xref: /openbsd-src/bin/ksh/syn.c (revision 505ee9ea3b177e2387d907a91ca7da069f3f14d8)
1 /*	$OpenBSD: syn.c,v 1.39 2018/04/24 08:25:16 kn Exp $	*/
2 
3 /*
4  * shell parser (C version)
5  */
6 
7 #include <string.h>
8 
9 #include "sh.h"
10 #include "c_test.h"
11 
12 struct nesting_state {
13 	int	start_token;	/* token than began nesting (eg, FOR) */
14 	int	start_line;	/* line nesting began on */
15 };
16 
17 static void	yyparse(void);
18 static struct op *pipeline(int);
19 static struct op *andor(void);
20 static struct op *c_list(int);
21 static struct ioword *synio(int);
22 static void	musthave(int, int);
23 static struct op *nested(int, int, int);
24 static struct op *get_command(int);
25 static struct op *dogroup(void);
26 static struct op *thenpart(void);
27 static struct op *elsepart(void);
28 static struct op *caselist(void);
29 static struct op *casepart(int);
30 static struct op *function_body(char *, int);
31 static char **	wordlist(void);
32 static struct op *block(int, struct op *, struct op *, char **);
33 static struct op *newtp(int);
34 static void	syntaxerr(const char *) __attribute__((__noreturn__));
35 static void	nesting_push(struct nesting_state *, int);
36 static void	nesting_pop(struct nesting_state *);
37 static int	assign_command(char *);
38 static int	inalias(struct source *);
39 static int	dbtestp_isa(Test_env *, Test_meta);
40 static const char *dbtestp_getopnd(Test_env *, Test_op, int);
41 static int	dbtestp_eval(Test_env *, Test_op, const char *, const char *,
42 		    int);
43 static void	dbtestp_error(Test_env *, int, const char *);
44 
45 static	struct	op	*outtree; /* yyparse output */
46 
47 static struct nesting_state nesting;	/* \n changed to ; */
48 
49 static	int	reject;		/* token(cf) gets symbol again */
50 static	int	symbol;		/* yylex value */
51 
52 #define	token(cf) \
53 	((reject) ? (reject = false, symbol) : (symbol = yylex(cf)))
54 #define	tpeek(cf) \
55 	((reject) ? (symbol) : (reject = true, symbol = yylex(cf)))
56 
57 static void
58 yyparse(void)
59 {
60 	int c;
61 
62 	reject = false;
63 
64 	outtree = c_list(source->type == SSTRING);
65 	c = tpeek(0);
66 	if (c == 0 && !outtree)
67 		outtree = newtp(TEOF);
68 	else if (c != '\n' && c != 0)
69 		syntaxerr(NULL);
70 }
71 
72 static struct op *
73 pipeline(int cf)
74 {
75 	struct op *t, *p, *tl = NULL;
76 
77 	t = get_command(cf);
78 	if (t != NULL) {
79 		while (token(0) == '|') {
80 			if ((p = get_command(CONTIN)) == NULL)
81 				syntaxerr(NULL);
82 			if (tl == NULL)
83 				t = tl = block(TPIPE, t, p, NULL);
84 			else
85 				tl = tl->right = block(TPIPE, tl->right, p, NULL);
86 		}
87 		reject = true;
88 	}
89 	return (t);
90 }
91 
92 static struct op *
93 andor(void)
94 {
95 	struct op *t, *p;
96 	int c;
97 
98 	t = pipeline(0);
99 	if (t != NULL) {
100 		while ((c = token(0)) == LOGAND || c == LOGOR) {
101 			if ((p = pipeline(CONTIN)) == NULL)
102 				syntaxerr(NULL);
103 			t = block(c == LOGAND? TAND: TOR, t, p, NULL);
104 		}
105 		reject = true;
106 	}
107 	return (t);
108 }
109 
110 static struct op *
111 c_list(int multi)
112 {
113 	struct op *t = NULL, *p, *tl = NULL;
114 	int c;
115 	int have_sep;
116 
117 	while (1) {
118 		p = andor();
119 		/* Token has always been read/rejected at this point, so
120 		 * we don't worry about what flags to pass token()
121 		 */
122 		c = token(0);
123 		have_sep = 1;
124 		if (c == '\n' && (multi || inalias(source))) {
125 			if (!p) /* ignore blank lines */
126 				continue;
127 		} else if (!p)
128 			break;
129 		else if (c == '&' || c == COPROC)
130 			p = block(c == '&' ? TASYNC : TCOPROC,
