xref: /freebsd/bin/sh/var.c (revision a0409676120c1e558d0ade943019934e0f15118d) 
1 /*-
2  * SPDX-License-Identifier: BSD-3-Clause
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 #ifndef lint
36 #if 0
37 static char sccsid[] = "@(#)var.c	8.3 (Berkeley) 5/4/95";
38 #endif
39 #endif /* not lint */
40 #include <sys/cdefs.h>
41 __FBSDID("$FreeBSD$");
42 
43 #include <unistd.h>
44 #include <stdlib.h>
45 #include <paths.h>
46 
47 /*
48  * Shell variables.
49  */
50 
51 #include <locale.h>
52 #include <langinfo.h>
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 "mail.h"
63 #include "var.h"
64 #include "memalloc.h"
65 #include "error.h"
66 #include "mystring.h"
67 #include "parser.h"
68 #include "builtins.h"
69 #ifndef NO_HISTORY
70 #include "myhistedit.h"
71 #endif
72 
73 
74 #ifndef VTABSIZE
75 #define VTABSIZE 39
76 #endif
77 
78 
79 struct varinit {
80 	struct var *var;
81 	int flags;
82 	const char *text;
83 	void (*func)(const char *);
84 };
85 
86 
87 #ifndef NO_HISTORY
88 struct var vhistsize;
89 struct var vterm;
90 #endif
91 struct var vifs;
92 struct var vmail;
93 struct var vmpath;
94 struct var vpath;
95 struct var vps1;
96 struct var vps2;
97 struct var vps4;
98 static struct var voptind;
99 struct var vdisvfork;
100 
101 struct localvar *localvars;
102 int forcelocal;
103 
104 static const struct varinit varinit[] = {
105 #ifndef NO_HISTORY
106 	{ &vhistsize,	VUNSET,				"HISTSIZE=",
107 	  sethistsize },
108 #endif
109 	{ &vifs,	0,				"IFS= \t\n",
110 	  NULL },
111 	{ &vmail,	VUNSET,				"MAIL=",
112 	  NULL },
113 	{ &vmpath,	VUNSET,				"MAILPATH=",
114 	  NULL },
115 	{ &vpath,	0,				"PATH=" _PATH_DEFPATH,
116 	  changepath },
117 	/*
118 	 * vps1 depends on uid
119 	 */
120 	{ &vps2,	0,				"PS2=> ",
121 	  NULL },
122 	{ &vps4,	0,				"PS4=+ ",
123 	  NULL },
124 #ifndef NO_HISTORY
125 	{ &vterm,	VUNSET,				"TERM=",
126 	  setterm },
127 #endif
128 	{ &voptind,	0,				"OPTIND=1",
129 	  getoptsreset },
130 	{ &vdisvfork,	VUNSET,				"SH_DISABLE_VFORK=",
131 	  NULL },
132 	{ NULL,	0,				NULL,
133 	  NULL }
134 };
135 
136 static struct var *vartab[VTABSIZE];
137 
138 static const char *const locale_names[7] = {
139 	"LC_COLLATE", "LC_CTYPE", "LC_MONETARY",
140 	"LC_NUMERIC", "LC_TIME", "LC_MESSAGES", NULL
141 };
142 static const int locale_categories[7] = {
143 	LC_COLLATE, LC_CTYPE, LC_MONETARY, LC_NUMERIC, LC_TIME, LC_MESSAGES, 0
144 };
145 
146 static int varequal(const char *, const char *);
147 static struct var *find_var(const char *, struct var ***, int *);
148 static int localevar(const char *);
149 static void setvareq_const(const char *s, int flags);
150 
151 extern char **environ;
152 
153 /*
154  * This routine initializes the builtin variables and imports the environment.
155  * It is called when the shell is initialized.
