shell/hush.c

/* vi: set sw=4 ts=4: */
/*
 * A prototype Bourne shell grammar parser.
 * Intended to follow the original Thompson and Ritchie
 * "small and simple is beautiful" philosophy, which
 * incidentally is a good match to today's BusyBox.
 *
 * Copyright (C) 2000,2001  Larry Doolittle <larry@doolittle.boa.org>
 * Copyright (C) 2008,2009  Denys Vlasenko <vda.linux@googlemail.com>
 *
 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
 *
 * Credits:
 *      The parser routines proper are all original material, first
 *      written Dec 2000 and Jan 2001 by Larry Doolittle.  The
 *      execution engine, the builtins, and much of the underlying
 *      support has been adapted from busybox-0.49pre's lash, which is
 *      Copyright (C) 1999-2004 by Erik Andersen <andersen@codepoet.org>
 *      written by Erik Andersen <andersen@codepoet.org>.  That, in turn,
 *      is based in part on ladsh.c, by Michael K. Johnson and Erik W.
 *      Troan, which they placed in the public domain.  I don't know
 *      how much of the Johnson/Troan code has survived the repeated
 *      rewrites.
 *
 * Other credits:
 *      o_addchr derived from similar w_addchar function in glibc-2.2.
 *      parse_redirect, redirect_opt_num, and big chunks of main
 *      and many builtins derived from contributions by Erik Andersen.
 *      Miscellaneous bugfixes from Matt Kraai.
 *
 * There are two big (and related) architecture differences between
 * this parser and the lash parser.  One is that this version is
 * actually designed from the ground up to understand nearly all
 * of the Bourne grammar.  The second, consequential change is that
 * the parser and input reader have been turned inside out.  Now,
 * the parser is in control, and asks for input as needed.  The old
 * way had the input reader in control, and it asked for parsing to
 * take place as needed.  The new way makes it much easier to properly
 * handle the recursion implicit in the various substitutions, especially
 * across continuation lines.
 *
 * TODOs:
 *      grep for "TODO" and fix (some of them are easy)
 *      special variables (done: PWD, PPID, RANDOM)
 *      tilde expansion
 *      aliases
 *      follow IFS rules more precisely, including update semantics
 *      builtins mandated by standards we don't support:
 *          [un]alias, command, fc, getopts, newgrp, readonly, times
 *      make complex ${var%...} constructs support optional
 *      make here documents optional
 *
 * Bash compat TODO:
 *      redirection of stdout+stderr: &> and >&
 *      reserved words: function select
 *      advanced test: [[ ]]
 *      process substitution: <(list) and >(list)
 *      =~: regex operator
 *      let EXPR [EXPR...]
 *          Each EXPR is an arithmetic expression (ARITHMETIC EVALUATION)
 *          If the last arg evaluates to 0, let returns 1; 0 otherwise.
 *          NB: let `echo 'a=a + 1'` - error (IOW: multi-word expansion is used)
 *      ((EXPR))
 *          The EXPR is evaluated according to ARITHMETIC EVALUATION.
 *          This is exactly equivalent to let "EXPR".
 *      $[EXPR]: synonym for $((EXPR))
 *
 * Won't do:
 *      In bash, export builtin is special, its arguments are assignments
 *          and therefore expansion of them should be "one-word" expansion:
 *              $ export i=`echo 'a  b'` # export has one arg: "i=a  b"
 *          compare with:
 *              $ ls i=`echo 'a  b'`     # ls has two args: "i=a" and "b"
 *              ls: cannot access i=a: No such file or directory
 *              ls: cannot access b: No such file or directory
 *          Note1: same applies to local builtin.
 *          Note2: bash 3.2.33(1) does this only if export word itself
 *          is not quoted:
 *              $ export i=`echo 'aaa  bbb'`; echo "$i"
 *              aaa  bbb
 *              $ "export" i=`echo 'aaa  bbb'`; echo "$i"
 *              aaa
 */
#if !(defined(__FreeBSD__) || defined(__OpenBSD__) || defined(__NetBSD__) \
	|| defined(__APPLE__) \
    )
# include <malloc.h>   /* for malloc_trim */
#endif
#include <glob.h>
/* #include <dmalloc.h> */
#if ENABLE_HUSH_CASE
# include <fnmatch.h>
#endif

#include "busybox.h"  /* for APPLET_IS_NOFORK/NOEXEC */
#include "unicode.h"
#include "shell_common.h"
#include "math.h"
#include "match.h"
#if ENABLE_HUSH_RANDOM_SUPPORT
# include "random.h"
#else
# define CLEAR_RANDOM_T(rnd) ((void)0)
#endif
#ifndef PIPE_BUF
# define PIPE_BUF 4096  /* amount of buffering in a pipe */
#endif

/* Not every libc has sighandler_t. Fix it */
typedef void (*hush_sighandler_t)(int);
#define sighandler_t hush_sighandler_t

//config:config HUSH
//config:	bool "hush"
//config:	default y
//config:	help
//config:	  hush is a small shell (25k). It handles the normal flow control
//config:	  constructs such as if/then/elif/else/fi, for/in/do/done, while loops,
//config:	  case/esac. Redirections, here documents, $((arithmetic))
//config:	  and functions are supported.
//config:
//config:	  It will compile and work on no-mmu systems.
//config:
//config:	  It does not handle select, aliases, tilde expansion,
//config:	  &>file and >&file redirection of stdout+stderr.
//config:
//config:config HUSH_BASH_COMPAT
//config:	bool "bash-compatible extensions"
//config:	default y
//config:	depends on HUSH
//config:	help
//config:	  Enable bash-compatible extensions.
//config:
//config:config HUSH_BRACE_EXPANSION
//config:	bool "Brace expansion"
//config:	default y
//config:	depends on HUSH_BASH_COMPAT
//config:	help
//config:	  Enable {abc,def} extension.
//config:
//config:config HUSH_HELP
//config:	bool "help builtin"
//config:	default y
//config:	depends on HUSH
//config:	help
//config:	  Enable help builtin in hush. Code size + ~1 kbyte.
//config:
//config:config HUSH_INTERACTIVE
//config:	bool "Interactive mode"
//config:	default y
//config:	depends on HUSH
//config:	help
//config:	  Enable interactive mode (prompt and command editing).
//config:	  Without this, hush simply reads and executes commands
//config:	  from stdin just like a shell script from a file.
//config:	  No prompt, no PS1/PS2 magic shell variables.
//config:
//config:config HUSH_SAVEHISTORY
//config:	bool "Save command history to .hush_history"
//config:	default y
//config:	depends on HUSH_INTERACTIVE && FEATURE_EDITING_SAVEHISTORY
//config:	help
//config:	  Enable history saving in hush.
//config:
//config:config HUSH_JOB
//config:	bool "Job control"
//config:	default y
//config:	depends on HUSH_INTERACTIVE
//config:	help
//config:	  Enable job control: Ctrl-Z backgrounds, Ctrl-C interrupts current
//config:	  command (not entire shell), fg/bg builtins work. Without this option,
//config:	  "cmd &" still works by simply spawning a process and immediately
//config:	  prompting for next command (or executing next command in a script),
//config:	  but no separate process group is formed.
//config:
//config:config HUSH_TICK
//config:	bool "Process substitution"
//config:	default y
//config:	depends on HUSH
//config:	help
//config:	  Enable process substitution `command` and $(command) in hush.
//config:
//config:config HUSH_IF
//config:	bool "Support if/then/elif/else/fi"
//config:	default y
//config:	depends on HUSH
//config:	help
//config:	  Enable if/then/elif/else/fi in hush.
//config:
//config:config HUSH_LOOPS
//config:	bool "Support for, while and until loops"
//config:	default y
//config:	depends on HUSH
//config:	help
//config:	  Enable for, while and until loops in hush.
//config:
//config:config HUSH_CASE
//config:	bool "Support case ... esac statement"
//config:	default y
//config:	depends on HUSH
//config:	help
//config:	  Enable case ... esac statement in hush. +400 bytes.
//config:
//config:config HUSH_FUNCTIONS
//config:	bool "Support funcname() { commands; } syntax"
//config:	default y
//config:	depends on HUSH
//config:	help
//config:	  Enable support for shell functions in hush. +800 bytes.
//config:
//config:config HUSH_LOCAL
//config:	bool "Support local builtin"
//config:	default y
//config:	depends on HUSH_FUNCTIONS
//config:	help
//config:	  Enable support for local variables in functions.
//config:
//config:config HUSH_RANDOM_SUPPORT
//config:	bool "Pseudorandom generator and $RANDOM variable"
//config:	default y
//config:	depends on HUSH
//config:	help
//config:	  Enable pseudorandom generator and dynamic variable "$RANDOM".
//config:	  Each read of "$RANDOM" will generate a new pseudorandom value.
//config:
//config:config HUSH_EXPORT_N
//config:	bool "Support 'export -n' option"
//config:	default y
//config:	depends on HUSH
//config:	help
//config:	  export -n unexports variables. It is a bash extension.
//config:
//config:config HUSH_MODE_X
//config:	bool "Support 'hush -x' option and 'set -x' command"
//config:	default y
//config:	depends on HUSH
//config:	help
//config:	  This instructs hush to print commands before execution.
//config:	  Adds ~300 bytes.
//config:
//config:config MSH
//config:	bool "msh (deprecated: aliased to hush)"
//config:	default n
//config:	select HUSH
//config:	help
//config:	  msh is deprecated and will be removed, please migrate to hush.
//config:

