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eval.c revision 1.2.6.1
      1 /*	$NetBSD: eval.c,v 1.2.6.1 1999/12/27 18:27:02 wrstuden Exp $	*/
      2 
      3 /*
      4  * Expansion - quoting, separation, substitution, globbing
      5  */
      6 
      7 #include "sh.h"
      8 #include <pwd.h>
      9 #include "ksh_dir.h"
     10 #include "ksh_stat.h"
     11 
     12 /*
     13  * string expansion
     14  *
     15  * first pass: quoting, IFS separation, ~, ${}, $() and $(()) substitution.
     16  * second pass: alternation ({,}), filename expansion (*?[]).
     17  */
     18 
     19 /* expansion generator state */
     20 typedef struct Expand {
     21 	/* int  type; */	/* see expand() */
     22 	const char *str;	/* string */
     23 	union {
     24 		const char **strv;/* string[] */
     25 		struct shf *shf;/* file */
     26 	} u;			/* source */
     27 	struct tbl *var;	/* variable in ${var..} */
     28 	short	split;		/* split "$@" / call waitlast $() */
     29 } Expand;
     30 
     31 #define	XBASE		0	/* scanning original */
     32 #define	XSUB		1	/* expanding ${} string */
     33 #define	XARGSEP		2	/* ifs0 between "$*" */
     34 #define	XARG		3	/* expanding $*, $@ */
     35 #define	XCOM		4	/* expanding $() */
     36 #define XNULLSUB	5	/* "$@" when $# is 0 (don't generate word) */
     37 
     38 /* States used for field splitting */
     39 #define IFS_WORD	0	/* word has chars (or quotes) */
     40 #define IFS_WS		1	/* have seen IFS white-space */
     41 #define IFS_NWS		2	/* have seen IFS non-white-space */
     42 
     43 static	int	varsub ARGS((Expand *xp, char *sp, char *word, int *stypep, int *slenp));
     44 static	int	comsub ARGS((Expand *xp, char *cp));
     45 static	char   *trimsub ARGS((char *str, char *pat, int how));
     46 static	void	glob ARGS((char *cp, XPtrV *wp, int markdirs));
     47 static	void	globit ARGS((XString *xs, char **xpp, char *sp, XPtrV *wp,
     48 			     int check));
     49 static char	*maybe_expand_tilde ARGS((char *p, XString *dsp, char **dpp,
     50 					  int isassign));
     51 static	char   *tilde ARGS((char *acp));
     52 static	char   *homedir ARGS((char *name));
     53 #ifdef BRACE_EXPAND
     54 static void	alt_expand ARGS((XPtrV *wp, char *start, char *exp_start,
     55 				 char *end, int fdo));
     56 #endif
     57 
     58 /* compile and expand word */
     59 char *
     60 substitute(cp, f)
     61 	const char *cp;
     62 	int f;
     63 {
     64 	struct source *s, *sold;
     65 
     66 	sold = source;
     67 	s = pushs(SWSTR, ATEMP);
     68 	s->start = s->str = cp;
     69 	source = s;
     70 	if (yylex(ONEWORD) != LWORD)
     71 		internal_errorf(1, "substitute");
     72 	source = sold;
     73 	afree(s, ATEMP);
     74 	return evalstr(yylval.cp, f);
     75 }
     76 
     77 /*
     78  * expand arg-list
     79  */
     80 char **
     81 eval(ap, f)
     82 	register char **ap;
     83 	int f;
     84 {
     85 	XPtrV w;
     86 
     87 	if (*ap == NULL)
     88 		return ap;
     89 	XPinit(w, 32);
     90 	XPput(w, NULL);		/* space for shell name */
     91 #ifdef	SHARPBANG
     92 	XPput(w, NULL);		/* and space for one arg */
     93 #endif
     94 	while (*ap != NULL)
     95 		expand(*ap++, &w, f);
     96 	XPput(w, NULL);
     97 #ifdef	SHARPBANG
     98 	return (char **) XPclose(w) + 2;
     99 #else
    100 	return (char **) XPclose(w) + 1;
    101 #endif
    102 }
    103 
    104 /*
    105  * expand string
    106  */
    107 char *
    108 evalstr(cp, f)
    109 	char *cp;
    110 	int f;
    111 {
    112 	XPtrV w;
    113 
    114 	XPinit(w, 1);
    115 	expand(cp, &w, f);
    116 	cp = (XPsize(w) == 0) ? null : (char*) *XPptrv(w);
    117 	XPfree(w);
    118 	return cp;
    119 }
    120 
    121 /*
    122  * expand string - return only one component
    123  * used from iosetup to expand redirection files
    124  */
    125 char *
    126 evalonestr(cp, f)
    127 	register char *cp;
    128 	int f;
    129 {
    130 	XPtrV w;
    131 
    132 	XPinit(w, 1);
    133 	expand(cp, &w, f);
    134 	switch (XPsize(w)) {
    135 	case 0:
    136 		cp = null;
    137 		break;
    138 	case 1:
    139 		cp = (char*) *XPptrv(w);
    140 		break;
    141 	default:
    142 		cp = evalstr(cp, f&~DOGLOB);
    143 		break;
    144 	}
    145 	XPfree(w);
    146 	return cp;
    147 }
    148 
    149 /* for nested substitution: ${var:=$var2} */
    150 typedef struct SubType {
    151 	short	stype;		/* [=+-?%#] action after expanded word */
    152 	short	base;		/* begin position of expanded word */
    153 	short	f;		/* saved value of f (DOPAT, etc) */
    154 	struct tbl *var;	/* variable for ${var..} */
    155 	short	quote;		/* saved value of quote (for ${..[%#]..}) */
    156 	struct SubType *prev;	/* old type */
    157 	struct SubType *next;	/* poped type (to avoid re-allocating) */
    158 } SubType;
    159 
    160 void
    161 expand(cp, wp, f)
    162 	char *cp;		/* input word */
    163 	register XPtrV *wp;	/* output words */
    164 	int f;			/* DO* flags */
    165 {
    166 	register int UNINITIALIZED(c);
    167 	register int type;	/* expansion type */
    168 	register int quote = 0;	/* quoted */
    169 	XString ds;		/* destination string */
    170 	register char *dp, *sp;	/* dest., source */
    171 	int fdo, word;		/* second pass flags; have word */
    172 	int doblank;		/* field spliting of parameter/command subst */
    173 	Expand x;		/* expansion variables */
    174 	SubType st_head, *st;