156  */
157 
158 void
159 initvar(void)
160 {
161 	char ppid[20];
162 	const struct varinit *ip;
163 	struct var *vp;
164 	struct var **vpp;
165 	char **envp;
166 
167 	for (ip = varinit ; (vp = ip->var) != NULL ; ip++) {
168 		if (find_var(ip->text, &vpp, &vp->name_len) != NULL)
169 			continue;
170 		vp->next = *vpp;
171 		*vpp = vp;
172 		vp->text = __DECONST(char *, ip->text);
173 		vp->flags = ip->flags | VSTRFIXED | VTEXTFIXED;
174 		vp->func = ip->func;
175 	}
176 	/*
177 	 * PS1 depends on uid
178 	 */
179 	if (find_var("PS1", &vpp, &vps1.name_len) == NULL) {
180 		vps1.next = *vpp;
181 		*vpp = &vps1;
182 		vps1.text = __DECONST(char *, geteuid() ? "PS1=$ " : "PS1=# ");
183 		vps1.flags = VSTRFIXED|VTEXTFIXED;
184 	}
185 	fmtstr(ppid, sizeof(ppid), "%d", (int)getppid());
186 	setvarsafe("PPID", ppid, 0);
187 	for (envp = environ ; *envp ; envp++) {
188 		if (strchr(*envp, '=')) {
189 			setvareq(*envp, VEXPORT|VTEXTFIXED);
190 		}
191 	}
192 	setvareq_const("OPTIND=1", 0);
193 	setvareq_const("IFS= \t\n", 0);
194 }
195 
196 /*
197  * Safe version of setvar, returns 1 on success 0 on failure.
198  */
199 
200 int
201 setvarsafe(const char *name, const char *val, int flags)
202 {
203 	struct jmploc jmploc;
204 	struct jmploc *const savehandler = handler;
205 	int err = 0;
206 	int inton;
207 
208 	inton = is_int_on();
209 	if (setjmp(jmploc.loc))
210 		err = 1;
211 	else {
212 		handler = &jmploc;
213 		setvar(name, val, flags);
214 	}
215 	handler = savehandler;
216 	SETINTON(inton);
217 	return err;
218 }
219 
220 /*
221  * Set the value of a variable.  The flags argument is stored with the
222  * flags of the variable.  If val is NULL, the variable is unset.
223  */
224 
225 void
226 setvar(const char *name, const char *val, int flags)
227 {
228 	const char *p;
229 	size_t len;
230 	size_t namelen;
231 	size_t vallen;
232 	char *nameeq;
233 	int isbad;
234 
235 	isbad = 0;
236 	p = name;
237 	if (! is_name(*p))
238 		isbad = 1;
239 	p++;
240 	for (;;) {
241 		if (! is_in_name(*p)) {
242 			if (*p == '\0' || *p == '=')
243 				break;
244 			isbad = 1;
245 		}
246 		p++;
247 	}
248 	namelen = p - name;
249 	if (isbad)
250 		error("%.*s: bad variable name", (int)namelen, name);
251 	len = namelen + 2;		/* 2 is space for '=' and '\0' */
252 	if (val == NULL) {
253 		flags |= VUNSET;
254 		vallen = 0;
255 	} else {
256 		vallen = strlen(val);
257 		len += vallen;
258 	}
259 	INTOFF;
260 	nameeq = ckmalloc(len);
261 	memcpy(nameeq, name, namelen);
262 	nameeq[namelen] = '=';
263 	if (val)
264 		memcpy(nameeq + namelen + 1, val, vallen + 1);
265 	else
266 		nameeq[namelen + 1] = '\0';
267 	setvareq(nameeq, flags);
268 	INTON;
269 }
270 
271 static int
272 localevar(const char *s)
273 {
274 	const char *const *ss;
275 
276 	if (*s != 'L')
277 		return 0;
278 	if (varequal(s + 1, "ANG"))
279 		return 1;
280 	if (strncmp(s + 1, "C_", 2) != 0)
281 		return 0;
282 	if (varequal(s + 3, "ALL"))
283 		return 1;
284 	for (ss = locale_names; *ss ; ss++)
285 		if (varequal(s + 3, *ss + 3))
286 			return 1;
287 	return 0;
288 }
289 
290 
291 /*
292  * Sets/unsets an environment variable from a pointer that may actually be a
293  * pointer into environ where the string should not be manipulated.