131 				  p, NULL, NULL);
132 		else if (c != ';')
133 			have_sep = 0;
134 		if (!t)
135 			t = p;
136 		else if (!tl)
137 			t = tl = block(TLIST, t, p, NULL);
138 		else
139 			tl = tl->right = block(TLIST, tl->right, p, NULL);
140 		if (!have_sep)
141 			break;
142 	}
143 	reject = true;
144 	return t;
145 }
146 
147 static struct ioword *
148 synio(int cf)
149 {
150 	struct ioword *iop;
151 	int ishere;
152 
153 	if (tpeek(cf) != REDIR)
154 		return NULL;
155 	reject = false;
156 	iop = yylval.iop;
157 	ishere = (iop->flag&IOTYPE) == IOHERE;
158 	musthave(LWORD, ishere ? HEREDELIM : 0);
159 	if (ishere) {
160 		iop->delim = yylval.cp;
161 		if (*ident != 0) /* unquoted */
162 			iop->flag |= IOEVAL;
163 		if (herep >= &heres[HERES])
164 			yyerror("too many <<'s\n");
165 		*herep++ = iop;
166 	} else
167 		iop->name = yylval.cp;
168 	return iop;
169 }
170 
171 static void
172 musthave(int c, int cf)
173 {
174 	if ((token(cf)) != c)
175 		syntaxerr(NULL);
176 }
177 
178 static struct op *
179 nested(int type, int smark, int emark)
180 {
181 	struct op *t;
182 	struct nesting_state old_nesting;
183 
184 	nesting_push(&old_nesting, smark);
185 	t = c_list(true);
186 	musthave(emark, KEYWORD|ALIAS);
187 	nesting_pop(&old_nesting);
188 	return (block(type, t, NULL, NULL));
189 }
190 
191 static struct op *
192 get_command(int cf)
193 {
194 	struct op *t;
195 	int c, iopn = 0, syniocf;
196 	struct ioword *iop, **iops;
197 	XPtrV args, vars;
198 	struct nesting_state old_nesting;
199 
200 	iops = areallocarray(NULL, NUFILE + 1,
201 	    sizeof(struct ioword *), ATEMP);
202 	XPinit(args, 16);
203 	XPinit(vars, 16);
204 
205 	syniocf = KEYWORD|ALIAS;
206 	switch (c = token(cf|KEYWORD|ALIAS|VARASN)) {
207 	default:
208 		reject = true;
209 		afree(iops, ATEMP);
210 		XPfree(args);
211 		XPfree(vars);
212 		return NULL; /* empty line */
213 
214 	case LWORD:
215 	case REDIR:
216 		reject = true;
217 		syniocf &= ~(KEYWORD|ALIAS);
218 		t = newtp(TCOM);
219 		t->lineno = source->line;
220 		while (1) {
221 			cf = (t->u.evalflags ? ARRAYVAR : 0) |
222 			    (XPsize(args) == 0 ? ALIAS|VARASN : CMDWORD);
223 			switch (tpeek(cf)) {
224 			case REDIR:
225 				if (iopn >= NUFILE)
226 					yyerror("too many redirections\n");
227 				iops[iopn++] = synio(cf);
228 				break;
229 
230 			case LWORD:
231 				reject = false;
232 				/* the iopn == 0 and XPsize(vars) == 0 are
233 				 * dubious but at&t ksh acts this way
234 				 */
235 				if (iopn == 0 && XPsize(vars) == 0 &&
236 				    XPsize(args) == 0 &&
237 				    assign_command(ident))
238 					t->u.evalflags = DOVACHECK;
239 				if ((XPsize(args) == 0 || Flag(FKEYWORD)) &&
240 				    is_wdvarassign(yylval.cp))
241 					XPput(vars, yylval.cp);
242 				else
243 					XPput(args, yylval.cp);
244 				break;
245 
246 			case '(':
247 				/* Check for "> foo (echo hi)", which at&t ksh
248 				 * allows (not POSIX, but not disallowed)
249 				 */
250 				afree(t, ATEMP);
251 				if (XPsize(args) == 0 && XPsize(vars) == 0) {
252 					reject = false;
253 					goto Subshell;
254 				}
255 				/* Must be a function */
256 				if (iopn != 0 || XPsize(args) != 1 ||
257 				    XPsize(vars) != 0)
258 					syntaxerr(NULL);
259 				reject = false;
260 				/*(*/
261 				musthave(')', 0);
262 				t = function_body(XPptrv(args)[0], false);
263 				goto Leave;
264 
265 			default:
266 				goto Leave;
267 			}
268 		}
269 	  Leave:
270 		break;
271 
272 	  Subshell:
273 	case '(':
274 		t = nested(TPAREN, '(', ')');
275 		break;
276 
277 	case '{': /*}*/
278 		t = nested(TBRACE, '{', '}');