//applet:IF_HUSH(APPLET(hush, BB_DIR_BIN, BB_SUID_DROP))
//applet:IF_MSH(APPLET(msh, BB_DIR_BIN, BB_SUID_DROP))
//applet:IF_FEATURE_SH_IS_HUSH(APPLET_ODDNAME(sh, hush, BB_DIR_BIN, BB_SUID_DROP, sh))
//applet:IF_FEATURE_BASH_IS_HUSH(APPLET_ODDNAME(bash, hush, BB_DIR_BIN, BB_SUID_DROP, bash))

//kbuild:lib-$(CONFIG_HUSH) += hush.o match.o shell_common.o
//kbuild:lib-$(CONFIG_HUSH_RANDOM_SUPPORT) += random.o

/* -i (interactive) and -s (read stdin) are also accepted,
 * but currently do nothing, therefore aren't shown in help.
 * NOMMU-specific options are not meant to be used by users,
 * therefore we don't show them either.
 */
//usage:#define hush_trivial_usage
//usage:	"[-nxl] [-c 'SCRIPT' [ARG0 [ARGS]] / FILE [ARGS]]"
//usage:#define hush_full_usage "\n\n"
//usage:	"Unix shell interpreter"

//usage:#define msh_trivial_usage hush_trivial_usage
//usage:#define msh_full_usage hush_full_usage

//usage:#if ENABLE_FEATURE_SH_IS_HUSH
//usage:# define sh_trivial_usage hush_trivial_usage
//usage:# define sh_full_usage    hush_full_usage
//usage:#endif
//usage:#if ENABLE_FEATURE_BASH_IS_HUSH
//usage:# define bash_trivial_usage hush_trivial_usage
//usage:# define bash_full_usage    hush_full_usage
//usage:#endif


/* Build knobs */
#define LEAK_HUNTING 0
#define BUILD_AS_NOMMU 0
/* Enable/disable sanity checks. Ok to enable in production,
 * only adds a bit of bloat. Set to >1 to get non-production level verbosity.
 * Keeping 1 for now even in released versions.
 */
#define HUSH_DEBUG 1
/* Slightly bigger (+200 bytes), but faster hush.
 * So far it only enables a trick with counting SIGCHLDs and forks,
 * which allows us to do fewer waitpid's.
 * (we can detect a case where neither forks were done nor SIGCHLDs happened
 * and therefore waitpid will return the same result as last time)
 */
#define ENABLE_HUSH_FAST 0
/* TODO: implement simplified code for users which do not need ${var%...} ops
 * So far ${var%...} ops are always enabled:
 */
#define ENABLE_HUSH_DOLLAR_OPS 1


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

#include "NUM_APPLETS.h"
#if NUM_APPLETS == 1
/* STANDALONE does not make sense, and won't compile */
# undef CONFIG_FEATURE_SH_STANDALONE
# undef ENABLE_FEATURE_SH_STANDALONE
# undef IF_FEATURE_SH_STANDALONE
# undef IF_NOT_FEATURE_SH_STANDALONE
# define ENABLE_FEATURE_SH_STANDALONE 0
# define IF_FEATURE_SH_STANDALONE(...)
# define IF_NOT_FEATURE_SH_STANDALONE(...) __VA_ARGS__
#endif

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

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

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

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

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

#define _SPECIAL_VARS_STR     "_*@$!?#"
#define SPECIAL_VARS_STR     ("_*@$!?#" + 1)
#define NUMERIC_SPECVARS_STR ("_*@$!?#" + 3)
#if ENABLE_HUSH_BASH_COMPAT
/* Support / and // replace ops */
/* Note that // is stored as \ in "encoded" string representation */
# define VAR_ENCODED_SUBST_OPS      "\\/%#:-=+?"
# define VAR_SUBST_OPS             ("\\/%#:-=+?" + 1)
# define MINUS_PLUS_EQUAL_QUESTION ("\\/%#:-=+?" + 5)
#else
# define VAR_ENCODED_SUBST_OPS      "%#:-=+?"
# define VAR_SUBST_OPS              "%#:-=+?"
# define MINUS_PLUS_EQUAL_QUESTION ("%#:-=+?" + 3)
#endif

#define SPECIAL_VAR_SYMBOL   3

struct variable;

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

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

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

typedef struct o_string {
	char *data;
	int length; /* position where data is appended */
	int maxlen;
	int o_expflags;
	/* At least some part of the string was inside '' or "",
	 * possibly empty one: word"", wo''rd etc. */
	smallint has_quoted_part;
	smallint has_empty_slot;
	smallint o_assignment; /* 0:maybe, 1:yes, 2:no */
} o_string;
enum {
	EXP_FLAG_SINGLEWORD     = 0x80, /* must be 0x80 */
	EXP_FLAG_GLOB           = 0x2,
	/* Protect newly added chars against globbing
	 * by prepending \ to *, ?, [, \ */
	EXP_FLAG_ESC_GLOB_CHARS = 0x1,
};
enum {
	MAYBE_ASSIGNMENT      = 0,
	DEFINITELY_ASSIGNMENT = 1,
	NOT_ASSIGNMENT        = 2,
	/* Not an assigment, but next word may be: "if v=xyz cmd;" */
	WORD_IS_KEYWORD       = 3,
};
/* Used for initialization: o_string foo = NULL_O_STRING; */
#define NULL_O_STRING { NULL }

#ifndef debug_printf_parse
static const char *const assignment_flag[] = {
	"MAYBE_ASSIGNMENT",
	"DEFINITELY_ASSIGNMENT",
	"NOT_ASSIGNMENT",
	"WORD_IS_KEYWORD",
};
#endif

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 promptmode; /* 0: PS1, 1: PS2 */
#endif
	int last_char;
	FILE *file;
	int (*get) (struct in_str *) FAST_FUNC;
	int (*peek) (struct in_str *) FAST_FUNC;
} in_str;
#define i_getch(input) ((input)->get(input))
#define i_peek(input) ((input)->peek(input))