294  */
295 static void
296 change_env(const char *s, int set)
297 {
298 	char *eqp;
299 	char *ss;
300 
301 	INTOFF;
302 	ss = savestr(s);
303 	if ((eqp = strchr(ss, '=')) != NULL)
304 		*eqp = '\0';
305 	if (set && eqp != NULL)
306 		(void) setenv(ss, eqp + 1, 1);
307 	else
308 		(void) unsetenv(ss);
309 	ckfree(ss);
310 	INTON;
311 
312 	return;
313 }
314 
315 
316 /*
317  * Same as setvar except that the variable and value are passed in
318  * the first argument as name=value.  Since the first argument will
319  * be actually stored in the table, it should not be a string that
320  * will go away.
321  */
322 
323 void
324 setvareq(char *s, int flags)
325 {
326 	struct var *vp, **vpp;
327 	int nlen;
328 
329 	if (aflag)
330 		flags |= VEXPORT;
331 	if (forcelocal && !(flags & (VNOSET | VNOLOCAL)))
332 		mklocal(s);
333 	vp = find_var(s, &vpp, &nlen);
334 	if (vp != NULL) {
335 		if (vp->flags & VREADONLY) {
336 			if ((flags & (VTEXTFIXED|VSTACK)) == 0)
337 				ckfree(s);
338 			error("%.*s: is read only", vp->name_len, vp->text);
339 		}
340 		if (flags & VNOSET) {
341 			if ((flags & (VTEXTFIXED|VSTACK)) == 0)
342 				ckfree(s);
343 			return;
344 		}
345 		INTOFF;
346 
347 		if (vp->func && (flags & VNOFUNC) == 0)
348 			(*vp->func)(s + vp->name_len + 1);
349 
350 		if ((vp->flags & (VTEXTFIXED|VSTACK)) == 0)
351 			ckfree(vp->text);
352 
353 		vp->flags &= ~(VTEXTFIXED|VSTACK|VUNSET);
354 		vp->flags |= flags;
355 		vp->text = s;
356 
357 		/*
358 		 * We could roll this to a function, to handle it as
359 		 * a regular variable function callback, but why bother?
360 		 *
361 		 * Note: this assumes iflag is not set to 1 initially.
362 		 * As part of initvar(), this is called before arguments
363 		 * are looked at.
364 		 */
365 		if ((vp == &vmpath || (vp == &vmail && ! mpathset())) &&
366 		    iflag == 1)
367 			chkmail(1);
368 		if ((vp->flags & VEXPORT) && localevar(s)) {
369 			change_env(s, 1);
370 			(void) setlocale(LC_ALL, "");
371 			updatecharset();
372 		}
373 		INTON;
374 		return;
375 	}
376 	/* not found */
377 	if (flags & VNOSET) {
378 		if ((flags & (VTEXTFIXED|VSTACK)) == 0)
379 			ckfree(s);
380 		return;
381 	}
382 	INTOFF;
383 	vp = ckmalloc(sizeof (*vp));
384 	vp->flags = flags;
385 	vp->text = s;
386 	vp->name_len = nlen;
387 	vp->next = *vpp;
388 	vp->func = NULL;
389 	*vpp = vp;
390 	if ((vp->flags & VEXPORT) && localevar(s)) {
391 		change_env(s, 1);
392 		(void) setlocale(LC_ALL, "");
393 		updatecharset();
394 	}
395 	INTON;
396 }
397 
398 
399 static void
400 setvareq_const(const char *s, int flags)
401 {
402 	setvareq(__DECONST(char *, s), flags | VTEXTFIXED);
403 }
404 
405 
406 /*
407  * Process a linked list of variable assignments.
408  */
409 
410 void
411 listsetvar(struct arglist *list, int flags)
412 {
413 	int i;
414 
415 	INTOFF;
416 	for (i = 0; i < list->count; i++)
417 		setvareq(savestr(list->args[i]), flags);
418 	INTON;
419 }
420 
421 
422 
423 /*
424  * Find the value of a variable.  Returns NULL if not set.
