var.c revision 293635 
1/*-
2 * Copyright (c) 1991, 1993
3 *	The Regents of the University of California.  All rights reserved.
4 *
5 * This code is derived from software contributed to Berkeley by
6 * Kenneth Almquist.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 *    notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 *    notice, this list of conditions and the following disclaimer in the
15 *    documentation and/or other materials provided with the distribution.
16 * 4. Neither the name of the University nor the names of its contributors
17 *    may be used to endorse or promote products derived from this software
18 *    without specific prior written permission.
19 *
20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30 * SUCH DAMAGE.
31 */
32
33#ifndef lint
34#if 0
35static char sccsid[] = "@(#)var.c	8.3 (Berkeley) 5/4/95";
36#endif
37#endif /* not lint */
38#include <sys/cdefs.h>
39__FBSDID("$FreeBSD: head/bin/sh/var.c 293635 2016-01-10 16:31:28Z jilles $");
40
41#include <unistd.h>
42#include <stdlib.h>
43#include <paths.h>
44
45/*
46 * Shell variables.
47 */
48
49#include <locale.h>
50#include <langinfo.h>
51
52#include "shell.h"
53#include "output.h"
54#include "expand.h"
55#include "nodes.h"	/* for other headers */
56#include "eval.h"	/* defines cmdenviron */
57#include "exec.h"
58#include "syntax.h"
59#include "options.h"
60#include "mail.h"
61#include "var.h"
62#include "memalloc.h"
63#include "error.h"
64#include "mystring.h"
65#include "parser.h"
66#include "builtins.h"
67#ifndef NO_HISTORY
68#include "myhistedit.h"
69#endif
70
71
72#define VTABSIZE 39
73
74
75struct varinit {
76	struct var *var;
77	int flags;
78	const char *text;
79	void (*func)(const char *);
80};
81
82
83#ifndef NO_HISTORY
84struct var vhistsize;
85struct var vterm;
86#endif
87struct var vifs;
88struct var vmail;
89struct var vmpath;
90struct var vpath;
91struct var vps1;
92struct var vps2;
93struct var vps4;
94static struct var voptind;
95struct var vdisvfork;
96
97struct localvar *localvars;
98int forcelocal;
99
100static const struct varinit varinit[] = {
101#ifndef NO_HISTORY
102	{ &vhistsize,	VUNSET,				"HISTSIZE=",
103	  sethistsize },
104#endif
105	{ &vifs,	0,				"IFS= \t\n",
106	  NULL },
107	{ &vmail,	VUNSET,				"MAIL=",
108	  NULL },
109	{ &vmpath,	VUNSET,				"MAILPATH=",
110	  NULL },
111	{ &vpath,	0,				"PATH=" _PATH_DEFPATH,
112	  changepath },
113	/*
114	 * vps1 depends on uid
115	 */
116	{ &vps2,	0,				"PS2=> ",
117	  NULL },
118	{ &vps4,	0,				"PS4=+ ",
119	  NULL },
120#ifndef NO_HISTORY
121	{ &vterm,	VUNSET,				"TERM=",
122	  setterm },
123#endif
124	{ &voptind,	0,				"OPTIND=1",
125	  getoptsreset },
126	{ &vdisvfork,	VUNSET,				"SH_DISABLE_VFORK=",
127	  NULL },
128	{ NULL,	0,				NULL,
129	  NULL }
130};
131
132static struct var *vartab[VTABSIZE];
133
134static const char *const locale_names[7] = {
135	"LC_COLLATE", "LC_CTYPE", "LC_MONETARY",
136	"LC_NUMERIC", "LC_TIME", "LC_MESSAGES", NULL
137};
138static const int locale_categories[7] = {
139	LC_COLLATE, LC_CTYPE, LC_MONETARY, LC_NUMERIC, LC_TIME, LC_MESSAGES, 0
140};
141
142static int varequal(const char *, const char *);
143static struct var *find_var(const char *, struct var ***, int *);
144static int localevar(const char *);
145static void setvareq_const(const char *s, int flags);
146
147extern char **environ;
148
149/*
150 * This routine initializes the builtin variables and imports the environment.