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

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

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

	HEREDOC_SKIPTABS = 1,
	HEREDOC_QUOTED   = 2,
} redir_type;


struct command {
	pid_t pid;                  /* 0 if exited */
	int assignment_cnt;         /* how many argv[i] are assignments? */
	smallint cmd_type;          /* CMD_xxx */
#define CMD_NORMAL   0
#define CMD_SUBSHELL 1
#if ENABLE_HUSH_BASH_COMPAT
/* used for "[[ EXPR ]]" */
# define CMD_SINGLEWORD_NOGLOB 2
#endif
#if ENABLE_HUSH_FUNCTIONS
# define CMD_FUNCDEF 3
#endif

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

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

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

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

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

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


/* set -/+o OPT support. (TODO: make it optional)
 * bash supports the following opts:
 * allexport       off
 * braceexpand     on
 * emacs           on
 * errexit         off
 * errtrace        off
 * functrace       off
 * hashall         on
 * histexpand      off
 * history         on
 * ignoreeof       off
 * interactive-comments    on
 * keyword         off
 * monitor         on
 * noclobber       off
 * noexec          off
 * noglob          off
 * nolog           off
 * notify          off
 * nounset         off
 * onecmd          off
 * physical        off
 * pipefail        off
 * posix           off
 * privileged      off
 * verbose         off
 * vi              off
 * xtrace          off
 */
static const char o_opt_strings[] ALIGN1 =
	"pipefail\0"
	"noexec\0"
#if ENABLE_HUSH_MODE_X
	"xtrace\0"
#endif
	;
enum {
	OPT_O_PIPEFAIL,
	OPT_O_NOEXEC,
#if ENABLE_HUSH_MODE_X
	OPT_O_XTRACE,
#endif
	NUM_OPT_O
};


/* "Globals" within this file */
/* Sorted roughly by size (smaller offsets == smaller code) */
struct globals {
	/* interactive_fd != 0 means we are an interactive shell.
	 * If we are, then saved_tty_pgrp can also be != 0, meaning
	 * that controlling tty is available. With saved_tty_pgrp == 0,
	 * job control still works, but terminal signals
	 * (^C, ^Z, ^Y, ^\) won't work at all, and background
	 * process groups can only be created with "cmd &".
	 * With saved_tty_pgrp != 0, hush will use tcsetpgrp()
	 * to give tty to the foreground process group,
	 * and will take it back when the group is stopped (^Z)
	 * or killed (^C).
	 */
#if ENABLE_HUSH_INTERACTIVE
	/* 'interactive_fd' is a fd# open to ctty, if we have one
	 * _AND_ if we decided to act interactively */
	int interactive_fd;
	const char *PS1;
	const char *PS2;
# define G_interactive_fd (G.interactive_fd)
#else
# define G_interactive_fd 0
#endif
#if ENABLE_FEATURE_EDITING
	line_input_t *line_input_state;
#endif
	pid_t root_pid;
	pid_t root_ppid;
	pid_t last_bg_pid;
#if ENABLE_HUSH_RANDOM_SUPPORT
	random_t random_gen;
#endif
#if ENABLE_HUSH_JOB
	int run_list_level;
	int last_jobid;
	pid_t saved_tty_pgrp;
	struct pipe *job_list;
# define G_saved_tty_pgrp (G.saved_tty_pgrp)
#else
# define G_saved_tty_pgrp 0
#endif
	char o_opt[NUM_OPT_O];
#if ENABLE_HUSH_MODE_X
# define G_x_mode (G.o_opt[OPT_O_XTRACE])
#else
# define G_x_mode 0
#endif
	smallint flag_SIGINT;
#if ENABLE_HUSH_LOOPS
	smallint flag_break_continue;
#endif
#if ENABLE_HUSH_FUNCTIONS
	/* 0: outside of a function (or sourced file)
	 * -1: inside of a function, ok to use return builtin
	 * 1: return is invoked, skip all till end of func
	 */
	smallint flag_return_in_progress;
#endif
	smallint exiting; /* used to prevent EXIT trap recursion */
	/* These four support $?, $#, and $1 */
	smalluint last_exitcode;
	/* are global_argv and global_argv[1..n] malloced? (note: not [0]) */
	smalluint global_args_malloced;
	/* how many non-NULL argv's we have. NB: $# + 1 */
	int global_argc;
	char **global_argv;
#if !BB_MMU
	char *argv0_for_re_execing;
#endif
#if ENABLE_HUSH_LOOPS
	unsigned depth_break_continue;
	unsigned depth_of_loop;
#endif
	const char *ifs;
	const char *cwd;
	struct variable *top_var;
	char **expanded_assignments;
#if ENABLE_HUSH_FUNCTIONS
	struct function *top_func;
# if ENABLE_HUSH_LOCAL
	struct variable **shadowed_vars_pp;
	unsigned func_nest_level;
# endif
#endif
	/* Signal and trap handling */
#if ENABLE_HUSH_FAST
	unsigned count_SIGCHLD;
	unsigned handled_SIGCHLD;
	smallint we_have_children;
#endif
	/* Which signals have non-DFL handler (even with no traps set)?
	 * Set at the start to:
	 * (SIGQUIT + maybe SPECIAL_INTERACTIVE_SIGS + maybe SPECIAL_JOBSTOP_SIGS)
	 * SPECIAL_INTERACTIVE_SIGS are cleared after fork.
	 * The rest is cleared right before execv syscalls.
	 * Other than these two times, never modified.
	 */
	unsigned special_sig_mask;
#if ENABLE_HUSH_JOB
	unsigned fatal_sig_mask;
# define G_fatal_sig_mask G.fatal_sig_mask
#else
# define G_fatal_sig_mask 0
#endif
	char **traps; /* char *traps[NSIG] */
	sigset_t pending_set;
#if HUSH_DEBUG
	unsigned long memleak_value;
	int debug_indent;
#endif
	struct sigaction sa;
	char user_input_buf[ENABLE_FEATURE_EDITING ? CONFIG_FEATURE_EDITING_MAX_LEN : 2];
};
#define G (*ptr_to_globals)
/* Not #defining name to G.name - this quickly gets unwieldy
 * (too many defines). Also, I actually prefer to see when a variable
 * is global, thus "G." prefix is a useful hint */
#define INIT_G() do { \
	SET_PTR_TO_GLOBALS(xzalloc(sizeof(G))); \
	/* memset(&G.sa, 0, sizeof(G.sa)); */  \
	sigfillset(&G.sa.sa_mask); \
	G.sa.sa_flags = SA_RESTART; \
} while (0)


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

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

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


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

#ifndef debug_printf
# define debug_printf(...) (indent(), fdprintf(2, __VA_ARGS__))
#endif

#ifndef debug_printf_parse
# define debug_printf_parse(...) (indent(), fdprintf(2, __VA_ARGS__))
#endif

#ifndef debug_printf_exec
#define debug_printf_exec(...) (indent(), fdprintf(2, __VA_ARGS__))
#endif

#ifndef debug_printf_env
# define debug_printf_env(...) (indent(), fdprintf(2, __VA_ARGS__))
#endif

#ifndef debug_printf_jobs
# define debug_printf_jobs(...) (indent(), fdprintf(2, __VA_ARGS__))
# define DEBUG_JOBS 1
#else
# define DEBUG_JOBS 0
#endif

#ifndef debug_printf_expand
# define debug_printf_expand(...) (indent(), fdprintf(2, __VA_ARGS__))
# define DEBUG_EXPAND 1
#else
# define DEBUG_EXPAND 0
#endif

#ifndef debug_printf_varexp
# define debug_printf_varexp(...) (indent(), fdprintf(2, __VA_ARGS__))
#endif

#ifndef debug_printf_glob
# define debug_printf_glob(...) (indent(), fdprintf(2, __VA_ARGS__))
# define DEBUG_GLOB 1
#else
# define DEBUG_GLOB 0
#endif

#ifndef debug_printf_list
# define debug_printf_list(...) (indent(), fdprintf(2, __VA_ARGS__))
#endif

#ifndef debug_printf_subst
# define debug_printf_subst(...) (indent(), fdprintf(2, __VA_ARGS__))
#endif