    175 	int UNINITIALIZED(newlines); /* For trailing newlines in COMSUB */
    176 	int saw_eq, tilde_ok;
    177 	int make_magic;
    178 
    179 	if (cp == NULL)
    180 		internal_errorf(1, "expand(NULL)");
    181 	/* for alias, readonly, set, typeset commands */
    182 	if ((f & DOVACHECK) && is_wdvarassign(cp)) {
    183 		f &= ~(DOVACHECK|DOBLANK|DOGLOB|DOTILDE);
    184 		f |= DOASNTILDE;
    185 	}
    186 	if (Flag(FNOGLOB))
    187 		f &= ~DOGLOB;
    188 	if (Flag(FMARKDIRS))
    189 		f |= DOMARKDIRS;
    190 #ifdef BRACE_EXPAND
    191 	if (Flag(FBRACEEXPAND) && (f & DOGLOB))
    192 		f |= DOBRACE_;
    193 #endif /* BRACE_EXPAND */
    194 
    195 	Xinit(ds, dp, 128, ATEMP);	/* init dest. string */
    196 	type = XBASE;
    197 	sp = cp;
    198 	fdo = 0;
    199 	saw_eq = 0;
    200 	tilde_ok = (f & (DOTILDE|DOASNTILDE)) ? 1 : 0; /* must be 1/0 */
    201 	doblank = 0;
    202 	make_magic = 0;
    203 	word = (f&DOBLANK) ? IFS_WS : IFS_WORD;
    204 	st_head.next = (SubType *) 0;
    205 	st = &st_head;
    206 
    207 	while (1) {
    208 		Xcheck(ds, dp);
    209 
    210 		switch (type) {
    211 		  case XBASE:	/* original prefixed string */
    212 			c = *sp++;
    213 			switch (c) {
    214 			  case EOS:
    215 				c = 0;
    216 				break;
    217 			  case CHAR:
    218 				c = *sp++;
    219 				break;
    220 			  case QCHAR:
    221 				quote |= 2; /* temporary quote */
    222 				c = *sp++;
    223 				break;
    224 			  case OQUOTE:
    225 				word = IFS_WORD;
    226 				tilde_ok = 0;
    227 				quote = 1;
    228 				continue;
    229 			  case CQUOTE:
    230 				quote = 0;
    231 				continue;
    232 			  case COMSUB:
    233 				tilde_ok = 0;
    234 				if (f & DONTRUNCOMMAND) {
    235 					word = IFS_WORD;
    236 					*dp++ = '$'; *dp++ = '(';
    237 					while (*sp != '\0') {
    238 						Xcheck(ds, dp);
    239 						*dp++ = *sp++;
    240 					}
    241 					*dp++ = ')';
    242 				} else {
    243 					type = comsub(&x, sp);
    244 					if (type == XCOM && (f&DOBLANK))
    245 						doblank++;
    246 					sp = strchr(sp, 0) + 1;
    247 					newlines = 0;
    248 				}
    249 				continue;
    250 			  case EXPRSUB:
    251 				word = IFS_WORD;
    252 				tilde_ok = 0;
    253 				if (f & DONTRUNCOMMAND) {
    254 					*dp++ = '$'; *dp++ = '('; *dp++ = '(';
    255 					while (*sp != '\0') {
    256 						Xcheck(ds, dp);
    257 						*dp++ = *sp++;
    258 					}
    259 					*dp++ = ')'; *dp++ = ')';
    260 				} else {
    261 					struct tbl v;
    262 					char *p;
    263 
    264 					v.flag = DEFINED|ISSET|INTEGER;
    265 					v.type = 10; /* not default */
    266 					v.name[0] = '\0';
    267 					v_evaluate(&v, substitute(sp, 0),
    268 						KSH_UNWIND_ERROR);
    269 					sp = strchr(sp, 0) + 1;
    270 					for (p = str_val(&v); *p; ) {
    271 						Xcheck(ds, dp);
    272 						*dp++ = *p++;
    273 					}
    274 				}
    275 				continue;
    276 			  case OSUBST: /* ${{#}var{:}[=+-?#%]word} */
    277 			  /* format is:
    278 			   *   OSUBST [{x] plain-variable-part \0
    279 			   *     compiled-word-part CSUBST [}x]
    280 			   * This is were all syntax checking gets done...
    281 			   */
    282 			  {
    283 				char *varname = ++sp; /* skip the { or x (}) */
    284 				int stype;
    285 				int slen;
    286 
    287 				sp = strchr(sp, '\0') + 1; /* skip variable */
    288 				type = varsub(&x, varname, sp, &stype, &slen);
    289 				if (type < 0) {
    290 					char endc;
    291 					char *str, *end;
    292 
    293 					end = (char *) wdscan(sp, CSUBST);
    294 					/* ({) the } or x is already skipped */
    295 					endc = *end;
    296 					*end = EOS;
    297 					str = snptreef((char *) 0, 64, "%S",
    298 							varname - 1);
    299 					*end = endc;
    300 					errorf("%s: bad substitution", str);
    301 				}
    302 				if (f&DOBLANK)
    303 					doblank++;
    304 				tilde_ok = 0;
    305 				if (type == XBASE) {	/* expand? */
    306 					if (!st->next) {
    307 						SubType *newst;
    308 
    309 						newst = (SubType *) alloc(
    310 							sizeof(SubType), ATEMP);
    311 						newst->next = (SubType *) 0;
    312 						newst->prev = st;
    313 						st->next = newst;
    314 					}
    315 					st = st->next;
    316 					st->stype = stype;
    317 					st->base = Xsavepos(ds, dp);
    318 					st->f = f;
    319 					st->var = x.var;
    320 					st->quote = quote;
    321 					/* skip qualifier(s) */
    322 					if (stype)
    323 						sp += slen;
    324 					switch (stype & 0x7f) {
    325 					  case '#':
    326 					  case '%':
    327 						/* ! DOBLANK,DOBRACE_,DOTILDE */
    328 						f = DOPAT | (f&DONTRUNCOMMAND)
    329 						    | DOTEMP_;
    330 						quote = 0;
    331 						/* Prepend open pattern (so |
    332 						 * in a trim will work as
    333 						 * expected)
    334 						 */
    335 						*dp++ = MAGIC;
    336 						*dp++ = '@' + 0x80;
    337 						break;
    338 					  case '=':
    339 						/* Enabling tilde expansion
    340 						 * after :'s here is
    341 						 * non-standard ksh, but is
    342 						 * consistent with rules for
    343 						 * other assignments.  Not
    344 						 * sure what POSIX thinks of
    345 						 * this.
    346 						 * Not doing tilde expansion
    347 						 * for integer variables is a
    348 						 * non-POSIX thing - makes
    349 						 * sense though, since ~ is
    350 						 * a arithmetic operator.