425  */
426 
427 char *
428 lookupvar(const char *name)
429 {
430 	struct var *v;
431 
432 	v = find_var(name, NULL, NULL);
433 	if (v == NULL || v->flags & VUNSET)
434 		return NULL;
435 	return v->text + v->name_len + 1;
436 }
437 
438 
439 
440 /*
441  * Search the environment of a builtin command.  If the second argument
442  * is nonzero, return the value of a variable even if it hasn't been
443  * exported.
444  */
445 
446 char *
447 bltinlookup(const char *name, int doall)
448 {
449 	struct var *v;
450 	char *result;
451 	int i;
452 
453 	result = NULL;
454 	if (cmdenviron) for (i = 0; i < cmdenviron->count; i++) {
455 		if (varequal(cmdenviron->args[i], name))
456 			result = strchr(cmdenviron->args[i], '=') + 1;
457 	}
458 	if (result != NULL)
459 		return result;
460 
461 	v = find_var(name, NULL, NULL);
462 	if (v == NULL || v->flags & VUNSET ||
463 	    (!doall && (v->flags & VEXPORT) == 0))
464 		return NULL;
465 	return v->text + v->name_len + 1;
466 }
467 
468 
469 /*
470  * Set up locale for a builtin (LANG/LC_* assignments).
471  */
472 void
473 bltinsetlocale(void)
474 {
475 	int act = 0;
476 	char *loc, *locdef;
477 	int i;
478 
479 	if (cmdenviron) for (i = 0; i < cmdenviron->count; i++) {
480 		if (localevar(cmdenviron->args[i])) {
481 			act = 1;
482 			break;
483 		}
484 	}
485 	if (!act)
486 		return;
487 	loc = bltinlookup("LC_ALL", 0);
488 	INTOFF;
489 	if (loc != NULL) {
490 		setlocale(LC_ALL, loc);
491 		INTON;
492 		updatecharset();
493 		return;
494 	}
495 	locdef = bltinlookup("LANG", 0);
496 	for (i = 0; locale_names[i] != NULL; i++) {
497 		loc = bltinlookup(locale_names[i], 0);
498 		if (loc == NULL)
499 			loc = locdef;
500 		if (loc != NULL)
501 			setlocale(locale_categories[i], loc);
502 	}
503 	INTON;
504 	updatecharset();
505 }
506 
507 /*
508  * Undo the effect of bltinlocaleset().
509  */
510 void
511 bltinunsetlocale(void)
512 {
513 	int i;
514 
515 	INTOFF;
516 	if (cmdenviron) for (i = 0; i < cmdenviron->count; i++) {
517 		if (localevar(cmdenviron->args[i])) {
518 			setlocale(LC_ALL, "");
519 			updatecharset();
520 			break;
521 		}
522 	}
523 	INTON;
524 }
525 
526 /*
527  * Update the localeisutf8 flag.
528  */
529 void
530 updatecharset(void)
531 {
532 	char *charset;
533 
534 	charset = nl_langinfo(CODESET);
535 	localeisutf8 = !strcmp(charset, "UTF-8");
536 }
537 
538 void
539 initcharset(void)
540 {
541 	updatecharset();
542 	initial_localeisutf8 = localeisutf8;
543 }
544 
545 /*
546  * Generate a list of exported variables.  This routine is used to construct
547  * the third argument to execve when executing a program.
