xref: /netbsd-src/bin/sh/var.c (revision d909946ca08dceb44d7d0f22ec9488679695d976) 
1 /*	$NetBSD: var.c,v 1.49 2016/03/31 16:16:35 christos Exp $	*/
2 
3 /*-
4  * Copyright (c) 1991, 1993
5  *	The Regents of the University of California.  All rights reserved.
6  *
7  * This code is derived from software contributed to Berkeley by
8  * Kenneth Almquist.
9  *
10  * Redistribution and use in source and binary forms, with or without
11  * modification, are permitted provided that the following conditions
12  * are met:
13  * 1. Redistributions of source code must retain the above copyright
14  *    notice, this list of conditions and the following disclaimer.
15  * 2. Redistributions in binary form must reproduce the above copyright
16  *    notice, this list of conditions and the following disclaimer in the
17  *    documentation and/or other materials provided with the distribution.
18  * 3. Neither the name of the University nor the names of its contributors
19  *    may be used to endorse or promote products derived from this software
20  *    without specific prior written permission.
21  *
22  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
23  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
24  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
25  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
26  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
27  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
28  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
29  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
30  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
31  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32  * SUCH DAMAGE.
33  */
34 
35 #include <sys/cdefs.h>
36 #ifndef lint
37 #if 0
38 static char sccsid[] = "@(#)var.c	8.3 (Berkeley) 5/4/95";
39 #else
40 __RCSID("$NetBSD: var.c,v 1.49 2016/03/31 16:16:35 christos Exp $");
41 #endif
42 #endif /* not lint */
43 
44 #include <unistd.h>
45 #include <stdlib.h>
46 #include <string.h>
47 #include <paths.h>
48 #include <limits.h>
49 
50 /*
51  * Shell variables.
52  */
53 
54 #include "shell.h"
55 #include "output.h"
56 #include "expand.h"
57 #include "nodes.h"	/* for other headers */
58 #include "eval.h"	/* defines cmdenviron */
59 #include "exec.h"
60 #include "syntax.h"
61 #include "options.h"
62 #include "builtins.h"
63 #include "mail.h"
64 #include "var.h"
65 #include "memalloc.h"
66 #include "error.h"
67 #include "mystring.h"
68 #include "parser.h"
69 #include "show.h"
70 #ifndef SMALL
71 #include "myhistedit.h"
72 #endif
73 
74 #ifdef SMALL
75 #define VTABSIZE 39
76 #else
77 #define VTABSIZE 517
78 #endif
79 
80 
81 struct varinit {
82 	struct var *var;
83 	int flags;
84 	const char *text;
85 	void (*func)(const char *);
86 };
87 
88 struct localvar *localvars;
89 
90 #ifndef SMALL
91 struct var vhistsize;
92 struct var vterm;
93 #endif
94 struct var vifs;
95 struct var vmail;
96 struct var vmpath;
97 struct var vpath;
98 struct var vps1;
99 struct var vps2;
100 struct var vps4;
101 struct var vvers;
102 struct var voptind;
103 
104 char ifs_default[] = " \t\n";
105 
106 const struct varinit varinit[] = {
107 #ifndef SMALL
108 	{ &vhistsize,	VSTRFIXED|VTEXTFIXED|VUNSET,	"HISTSIZE=",
109 	  sethistsize },
110 #endif