    351 						 */
    352 						if (!(x.var->flag & INTEGER))
    353 							f |= DOASNTILDE|DOTILDE;
    354 						f |= DOTEMP_;
    355 						/* These will be done after the
    356 						 * value has been assigned.
    357 						 */
    358 						f &= ~(DOBLANK|DOGLOB|DOBRACE_);
    359 						tilde_ok = 1;
    360 						break;
    361 					  case '?':
    362 						f &= ~DOBLANK;
    363 						f |= DOTEMP_;
    364 						/* fall through */
    365 					  default:
    366 						/* Enable tilde expansion */
    367 						tilde_ok = 1;
    368 						f |= DOTILDE;
    369 					}
    370 				} else
    371 					/* skip word */
    372 					sp = (char *) wdscan(sp, CSUBST);
    373 				continue;
    374 			  }
    375 			  case CSUBST: /* only get here if expanding word */
    376 				sp++; /* ({) skip the } or x */
    377 				tilde_ok = 0;	/* in case of ${unset:-} */
    378 				*dp = '\0';
    379 				quote = st->quote;
    380 				f = st->f;
    381 				if (f&DOBLANK)
    382 					doblank--;
    383 				switch (st->stype&0x7f) {
    384 				  case '#':
    385 				  case '%':
    386 					/* Append end-pattern */
    387 					*dp++ = MAGIC; *dp++ = ')'; *dp = '\0';
    388 					dp = Xrestpos(ds, dp, st->base);
    389 					/* Must use st->var since calling
    390 					 * global would break things
    391 					 * like x[i+=1].
    392 					 */
    393 					x.str = trimsub(str_val(st->var),
    394 						dp, st->stype);
    395 					type = XSUB;
    396 					if (f&DOBLANK)
    397 						doblank++;
    398 					st = st->prev;
    399 					continue;
    400 				  case '=':
    401 					/* Restore our position and substitute
    402 					 * the value of st->var (may not be
    403 					 * the assigned value in the presence
    404 					 * of integer/right-adj/etc attributes).
    405 					 */
    406 					dp = Xrestpos(ds, dp, st->base);
    407 					/* Must use st->var since calling
    408 					 * global would cause with things
    409 					 * like x[i+=1] to be evaluated twice.
    410 					 */
    411 					/* Note: not exported by FEXPORT
    412 					 * in at&t ksh.
    413 					 */
    414 					/* XXX POSIX says readonly is only
    415 					 * fatal for special builtins (setstr
    416 					 * does readonly check).
    417 					 */
    418 					setstr(st->var, debunk(
    419 						(char *) alloc(strlen(dp) + 1,
    420 							ATEMP), dp),
    421 						KSH_UNWIND_ERROR);
    422 					x.str = str_val(st->var);
    423 					type = XSUB;
    424 					if (f&DOBLANK)
    425 						doblank++;
    426 					st = st->prev;
    427 					continue;
    428 				  case '?':
    429 				    {
    430 					char *s = Xrestpos(ds, dp, st->base);
    431 
    432 					errorf("%s: %s", st->var->name,
    433 					    dp == s ?
    434 					      "parameter null or not set"
    435 					    : (debunk(s, s), s));
    436 				    }
    437 				}
    438 				st = st->prev;
    439 				type = XBASE;
    440 				continue;
    441 
    442 			  case OPAT: /* open pattern: *(foo|bar) */
    443 				/* Next char is the type of pattern */
    444 				make_magic = 1;
    445 				c = *sp++ + 0x80;
    446 				break;
    447 
    448 			  case SPAT: /* pattern seperator (|) */
    449 				make_magic = 1;
    450 				c = '|';
    451 				break;
    452 
    453 			  case CPAT: /* close pattern */
    454 				make_magic = 1;
    455 				c = /*(*/ ')';
    456 				break;
    457 			}
    458 			break;
    459 
    460 		  case XNULLSUB:
    461 			/* Special case for "$@" (and "${foo[@]}") - no
    462 			 * word is generated if $# is 0 (unless there is
    463 			 * other stuff inside the quotes).
    464 			 */
    465 			type = XBASE;
    466 			if (f&DOBLANK) {
    467 				doblank--;
    468 				/* not really correct: x=; "$x$@" should
    469 				 * generate a null argument and
    470 				 * set A; "${@:+}" shouldn't.
    471 				 */
    472 				if (dp == Xstring(ds, dp))
    473 					word = IFS_WS;
    474 			}
    475 			continue;
    476 
    477 		  case XSUB:
    478 			if ((c = *x.str++) == 0) {
    479 				type = XBASE;
    480 				if (f&DOBLANK)
    481 					doblank--;
    482 				continue;
    483 			}
    484 			break;
    485 
    486 		  case XARGSEP:
    487 			type = XARG;
    488 			quote = 1;
    489 		  case XARG:
    490 			if ((c = *x.str++) == '\0') {
    491 				/* force null words to be created so
    492 				 * set -- '' 2 ''; foo "$@" will do
    493 				 * the right thing
    494 				 */
    495 				if (quote && x.split)
    496 					word = IFS_WORD;
    497 				if ((x.str = *x.u.strv++) == NULL) {
    498 					type = XBASE;
    499 					if (f&DOBLANK)
    500 						doblank--;
    501 					continue;
    502 				}
    503 				c = ifs0;
    504 				if (c == 0) {
    505 					if (quote && !x.split)
    506 						continue;
    507 					c = ' ';
    508 				}
    509 				if (quote && x.split) {
    510 					/* terminate word for "$@" */
    511 					type = XARGSEP;
    512 					quote = 0;
    513 				}
    514 			}
    515 			break;
    516 
    517 		  case XCOM:
    518 			if (newlines) {		/* Spit out saved nl's */
    519 				c = '\n';
    520 				--newlines;
    521 			} else {
    522 				while ((c = shf_getc(x.u.shf)) == 0 || c == '\n')
    523 				    if (c == '\n')
    524 					    newlines++;	/* Save newlines */
    525 				if (newlines && c != EOF) {
    526 					shf_ungetc(c, x.u.shf);
    527 					c = '\n';
    528 					--newlines;
    529 				}
    530 			}
    531 			if (c == EOF) {
    532 				newlines = 0;
    533 				shf_close(x.u.shf);
    534 				if (x.split)
    535 					subst_exstat = waitlast();
    536 				type = XBASE;
    537 				if (f&DOBLANK)
    538 					doblank--;
    539 				continue;
    540 			}
    541 			break;
    542 		}
    543 
    544 		/* check for end of word or IFS separation */
    545 		if (c == 0 || (!quote && (f & DOBLANK) && doblank && !make_magic
    546 			       && ctype(c, C_IFS)))
    547 		{
    548 			/* How words are broken up:
    549 			 *		   |       value of c
    550 			 *	  word	   |	ws	nws	0
    551 			 *	-----------------------------------
    552 			 *	IFS_WORD	w/WS	w/NWS	w
    553 			 *	IFS_WS		-/WS	w/NWS	-
    554 			 *	IFS_NWS		-/NWS	w/NWS	w
    555 			 *   (w means generate a word)
    556 			 * Note that IFS_NWS/0 generates a word (at&t ksh
    557 			 * doesn't do this, but POSIX does).