548  */
549 
550 char **
551 environment(void)
552 {
553 	int nenv;
554 	struct var **vpp;
555 	struct var *vp;
556 	char **env, **ep;
557 
558 	nenv = 0;
559 	for (vpp = vartab ; vpp < vartab + VTABSIZE ; vpp++) {
560 		for (vp = *vpp ; vp ; vp = vp->next)
561 			if ((vp->flags & (VEXPORT|VUNSET)) == VEXPORT)
562 				nenv++;
563 	}
564 	ep = env = stalloc((nenv + 1) * sizeof *env);
565 	for (vpp = vartab ; vpp < vartab + VTABSIZE ; vpp++) {
566 		for (vp = *vpp ; vp ; vp = vp->next)
567 			if ((vp->flags & (VEXPORT|VUNSET)) == VEXPORT)
568 				*ep++ = vp->text;
569 	}
570 	*ep = NULL;
571 	return env;
572 }
573 
574 
575 static int
576 var_compare(const void *a, const void *b)
577 {
578 	const char *const *sa, *const *sb;
579 
580 	sa = a;
581 	sb = b;
582 	/*
583 	 * This compares two var=value strings which creates a different
584 	 * order from what you would probably expect.  POSIX is somewhat
585 	 * ambiguous on what should be sorted exactly.
586 	 */
587 	return strcoll(*sa, *sb);
588 }
589 
590 
591 /*
592  * Command to list all variables which are set.  This is invoked from the
593  * set command when it is called without any options or operands.
594  */
595 
596 int
597 showvarscmd(int argc __unused, char **argv __unused)
598 {
599 	struct var **vpp;
600 	struct var *vp;
601 	const char *s;
602 	const char **vars;
603 	int i, n;
604 
605 	/*
606 	 * POSIX requires us to sort the variables.
607 	 */
608 	n = 0;
609 	for (vpp = vartab; vpp < vartab + VTABSIZE; vpp++) {
610 		for (vp = *vpp; vp; vp = vp->next) {
611 			if (!(vp->flags & VUNSET))
612 				n++;
613 		}
614 	}
615 
616 	INTOFF;
617 	vars = ckmalloc(n * sizeof(*vars));
618 	i = 0;
619 	for (vpp = vartab; vpp < vartab + VTABSIZE; vpp++) {
620 		for (vp = *vpp; vp; vp = vp->next) {
621 			if (!(vp->flags & VUNSET))
622 				vars[i++] = vp->text;
623 		}
624 	}
625 
626 	qsort(vars, n, sizeof(*vars), var_compare);
627 	for (i = 0; i < n; i++) {
628 		/*
629 		 * Skip improper variable names so the output remains usable as
630 		 * shell input.
631 		 */
632 		if (!isassignment(vars[i]))
633 			continue;
634 		s = strchr(vars[i], '=');
635 		s++;
636 		outbin(vars[i], s - vars[i], out1);
637 		out1qstr(s);
638 		out1c('\n');
639 	}
640 	ckfree(vars);
641 	INTON;
642 
643 	return 0;
644 }
645 
646 
647 
648 /*
649  * The export and readonly commands.
650  */
651 
652 int
653 exportcmd(int argc __unused, char **argv)
654 {
655 	struct var **vpp;
656 	struct var *vp;
657 	char **ap;
658 	char *name;
659 	char *p;
660 	char *cmdname;
661 	int ch, values;
662 	int flag = argv[0][0] == 'r'? VREADONLY : VEXPORT;
663 
664 	cmdname = argv[0];
665 	values = 0;
666 	while ((ch = nextopt("p")) != '\0') {
667 		switch (ch) {
668 		case 'p':
669 			values = 1;
670 			break;
671 		}
672 	}
673 
674 	if (values && *argptr != NULL)
675 		error("-p requires no arguments");
676 	if (*argptr != NULL) {
677 		for (ap = argptr; (name = *ap) != NULL; ap++) {
678 			if ((p = strchr(name, '=')) != NULL) {
679 				p++;
680 			} else {
681 				vp = find_var(name, NULL, NULL);
682 				if (vp != NULL) {
683 					vp->flags |= flag;
684 					if ((vp->flags & VEXPORT) && localevar(vp->text)) {
685 						change_env(vp->text, 1);
686 						(void) setlocale(LC_ALL, "");
687 						updatecharset();
688 					}
689 					continue;
690 				}
691 			}
692 			setvar(name, p, flag);
693 		}
694 	} else {
695 		for (vpp = vartab ; vpp < vartab + VTABSIZE ; vpp++) {
696 			for (vp = *vpp ; vp ; vp = vp->next) {
697 				if (vp->flags & flag) {
698 					if (values) {
699 						/*
700 						 * Skip improper variable names
701 						 * so the output remains usable
702 						 * as shell input.