111 	{ &vifs,	VSTRFIXED|VTEXTFIXED,		"IFS= \t\n",
112 	  NULL },
113 	{ &vmail,	VSTRFIXED|VTEXTFIXED|VUNSET,	"MAIL=",
114 	  NULL },
115 	{ &vmpath,	VSTRFIXED|VTEXTFIXED|VUNSET,	"MAILPATH=",
116 	  NULL },
117 	{ &vvers,	VSTRFIXED|VTEXTFIXED|VNOEXPORT, "NETBSD_SHELL=",
118 	  NULL },
119 	{ &vpath,	VSTRFIXED|VTEXTFIXED,		"PATH=" _PATH_DEFPATH,
120 	  changepath },
121 	/*
122 	 * vps1 depends on uid
123 	 */
124 	{ &vps2,	VSTRFIXED|VTEXTFIXED,		"PS2=> ",
125 	  NULL },
126 	{ &vps4,	VSTRFIXED|VTEXTFIXED,		"PS4=+ ",
127 	  NULL },
128 #ifndef SMALL
129 	{ &vterm,	VSTRFIXED|VTEXTFIXED|VUNSET,	"TERM=",
130 	  setterm },
131 #endif
132 	{ &voptind,	VSTRFIXED|VTEXTFIXED|VNOFUNC,	"OPTIND=1",
133 	  getoptsreset },
134 	{ NULL,	0,				NULL,
135 	  NULL }
136 };
137 
138 struct var *vartab[VTABSIZE];
139 
140 STATIC int strequal(const char *, const char *);
141 STATIC struct var *find_var(const char *, struct var ***, int *);
142 
143 /*
144  * Initialize the varable symbol tables and import the environment
145  */
146 
147 #ifdef mkinit
148 INCLUDE <stdio.h>
149 INCLUDE <unistd.h>
150 INCLUDE "var.h"
151 INCLUDE "version.h"
152 MKINIT char **environ;
153 INIT {
154 	char **envp;
155 	char buf[64];
156 
157 	initvar();
158 	for (envp = environ ; *envp ; envp++) {
159 		if (strchr(*envp, '=')) {
160 			setvareq(*envp, VEXPORT|VTEXTFIXED);
161 		}
162 	}
163 
164 	/*
165 	 * PPID is readonly
166 	 *	set after processing environ to override anything there
167 	 * Always default IFS, ignore any value from environment.
168 	 */
169 	snprintf(buf, sizeof(buf), "%d", (int)getppid());
170 	setvar("PPID", buf, VREADONLY);
171 	setvar("IFS", ifs_default, VTEXTFIXED);
172 	setvar("NETBSD_SHELL", NETBSD_SHELL, VTEXTFIXED|VREADONLY|VNOEXPORT);
173 }
174 #endif
175 
176 
177 /*
178  * This routine initializes the builtin variables.  It is called when the
179  * shell is initialized and again when a shell procedure is spawned.
180  */
181 
182 void
183 initvar(void)
184 {
185 	const struct varinit *ip;
186 	struct var *vp;
187 	struct var **vpp;
188 
189 	for (ip = varinit ; (vp = ip->var) != NULL ; ip++) {
190 		if (find_var(ip->text, &vpp, &vp->name_len) != NULL)
191 			continue;
192 		vp->next = *vpp;
193 		*vpp = vp;
194 		vp->text = strdup(ip->text);
195 		vp->flags = ip->flags;
196 		vp->func = ip->func;
197 	}
198 	/*
199 	 * PS1 depends on uid
200 	 */
201 	if (find_var("PS1", &vpp, &vps1.name_len) == NULL) {
202 		vps1.next = *vpp;
203 		*vpp = &vps1;
204 		vps1.flags = VSTRFIXED|VTEXTFIXED;
205 		vps1.text = NULL;
206 		choose_ps1();
207 	}
208 }
209 
210 void
211 choose_ps1(void)
212 {
213 	free(vps1.text);
214 	vps1.text = strdup(geteuid() ? "PS1=$ " : "PS1=# ");
215 }
216 
217 /*
218  * Safe version of setvar, returns 1 on success 0 on failure.
219  */
220 
221 int
222 setvarsafe(const char *name, const char *val, int flags)
223 {
224 	struct jmploc jmploc;
225 	struct jmploc *volatile savehandler = handler;
226 	int volatile err = 0;
227 
228 	if (setjmp(jmploc.loc))
229 		err = 1;
230 	else {
231 		handler = &jmploc;
232 		setvar(name, val, flags);
233 	}
234 	handler = savehandler;
235 	return err;
236 }
237 
238 /*
239  * Set the value of a variable.  The flags argument is ored with the
240  * flags of the variable.  If val is NULL, the variable is unset.