    558 			 */
    559 			if (word == IFS_WORD
    560 			    || (!ctype(c, C_IFSWS) && (c || word == IFS_NWS)))
    561 			{
    562 				char *p;
    563 
    564 				*dp++ = '\0';
    565 				p = Xclose(ds, dp);
    566 #ifdef BRACE_EXPAND
    567 				if (fdo & DOBRACE_)
    568 					/* also does globbing */
    569 					alt_expand(wp, p, p,
    570 						   p + Xlength(ds, (dp - 1)),
    571 						   fdo | (f & DOMARKDIRS));
    572 				else
    573 #endif /* BRACE_EXPAND */
    574 				if (fdo & DOGLOB)
    575 					glob(p, wp, f & DOMARKDIRS);
    576 				else if ((f & DOPAT) || !(fdo & DOMAGIC_))
    577 					XPput(*wp, p);
    578 				else
    579 					XPput(*wp, debunk(p, p));
    580 				fdo = 0;
    581 				saw_eq = 0;
    582 				tilde_ok = (f & (DOTILDE|DOASNTILDE)) ? 1 : 0;
    583 				if (c != 0)
    584 					Xinit(ds, dp, 128, ATEMP);
    585 			}
    586 			if (c == 0)
    587 				return;
    588 			if (word != IFS_NWS)
    589 				word = ctype(c, C_IFSWS) ? IFS_WS : IFS_NWS;
    590 		} else {
    591 			/* age tilde_ok info - ~ code tests second bit */
    592 			tilde_ok <<= 1;
    593 			/* mark any special second pass chars */
    594 			if (!quote)
    595 				switch (c) {
    596 				  case '[':
    597 				  case NOT:
    598 				  case '-':
    599 				  case ']':
    600 					/* For character classes - doesn't hurt
    601 					 * to have magic !,-,]'s outside of
    602 					 * [...] expressions.
    603 					 */
    604 					if (f & (DOPAT | DOGLOB)) {
    605 						fdo |= DOMAGIC_;
    606 						if (c == '[')
    607 							fdo |= f & DOGLOB;
    608 						*dp++ = MAGIC;
    609 					}
    610 					break;
    611 				  case '*':
    612 				  case '?':
    613 					if (f & (DOPAT | DOGLOB)) {
    614 						fdo |= DOMAGIC_ | (f & DOGLOB);
    615 						*dp++ = MAGIC;
    616 					}
    617 					break;
    618 #ifdef BRACE_EXPAND
    619 				  case OBRACE:
    620 				  case ',':
    621 				  case CBRACE:
    622 					if ((f & DOBRACE_) && (c == OBRACE
    623 						|| (fdo & DOBRACE_)))
    624 					{
    625 						fdo |= DOBRACE_|DOMAGIC_;
    626 						*dp++ = MAGIC;
    627 					}
    628 					break;
    629 #endif /* BRACE_EXPAND */
    630 				  case '=':
    631 					/* Note first unquoted = for ~ */
    632 					if (!(f & DOTEMP_) && !saw_eq) {
    633 						saw_eq = 1;
    634 						tilde_ok = 1;
    635 					}
    636 					break;
    637 				  case PATHSEP: /* : */
    638 					/* Note unquoted : for ~ */
    639 					if (!(f & DOTEMP_) && (f & DOASNTILDE))
    640 						tilde_ok = 1;
    641 					break;
    642 				  case '~':
    643 					/* tilde_ok is reset whenever
    644 					 * any of ' " $( $(( ${ } are seen.
    645 					 * Note that tilde_ok must be preserved
    646 					 * through the sequence ${A=a=}~
    647 					 */
    648 					if (type == XBASE
    649 					    && (f & (DOTILDE|DOASNTILDE))
    650 					    && (tilde_ok & 2))
    651 					{
    652 						char *p, *dp_x;
    653 
    654 						dp_x = dp;
    655 						p = maybe_expand_tilde(sp,
    656 							&ds, &dp_x,
    657 							f & DOASNTILDE);
    658 						if (p) {
    659 							if (dp != dp_x)
    660 								word = IFS_WORD;
    661 							dp = dp_x;
    662 							sp = p;
    663 							continue;
    664 						}
    665 					}
    666 					break;
    667 				}
    668 			else
    669 				quote &= ~2; /* undo temporary */
    670 
    671 			if (make_magic) {
    672 				make_magic = 0;
    673 				fdo |= DOMAGIC_ | (f & DOGLOB);
    674 				*dp++ = MAGIC;
    675 			} else if (ISMAGIC(c)) {
    676 				fdo |= DOMAGIC_;
    677 				*dp++ = MAGIC;
    678 			}
    679 			*dp++ = c; /* save output char */
    680 			word = IFS_WORD;
    681 		}
    682 	}
    683 }
    684 
    685 /*
    686  * Prepare to generate the string returned by ${} substitution.