703 						 */
704 						if (!isassignment(vp->text))
705 							continue;
706 						out1str(cmdname);
707 						out1c(' ');
708 					}
709 					if (values && !(vp->flags & VUNSET)) {
710 						outbin(vp->text,
711 						    vp->name_len + 1, out1);
712 						out1qstr(vp->text +
713 						    vp->name_len + 1);
714 					} else
715 						outbin(vp->text, vp->name_len,
716 						    out1);
717 					out1c('\n');
718 				}
719 			}
720 		}
721 	}
722 	return 0;
723 }
724 
725 
726 /*
727  * The "local" command.
728  */
729 
730 int
731 localcmd(int argc __unused, char **argv __unused)
732 {
733 	char *name;
734 
735 	nextopt("");
736 	if (! in_function())
737 		error("Not in a function");
738 	while ((name = *argptr++) != NULL) {
739 		mklocal(name);
740 	}
741 	return 0;
742 }
743 
744 
745 /*
746  * Make a variable a local variable.  When a variable is made local, it's
747  * value and flags are saved in a localvar structure.  The saved values
748  * will be restored when the shell function returns.  We handle the name
749  * "-" as a special case.
750  */
751 
752 void
753 mklocal(char *name)
754 {
755 	struct localvar *lvp;
756 	struct var **vpp;
757 	struct var *vp;
758 
759 	INTOFF;
760 	lvp = ckmalloc(sizeof (struct localvar));
761 	if (name[0] == '-' && name[1] == '\0') {
762 		lvp->text = ckmalloc(sizeof optval);
763 		memcpy(lvp->text, optval, sizeof optval);
764 		vp = NULL;
765 	} else {
766 		vp = find_var(name, &vpp, NULL);
767 		if (vp == NULL) {
768 			if (strchr(name, '='))
769 				setvareq(savestr(name), VSTRFIXED | VNOLOCAL);
770 			else
771 				setvar(name, NULL, VSTRFIXED | VNOLOCAL);
772 			vp = *vpp;	/* the new variable */
773 			lvp->text = NULL;
774 			lvp->flags = VUNSET;
775 		} else {
776 			lvp->text = vp->text;
777 			lvp->flags = vp->flags;
778 			vp->flags |= VSTRFIXED|VTEXTFIXED;
779 			if (name[vp->name_len] == '=')
780 				setvareq(savestr(name), VNOLOCAL);
781 		}
782 	}
783 	lvp->vp = vp;
784 	lvp->next = localvars;
785 	localvars = lvp;
786 	INTON;
787 }
788 
789 
790 /*
791  * Called after a function returns.
792  */
793 
794 void
795 poplocalvars(void)
796 {
797 	struct localvar *lvp;
798 	struct var *vp;
799 	int islocalevar;
800 
801 	INTOFF;
802 	while ((lvp = localvars) != NULL) {
803 		localvars = lvp->next;
804 		vp = lvp->vp;
805 		if (vp == NULL) {	/* $- saved */
806 			memcpy(optval, lvp->text, sizeof optval);
807 			ckfree(lvp->text);
808 			optschanged();
809 		} else if ((lvp->flags & (VUNSET|VSTRFIXED)) == VUNSET) {
810 			vp->flags &= ~VREADONLY;
811 			(void)unsetvar(vp->text);
812 		} else {
813 			islocalevar = (vp->flags | lvp->flags) & VEXPORT &&
814 			    localevar(lvp->text);
815 			if ((vp->flags & VTEXTFIXED) == 0)
816 				ckfree(vp->text);
817 			vp->flags = lvp->flags;
818 			vp->text = lvp->text;
819 			if (vp->func)
820 				(*vp->func)(vp->text + vp->name_len + 1);
821 			if (islocalevar) {
822 				change_env(vp->text, vp->flags & VEXPORT &&
823 				    (vp->flags & VUNSET) == 0);
824 				setlocale(LC_ALL, "");
825 				updatecharset();
826 			}
827 		}
828 		ckfree(lvp);
829 	}
830 	INTON;
831 }
832 
833 
834 int
835 setvarcmd(int argc, char **argv)
836 {
837 	if (argc <= 2)
838 		return unsetcmd(argc, argv);
839 	else if (argc == 3)
840 		setvar(argv[1], argv[2], 0);
841 	else
842 		error("too many arguments");
843 	return 0;
844 }
845 
846 
847 /*
848  * The unset builtin command.