#ifndef debug_printf_clean
# define debug_printf_clean(...) (indent(), fdprintf(2, __VA_ARGS__))
# define DEBUG_CLEAN 1
#else
# define DEBUG_CLEAN 0
#endif

#if DEBUG_EXPAND
static void debug_print_strings(const char *prefix, char **vv)
{
	indent();
	fdprintf(2, "%s:\n", prefix);
	while (*vv)
		fdprintf(2, " '%s'\n", *vv++);
}
#else
# define debug_print_strings(prefix, vv) ((void)0)
#endif


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


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

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

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

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

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

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

static void syntax_error_unterm_ch(unsigned lineno, char ch)
{
	char msg[2] = { ch, '\0' };
	syntax_error_unterm_str(lineno, msg);
}

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

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


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


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

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

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

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

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

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


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

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

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

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

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

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

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


/* Basic theory of signal handling in shell
 * ========================================
 * This does not describe what hush does, rather, it is current understanding
 * what it _should_ do. If it doesn't, it's a bug.
 * http://www.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#trap
 *
 * Signals are handled only after each pipe ("cmd | cmd | cmd" thing)
 * is finished or backgrounded. It is the same in interactive and
 * non-interactive shells, and is the same regardless of whether
 * a user trap handler is installed or a shell special one is in effect.
 * ^C or ^Z from keyboard seems to execute "at once" because it usually
 * backgrounds (i.e. stops) or kills all members of currently running
 * pipe.
 *
 * Wait builtin in interruptible by signals for which user trap is set
 * or by SIGINT in interactive shell.
 *
 * Trap handlers will execute even within trap handlers. (right?)
 *
 * User trap handlers are forgotten when subshell ("(cmd)") is entered,
 * except for handlers set to '' (empty string).
 *
 * If job control is off, backgrounded commands ("cmd &")
 * have SIGINT, SIGQUIT set to SIG_IGN.
 *
 * Commands which are run in command substitution ("`cmd`")
 * have SIGTTIN, SIGTTOU, SIGTSTP set to SIG_IGN.
 *
 * Ordinary commands have signals set to SIG_IGN/DFL as inherited
 * by the shell from its parent.
 *
 * Signals which differ from SIG_DFL action
 * (note: child (i.e., [v]forked) shell is not an interactive shell):
 *
 * SIGQUIT: ignore
 * SIGTERM (interactive): ignore
 * SIGHUP (interactive):
 *    send SIGCONT to stopped jobs, send SIGHUP to all jobs and exit
 * SIGTTIN, SIGTTOU, SIGTSTP (if job control is on): ignore
 *    Note that ^Z is handled not by trapping SIGTSTP, but by seeing
 *    that all pipe members are stopped. Try this in bash:
 *    while :; do :; done - ^Z does not background it
 *    (while :; do :; done) - ^Z backgrounds it
 * SIGINT (interactive): wait for last pipe, ignore the rest
 *    of the command line, show prompt. NB: ^C does not send SIGINT
 *    to interactive shell while shell is waiting for a pipe,
 *    since shell is bg'ed (is not in foreground process group).
 *    Example 1: this waits 5 sec, but does not execute ls:
 *    "echo $$; sleep 5; ls -l" + "kill -INT <pid>"
 *    Example 2: this does not wait and does not execute ls:
 *    "echo $$; sleep 5 & wait; ls -l" + "kill -INT <pid>"
 *    Example 3: this does not wait 5 sec, but executes ls:
 *    "sleep 5; ls -l" + press ^C
 *    Example 4: this does not wait and does not execute ls:
 *    "sleep 5 & wait; ls -l" + press ^C
 *
 * (What happens to signals which are IGN on shell start?)
 * (What happens with signal mask on shell start?)
 *
 * Old implementation
 * ==================
 * We use in-kernel pending signal mask to determine which signals were sent.
 * We block all signals which we don't want to take action immediately,
 * i.e. we block all signals which need to have special handling as described
 * above, and all signals which have traps set.
 * After each pipe execution, we extract any pending signals via sigtimedwait()
 * and act on them.
 *
 * unsigned special_sig_mask: a mask of such "special" signals
 * sigset_t blocked_set:  current blocked signal set
 *
 * "trap - SIGxxx":
 *    clear bit in blocked_set unless it is also in special_sig_mask
 * "trap 'cmd' SIGxxx":
 *    set bit in blocked_set (even if 'cmd' is '')
 * after [v]fork, if we plan to be a shell:
 *    unblock signals with special interactive handling
 *    (child shell is not interactive),
 *    unset all traps except '' (note: regardless of child shell's type - {}, (), etc)
 * after [v]fork, if we plan to exec:
 *    POSIX says fork clears pending signal mask in child - no need to clear it.
 *    Restore blocked signal set to one inherited by shell just prior to exec.
 *
 * Note: as a result, we do not use signal handlers much. The only uses
 * are to count SIGCHLDs
 * and to restore tty pgrp on signal-induced exit.
 *
 * Note 2 (compat):
 * Standard says "When a subshell is entered, traps that are not being ignored
 * are set to the default actions". bash interprets it so that traps which
 * are set to '' (ignore) are NOT reset to defaults. We do the same.
 *
 * Problem: the above approach makes it unwieldy to catch signals while
 * we are in read builtin, of while we read commands from stdin:
 * masked signals are not visible!
 *
 * New implementation
 * ==================
 * We record each signal we are interested in by installing signal handler
 * for them - a bit like emulating kernel pending signal mask in userspace.
 * We are interested in: signals which need to have special handling
 * as described above, and all signals which have traps set.
 * Signals are rocorded in pending_set.
 * After each pipe execution, we extract any pending signals
 * and act on them.
 *
 * unsigned special_sig_mask: a mask of shell-special signals.
 * unsigned fatal_sig_mask: a mask of signals on which we restore tty pgrp.
 * char *traps[sig] if trap for sig is set (even if it's '').
 * sigset_t pending_set: set of sigs we received.
 *
 * "trap - SIGxxx":
 *    if sig is in special_sig_mask, set handler back to:
 *        record_pending_signo, or to IGN if it's a tty stop signal
 *    if sig is in fatal_sig_mask, set handler back to sigexit.
 *    else: set handler back to SIG_DFL
 * "trap 'cmd' SIGxxx":
 *    set handler to record_pending_signo.
 * "trap '' SIGxxx":
 *    set handler to SIG_IGN.
 * after [v]fork, if we plan to be a shell:
 *    set signals with special interactive handling to SIG_DFL
 *    (because child shell is not interactive),
 *    unset all traps except '' (note: regardless of child shell's type - {}, (), etc)
 * after [v]fork, if we plan to exec:
 *    POSIX says fork clears pending signal mask in child - no need to clear it.
 *
 * To make wait builtin interruptible, we handle SIGCHLD as special signal,
 * otherwise (if we leave it SIG_DFL) sigsuspend in wait builtin will not wake up on it.
 *
 * Note (compat):
 * Standard says "When a subshell is entered, traps that are not being ignored
 * are set to the default actions". bash interprets it so that traps which
 * are set to '' (ignore) are NOT reset to defaults. We do the same.
 */
enum {
	SPECIAL_INTERACTIVE_SIGS = 0
		| (1 << SIGTERM)
		| (1 << SIGINT)
		| (1 << SIGHUP)
		,
	SPECIAL_JOBSTOP_SIGS = 0
#if ENABLE_HUSH_JOB
		| (1 << SIGTTIN)
		| (1 << SIGTTOU)
		| (1 << SIGTSTP)
#endif
		,
};

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

static sighandler_t install_sighandler(int sig, sighandler_t handler)
{
	struct sigaction old_sa;