    687  */
    688 static int
    689 varsub(xp, sp, word, stypep, slenp)
    690 	Expand *xp;
    691 	char *sp;
    692 	char *word;
    693 	int *stypep;	/* becomes qualifier type */
    694 	int *slenp;	/* " " len (=, :=, etc.) valid iff *stypep != 0 */
    695 {
    696 	int c;
    697 	int state;	/* next state: XBASE, XARG, XSUB, XNULLSUB */
    698 	int stype;	/* substitution type */
    699 	int slen;
    700 	char *p;
    701 	struct tbl *vp;
    702 
    703 	if (sp[0] == '\0')	/* Bad variable name */
    704 		return -1;
    705 
    706 	xp->var = (struct tbl *) 0;
    707 
    708 	/* ${#var}, string length or array size */
    709 	if (sp[0] == '#' && (c = sp[1]) != '\0') {
    710 		int zero_ok = 0;
    711 
    712 		/* Can't have any modifiers for ${#...} */
    713 		if (*word != CSUBST)
    714 			return -1;
    715 		sp++;
    716 		/* Check for size of array */
    717 		if ((p=strchr(sp,'[')) && (p[1]=='*'||p[1]=='@') && p[2]==']') {
    718 			int n = 0;
    719 			int max = 0;
    720 			vp = global(arrayname(sp));
    721 			if (vp->flag & (ISSET|ARRAY))
    722 				zero_ok = 1;
    723 			for (; vp; vp = vp->u.array)
    724 				if (vp->flag & ISSET) {
    725 					max = vp->index + 1;
    726 					n++;
    727 				}
    728 			c = n; /* ksh88/ksh93 go for number, not max index */
    729 		} else if (c == '*' || c == '@')
    730 			c = e->loc->argc;
    731 		else {
    732 			p = str_val(global(sp));
    733 			zero_ok = p != null;
    734 			c = strlen(p);
    735 		}
    736 		if (Flag(FNOUNSET) && c == 0 && !zero_ok)
    737 			errorf("%s: parameter not set", sp);
    738 		*stypep = 0; /* unqualified variable/string substitution */
    739 		xp->str = str_save(ulton((unsigned long)c, 10), ATEMP);
    740 		return XSUB;
    741 	}
    742 
    743 	/* Check for qualifiers in word part */
    744 	stype = 0;
    745 	c = word[slen = 0] == CHAR ? word[1] : 0;
    746 	if (c == ':') {
    747 		slen += 2;
    748 		stype = 0x80;
    749 		c = word[slen + 0] == CHAR ? word[slen + 1] : 0;
    750 	}
    751 	if (ctype(c, C_SUBOP1)) {
    752 		slen += 2;
    753 		stype |= c;
    754 	} else if (ctype(c, C_SUBOP2)) { /* Note: ksh88 allows :%, :%%, etc */
    755 		slen += 2;
    756 		stype = c;
    757 		if (word[slen + 0] == CHAR && c == word[slen + 1]) {
    758 			stype |= 0x80;
    759 			slen += 2;
    760 		}
    761 	} else if (stype)	/* : is not ok */
    762 		return -1;
    763 	if (!stype && *word != CSUBST)
    764 		return -1;
    765 	*stypep = stype;
    766 	*slenp = slen;
    767 
    768 	c = sp[0];
    769 	if (c == '*' || c == '@') {
    770 		switch (stype & 0x7f) {
    771 		  case '=':	/* can't assign to a vector */
    772 		  case '%':	/* can't trim a vector (yet) */
    773 		  case '#':
    774 			return -1;
    775 		}
    776 		if (e->loc->argc == 0) {
    777 			xp->str = null;
    778 			state = c == '@' ? XNULLSUB : XSUB;
    779 		} else {
    780 			xp->u.strv = (const char **) e->loc->argv + 1;
    781 			xp->str = *xp->u.strv++;
    782 			xp->split = c == '@'; /* $@ */
    783 			state = XARG;
    784 		}
    785 	} else {
    786 		if ((p=strchr(sp,'[')) && (p[1]=='*'||p[1]=='@') && p[2]==']') {
    787 			XPtrV wv;
    788 
    789 			switch (stype & 0x7f) {
    790 			  case '=':	/* can't assign to a vector */
    791 			  case '%':	/* can't trim a vector (yet) */
    792 			  case '#':
    793 				return -1;
    794 			}
    795 			XPinit(wv, 32);
    796 			vp = global(arrayname(sp));
    797 			for (; vp; vp = vp->u.array) {
    798 				if (!(vp->flag&ISSET))
    799 					continue;
    800 				XPput(wv, str_val(vp));
    801 			}
    802 			if (XPsize(wv) == 0) {
    803 				xp->str = null;
    804 				state = p[1] == '@' ? XNULLSUB : XSUB;
    805 				XPfree(wv);
    806 			} else {
    807 				XPput(wv, 0);
    808 				xp->u.strv = (const char **) XPptrv(wv);
    809 				xp->str = *xp->u.strv++;
    810 				xp->split = p[1] == '@'; /* ${foo[@]} */
    811 				state = XARG;
    812 			}
    813 		} else {
    814 			/* Can't assign things like $! or $1 */
    815 			if ((stype & 0x7f) == '='
    816 			    && (ctype(*sp, C_VAR1) || digit(*sp)))
    817 				return -1;
    818 			xp->var = global(sp);
    819 			xp->str = str_val(xp->var);
    820 			state = XSUB;
    821 		}
    822 	}
    823 
    824 	c = stype&0x7f;
    825 	/* test the compiler's code generator */
    826 	if (ctype(c, C_SUBOP2) ||
    827 	    (((stype&0x80) ? *xp->str=='\0' : xp->str==null) ? /* undef? */
    828 	     c == '=' || c == '-' || c == '?' : c == '+'))
    829 		state = XBASE;	/* expand word instead of variable value */
    830 	if (Flag(FNOUNSET) && xp->str == null
    831 	    && (ctype(c, C_SUBOP2) || (state != XBASE && c != '+')))
    832 		errorf("%s: parameter not set", sp);
    833 	return state;
    834 }
    835 
    836 /*
    837  * Run the command in $(...) and read its output.