151 * It is called when the shell is initialized.
152 */
153
154void
155initvar(void)
156{
157	char ppid[20];
158	const struct varinit *ip;
159	struct var *vp;
160	struct var **vpp;
161	char **envp;
162
163	for (ip = varinit ; (vp = ip->var) != NULL ; ip++) {
164		if (find_var(ip->text, &vpp, &vp->name_len) != NULL)
165			continue;
166		vp->next = *vpp;
167		*vpp = vp;
168		vp->text = __DECONST(char *, ip->text);
169		vp->flags = ip->flags | VSTRFIXED | VTEXTFIXED;
170		vp->func = ip->func;
171	}
172	/*
173	 * PS1 depends on uid
174	 */
175	if (find_var("PS1", &vpp, &vps1.name_len) == NULL) {
176		vps1.next = *vpp;
177		*vpp = &vps1;
178		vps1.text = __DECONST(char *, geteuid() ? "PS1=$ " : "PS1=# ");
179		vps1.flags = VSTRFIXED|VTEXTFIXED;
180	}
181	fmtstr(ppid, sizeof(ppid), "%d", (int)getppid());
182	setvarsafe("PPID", ppid, 0);
183	for (envp = environ ; *envp ; envp++) {
184		if (strchr(*envp, '=')) {
185			setvareq(*envp, VEXPORT|VTEXTFIXED);
186		}
187	}
188	setvareq_const("OPTIND=1", 0);
189}
190
191/*
192 * Safe version of setvar, returns 1 on success 0 on failure.
193 */
194
195int
196setvarsafe(const char *name, const char *val, int flags)
197{
198	struct jmploc jmploc;
199	struct jmploc *const savehandler = handler;
200	int err = 0;
201	int inton;
202
203	inton = is_int_on();
204	if (setjmp(jmploc.loc))
205		err = 1;
206	else {
207		handler = &jmploc;
208		setvar(name, val, flags);
209	}
210	handler = savehandler;
211	SETINTON(inton);
212	return err;
213}
214
215/*
216 * Set the value of a variable.  The flags argument is stored with the
217 * flags of the variable.  If val is NULL, the variable is unset.
218 */
219
220void
221setvar(const char *name, const char *val, int flags)
222{
223	const char *p;
224	size_t len;
225	size_t namelen;
226	size_t vallen;
227	char *nameeq;
228	int isbad;
229
230	isbad = 0;
231	p = name;
232	if (! is_name(*p))
233		isbad = 1;
234	p++;
235	for (;;) {
236		if (! is_in_name(*p)) {
237			if (*p == '\0' || *p == '=')
238				break;
239			isbad = 1;
240		}
241		p++;
242	}
243	namelen = p - name;
244	if (isbad)
245		error("%.*s: bad variable name", (int)namelen, name);
246	len = namelen + 2;		/* 2 is space for '=' and '\0' */
247	if (val == NULL) {
248		flags |= VUNSET;
249		vallen = 0;
250	} else {
251		vallen = strlen(val);
252		len += vallen;
253	}
254	INTOFF;
255	nameeq = ckmalloc(len);
256	memcpy(nameeq, name, namelen);
257	nameeq[namelen] = '=';
258	if (val)
259		memcpy(nameeq + namelen + 1, val, vallen + 1);
260	else
261		nameeq[namelen + 1] = '\0';
262	setvareq(nameeq, flags);
263	INTON;
264}
265
266static int
267localevar(const char *s)
268{
269	const char *const *ss;
270
271	if (*s != 'L')
272		return 0;
273	if (varequal(s + 1, "ANG"))
274		return 1;
275	if (strncmp(s + 1, "C_", 2) != 0)
276		return 0;
277	if (varequal(s + 3, "ALL"))
278		return 1;
279	for (ss = locale_names; *ss ; ss++)
280		if (varequal(s + 3, *ss + 3))
281			return 1;
282	return 0;
283}
284
285
286/*
287 * Sets/unsets an environment variable from a pointer that may actually be a
288 * pointer into environ where the string should not be manipulated.