279 		break;
280 
281 	case MDPAREN:
282 	  {
283 		static const char let_cmd[] = {
284 			CHAR, 'l', CHAR, 'e',
285 			CHAR, 't', EOS
286 		};
287 		/* Leave KEYWORD in syniocf (allow if (( 1 )) then ...) */
288 		t = newtp(TCOM);
289 		t->lineno = source->line;
290 		reject = false;
291 		XPput(args, wdcopy(let_cmd, ATEMP));
292 		musthave(LWORD,LETEXPR);
293 		XPput(args, yylval.cp);
294 		break;
295 	  }
296 
297 	case DBRACKET: /* [[ .. ]] */
298 		/* Leave KEYWORD in syniocf (allow if [[ -n 1 ]] then ...) */
299 		t = newtp(TDBRACKET);
300 		reject = false;
301 		{
302 			Test_env te;
303 
304 			te.flags = TEF_DBRACKET;
305 			te.pos.av = &args;
306 			te.isa = dbtestp_isa;
307 			te.getopnd = dbtestp_getopnd;
308 			te.eval = dbtestp_eval;
309 			te.error = dbtestp_error;
310 
311 			test_parse(&te);
312 		}
313 		break;
314 
315 	case FOR:
316 	case SELECT:
317 		t = newtp((c == FOR) ? TFOR : TSELECT);
318 		musthave(LWORD, ARRAYVAR);
319 		if (!is_wdvarname(yylval.cp, true))
320 			yyerror("%s: bad identifier\n",
321 			    c == FOR ? "for" : "select");
322 		t->str = str_save(ident, ATEMP);
323 		nesting_push(&old_nesting, c);
324 		t->vars = wordlist();
325 		t->left = dogroup();
326 		nesting_pop(&old_nesting);
327 		break;
328 
329 	case WHILE:
330 	case UNTIL:
331 		nesting_push(&old_nesting, c);
332 		t = newtp((c == WHILE) ? TWHILE : TUNTIL);
333 		t->left = c_list(true);
334 		t->right = dogroup();
335 		nesting_pop(&old_nesting);
336 		break;
337 
338 	case CASE:
339 		t = newtp(TCASE);
340 		musthave(LWORD, 0);
341 		t->str = yylval.cp;
342 		nesting_push(&old_nesting, c);
343 		t->left = caselist();
344 		nesting_pop(&old_nesting);
345 		break;
346 
347 	case IF:
348 		nesting_push(&old_nesting, c);
349 		t = newtp(TIF);
350 		t->left = c_list(true);
351 		t->right = thenpart();
352 		musthave(FI, KEYWORD|ALIAS);
353 		nesting_pop(&old_nesting);
354 		break;
355 
356 	case BANG:
357 		syniocf &= ~(KEYWORD|ALIAS);
358 		t = pipeline(0);
359 		if (t == NULL)
360 			syntaxerr(NULL);
361 		t = block(TBANG, NULL, t, NULL);
362 		break;
363 
364 	case TIME:
365 		syniocf &= ~(KEYWORD|ALIAS);
366 		t = pipeline(0);
367 		if (t) {
368 			if (t->str) {
369 				t->str = str_save(t->str, ATEMP);
370 			} else {
371 				t->str = alloc(2, ATEMP);
372 				t->str[0] = '\0'; /* TF_* flags */
373 				t->str[1] = '\0';
374 			}
375 		}
376 		t = block(TTIME, t, NULL, NULL);
377 		break;
378 
379 	case FUNCTION:
380 		musthave(LWORD, 0);
381 		t = function_body(yylval.cp, true);
382 		break;
383 	}
384 
385 	while ((iop = synio(syniocf)) != NULL) {
386 		if (iopn >= NUFILE)
387 			yyerror("too many redirections\n");
388 		iops[iopn++] = iop;
389 	}
390 
391 	if (iopn == 0) {
392 		afree(iops, ATEMP);
393 		t->ioact = NULL;
394 	} else {
395 		iops[iopn++] = NULL;
396 		iops = areallocarray(iops, iopn,
397 		    sizeof(struct ioword *), ATEMP);
398 		t->ioact = iops;
399 	}
400 
401 	if (t->type == TCOM || t->type == TDBRACKET) {
402 		XPput(args, NULL);
403 		t->args = (char **) XPclose(args);
404 		XPput(vars, NULL);
405 		t->vars = (char **) XPclose(vars);
406 	} else {
407 		XPfree(args);
408 		XPfree(vars);
409 	}
410 
411 	return t;
412 }
413 
414 static struct op *
415 dogroup(void)
416 {
417 	int c;
418 	struct op *list;
419 
420 	c = token(CONTIN|KEYWORD|ALIAS);
421 	/* A {...} can be used instead of do...done for for/select loops
422 	 * but not for while/until loops - we don't need to check if it
423 	 * is a while loop because it would have been parsed as part of
424 	 * the conditional command list...