    838  */
    839 static int
    840 comsub(xp, cp)
    841 	register Expand *xp;
    842 	char *cp;
    843 {
    844 	Source *s, *sold;
    845 	register struct op *t;
    846 	struct shf *shf;
    847 
    848 	s = pushs(SSTRING, ATEMP);
    849 	s->start = s->str = cp;
    850 	sold = source;
    851 	t = compile(s);
    852 	source = sold;
    853 
    854 	if (t == NULL)
    855 		return XBASE;
    856 
    857 	if (t != NULL && t->type == TCOM && /* $(<file) */
    858 	    *t->args == NULL && *t->vars == NULL && t->ioact != NULL) {
    859 		register struct ioword *io = *t->ioact;
    860 		char *name;
    861 
    862 		if ((io->flag&IOTYPE) != IOREAD)
    863 			errorf("funny $() command: %s",
    864 				snptreef((char *) 0, 32, "%R", io));
    865 		shf = shf_open(name = evalstr(io->name, DOTILDE), O_RDONLY, 0,
    866 			SHF_MAPHI|SHF_CLEXEC);
    867 		if (shf == NULL)
    868 			errorf("%s: cannot open $() input", name);
    869 		xp->split = 0;	/* no waitlast() */
    870 	} else {
    871 		int ofd1, pv[2];
    872 		openpipe(pv);
    873 		shf = shf_fdopen(pv[0], SHF_RD, (struct shf *) 0);
    874 		ofd1 = savefd(1, 0);	/* fd 1 may be closed... */
    875 		ksh_dup2(pv[1], 1, FALSE);
    876 		close(pv[1]);
    877 		execute(t, XFORK|XXCOM|XPIPEO);
    878 		restfd(1, ofd1);
    879 		startlast();
    880 		xp->split = 1;	/* waitlast() */
    881 	}
    882 
    883 	xp->u.shf = shf;
    884 	return XCOM;
    885 }
    886 
    887 /*
    888  * perform #pattern and %pattern substitution in ${}
    889  */
    890 
    891 static char *
    892 trimsub(str, pat, how)
    893 	register char *str;
    894 	char *pat;
    895 	int how;
    896 {
    897 	register char *end = strchr(str, 0);
    898 	register char *p, c;
    899 
    900 	switch (how&0xff) {	/* UCHAR_MAX maybe? */
    901 	  case '#':		/* shortest at begining */
    902 		for (p = str; p <= end; p++) {
    903 			c = *p; *p = '\0';
    904 			if (gmatch(str, pat, FALSE)) {
    905 				*p = c;
    906 				return p;
    907 			}
    908 			*p = c;
    909 		}
    910 		break;
    911 	  case '#'|0x80:	/* longest match at begining */
    912 		for (p = end; p >= str; p--) {
    913 			c = *p; *p = '\0';
    914 			if (gmatch(str, pat, FALSE)) {
    915 				*p = c;
    916 				return p;
    917 			}
    918 			*p = c;
    919 		}
    920 		break;
    921 	  case '%':		/* shortest match at end */
    922 		for (p = end; p >= str; p--) {
    923 			if (gmatch(p, pat, FALSE))
    924 				return str_nsave(str, p - str, ATEMP);
    925 		}
    926 		break;
    927 	  case '%'|0x80:	/* longest match at end */
    928 		for (p = str; p <= end; p++) {
    929 			if (gmatch(p, pat, FALSE))
    930 				return str_nsave(str, p - str, ATEMP);
    931 		}
    932 		break;
    933 	}
    934 
    935 	return str;		/* no match, return string */
    936 }
    937 
    938 /*
    939  * glob
    940  * Name derived from V6's /etc/glob, the program that expanded filenames.
    941  */
    942 
    943 /* XXX cp not const 'cause slashes are temporarily replaced with nulls... */
    944 static void
    945 glob(cp, wp, markdirs)
    946 	char *cp;
    947 	register XPtrV *wp;
    948 	int markdirs;
    949 {
    950 	int oldsize = XPsize(*wp);
    951 
    952 	if (glob_str(cp, wp, markdirs) == 0)
    953 		XPput(*wp, debunk(cp, cp));
    954 	else
    955 		qsortp(XPptrv(*wp) + oldsize, (size_t)(XPsize(*wp) - oldsize),
    956 			xstrcmp);
    957 }
    958 
    959 #define GF_NONE		0
    960 #define GF_EXCHECK	BIT(0)		/* do existance check on file */
    961 #define GF_GLOBBED	BIT(1)		/* some globbing has been done */
    962 #define GF_MARKDIR	BIT(2)		/* add trailing / to directories */
    963 
    964 /* Apply file globbing to cp and store the matching files in wp.  Returns
    965  * the number of matches found.
    966  */
    967 int
    968 glob_str(cp, wp, markdirs)
    969 	char *cp;
    970 	XPtrV *wp;
    971 	int markdirs;
    972 {
    973 	int oldsize = XPsize(*wp);
    974 	XString xs;
    975 	char *xp;
    976 
    977 	Xinit(xs, xp, 256, ATEMP);
    978 	globit(&xs, &xp, cp, wp, markdirs ? GF_MARKDIR : GF_NONE);
    979 	Xfree(xs, xp);
    980 
    981 	return XPsize(*wp) - oldsize;
    982 }
    983 
    984 static void
    985 globit(xs, xpp, sp, wp, check)
    986 	XString *xs;		/* dest string */
    987 	char **xpp;		/* ptr to dest end */
    988 	char *sp;		/* source path */
    989 	register XPtrV *wp;	/* output list */
    990 	int check;		/* GF_* flags */
    991 {
    992 	register char *np;	/* next source component */
    993 	char *xp = *xpp;
    994 	char *se;
    995 	char odirsep;
    996 
    997 	/* This to allow long expansions to be interrupted */
    998 	intrcheck();
    999 
   1000 	if (sp == NULL) {	/* end of source path */
   1001 		/* We only need to check if the file exists if a pattern
   1002 		 * is followed by a non-pattern (eg, foo*x/bar; no check
   1003 		 * is needed for foo* since the match must exist) or if
   1004 		 * any patterns were expanded and the markdirs option is set.
   1005 		 * Symlinks make things a bit tricky...
   1006 		 */
   1007 		if ((check & GF_EXCHECK)
   1008 		    || ((check & GF_MARKDIR) && (check & GF_GLOBBED)))
   1009 		{
   1010 #define stat_check()	(stat_done ? stat_done : \
   1011 			    (stat_done = stat(Xstring(*xs, xp), &statb) < 0 \
   1012 				? -1 : 1))
   1013 			struct stat lstatb, statb;
   1014 			int stat_done = 0;	 /* -1: failed, 1 ok */
   1015 
   1016 			if (lstat(Xstring(*xs, xp), &lstatb) < 0)
   1017 				return;
   1018 			/* special case for systems which strip trailing
   1019 			 * slashes from regular files (eg, /etc/passwd/).
   1020 			 * SunOS 4.1.3 does this...
   1021 			 */
   1022 			if ((check & GF_EXCHECK) && xp > Xstring(*xs, xp)
   1023 			    && ISDIRSEP(xp[-1]) && !S_ISDIR(lstatb.st_mode)
   1024 #ifdef S_ISLNK
   1025 			    && (!S_ISLNK(lstatb.st_mode)
   1026 				|| stat_check() < 0
   1027 				|| !S_ISDIR(statb.st_mode))
   1028 #endif /* S_ISLNK */
   1029 				)
   1030 				return;
   1031 			/* Possibly tack on a trailing / if there isn't already
   1032 			 * one and if the file is a directory or a symlink to a
   1033 			 * directory
   1034 			 */
   1035 			if (((check & GF_MARKDIR) && (check & GF_GLOBBED))
   1036 			    && xp > Xstring(*xs, xp) && !ISDIRSEP(xp[-1])
   1037 			    && (S_ISDIR(lstatb.st_mode)
   1038 #ifdef S_ISLNK
   1039 				|| (S_ISLNK(lstatb.st_mode)
   1040 				    && stat_check() > 0
   1041 				    && S_ISDIR(statb.st_mode))
   1042 #endif /* S_ISLNK */
   1043 				    ))
   1044 			{
   1045 				*xp++ = DIRSEP;
   1046 				*xp = '\0';
   1047 			}
   1048 		}
   1049 #ifdef OS2 /* Done this way to avoid bug in gcc 2.7.2... */
   1050     /* Ugly kludge required for command
   1051      * completion - see how search_access()
   1052      * is implemented for OS/2...