	/* We could use signal() to install handlers... almost:
	 * except that we need to mask ALL signals while handlers run.
	 * I saw signal nesting in strace, race window isn't small.
	 * SA_RESTART is also needed, but in Linux, signal()
	 * sets SA_RESTART too.
	 */
	/* memset(&G.sa, 0, sizeof(G.sa)); - already done */
	/* sigfillset(&G.sa.sa_mask);      - already done */
	/* G.sa.sa_flags = SA_RESTART;     - already done */
	G.sa.sa_handler = handler;
	sigaction(sig, &G.sa, &old_sa);
	return old_sa.sa_handler;
}

#if ENABLE_HUSH_JOB

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

/* Restores tty foreground process group, and exits.
 * May be called as signal handler for fatal signal
 * (will resend signal to itself, producing correct exit state)
 * or called directly with -EXITCODE.
 * We also call it if xfunc is exiting. */
static void sigexit(int sig) NORETURN;
static void sigexit(int sig)
{
	/* Careful: we can end up here after [v]fork. Do not restore
	 * tty pgrp then, only top-level shell process does that */
	if (G_saved_tty_pgrp && getpid() == G.root_pid) {
		/* Disable all signals: job control, SIGPIPE, etc.
		 * Mostly paranoid measure, to prevent infinite SIGTTOU.
		 */
		sigprocmask_allsigs(SIG_BLOCK);
		tcsetpgrp(G_interactive_fd, G_saved_tty_pgrp);
	}

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

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

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

#endif

static sighandler_t pick_sighandler(unsigned sig)
{
	sighandler_t handler = SIG_DFL;
	if (sig < sizeof(unsigned)*8) {
		unsigned sigmask = (1 << sig);

#if ENABLE_HUSH_JOB
		/* is sig fatal? */
		if (G_fatal_sig_mask & sigmask)
			handler = sigexit;
		else
#endif
		/* sig has special handling? */
		if (G.special_sig_mask & sigmask) {
			handler = record_pending_signo;
			/* TTIN/TTOU/TSTP can't be set to record_pending_signo
			 * in order to ignore them: they will be raised
			 * in an endless loop when we try to do some
			 * terminal ioctls! We do have to _ignore_ these.
			 */
			if (SPECIAL_JOBSTOP_SIGS & sigmask)
				handler = SIG_IGN;
		}
	}
	return handler;
}

/* Restores tty foreground process group, and exits. */
static void hush_exit(int exitcode) NORETURN;
static void hush_exit(int exitcode)
{
#if ENABLE_FEATURE_EDITING_SAVE_ON_EXIT
	save_history(G.line_input_state);
#endif

	fflush_all();
	if (G.exiting <= 0 && G.traps && G.traps[0] && G.traps[0][0]) {
		char *argv[3];
		/* argv[0] is unused */
		argv[1] = G.traps[0];
		argv[2] = NULL;
		G.exiting = 1; /* prevent EXIT trap recursion */
		/* Note: G.traps[0] is not cleared!
		 * "trap" will still show it, if executed
		 * in the handler */
		builtin_eval(argv);
	}

#if ENABLE_FEATURE_CLEAN_UP
	{
		struct variable *cur_var;
		if (G.cwd != bb_msg_unknown)
			free((char*)G.cwd);
		cur_var = G.top_var;
		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

#if ENABLE_HUSH_JOB
	fflush_all();
	sigexit(- (exitcode & 0xff));
#else
	exit(exitcode);
#endif
}


//TODO: return a mask of ALL handled sigs?
static int check_and_run_traps(void)
{
	int last_sig = 0;

	while (1) {
		int sig;

		if (sigisemptyset(&G.pending_set))
			break;
		sig = 0;
		do {
			sig++;
			if (sigismember(&G.pending_set, sig)) {
				sigdelset(&G.pending_set, sig);
				goto got_sig;
			}
		} while (sig < NSIG);
		break;
 got_sig:
		if (G.traps && G.traps[sig]) {
			if (G.traps[sig][0]) {
				/* We have user-defined handler */
				smalluint save_rcode;
				char *argv[3];
				/* argv[0] is unused */
				argv[1] = G.traps[sig];
				argv[2] = NULL;
				save_rcode = G.last_exitcode;
				builtin_eval(argv);
				G.last_exitcode = save_rcode;
				last_sig = sig;
			} /* else: "" trap, ignoring signal */
			continue;
		}
		/* not a trap: special action */
		switch (sig) {
		case SIGINT:
			/* Builtin was ^C'ed, make it look prettier: */
			bb_putchar('\n');
			G.flag_SIGINT = 1;
			last_sig = sig;
			break;
#if ENABLE_HUSH_JOB
		case SIGHUP: {
			struct pipe *job;
			/* bash is observed to signal whole process groups,
			 * not individual processes */
			for (job = G.job_list; job; job = job->next) {
				if (job->pgrp <= 0)
					continue;
				debug_printf_exec("HUPing pgrp %d\n", job->pgrp);
				if (kill(- job->pgrp, SIGHUP) == 0)
					kill(- job->pgrp, SIGCONT);
			}
			sigexit(SIGHUP);
		}
#endif
#if ENABLE_HUSH_FAST
		case SIGCHLD:
			G.count_SIGCHLD++;
//bb_error_msg("[%d] check_and_run_traps: G.count_SIGCHLD:%d G.handled_SIGCHLD:%d", getpid(), G.count_SIGCHLD, G.handled_SIGCHLD);
			/* Note:
			 * We dont do 'last_sig = sig' here -> NOT returning this sig.
			 * This simplifies wait builtin a bit.
			 */
			break;
#endif
		default: /* ignored: */
			/* SIGTERM, SIGQUIT, SIGTTIN, SIGTTOU, SIGTSTP */
			/* Note:
			 * We dont do 'last_sig = sig' here -> NOT returning this sig.
			 * Example: wait is not interrupted by TERM
			 * in interactive shell, because TERM is ignored.
			 */
			break;
		}
	}
	return last_sig;
}


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


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

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

static const char* FAST_FUNC get_local_var_value(const char *name)
{
	struct variable **vpp;
	unsigned len = strlen(name);

	if (G.expanded_assignments) {
		char **cpp = G.expanded_assignments;
		while (*cpp) {
			char *cp = *cpp;
			if (strncmp(cp, name, len) == 0 && cp[len] == '=')
				return cp + len + 1;
			cpp++;
		}
	}

	vpp = get_ptr_to_local_var(name, len);
	if (vpp)
		return (*vpp)->varstr + len + 1;

	if (strcmp(name, "PPID") == 0)
		return utoa(G.root_ppid);
	// bash compat: UID? EUID?
#if ENABLE_HUSH_RANDOM_SUPPORT
	if (strcmp(name, "RANDOM") == 0)
		return utoa(next_random(&G.random_gen));
#endif
	return NULL;
}

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

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

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

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

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

/* Used at startup and after each cd */
static void set_pwd_var(int exp)
{
	set_local_var(xasprintf("PWD=%s", get_cwd(/*force:*/ 1)),
		/*exp:*/ exp, /*lvl:*/ 0, /*ro:*/ 0);
}

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

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

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

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

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

static void FAST_FUNC set_local_var_from_halves(const char *name, const char *val)
{
	char *var = xasprintf("%s=%s", name, val);
	set_local_var(var, /*flags:*/ 0, /*lvl:*/ 0, /*ro:*/ 0);
}


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

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

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

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

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


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

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

#if ENABLE_HUSH_INTERACTIVE

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

static const char *setup_prompt_string(int promptmode)
{
	const char *prompt_str;
	debug_printf("setup_prompt_string %d ", promptmode);
	if (!ENABLE_FEATURE_EDITING_FANCY_PROMPT) {
		/* Set up the prompt */
		if (promptmode == 0) { /* PS1 */
			free((char*)G.PS1);
			/* bash uses $PWD value, even if it is set by user.
			 * It uses current dir only if PWD is unset.
			 * We always use current dir. */
			G.PS1 = xasprintf("%s %c ", get_cwd(0), (geteuid() != 0) ? '$' : '#');
			prompt_str = G.PS1;
		} else
			prompt_str = G.PS2;
	} else
		prompt_str = (promptmode == 0) ? G.PS1 : G.PS2;
	debug_printf("result '%s'\n", prompt_str);
	return prompt_str;
}