849  */
850 
851 int
852 unsetcmd(int argc __unused, char **argv __unused)
853 {
854 	char **ap;
855 	int i;
856 	int flg_func = 0;
857 	int flg_var = 0;
858 	int ret = 0;
859 
860 	while ((i = nextopt("vf")) != '\0') {
861 		if (i == 'f')
862 			flg_func = 1;
863 		else
864 			flg_var = 1;
865 	}
866 	if (flg_func == 0 && flg_var == 0)
867 		flg_var = 1;
868 
869 	INTOFF;
870 	for (ap = argptr; *ap ; ap++) {
871 		if (flg_func)
872 			ret |= unsetfunc(*ap);
873 		if (flg_var)
874 			ret |= unsetvar(*ap);
875 	}
876 	INTON;
877 	return ret;
878 }
879 
880 
881 /*
882  * Unset the specified variable.
883  * Called with interrupts off.
884  */
885 
886 int
887 unsetvar(const char *s)
888 {
889 	struct var **vpp;
890 	struct var *vp;
891 
892 	vp = find_var(s, &vpp, NULL);
893 	if (vp == NULL)
894 		return (0);
895 	if (vp->flags & VREADONLY)
896 		return (1);
897 	if (vp->text[vp->name_len + 1] != '\0')
898 		setvar(s, "", 0);
899 	if ((vp->flags & VEXPORT) && localevar(vp->text)) {
900 		change_env(s, 0);
901 		setlocale(LC_ALL, "");
902 		updatecharset();
903 	}
904 	vp->flags &= ~VEXPORT;
905 	vp->flags |= VUNSET;
906 	if ((vp->flags & VSTRFIXED) == 0) {
907 		if ((vp->flags & VTEXTFIXED) == 0)
908 			ckfree(vp->text);
909 		*vpp = vp->next;
910 		ckfree(vp);
911 	}
912 	return (0);
913 }
914 
915 
916 
917 /*
918  * Returns true if the two strings specify the same variable.  The first
919  * variable name is terminated by '='; the second may be terminated by
920  * either '=' or '\0'.
921  */
922 
923 static int
924 varequal(const char *p, const char *q)
925 {
926 	while (*p == *q++) {
927 		if (*p++ == '=')
928 			return 1;
929 	}
930 	if (*p == '=' && *(q - 1) == '\0')
931 		return 1;
932 	return 0;
933 }
934 
935 /*
936  * Search for a variable.
937  * 'name' may be terminated by '=' or a NUL.
938  * vppp is set to the pointer to vp, or the list head if vp isn't found
939  * lenp is set to the number of characters in 'name'
940  */
941 
942 static struct var *
943 find_var(const char *name, struct var ***vppp, int *lenp)
944 {
945 	unsigned int hashval;
946 	int len;
947 	struct var *vp, **vpp;
948 	const char *p = name;
949 
950 	hashval = 0;
951 	while (*p && *p != '=')
952 		hashval = 2 * hashval + (unsigned char)*p++;
953 	len = p - name;
954 
955 	if (lenp)
956 		*lenp = len;
957 	vpp = &vartab[hashval % VTABSIZE];
958 	if (vppp)
959 		*vppp = vpp;
960 
961 	for (vp = *vpp ; vp ; vpp = &vp->next, vp = *vpp) {
962 		if (vp->name_len != len)
963 			continue;
964 		if (memcmp(vp->text, name, len) != 0)
965 			continue;
966 		if (vppp)
967 			*vppp = vpp;
968 		return vp;
969 	}
970 	return NULL;
971 }
972