241  */
242 
243 void
244 setvar(const char *name, const char *val, int flags)
245 {
246 	const char *p;
247 	const char *q;
248 	char *d;
249 	int len;
250 	int namelen;
251 	char *nameeq;
252 	int isbad;
253 
254 	isbad = 0;
255 	p = name;
256 	if (! is_name(*p))
257 		isbad = 1;
258 	p++;
259 	for (;;) {
260 		if (! is_in_name(*p)) {
261 			if (*p == '\0' || *p == '=')
262 				break;
263 			isbad = 1;
264 		}
265 		p++;
266 	}
267 	namelen = p - name;
268 	if (isbad)
269 		error("%.*s: bad variable name", namelen, name);
270 	len = namelen + 2;		/* 2 is space for '=' and '\0' */
271 	if (val == NULL) {
272 		flags |= VUNSET;
273 	} else {
274 		len += strlen(val);
275 	}
276 	d = nameeq = ckmalloc(len);
277 	q = name;
278 	while (--namelen >= 0)
279 		*d++ = *q++;
280 	*d++ = '=';
281 	*d = '\0';
282 	if (val)
283 		scopy(val, d);
284 	setvareq(nameeq, flags);
285 }
286 
287 
288 
289 /*
290  * Same as setvar except that the variable and value are passed in
291  * the first argument as name=value.  Since the first argument will
292  * be actually stored in the table, it should not be a string that
293  * will go away.
294  */
295 
296 void
297 setvareq(char *s, int flags)
298 {
299 	struct var *vp, **vpp;
300 	int nlen;
301 
302 	if (aflag && !(flags & VNOEXPORT))
303 		flags |= VEXPORT;
304 	vp = find_var(s, &vpp, &nlen);
305 	if (vp != NULL) {
306 		if (vp->flags & VREADONLY)
307 			error("%.*s: is read only", vp->name_len, s);
308 		if (flags & VNOSET)
309 			return;
310 		INTOFF;
311 
312 		if (vp->func && (flags & VNOFUNC) == 0)
313 			(*vp->func)(s + vp->name_len + 1);
314 
315 		if ((vp->flags & (VTEXTFIXED|VSTACK)) == 0)
316 			ckfree(vp->text);
317 
318 		vp->flags &= ~(VTEXTFIXED|VSTACK|VUNSET);
319 		if (flags & VNOEXPORT)
320 			vp->flags &= ~VEXPORT;
321 		vp->flags |= flags & ~VNOFUNC;
322 		vp->text = s;
323 
324 		/*
325 		 * We could roll this to a function, to handle it as
326 		 * a regular variable function callback, but why bother?
327 		 */
328 		if (vp == &vmpath || (vp == &vmail && ! mpathset()))
329 			chkmail(1);
330 		INTON;
331 		return;
332 	}
333 	/* not found */
334 	if (flags & VNOSET)
335 		return;
336 	vp = ckmalloc(sizeof (*vp));
337 	vp->flags = flags & ~VNOFUNC;
338 	vp->text = s;
339 	vp->name_len = nlen;
340 	vp->next = *vpp;
341 	vp->func = NULL;
342 	*vpp = vp;
343 }
344 
345 
346 
347 /*
348  * Process a linked list of variable assignments.
349  */
350 
351 void
352 listsetvar(struct strlist *list, int flags)
353 {
354 	struct strlist *lp;
355 
356 	INTOFF;
357 	for (lp = list ; lp ; lp = lp->next) {
358 		setvareq(savestr(lp->text), flags);
359 	}
360 	INTON;
361 }
362 
363 void
364 listmklocal(struct strlist *list, int flags)
365 {
366 	struct strlist *lp;
367 
368 	for (lp = list ; lp ; lp = lp->next)
369 		mklocal(lp->text, flags);
370 }
371 
372 
373 /*
374  * Find the value of a variable.  Returns NULL if not set.