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

	prompt_str = setup_prompt_string(i->promptmode);
# if ENABLE_FEATURE_EDITING
	/* Enable command line editing only while a command line
	 * is actually being read */
	do {
		/* Unicode support should be activated even if LANG is set
		 * _during_ shell execution, not only if it was set when
		 * shell was started. Therefore, re-check LANG every time:
		 */
		reinit_unicode(get_local_var_value("LANG"));

		G.flag_SIGINT = 0;
		/* buglet: SIGINT will not make new prompt to appear _at once_,
		 * only after <Enter>. (^C will work) */
		r = read_line_input(G.line_input_state, prompt_str, G.user_input_buf, CONFIG_FEATURE_EDITING_MAX_LEN-1, /*timeout*/ -1);
		/* catch *SIGINT* etc (^C is handled by read_line_input) */
		check_and_run_traps();
	} while (r == 0 || G.flag_SIGINT); /* repeat if ^C or SIGINT */
	i->eof_flag = (r < 0);
	if (i->eof_flag) { /* EOF/error detected */
		G.user_input_buf[0] = EOF; /* yes, it will be truncated, it's ok */
		G.user_input_buf[1] = '\0';
	}
# else
	do {
		G.flag_SIGINT = 0;
		if (i->last_char == '\0' || i->last_char == '\n') {
			/* Why check_and_run_traps here? Try this interactively:
			 * $ trap 'echo INT' INT; (sleep 2; kill -INT $$) &
			 * $ <[enter], repeatedly...>
			 * Without check_and_run_traps, handler never runs.
			 */
			check_and_run_traps();
			fputs(prompt_str, stdout);
		}
		fflush_all();
		G.user_input_buf[0] = r = fgetc(i->file);
		/*G.user_input_buf[1] = '\0'; - already is and never changed */
	} while (G.flag_SIGINT);
	i->eof_flag = (r == EOF);
# endif
	i->p = G.user_input_buf;
}

#endif  /* INTERACTIVE */

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

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

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

static void setup_file_in_str(struct in_str *i, FILE *f)
{
	memset(i, 0, sizeof(*i));
	i->peek = file_peek;
	i->get = file_get;
	/* i->promptmode = 0; - PS1 (memset did it) */
	i->file = f;
	/* i->p = NULL; */
}

static void setup_string_in_str(struct in_str *i, const char *s)
{
	memset(i, 0, sizeof(*i));
	i->peek = static_peek;
	i->get = static_get;
	/* i->promptmode = 0; - PS1 (memset did it) */
	i->p = s;
	/* i->eof_flag = 0; */
}


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

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

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

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

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

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

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

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

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

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

/*
 * HUSH_BRACE_EXPANSION code needs corresponding quoting on variable expansion side.
 * Currently, "v='{q,w}'; echo $v" erroneously expands braces in $v.
 * Apparently, on unquoted $v bash still does globbing
 * ("v='*.txt'; echo $v" prints all .txt files),
 * but NOT brace expansion! Thus, there should be TWO independent
 * quoting mechanisms on $v expansion side: one protects
 * $v from brace expansion, and other additionally protects "$v" against globbing.
 * We have only second one.
 */

#if ENABLE_HUSH_BRACE_EXPANSION
# define MAYBE_BRACES "{}"
#else
# define MAYBE_BRACES ""
#endif

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

static void o_addQchr(o_string *o, int ch)
{
	int sz = 1;
	if ((o->o_expflags & EXP_FLAG_ESC_GLOB_CHARS)
	 && strchr("*?[\\" MAYBE_BRACES, 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_addqblock(o_string *o, const char *str, int len)
{
	while (len) {
		char ch;
		int sz;
		int ordinary_cnt = strcspn(str, "*?[\\" MAYBE_BRACES);
		if (ordinary_cnt > len) /* paranoia */
			ordinary_cnt = len;
		o_addblock(o, str, ordinary_cnt);
		if (ordinary_cnt == len)
			return; /* NUL is already added by o_addblock */
		str += ordinary_cnt;
		len -= ordinary_cnt + 1; /* we are processing + 1 char below */

		ch = *str++;
		sz = 1;
		if (ch) { /* it is necessarily one of "*?[\\" MAYBE_BRACES */
			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_addQblock(o_string *o, const char *str, int len)
{
	if (!(o->o_expflags & EXP_FLAG_ESC_GLOB_CHARS)) {
		o_addblock(o, str, len);
		return;
	}
	o_addqblock(o, str, len);
}

static void o_addQstr(o_string *o, const char *str)
{
	o_addQblock(o, str, strlen(str));
}

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

	indent();
	fdprintf(2, "%s: list:%p n:%d string_start:%d length:%d maxlen:%d glob:%d quoted:%d escape:%d\n",
			prefix, list, n, string_start, o->length, o->maxlen,
			!!(o->o_expflags & EXP_FLAG_GLOB),
			o->has_quoted_part,
			!!(o->o_expflags & EXP_FLAG_ESC_GLOB_CHARS));
	while (i < n) {
		indent();
		fdprintf(2, " list[%d]=%d '%s' %p\n", i, (int)(uintptr_t)list[i],
				o->data + (int)(uintptr_t)list[i] + string_start,
				o->data + (int)(uintptr_t)list[i] + string_start);
		i++;
	}
	if (n) {
		const char *p = o->data + (int)(uintptr_t)list[n - 1] + string_start;
		indent();
		fdprintf(2, " total_sz:%ld\n", (long)((p + strlen(p) + 1) - o->data));
	}
}
#else
# define debug_print_list(prefix, o, n) ((void)0)
#endif

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

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

#if ENABLE_HUSH_BRACE_EXPANSION
/* There in a GNU extension, GLOB_BRACE, but it is not usable:
 * first, it processes even {a} (no commas), second,
 * I didn't manage to make it return strings when they don't match
 * existing files. Need to re-implement it.
 */

/* Helper */
static int glob_needed(const char *s)
{
	while (*s) {
		if (*s == '\\') {
			if (!s[1])
				return 0;
			s += 2;
			continue;
		}
		if (*s == '*' || *s == '[' || *s == '?' || *s == '{')
			return 1;
		s++;
	}
	return 0;
}
/* Return pointer to next closing brace or to comma */
static const char *next_brace_sub(const char *cp)
{
	unsigned depth = 0;
	cp++;
	while (*cp != '\0') {
		if (*cp == '\\') {
			if (*++cp == '\0')
				break;
			cp++;
			continue;
		}
		if ((*cp == '}' && depth-- == 0) || (*cp == ',' && depth == 0))
			break;
		if (*cp++ == '{')
			depth++;
	}

	return *cp != '\0' ? cp : NULL;
}
/* Recursive brace globber. Note: may garble pattern[]. */
static int glob_brace(char *pattern, o_string *o, int n)
{
	char *new_pattern_buf;
	const char *begin;
	const char *next;
	const char *rest;
	const char *p;
	size_t rest_len;

	debug_printf_glob("glob_brace('%s')\n", pattern);

	begin = pattern;
	while (1) {
		if (*begin == '\0')
			goto simple_glob;
		if (*begin == '{') {
			/* Find the first sub-pattern and at the same time
			 * find the rest after the closing brace */
			next = next_brace_sub(begin);
			if (next == NULL) {
				/* An illegal expression */
				goto simple_glob;
			}
			if (*next == '}') {
				/* "{abc}" with no commas - illegal
				 * brace expr, disregard and skip it */
				begin = next + 1;
				continue;
			}
			break;
		}
		if (*begin == '\\' && begin[1] != '\0')
			begin++;
		begin++;
	}
	debug_printf_glob("begin:%s\n", begin);
	debug_printf_glob("next:%s\n", next);