425 	 */
426 	if (c == DO)
427 		c = DONE;
428 	else if (c == '{')
429 		c = '}';
430 	else
431 		syntaxerr(NULL);
432 	list = c_list(true);
433 	musthave(c, KEYWORD|ALIAS);
434 	return list;
435 }
436 
437 static struct op *
438 thenpart(void)
439 {
440 	struct op *t;
441 
442 	musthave(THEN, KEYWORD|ALIAS);
443 	t = newtp(0);
444 	t->left = c_list(true);
445 	if (t->left == NULL)
446 		syntaxerr(NULL);
447 	t->right = elsepart();
448 	return (t);
449 }
450 
451 static struct op *
452 elsepart(void)
453 {
454 	struct op *t;
455 
456 	switch (token(KEYWORD|ALIAS|VARASN)) {
457 	case ELSE:
458 		if ((t = c_list(true)) == NULL)
459 			syntaxerr(NULL);
460 		return (t);
461 
462 	case ELIF:
463 		t = newtp(TELIF);
464 		t->left = c_list(true);
465 		t->right = thenpart();
466 		return (t);
467 
468 	default:
469 		reject = true;
470 	}
471 	return NULL;
472 }
473 
474 static struct op *
475 caselist(void)
476 {
477 	struct op *t, *tl;
478 	int c;
479 
480 	c = token(CONTIN|KEYWORD|ALIAS);
481 	/* A {...} can be used instead of in...esac for case statements */
482 	if (c == IN)
483 		c = ESAC;
484 	else if (c == '{')
485 		c = '}';
486 	else
487 		syntaxerr(NULL);
488 	t = tl = NULL;
489 	while ((tpeek(CONTIN|KEYWORD|ESACONLY)) != c) { /* no ALIAS here */
490 		struct op *tc = casepart(c);
491 		if (tl == NULL)
492 			t = tl = tc, tl->right = NULL;
493 		else
494 			tl->right = tc, tl = tc;
495 	}
496 	musthave(c, KEYWORD|ALIAS);
497 	return (t);
498 }
499 
500 static struct op *
501 casepart(int endtok)
502 {
503 	struct op *t;
504 	int c;
505 	XPtrV ptns;
506 
507 	XPinit(ptns, 16);
508 	t = newtp(TPAT);
509 	c = token(CONTIN|KEYWORD); /* no ALIAS here */
510 	if (c != '(')
511 		reject = true;
512 	do {
513 		musthave(LWORD, 0);
514 		XPput(ptns, yylval.cp);
515 	} while ((c = token(0)) == '|');
516 	reject = true;
517 	XPput(ptns, NULL);
518 	t->vars = (char **) XPclose(ptns);
519 	musthave(')', 0);
520 
521 	t->left = c_list(true);
522 	/* Note: Posix requires the ;; */
523 	if ((tpeek(CONTIN|KEYWORD|ALIAS)) != endtok)
524 		musthave(BREAK, CONTIN|KEYWORD|ALIAS);
525 	return (t);
526 }
527 
528 static struct op *
529 function_body(char *name,
530     int ksh_func)		/* function foo { ... } vs foo() { .. } */
531 {
532 	char *sname, *p;
533 	struct op *t;
534 	int old_func_parse;
535 
536 	sname = wdstrip(name);
537 	/* Check for valid characters in name.  posix and ksh93 say only
538 	 * allow [a-zA-Z_0-9] but this allows more as old pdksh's have
539 	 * allowed more (the following were never allowed:
540 	 *	nul space nl tab $ ' " \ ` ( ) & | ; = < >
541 	 *  C_QUOTE covers all but = and adds # [ ? *)
542 	 */
543 	for (p = sname; *p; p++)
544 		if (ctype(*p, C_QUOTE) || *p == '=')
545 			yyerror("%s: invalid function name\n", sname);
546 
547 	t = newtp(TFUNCT);
548 	t->str = sname;
549 	t->u.ksh_func = ksh_func;
550 	t->lineno = source->line;
551 
552 	/* Note that POSIX allows only compound statements after foo(), sh and
553 	 * at&t ksh allow any command, go with the later since it shouldn't
554 	 * break anything.  However, for function foo, at&t ksh only accepts
555 	 * an open-brace.
