR=value]' handler */
static int builtin_set(char **argv)
{
        char *temp = argv[1];
        struct variable *e;

        if (temp == NULL)
                for (e = top_var; e; e = e->next)
                        puts(e->varstr);
        else
                set_local_var(xstrdup(temp), 0);

        return EXIT_SUCCESS;
}

static int builtin_shift(char **argv)
{
        int n = 1;
        if (argv[1]) {
                n = atoi(argv[1]);
        }
        if (n >= 0 && n < global_argc) {
                global_argv[n] = global_argv[0];
                global_argc -= n;
                global_argv += n;
                return EXIT_SUCCESS;
        }
        return EXIT_FAILURE;
}

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

        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 global_argv
         * (pointer only is OK!) on this stack frame,
         * set global_argv=argv+1, recurse, and restore. */
        status = parse_and_run_file(input);
        fclose(input);
        return status;
}

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

static int builtin_unset(char **argv)
{
        /* bash always returns true */
        unset_local_var(argv[1]);
        return EXIT_SUCCESS;
}

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

static int builtin_continue(char **argv)
{
        if (depth_of_loop) {
                flag_break_continue++; /* BC_CONTINUE = 2 = 1+1 */
                return builtin_break(argv);
        }
        bb_error_msg("%s: only meaningful in a loop", "continue");
        return EXIT_SUCCESS; /* bash compat */
}
#endif