	/* Now find the end of the whole brace expression */
	rest = next;
	while (*rest != '}') {
		rest = next_brace_sub(rest);
		if (rest == NULL) {
			/* An illegal expression */
			goto simple_glob;
		}
		debug_printf_glob("rest:%s\n", rest);
	}
	rest_len = strlen(++rest) + 1;

	/* We are sure the brace expression is well-formed */

	/* Allocate working buffer large enough for our work */
	new_pattern_buf = xmalloc(strlen(pattern));

	/* We have a brace expression.  BEGIN points to the opening {,
	 * NEXT points past the terminator of the first element, and REST
	 * points past the final }.  We will accumulate result names from
	 * recursive runs for each brace alternative in the buffer using
	 * GLOB_APPEND.  */

	p = begin + 1;
	while (1) {
		/* Construct the new glob expression */
		memcpy(
			mempcpy(
				mempcpy(new_pattern_buf,
					/* We know the prefix for all sub-patterns */
					pattern, begin - pattern),
				p, next - p),
			rest, rest_len);

		/* Note: glob_brace() may garble new_pattern_buf[].
		 * That's why we re-copy prefix every time (1st memcpy above).
		 */
		n = glob_brace(new_pattern_buf, o, n);
		if (*next == '}') {
			/* We saw the last entry */
			break;
		}
		p = next + 1;
		next = next_brace_sub(next);
	}
	free(new_pattern_buf);
	return n;

 simple_glob:
	{
		int gr;
		glob_t globdata;

		memset(&globdata, 0, sizeof(globdata));
		gr = glob(pattern, 0, NULL, &globdata);
		debug_printf_glob("glob('%s'):%d\n", pattern, gr);
		if (gr != 0) {
			if (gr == GLOB_NOMATCH) {
				globfree(&globdata);
				/* NB: garbles parameter */
				unbackslash(pattern);
				o_addstr_with_NUL(o, pattern);
				debug_printf_glob("glob pattern '%s' is literal\n", pattern);
				return o_save_ptr_helper(o, n);
			}
			if (gr == GLOB_NOSPACE)
				bb_error_msg_and_die(bb_msg_memory_exhausted);
			/* GLOB_ABORTED? Only happens with GLOB_ERR flag,
			 * but we didn't specify it. Paranoia again. */
			bb_error_msg_and_die("glob error %d on '%s'", gr, pattern);
		}
		if (globdata.gl_pathv && globdata.gl_pathv[0]) {
			char **argv = globdata.gl_pathv;
			while (1) {
				o_addstr_with_NUL(o, *argv);
				n = o_save_ptr_helper(o, n);
				argv++;
				if (!*argv)
					break;
			}
		}
		globfree(&globdata);
	}
	return n;
}
/* Performs globbing on last list[],
 * saving each result as a new list[].
 */
static int perform_glob(o_string *o, int n)
{
	char *pattern, *copy;

	debug_printf_glob("start perform_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)) {
		/* unbackslash last string in o in place, fix length */
		o->length = unbackslash(pattern) - o->data;
		debug_printf_glob("glob pattern '%s' is literal\n", pattern);
		return o_save_ptr_helper(o, n);
	}

	copy = xstrdup(pattern);
	/* "forget" pattern in o */
	o->length = pattern - o->data;
	n = glob_brace(copy, o, n);
	free(copy);
	if (DEBUG_GLOB)
		debug_print_list("perform_glob returning", o, n);
	return n;
}

#else /* !HUSH_BRACE_EXPANSION */

/* Helper */
static int glob_needed(const char *s)
{
	while (*s) {
		if (*s == '\\') {
			if (!s[1])
				return 0;
			s += 2;
			continue;
		}
		if (*s == '*' || *s == '[' || *s == '?')
			return 1;
		s++;
	}
	return 0;
}
/* Performs globbing on last list[],
 * saving each result as a new list[].
 */
static int perform_glob(o_string *o, int n)
{
	glob_t globdata;
	int gr;
	char *pattern;

	debug_printf_glob("start perform_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:
		/* unbackslash last string in o in place, fix length */
		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));
	/* Can't use GLOB_NOCHECK: it does not unescape the string.
	 * If we glob "*.\*" and don't find anything, we need
	 * to fall back to using literal "*.*", but GLOB_NOCHECK
	 * will return "*.\*"!
	 */
	gr = glob(pattern, 0, NULL, &globdata);
	debug_printf_glob("glob('%s'):%d\n", pattern, gr);
	if (gr != 0) {
		if (gr == GLOB_NOMATCH) {
			globfree(&globdata);
			goto literal;
		}
		if (gr == GLOB_NOSPACE)
			bb_error_msg_and_die(bb_msg_memory_exhausted);
		/* GLOB_ABORTED? Only happens with GLOB_ERR flag,
		 * but we didn't specify it. Paranoia again. */
		bb_error_msg_and_die("glob error %d on '%s'", gr, pattern);
	}
	if (globdata.gl_pathv && globdata.gl_pathv[0]) {
		char **argv = globdata.gl_pathv;
		/* "forget" pattern in o */
		o->length = pattern - o->data;
		while (1) {
			o_addstr_with_NUL(o, *argv);
			n = o_save_ptr_helper(o, n);
			argv++;
			if (!*argv)
				break;
		}
	}
	globfree(&globdata);
	if (DEBUG_GLOB)
		debug_print_list("perform_glob returning", o, n);
	return n;
}

#endif /* !HUSH_BRACE_EXPANSION */

/* If o->o_expflags & EXP_FLAG_GLOB, 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_expflags & EXP_FLAG_GLOB) {
		/* If o->has_empty_slot, list[n] was already globbed
		 * (if it was requested back then when it was filled)
		 * so don't do that again! */
		if (!o->has_empty_slot)
			return perform_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)(uintptr_t)list[n] + string_start;
	}
	return list;
}

static void free_pipe_list(struct pipe *pi);

/* Returns pi->next - next pipe in the list */
static struct pipe *free_pipe(struct pipe *pi)
{
	struct pipe *next;
	int i;

	debug_printf_clean("free_pipe (pid %d)\n", getpid());
	for (i = 0; i < pi->num_cmds; i++) {
		struct command *command;
		struct redir_struct *r, *rnext;

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

	next = pi->next;
	free(pi);
	return next;
}

static void free_pipe_list(struct pipe *pi)
{
	while (pi) {
#if HAS_KEYWORDS
		debug_printf_clean("pipe reserved word %d\n", pi->res_word);
#endif
		debug_printf_clean("pipe followup code %d\n", pi->followup);
		pi = free_pipe(pi);
	}
}


/*** Parsing routines ***/

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

	int pin, prn;

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

			fdprintf(2, "%*s cmd %d assignment_cnt:%d",
					lvl*2, "", prn,
					command->assignment_cnt);
			if (command->group) {
				fdprintf(2, " group %s: (argv=%p)%s%s\n",
						CMDTYPE[command->cmd_type],
						argv
# if !BB_MMU
						, " group_as_string:", command->group_as_string
# else
						, "", ""
# endif
				);
				debug_print_tree(command->group, lvl+1);
				prn++;
				continue;
			}
			if (argv) while (*argv) {
				fdprintf(2, " '%s'", *argv);
				argv++;
			}
			fdprintf(2, "\n");
			prn++;
		}
		pi = pi->next;
		pin++;
	}
}
#endif /* debug_print_tree */

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

/* Command (member of a pipe) is complete, or we start a new pipe
 * if ctx->command is NULL.
 * No errors possible here.
 */
static int done_command(struct parse_context *ctx)
{
	/* The command is really already in the pipe structure, so
	 * advance the pipe counter and make a new, null command. */
	struct pipe *pi = ctx->pipe;
	struct command *command = ctx->command;

	if (command) {
		if (IS_NULL_CMD(command)) {
			debug_printf_parse("done_command: skipping null cmd, num_cmds=%d\n", pi->num_cmds);
			goto clear_and_ret;
		}
		pi->num_cmds++;
		debug_printf_parse("done_command: ++num_cmds=%d\n", pi->num_cmds);
		//debug_print_tree(ctx->list_head, 20);
	} else {
		debug_printf_parse("done_command: initializing, num_cmds=%d\n", pi->num_cmds);
	}