375  */
376 
377 char *
378 lookupvar(const char *name)
379 {
380 	struct var *v;
381 
382 	v = find_var(name, NULL, NULL);
383 	if (v == NULL || v->flags & VUNSET)
384 		return NULL;
385 	return v->text + v->name_len + 1;
386 }
387 
388 
389 
390 /*
391  * Search the environment of a builtin command.  If the second argument
392  * is nonzero, return the value of a variable even if it hasn't been
393  * exported.
394  */
395 
396 char *
397 bltinlookup(const char *name, int doall)
398 {
399 	struct strlist *sp;
400 	struct var *v;
401 
402 	for (sp = cmdenviron ; sp ; sp = sp->next) {
403 		if (strequal(sp->text, name))
404 			return strchr(sp->text, '=') + 1;
405 	}
406 
407 	v = find_var(name, NULL, NULL);
408 
409 	if (v == NULL || v->flags & VUNSET || (!doall && !(v->flags & VEXPORT)))
410 		return NULL;
411 	return v->text + v->name_len + 1;
412 }
413 
414 
415 
416 /*
417  * Generate a list of exported variables.  This routine is used to construct
418  * the third argument to execve when executing a program.
419  */
420 
421 char **
422 environment(void)
423 {
424 	int nenv;
425 	struct var **vpp;
426 	struct var *vp;
427 	char **env;
428 	char **ep;
429 
430 	nenv = 0;
431 	for (vpp = vartab ; vpp < vartab + VTABSIZE ; vpp++) {
432 		for (vp = *vpp ; vp ; vp = vp->next)
433 			if (vp->flags & VEXPORT)
434 				nenv++;
435 	}
436 	ep = env = stalloc((nenv + 1) * sizeof *env);
437 	for (vpp = vartab ; vpp < vartab + VTABSIZE ; vpp++) {
438 		for (vp = *vpp ; vp ; vp = vp->next)
439 			if (vp->flags & VEXPORT)
440 				*ep++ = vp->text;
441 	}
442 	*ep = NULL;
443 	return env;
444 }
445 
446 
447 /*
448  * Called when a shell procedure is invoked to clear out nonexported
449  * variables.  It is also necessary to reallocate variables of with
450  * VSTACK set since these are currently allocated on the stack.
451  */
452 
453 #ifdef mkinit
454 void shprocvar(void);
455 
456 SHELLPROC {
457 	shprocvar();
458 }
459 #endif
460 
461 void
462 shprocvar(void)
463 {
464 	struct var **vpp;
465 	struct var *vp, **prev;
466 
467 	for (vpp = vartab ; vpp < vartab + VTABSIZE ; vpp++) {
468 		for (prev = vpp ; (vp = *prev) != NULL ; ) {
469 			if ((vp->flags & VEXPORT) == 0) {
470 				*prev = vp->next;
471 				if ((vp->flags & VTEXTFIXED) == 0)
472 					ckfree(vp->text);
473 				if ((vp->flags & VSTRFIXED) == 0)
474 					ckfree(vp);
475 			} else {
476 				if (vp->flags & VSTACK) {
477 					vp->text = savestr(vp->text);
478 					vp->flags &=~ VSTACK;
479 				}
480 				prev = &vp->next;
481 			}
482 		}
483 	}
484 	initvar();
485 }
486 
487 
488 
489 /*
490  * Command to list all variables which are set.  Currently this command
491  * is invoked from the set command when the set command is called without
492  * any variables.