556 	 */
557 	if (ksh_func) {
558 		musthave('{', CONTIN|KEYWORD|ALIAS); /* } */
559 		reject = true;
560 	}
561 
562 	old_func_parse = genv->flags & EF_FUNC_PARSE;
563 	genv->flags |= EF_FUNC_PARSE;
564 	if ((t->left = get_command(CONTIN)) == NULL) {
565 		/*
566 		 * Probably something like foo() followed by eof or ;.
567 		 * This is accepted by sh and ksh88.
568 		 * To make "typeset -f foo" work reliably (so its output can
569 		 * be used as input), we pretend there is a colon here.
570 		 */
571 		t->left = newtp(TCOM);
572 		t->left->args = areallocarray(NULL, 2, sizeof(char *), ATEMP);
573 		t->left->args[0] = alloc(3, ATEMP);
574 		t->left->args[0][0] = CHAR;
575 		t->left->args[0][1] = ':';
576 		t->left->args[0][2] = EOS;
577 		t->left->args[1] = NULL;
578 		t->left->vars = alloc(sizeof(char *), ATEMP);
579 		t->left->vars[0] = NULL;
580 		t->left->lineno = 1;
581 	}
582 	if (!old_func_parse)
583 		genv->flags &= ~EF_FUNC_PARSE;
584 
585 	return t;
586 }
587 
588 static char **
589 wordlist(void)
590 {
591 	int c;
592 	XPtrV args;
593 
594 	XPinit(args, 16);
595 	/* Posix does not do alias expansion here... */
596 	if ((c = token(CONTIN|KEYWORD|ALIAS)) != IN) {
597 		if (c != ';') /* non-POSIX, but at&t ksh accepts a ; here */
598 			reject = true;
599 		return NULL;
600 	}
601 	while ((c = token(0)) == LWORD)
602 		XPput(args, yylval.cp);
603 	if (c != '\n' && c != ';')
604 		syntaxerr(NULL);
605 	XPput(args, NULL);
606 	return (char **) XPclose(args);
607 }
608 
609 /*
610  * supporting functions
611  */
612 
613 static struct op *
614 block(int type, struct op *t1, struct op *t2, char **wp)
615 {
616 	struct op *t;
617 
618 	t = newtp(type);
619 	t->left = t1;
620 	t->right = t2;
621 	t->vars = wp;
622 	return (t);
623 }
624 
625 const	struct tokeninfo {
626 	const char *name;
627 	short	val;
628 	short	reserved;
629 } tokentab[] = {
630 	/* Reserved words */
631 	{ "if",		IF,	true },
632 	{ "then",	THEN,	true },
633 	{ "else",	ELSE,	true },
634 	{ "elif",	ELIF,	true },
635 	{ "fi",		FI,	true },
636 	{ "case",	CASE,	true },
637 	{ "esac",	ESAC,	true },
638 	{ "for",	FOR,	true },
639 	{ "select",	SELECT,	true },
640 	{ "while",	WHILE,	true },
641 	{ "until",	UNTIL,	true },
642 	{ "do",		DO,	true },
643 	{ "done",	DONE,	true },
644 	{ "in",		IN,	true },
645 	{ "function",	FUNCTION, true },
646 	{ "time",	TIME,	true },
647 	{ "{",		'{',	true },
648 	{ "}",		'}',	true },
649 	{ "!",		BANG,	true },
650 	{ "[[",		DBRACKET, true },
651 	/* Lexical tokens (0[EOF], LWORD and REDIR handled specially) */
652 	{ "&&",		LOGAND,	false },
653 	{ "||",		LOGOR,	false },
654 	{ ";;",		BREAK,	false },
655 	{ "((",		MDPAREN, false },
656 	{ "|&",		COPROC,	false },
657 	/* and some special cases... */
658 	{ "newline",	'\n',	false },
659 	{ 0 }
660 };
661 
662 void
663 initkeywords(void)
664 {
665 	struct tokeninfo const *tt;
666 	struct tbl *p;
667 
668 	ktinit(&keywords, APERM, 32); /* must be 2^n (currently 20 keywords) */
669 	for (tt = tokentab; tt->name; tt++) {
670 		if (tt->reserved) {
671 			p = ktenter(&keywords, tt->name, hash(tt->name));
672 			p->flag |= DEFINED|ISSET;