	/* Only real trickiness here is that the uncommitted
	 * command structure is not counted in pi->num_cmds. */
	pi->cmds = xrealloc(pi->cmds, sizeof(*pi->cmds) * (pi->num_cmds+1));
	ctx->command = command = &pi->cmds[pi->num_cmds];
 clear_and_ret:
	memset(command, 0, sizeof(*command));
	return pi->num_cmds; /* used only for 0/nonzero check */
}

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

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

	/* 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. */
	if (not_null
#if ENABLE_HUSH_IF
	 || ctx->ctx_res_w == RES_FI
#endif
#if ENABLE_HUSH_LOOPS
	 || ctx->ctx_res_w == RES_DONE
	 || ctx->ctx_res_w == RES_FOR
	 || ctx->ctx_res_w == RES_IN
#endif
#if ENABLE_HUSH_CASE
	 || ctx->ctx_res_w == RES_ESAC
#endif
	) {
		struct pipe *new_p;
		debug_printf_parse("done_pipe: adding new pipe: "
				"not_null:%d ctx->ctx_res_w:%d\n",
				not_null, ctx->ctx_res_w);
		new_p = new_pipe();
		ctx->pipe->next = new_p;
		ctx->pipe = new_p;
		/* RES_THEN, RES_DO etc are "sticky" -
		 * they remain set for pipes 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_CASE_BODY;
		if (ctx->ctx_res_w == RES_CASE)
			ctx->ctx_res_w = RES_CASE_IN;
#endif
		ctx->command = NULL; /* trick done_command below */
		/* Create the memory for command, roughly:
		 * ctx->pipe->cmds = new struct command;
		 * ctx->command = &ctx->pipe->cmds[0];
		 */
		done_command(ctx);
		//debug_print_tree(ctx->list_head, 10);
	}
	debug_printf_parse("done_pipe return\n");
}

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

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

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

	for (r = reserved_list; r < reserved_list + ARRAY_SIZE(reserved_list); r++) {
		if (strcmp(word->data, r->literal) == 0)
			return r;
	}
	return NULL;
}
/* Return 0: not a keyword, 1: keyword
 */
static int reserved_word(o_string *word, struct parse_context *ctx)
{
# if ENABLE_HUSH_CASE
	static const struct reserved_combo reserved_match = {
		"",        RES_MATCH, NOT_ASSIGNMENT , FLAG_MATCH | FLAG_ESAC
	};
# endif
	const struct reserved_combo *r;

	if (word->has_quoted_part)
		return 0;
	r = match_reserved_word(word);
	if (!r)
		return 0;

	debug_printf("found reserved word %s, res %d\n", r->literal, r->res);
# if ENABLE_HUSH_CASE
	if (r->res == RES_IN && ctx->ctx_res_w == RES_CASE_IN) {
		/* "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_error("! ! command");
			ctx->ctx_res_w = RES_SNTX;
		}
		ctx->ctx_inverted = 1;
		return 1;
	}
	if (r->flag & FLAG_START) {
		struct parse_context *old;

		old = xmalloc(sizeof(*old));
		debug_printf_parse("push stack %p\n", old);
		*old = *ctx;   /* physical copy */
		initialize_context(ctx);
		ctx->stack = old;
	} else if (/*ctx->ctx_res_w == RES_NONE ||*/ !(ctx->old_flag & (1 << r->res))) {
		syntax_error_at(word->data);
		ctx->ctx_res_w = RES_SNTX;
		return 1;
	} else {
		/* "{...} fi" is ok. "{...} if" is not
		 * Example:
		 * if { echo foo; } then { echo bar; } fi */
		if (ctx->command->group)
			done_pipe(ctx, PIPE_SEQ);
	}

	ctx->ctx_res_w = r->res;
	ctx->old_flag = r->flag;
	word->o_assignment = r->assignment_flag;
	debug_printf_parse("word->o_assignment='%s'\n", assignment_flag[word->o_assignment]);

	if (ctx->old_flag & FLAG_END) {
		struct parse_context *old;

		done_pipe(ctx, PIPE_SEQ);
		debug_printf_parse("pop stack %p\n", ctx->stack);
		old = ctx->stack;
		old->command->group = ctx->list_head;
		old->command->cmd_type = CMD_NORMAL;
# if !BB_MMU
		o_addstr(&old->as_string, ctx->as_string.data);
		o_free_unsafe(&ctx->as_string);
		old->command->group_as_string = xstrdup(old->as_string.data);
		debug_printf_parse("pop, remembering as:'%s'\n",
				old->command->group_as_string);
# endif
		*ctx = *old;   /* physical copy */
		free(old);
	}
	return 1;
}
#endif /* HAS_KEYWORDS */

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

	debug_printf_parse("done_word entered: '%s' %p\n", word->data, command);
	if (word->length == 0 && !word->has_quoted_part) {
		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" */
		/* http://www.opengroup.org/onlinepubs/009695399/utilities/xcu_chap02.html
		 * "2.7 Redirection
		 * ...the word that follows the redirection operator
		 * shall be subjected to tilde expansion, parameter expansion,
		 * command substitution, arithmetic expansion, and quote
		 * removal. Pathname expansion shall not be performed
		 * on the word by a non-interactive shell; an interactive
		 * shell may perform it, but shall do so only when
		 * the expansion would result in one word."
		 */
		ctx->pending_redirect->rd_filename = xstrdup(word->data);
		/* Cater for >\file case:
		 * >\a creates file a; >\\a, >"\a", >"\\a" create file \a
		 * Same with heredocs:
		 * for <<\H delim is H; <<\\H, <<"\H", <<"\\H" - \H
		 */
		if (ctx->pending_redirect->rd_type == REDIRECT_HEREDOC) {
			unbackslash(ctx->pending_redirect->rd_filename);
			/* Is it <<"HEREDOC"? */
			if (word->has_quoted_part) {
				ctx->pending_redirect->rd_dup |= HEREDOC_QUOTED;
			}
		}
		debug_printf_parse("word stored in rd_filename: '%s'\n", word->data);
		ctx->pending_redirect = NULL;
	} else {
#if HAS_KEYWORDS
# if ENABLE_HUSH_CASE
		if (ctx->ctx_dsemicolon
		 && strcmp(word->data, "esac") != 0 /* not "... pattern) cmd;; esac" */
		) {
			/* already done when ctx_dsemicolon was set to 1: */
			/* ctx->ctx_res_w = RES_MATCH; */
			ctx->ctx_dsemicolon = 0;
		} else
# endif
		if (!command->argv /* if it's the first word... */
# if ENABLE_HUSH_LOOPS
		 && ctx->ctx_res_w != RES_FOR /* ...not after FOR or IN */
		 && ctx->ctx_res_w != RES_IN
# endif
# if ENABLE_HUSH_CASE
		 && ctx->ctx_res_w != RES_CASE
# endif
		) {
			int reserved = reserved_word(word, ctx);
			debug_printf_parse("checking for reserved-ness: %d\n", reserved);
			if (reserved) {
				o_reset_to_empty_unquoted(word);
				debug_printf_parse("done_word return %d\n",
						(ctx->ctx_res_w == RES_SNTX));
				return (ctx->ctx_res_w == RES_SNTX);
			}
# if ENABLE_HUSH_BASH_COMPAT
			if (strcmp(word->data, "[[") == 0) {
				command->cmd_type = CMD_SINGLEWORD_NOGLOB;
			}
			/* fall through */
# endif
		}
#endif
		if (command->group) {
			/* "{ echo foo; } echo bar" - bad */
			syntax_error_at(word->data);
			debug_printf_parse("d