493  */
494 
495 void
496 print_quoted(const char *p)
497 {
498 	const char *q;
499 
500 	if (strcspn(p, "|&;<>()$`\\\"' \t\n*?[]#~=%") == strlen(p)) {
501 		out1fmt("%s", p);
502 		return;
503 	}
504 	while (*p) {
505 		if (*p == '\'') {
506 			out1fmt("\\'");
507 			p++;
508 			continue;
509 		}
510 		q = strchr(p, '\'');
511 		if (!q) {
512 			out1fmt("'%s'", p );
513 			return;
514 		}
515 		out1fmt("'%.*s'", (int)(q - p), p );
516 		p = q;
517 	}
518 }
519 
520 static int
521 sort_var(const void *v_v1, const void *v_v2)
522 {
523 	const struct var * const *v1 = v_v1;
524 	const struct var * const *v2 = v_v2;
525 
526 	/* XXX Will anyone notice we include the '=' of the shorter name? */
527 	return strcoll((*v1)->text, (*v2)->text);
528 }
529 
530 /*
531  * POSIX requires that 'set' (but not export or readonly) output the
532  * variables in lexicographic order - by the locale's collating order (sigh).
533  * Maybe we could keep them in an ordered balanced binary tree
534  * instead of hashed lists.
535  * For now just roll 'em through qsort for printing...
536  */
537 
538 int
539 showvars(const char *name, int flag, int show_value, const char *xtra)
540 {
541 	struct var **vpp;
542 	struct var *vp;
543 	const char *p;
544 
545 	static struct var **list;	/* static in case we are interrupted */
546 	static int list_len;
547 	int count = 0;
548 
549 	if (!list) {
550 		list_len = 32;
551 		list = ckmalloc(list_len * sizeof *list);
552 	}
553 
554 	for (vpp = vartab ; vpp < vartab + VTABSIZE ; vpp++) {
555 		for (vp = *vpp ; vp ; vp = vp->next) {
556 			if (flag && !(vp->flags & flag))
557 				continue;
558 			if (vp->flags & VUNSET && !(show_value & 2))
559 				continue;
560 			if (count >= list_len) {
561 				list = ckrealloc(list,
562 					(list_len << 1) * sizeof *list);
563 				list_len <<= 1;
564 			}
565 			list[count++] = vp;
566 		}
567 	}
568 
569 	qsort(list, count, sizeof *list, sort_var);
570 
571 	for (vpp = list; count--; vpp++) {
572 		vp = *vpp;
573 		if (name)
574 			out1fmt("%s ", name);
575 		if (xtra)
576 			out1fmt("%s ", xtra);
577 		for (p = vp->text ; *p != '=' ; p++)
578 			out1c(*p);
579 		if (!(vp->flags & VUNSET) && show_value) {
580 			out1fmt("=");
581 			print_quoted(++p);
582 		}
583 		out1c('\n');
584 	}
585 	return 0;
586 }
587 
588 
589 
590 /*
591  * The export and readonly commands.
592  */
593 
594 int
595 exportcmd(int argc, char **argv)
596 {
597 	struct var *vp;
598 	char *name;
599 	const char *p;
600 	int flag = argv[0][0] == 'r'? VREADONLY : VEXPORT;
601 	int pflg = 0;
602 	int nflg = 0;
603 	int xflg = 0;
604 	int res;
605 	int c;
606 
607 
608 	while ((c = nextopt("npx")) != '\0') {
609 		switch (c) {
610 		case 'p':
611 			if (nflg)
612 				return 1;
613 			pflg = 3;
614 			break;
615 		case 'n':
616 			if (pflg || xflg || flag == VREADONLY)
617 				return 1;
618 			nflg = 1;
619 			break;
620 		case 'x':
621 			if (nflg || flag == VREADONLY)
622 				return 1;
623 			flag = VNOEXPORT;
624 			xflg = 1;
625 			break;
626 		default:
627 			return 1;
628 		}
629 	}
630 
631 	if (nflg && *argptr == NULL)
632 		return 1;
633 
634 	if (pflg || *argptr == NULL) {
635 		showvars( pflg ? argv[0] : 0, flag, pflg,
636 		    pflg && xflg ? "-x" : NULL );
637 		return 0;
638 	}
639 
640 	res = 0;
641 	while ((name = *argptr++) != NULL) {
642 		if ((p = strchr(name, '=')) != NULL) {
643 			p++;
644 		} else {
645 			vp = find_var(name, NULL, NULL);
646 			if (vp != NULL) {
647 				if (nflg)
648 					vp->flags &= ~flag;
649 				else if (flag&VEXPORT && vp->flags&VNOEXPORT)
650 					res = 1;
651 				else {
652 					vp->flags |= flag;
653 					if (flag == VNOEXPORT)
654 						vp->flags &= ~VEXPORT;
655 				}
656 				continue;
657 			}
658 		}
659 		if (!nflg)
660 			setvar(name, p, flag);
661 	}
662 	return res;
663 }
664 
665 
666 /*
667  * The "local" command.