673 			p->type = CKEYWD;
674 			p->val.i = tt->val;
675 		}
676 	}
677 }
678 
679 static void
680 syntaxerr(const char *what)
681 {
682 	char redir[6];	/* 2<<- is the longest redirection, I think */
683 	const char *s;
684 	struct tokeninfo const *tt;
685 	int c;
686 
687 	if (!what)
688 		what = "unexpected";
689 	reject = true;
690 	c = token(0);
691     Again:
692 	switch (c) {
693 	case 0:
694 		if (nesting.start_token) {
695 			c = nesting.start_token;
696 			source->errline = nesting.start_line;
697 			what = "unmatched";
698 			goto Again;
699 		}
700 		/* don't quote the EOF */
701 		yyerror("syntax error: unexpected EOF\n");
702 		/* NOTREACHED */
703 
704 	case LWORD:
705 		s = snptreef(NULL, 32, "%S", yylval.cp);
706 		break;
707 
708 	case REDIR:
709 		s = snptreef(redir, sizeof(redir), "%R", yylval.iop);
710 		break;
711 
712 	default:
713 		for (tt = tokentab; tt->name; tt++)
714 			if (tt->val == c)
715 			    break;
716 		if (tt->name)
717 			s = tt->name;
718 		else {
719 			if (c > 0 && c < 256) {
720 				redir[0] = c;
721 				redir[1] = '\0';
722 			} else
723 				shf_snprintf(redir, sizeof(redir),
724 					"?%d", c);
725 			s = redir;
726 		}
727 	}
728 	yyerror("syntax error: `%s' %s\n", s, what);
729 }
730 
731 static void
732 nesting_push(struct nesting_state *save, int tok)
733 {
734 	*save = nesting;
735 	nesting.start_token = tok;
736 	nesting.start_line = source->line;
737 }
738 
739 static void
740 nesting_pop(struct nesting_state *saved)
741 {
742 	nesting = *saved;
743 }
744 
745 static struct op *
746 newtp(int type)
747 {
748 	struct op *t;
749 
750 	t = alloc(sizeof(*t), ATEMP);
751 	t->type = type;
752 	t->u.evalflags = 0;
753 	t->args = t->vars = NULL;
754 	t->ioact = NULL;
755 	t->left = t->right = NULL;
756 	t->str = NULL;
757 	return (t);
758 }
759 
760 struct op *
761 compile(Source *s)
762 {
763 	nesting.start_token = 0;
764 	nesting.start_line = 0;
765 	herep = heres;
766 	source = s;
767 	yyparse();
768 	return outtree;
769 }
770 
771 /* This kludge exists to take care of sh/at&t ksh oddity in which
772  * the arguments of alias/export/readonly/typeset have no field
773  * splitting, file globbing, or (normal) tilde expansion done.
774  * at&t ksh seems to do something similar to this since
775  *	$ touch a=a; typeset a=[ab]; echo "$a"
776  *	a=[ab]
777  *	$ x=typeset; $x a=[ab]; echo "$a"
778  *	a=a
779  *	$
780  */
781 static int
782 assign_command(char *s)
783 {
784 	if (Flag(FPOSIX) || !*s)
785 		return 0;
786 	return (strcmp(s, "alias") == 0) ||
787 	    (strcmp(s, "export") == 0) ||
788 	    (strcmp(s, "readonly") == 0) ||
789 	    (strcmp(s, "typeset") == 0);
790 }
791 
792 /* Check if we are in the middle of reading an alias */
793 static int
794 inalias(struct source *s)
795 {
796 	for (; s && s->type == SALIAS; s = s->next)
797 		if (!(s->flags & SF_ALIASEND))
798 			return 1;
799 	return 0;
800 }
801 
802 
803 /* Order important - indexed by Test_meta values
804  * Note that ||, &&, ( and ) can't appear in as unquoted strings
805  * in normal shell input, so these can be interpreted unambiguously
806  * in the evaluation pass.