   1053      */
   1054 # define KLUDGE_VAL	4
   1055 #else /* OS2 */
   1056 # define KLUDGE_VAL	0
   1057 #endif /* OS2 */
   1058 		XPput(*wp, str_nsave(Xstring(*xs, xp), Xlength(*xs, xp)
   1059 			+ KLUDGE_VAL, ATEMP));
   1060 		return;
   1061 	}
   1062 
   1063 	if (xp > Xstring(*xs, xp))
   1064 		*xp++ = DIRSEP;
   1065 	while (ISDIRSEP(*sp)) {
   1066 		Xcheck(*xs, xp);
   1067 		*xp++ = *sp++;
   1068 	}
   1069 	np = ksh_strchr_dirsep(sp);
   1070 	if (np != NULL) {
   1071 		se = np;
   1072 		odirsep = *np;	/* don't assume DIRSEP, can be multiple kinds */
   1073 		*np++ = '\0';
   1074 	} else {
   1075 		odirsep = '\0'; /* keep gcc quiet */
   1076 		se = sp + strlen(sp);
   1077 	}
   1078 
   1079 
   1080 	/* Check if sp needs globbing - done to avoid pattern checks for strings
   1081 	 * containing MAGIC characters, open ['s without the matching close ],
   1082 	 * etc. (otherwise opendir() will be called which may fail because the
   1083 	 * directory isn't readable - if no globbing is needed, only execute
   1084 	 * permission should be required (as per POSIX)).
   1085 	 */
   1086 	if (!has_globbing(sp, se)) {
   1087 		XcheckN(*xs, xp, se - sp + 1);
   1088 		debunk(xp, sp);
   1089 		xp += strlen(xp);
   1090 		*xpp = xp;
   1091 		globit(xs, xpp, np, wp, check);
   1092 	} else {
   1093 		DIR *dirp;
   1094 		struct dirent *d;
   1095 		char *name;
   1096 		int len;
   1097 		int prefix_len;
   1098 
   1099 		/* xp = *xpp;	   copy_non_glob() may have re-alloc'd xs */
   1100 		*xp = '\0';
   1101 		prefix_len = Xlength(*xs, xp);
   1102 		dirp = ksh_opendir(prefix_len ? Xstring(*xs, xp) : ".");
   1103 		if (dirp == NULL)
   1104 			goto Nodir;
   1105 		while ((d = readdir(dirp)) != NULL) {
   1106 			name = d->d_name;
   1107 			if (name[0] == '.' &&
   1108 			    (name[1] == 0 || (name[1] == '.' && name[2] == 0)))
   1109 				continue; /* always ignore . and .. */
   1110 			if ((*name == '.' && *sp != '.')
   1111 			    || !gmatch(name, sp, TRUE))
   1112 				continue;
   1113 
   1114 			len = NLENGTH(d) + 1;
   1115 			XcheckN(*xs, xp, len);
   1116 			memcpy(xp, name, len);
   1117 			*xpp = xp + len - 1;
   1118 			globit(xs, xpp, np, wp,
   1119 				(check & GF_MARKDIR) | GF_GLOBBED
   1120 				| (np ? GF_EXCHECK : GF_NONE));
   1121 			xp = Xstring(*xs, xp) + prefix_len;
   1122 		}
   1123 		closedir(dirp);
   1124 	  Nodir:;
   1125 	}
   1126 
   1127 	if (np != NULL)
   1128 		*--np = odirsep;
   1129 }
   1130 
   1131 #if 0
   1132 /* Check if p contains something that needs globbing; if it does, 0 is
   1133  * returned; if not, p is copied into xs/xp after stripping any MAGICs
   1134  */
   1135 static int	copy_non_glob ARGS((XString *xs, char **xpp, char *p));
   1136 static int
   1137 copy_non_glob(xs, xpp, p)
   1138 	XString *xs;
   1139 	char **xpp;
   1140 	char *p;
   1141 {
   1142 	char *xp;
   1143 	int len = strlen(p);
   1144 
   1145 	XcheckN(*xs, *xpp, len);
   1146 	xp = *xpp;
   1147 	for (; *p; p++) {
   1148 		if (ISMAGIC(*p)) {
   1149 			int c = *++p;
   1150 
   1151 			if (c == '*' || c == '?')
   1152 				return 0;
   1153 			if (*p == '[') {
   1154 				char *q = p + 1;
   1155 
   1156 				if (ISMAGIC(*q) && q[1] == NOT)
   1157 					q += 2;
   1158 				if (ISMAGIC(*q) && q[1] == ']')
   1159 					q += 2;
   1160 				for (; *q; q++)
   1161 					if (ISMAGIC(*q) && *++q == ']')
   1162 						return 0;
   1163 				/* pass a literal [ through */
   1164 			}
   1165 			/* must be a MAGIC-MAGIC, or MAGIC-!, MAGIC--, etc. */
   1166 		}
   1167 		*xp++ = *p;
   1168 	}
   1169 	*xp = '\0';
   1170 	*xpp = xp;
   1171 	return 1;
   1172 }
   1173 #endif /* 0 */
   1174 
   1175 /* remove MAGIC from string */
   1176 char *
   1177 debunk(dp, sp)
   1178 	char *dp;
   1179 	const char *sp;
   1180 {
   1181 	char *d, *s;
   1182 
   1183 	if ((s = strchr(sp, MAGIC))) {
   1184 		memcpy(dp, sp, s - sp);
   1185 		for (d = dp + (s - sp); *s; s++)
   1186 			if (!ISMAGIC(*s) || !(*++s & 0x80)
   1187 			    || !strchr("*+?@! ", *s & 0x7f))
   1188 				*d++ = *s;
   1189 			else {
   1190 				/* extended pattern operators: *+?@! */
   1191 				if ((*s & 0x7f) != ' ')
   1192 					*d++ = *s & 0x7f;
   1193 				*d++ = '(';
   1194 			}
   1195 		*d = '\0';
   1196 	} else if (dp != sp)
   1197 		strcpy(dp, sp);
   1198 	return dp;
   1199 }
   1200 
   1201 /* Check if p is an unquoted name, possibly followed by a / or :.  If so
   1202  * puts the expanded version in *dcp,dp and returns a pointer in p just
   1203  * past the name, otherwise returns 0.