668  */
669 
670 int
671 localcmd(int argc, char **argv)
672 {
673 	char *name;
674 
675 	if (! in_function())
676 		error("Not in a function");
677 	while ((name = *argptr++) != NULL) {
678 		mklocal(name, 0);
679 	}
680 	return 0;
681 }
682 
683 
684 /*
685  * Make a variable a local variable.  When a variable is made local, its
686  * value and flags are saved in a localvar structure.  The saved values
687  * will be restored when the shell function returns.  We handle the name
688  * "-" as a special case.
689  */
690 
691 void
692 mklocal(const char *name, int flags)
693 {
694 	struct localvar *lvp;
695 	struct var **vpp;
696 	struct var *vp;
697 
698 	INTOFF;
699 	lvp = ckmalloc(sizeof (struct localvar));
700 	if (name[0] == '-' && name[1] == '\0') {
701 		char *p;
702 		p = ckmalloc(sizeof_optlist);
703 		lvp->text = memcpy(p, optlist, sizeof_optlist);
704 		vp = NULL;
705 	} else {
706 		vp = find_var(name, &vpp, NULL);
707 		if (vp == NULL) {
708 			if (strchr(name, '='))
709 				setvareq(savestr(name), VSTRFIXED|flags);
710 			else
711 				setvar(name, NULL, VSTRFIXED|flags);
712 			vp = *vpp;	/* the new variable */
713 			lvp->text = NULL;
714 			lvp->flags = VUNSET;
715 		} else {
716 			lvp->text = vp->text;
717 			lvp->flags = vp->flags;
718 			vp->flags |= VSTRFIXED|VTEXTFIXED;
719 			if (name[vp->name_len] == '=')
720 				setvareq(savestr(name), flags);
721 		}
722 	}
723 	lvp->vp = vp;
724 	lvp->next = localvars;
725 	localvars = lvp;
726 	INTON;
727 }
728 
729 
730 /*
731  * Called after a function returns.
732  */
733 
734 void
735 poplocalvars(void)
736 {
737 	struct localvar *lvp;
738 	struct var *vp;
739 
740 	while ((lvp = localvars) != NULL) {
741 		localvars = lvp->next;
742 		vp = lvp->vp;
743 		TRACE(("poplocalvar %s", vp ? vp->text : "-"));
744 		if (vp == NULL) {	/* $- saved */
745 			memcpy(optlist, lvp->text, sizeof_optlist);
746 			ckfree(lvp->text);
747 		} else if ((lvp->flags & (VUNSET|VSTRFIXED)) == VUNSET) {
748 			(void)unsetvar(vp->text, 0);
749 		} else {
750 			if (vp->func && (vp->flags & VNOFUNC) == 0)
751 				(*vp->func)(lvp->text + vp->name_len + 1);
752 			if ((vp->flags & VTEXTFIXED) == 0)
753 				ckfree(vp->text);
754 			vp->flags = lvp->flags;
755 			vp->text = lvp->text;
756 		}
757 		ckfree(lvp);
758 	}
759 }
760 
761 
762 int
763 setvarcmd(int argc, char **argv)
764 {
765 	if (argc <= 2)
766 		return unsetcmd(argc, argv);
767 	else if (argc == 3)
768 		setvar(argv[1], argv[2], 0);
769 	else
770 		error("List assignment not implemented");
771 	return 0;
772 }
773 
774 
775 /*
776  * The unset builtin command.  We unset the function before we unset the
777  * variable to allow a function to be unset when there is a readonly variable
778  * with the same name.