807  */
808 static const char dbtest_or[] = { CHAR, '|', CHAR, '|', EOS };
809 static const char dbtest_and[] = { CHAR, '&', CHAR, '&', EOS };
810 static const char dbtest_not[] = { CHAR, '!', EOS };
811 static const char dbtest_oparen[] = { CHAR, '(', EOS };
812 static const char dbtest_cparen[] = { CHAR, ')', EOS };
813 const char *const dbtest_tokens[] = {
814 	dbtest_or, dbtest_and, dbtest_not,
815 	dbtest_oparen, dbtest_cparen
816 };
817 const char db_close[] = { CHAR, ']', CHAR, ']', EOS };
818 const char db_lthan[] = { CHAR, '<', EOS };
819 const char db_gthan[] = { CHAR, '>', EOS };
820 
821 /* Test if the current token is a whatever.  Accepts the current token if
822  * it is.  Returns 0 if it is not, non-zero if it is (in the case of
823  * TM_UNOP and TM_BINOP, the returned value is a Test_op).
824  */
825 static int
826 dbtestp_isa(Test_env *te, Test_meta meta)
827 {
828 	int c = tpeek(ARRAYVAR | (meta == TM_BINOP ? 0 : CONTIN));
829 	int uqword = 0;
830 	char *save = NULL;
831 	int ret = 0;
832 
833 	/* unquoted word? */
834 	uqword = c == LWORD && *ident;
835 
836 	if (meta == TM_OR)
837 		ret = c == LOGOR;
838 	else if (meta == TM_AND)
839 		ret = c == LOGAND;
840 	else if (meta == TM_NOT)
841 		ret = uqword && strcmp(yylval.cp, dbtest_tokens[(int) TM_NOT]) == 0;
842 	else if (meta == TM_OPAREN)
843 		ret = c == '(' /*)*/;
844 	else if (meta == TM_CPAREN)
845 		ret = c == /*(*/ ')';
846 	else if (meta == TM_UNOP || meta == TM_BINOP) {
847 		if (meta == TM_BINOP && c == REDIR &&
848 		    (yylval.iop->flag == IOREAD || yylval.iop->flag == IOWRITE)) {
849 			ret = 1;
850 			save = wdcopy(yylval.iop->flag == IOREAD ?
851 			    db_lthan : db_gthan, ATEMP);
852 		} else if (uqword && (ret = (int) test_isop(te, meta, ident)))
853 			save = yylval.cp;
854 	} else /* meta == TM_END */
855 		ret = uqword && strcmp(yylval.cp, db_close) == 0;
856 	if (ret) {
857 		reject = false;
858 		if (meta != TM_END) {
859 			if (!save)
860 				save = wdcopy(dbtest_tokens[(int) meta], ATEMP);
861 			XPput(*te->pos.av, save);
862 		}
863 	}
864 	return ret;
865 }
866 
867 static const char *
868 dbtestp_getopnd(Test_env *te, Test_op op, int do_eval)
869 {
870 	int c = tpeek(ARRAYVAR);
871 
872 	if (c != LWORD)
873 		return NULL;
874 
875 	reject = false;
876 	XPput(*te->pos.av, yylval.cp);
877 
878 	return null;
879 }
880 
881 static int
882 dbtestp_eval(Test_env *te, Test_op op, const char *opnd1, const char *opnd2,
883     int do_eval)
884 {
885 	return 1;
886 }
887 
888 static void
889 dbtestp_error(Test_env *te, int offset, const char *msg)
890 {
891 	te->flags |= TEF_ERROR;
892 
893 	if (offset < 0) {
894 		reject = true;
895 		/* Kludgy to say the least... */
896 		symbol = LWORD;
897 		yylval.cp = *(XPptrv(*te->pos.av) + XPsize(*te->pos.av) +
898 		    offset);
899 	}
900 	syntaxerr(msg);
901 }
902