   1204  */
   1205 static char *
   1206 maybe_expand_tilde(p, dsp, dpp, isassign)
   1207 	char *p;
   1208 	XString *dsp;
   1209 	char **dpp;
   1210 	int isassign;
   1211 {
   1212 	XString ts;
   1213 	char *dp = *dpp;
   1214 	char *tp, *r;
   1215 
   1216 	Xinit(ts, tp, 16, ATEMP);
   1217 	/* : only for DOASNTILDE form */
   1218 	while (p[0] == CHAR && !ISDIRSEP(p[1])
   1219 	       && (!isassign || p[1] != PATHSEP))
   1220 	{
   1221 		Xcheck(ts, tp);
   1222 		*tp++ = p[1];
   1223 		p += 2;
   1224 	}
   1225 	*tp = '\0';
   1226 	r = (p[0] == EOS || p[0] == CHAR || p[0] == CSUBST) ? tilde(Xstring(ts, tp)) : (char *) 0;
   1227 	Xfree(ts, tp);
   1228 	if (r) {
   1229 		while (*r) {
   1230 			Xcheck(*dsp, dp);
   1231 			if (ISMAGIC(*r))
   1232 				*dp++ = MAGIC;
   1233 			*dp++ = *r++;
   1234 		}
   1235 		*dpp = dp;
   1236 		r = p;
   1237 	}
   1238 	return r;
   1239 }
   1240 
   1241 /*
   1242  * tilde expansion
   1243  *
   1244  * based on a version by Arnold Robbins
   1245  */
   1246 
   1247 static char *
   1248 tilde(cp)
   1249 	char *cp;
   1250 {
   1251 	char *dp;
   1252 
   1253 	if (cp[0] == '\0')
   1254 		dp = str_val(global("HOME"));
   1255 	else if (cp[0] == '+' && cp[1] == '\0')
   1256 		dp = str_val(global("PWD"));
   1257 	else if (cp[0] == '-' && cp[1] == '\0')
   1258 		dp = str_val(global("OLDPWD"));
   1259 	else
   1260 		dp = homedir(cp);
   1261 	/* If HOME, PWD or OLDPWD are not set, don't expand ~ */
   1262 	if (dp == null)
   1263 		dp = (char *) 0;
   1264 	return dp;
   1265 }
   1266 
   1267 /*
   1268  * map userid to user's home directory.
   1269  * note that 4.3's getpw adds more than 6K to the shell,
   1270  * and the YP version probably adds much more.
   1271  * we might consider our own version of getpwnam() to keep the size down.
   1272  */
   1273 
   1274 static char *
   1275 homedir(name)
   1276 	char *name;
   1277 {
   1278 	register struct tbl *ap;
   1279 
   1280 	ap = tenter(&homedirs, name, hash(name));
   1281 	if (!(ap->flag & ISSET)) {
   1282 #ifdef OS2
   1283 		/* No usernames in OS2 - punt */
   1284 		return NULL;
   1285 #else /* OS2 */
   1286 		struct passwd *pw;
   1287 
   1288 		pw = getpwnam(name);
   1289 		if (pw == NULL)
   1290 			return NULL;
   1291 		ap->val.s = str_save(pw->pw_dir, APERM);
   1292 		ap->flag |= DEFINED|ISSET|ALLOC;
   1293 #endif /* OS2 */
   1294 	}
   1295 	return ap->val.s;
   1296 }
   1297 
   1298 #ifdef BRACE_EXPAND
   1299 static void
   1300 alt_expand(wp, start, exp_start, end, fdo)
   1301 	XPtrV *wp;
   1302 	char *start, *exp_start;
   1303 	char *end;
   1304 	int fdo;
   1305 {
   1306 	int UNINITIALIZED(count);
   1307 	char *brace_start, *brace_end, *UNINITIALIZED(comma);
   1308 	char *field_start;
   1309 	char *p;
   1310 
   1311 	/* search for open brace */
   1312 	for (p = exp_start; (p = strchr(p, MAGIC)) && p[1] != OBRACE; p += 2)
   1313 		;
   1314 	brace_start = p;
   1315 
   1316 	/* find matching close brace, if any */
   1317 	if (p) {
   1318 		comma = (char *) 0;
   1319 		count = 1;
   1320 		for (p += 2; *p && count; p++) {
   1321 			if (ISMAGIC(*p)) {
   1322 				if (*++p == OBRACE)
   1323 					count++;
   1324 				else if (*p == CBRACE)
   1325 					--count;
   1326 				else if (*p == ',' && count == 1)
   1327 					comma = p;
   1328 			}
   1329 		}
   1330 	}
   1331 	/* no valid expansions... */
   1332 	if (!p || count != 0) {
   1333 		/* Note that given a{{b,c} we do not expand anything (this is
   1334 		 * what at&t ksh does.  This may be changed to do the {b,c}
   1335 		 * expansion. }
   1336 		 */
   1337 		if (fdo & DOGLOB)
   1338 			glob(start, wp, fdo & DOMARKDIRS);
   1339 		else
   1340 			XPput(*wp, debunk(start, start));
   1341 		return;
   1342 	}
   1343 	brace_end = p;
   1344 	if (!comma) {
   1345 		alt_expand(wp, start, brace_end, end, fdo);
   1346 		return;
   1347 	}
   1348 
   1349 	/* expand expression */
   1350 	field_start = brace_start + 2;
   1351 	count = 1;
   1352 	for (p = brace_start + 2; p != brace_end; p++) {
   1353 		if (ISMAGIC(*p)) {
   1354 			if (*++p == OBRACE)
   1355 				count++;
   1356 			else if ((*p == CBRACE && --count == 0)
   1357 				 || (*p == ',' && count == 1))
   1358 			{
   1359 				char *new;
   1360 				int l1, l2, l3;
   1361 
   1362 				l1 = brace_start - start;
   1363 				l2 = (p - 1) - field_start;
   1364 				l3 = end - brace_end;
   1365 				new = (char *) alloc(l1 + l2 + l3 + 1, ATEMP);
   1366 				memcpy(new, start, l1);
   1367 				memcpy(new + l1, field_start, l2);
   1368 				memcpy(new + l1 + l2, brace_end, l3);
   1369 				new[l1 + l2 + l3] = '\0';
   1370 				alt_expand(wp, new, new + l1,
   1371 					   new + l1 + l2 + l3, fdo);
   1372 				field_start = p + 1;
   1373 			}
   1374 		}
   1375 	}
   1376 	return;
   1377 }
   1378 #endif /* BRACE_EXPAND */
   1379