779  */
780 
781 int
782 unsetcmd(int argc, char **argv)
783 {
784 	char **ap;
785 	int i;
786 	int flg_func = 0;
787 	int flg_var = 0;
788 	int ret = 0;
789 
790 	while ((i = nextopt("evf")) != '\0') {
791 		if (i == 'f')
792 			flg_func = 1;
793 		else
794 			flg_var = i;
795 	}
796 	if (flg_func == 0 && flg_var == 0)
797 		flg_var = 1;
798 
799 	for (ap = argptr; *ap ; ap++) {
800 		if (flg_func)
801 			ret |= unsetfunc(*ap);
802 		if (flg_var)
803 			ret |= unsetvar(*ap, flg_var == 'e');
804 	}
805 	return ret;
806 }
807 
808 
809 /*
810  * Unset the specified variable.
811  */
812 
813 int
814 unsetvar(const char *s, int unexport)
815 {
816 	struct var **vpp;
817 	struct var *vp;
818 
819 	vp = find_var(s, &vpp, NULL);
820 	if (vp == NULL)
821 		return 0;
822 
823 	if (vp->flags & VREADONLY && !unexport)
824 		return 1;
825 
826 	INTOFF;
827 	if (unexport) {
828 		vp->flags &= ~VEXPORT;
829 	} else {
830 		if (vp->text[vp->name_len + 1] != '\0')
831 			setvar(s, nullstr, 0);
832 		vp->flags &= ~VEXPORT;
833 		vp->flags |= VUNSET;
834 		if ((vp->flags & VSTRFIXED) == 0) {
835 			if ((vp->flags & VTEXTFIXED) == 0)
836 				ckfree(vp->text);
837 			*vpp = vp->next;
838 			ckfree(vp);
839 		}
840 	}
841 	INTON;
842 	return 0;
843 }
844 
845 
846 /*
847  * Returns true if the two strings specify the same varable.  The first
848  * variable name is terminated by '='; the second may be terminated by
849  * either '=' or '\0'.
850  */
851 
852 STATIC int
853 strequal(const char *p, const char *q)
854 {
855 	while (*p == *q++) {
856 		if (*p++ == '=')
857 			return 1;
858 	}
859 	if (*p == '=' && *(q - 1) == '\0')
860 		return 1;
861 	return 0;
862 }
863 
864 /*
865  * Search for a variable.
866  * 'name' may be terminated by '=' or a NUL.
867  * vppp is set to the pointer to vp, or the list head if vp isn't found
868  * lenp is set to the number of charactets in 'name'
869  */
870 
871 STATIC struct var *
872 find_var(const char *name, struct var ***vppp, int *lenp)
873 {
874 	unsigned int hashval;
875 	int len;
876 	struct var *vp, **vpp;
877 	const char *p = name;
878 
879 	hashval = 0;
880 	while (*p && *p != '=')
881 		hashval = 2 * hashval + (unsigned char)*p++;
882 	len = p - name;
883 
884 	if (lenp)
885 		*lenp = len;
886 	vpp = &vartab[hashval % VTABSIZE];
887 	if (vppp)
888 		*vppp = vpp;
889 
890 	for (vp = *vpp ; vp ; vpp = &vp->next, vp = *vpp) {
891 		if (vp->name_len != len)
892 			continue;
893 		if (memcmp(vp->text, name, len) != 0)
894 			continue;
895 		if (vppp)
896 			*vppp = vpp;
897 		return vp;
898 	}
899 	return NULL;
900 }
901