289 */
290static void
291change_env(const char *s, int set)
292{
293	char *eqp;
294	char *ss;
295
296	INTOFF;
297	ss = savestr(s);
298	if ((eqp = strchr(ss, '=')) != NULL)
299		*eqp = '\0';
300	if (set && eqp != NULL)
301		(void) setenv(ss, eqp + 1, 1);
302	else
303		(void) unsetenv(ss);
304	ckfree(ss);
305	INTON;
306
307	return;
308}
309
310
311/*
312 * Same as setvar except that the variable and value are passed in
313 * the first argument as name=value.  Since the first argument will
314 * be actually stored in the table, it should not be a string that
315 * will go away.
316 */
317
318void
319setvareq(char *s, int flags)
320{
321	struct var *vp, **vpp;
322	int nlen;
323
324	if (aflag)
325		flags |= VEXPORT;
326	if (forcelocal && !(flags & (VNOSET | VNOLOCAL)))
327		mklocal(s);
328	vp = find_var(s, &vpp, &nlen);
329	if (vp != NULL) {
330		if (vp->flags & VREADONLY) {
331			if ((flags & (VTEXTFIXED|VSTACK)) == 0)
332				ckfree(s);
333			error("%.*s: is read only", vp->name_len, vp->text);
334		}
335		if (flags & VNOSET) {
336			if ((flags & (VTEXTFIXED|VSTACK)) == 0)
337				ckfree(s);
338			return;
339		}
340		INTOFF;
341
342		if (vp->func && (flags & VNOFUNC) == 0)
343			(*vp->func)(s + vp->name_len + 1);
344
345		if ((vp->flags & (VTEXTFIXED|VSTACK)) == 0)
346			ckfree(vp->text);
347
348		vp->flags &= ~(VTEXTFIXED|VSTACK|VUNSET);
349		vp->flags |= flags;
350		vp->text = s;
351
352		/*
353		 * We could roll this to a function, to handle it as
354		 * a regular variable function callback, but why bother?
355		 *
356		 * Note: this assumes iflag is not set to 1 initially.
357		 * As part of initvar(), this is called before arguments
358		 * are looked at.
359		 */
360		if ((vp == &vmpath || (vp == &vmail && ! mpathset())) &&
361		    iflag == 1)
362			chkmail(1);
363		if ((vp->flags & VEXPORT) && localevar(s)) {
364			change_env(s, 1);
365			(void) setlocale(LC_ALL, "");
366			updatecharset();
367		}
368		INTON;
369		return;
370	}
371	/* not found */
372	if (flags & VNOSET) {
373		if ((flags & (VTEXTFIXED|VSTACK)) == 0)
374			ckfree(s);
375		return;
376	}
377	INTOFF;
378	vp = ckmalloc(sizeof (*vp));
379	vp->flags = flags;
380	vp->text = s;
381	vp->name_len = nlen;
382	vp->next = *vpp;
383	vp->func = NULL;
384	*vpp = vp;
385	if ((vp->flags & VEXPORT) && localevar(s)) {
386		change_env(s, 1);
387		(void) setlocale(LC_ALL, "");
388		updatecharset();
389	}
390	INTON;
391}
392
393
394static void
395setvareq_const(const char *s, int flags)
396{
397	setvareq(__DECONST(char *, s), flags | VTEXTFIXED);
398}
399
400
401/*
402 * Process a linked list of variable assignments.
403 */
404
405void
406listsetvar(struct arglist *list, int flags)
407{
408	int i;
409
410	INTOFF;
411	for (i = 0; i < list->count; i++)
412		setvareq(savestr(list->args[i]), flags);
413	INTON;
414}
415
416
417
418/*
419 * Find the value of a variable.  Returns NULL if not set.
420 */
421
422char *
423lookupvar(const char *name)
424{
425	struct var *v;
426
427	v = find_var(name, NULL, NULL);
428	if (v == NULL || v->flags & VUNSET)
429		return NULL;
430	return v->text + v->name_len + 1;
431}
432
433
434
435/*
436 * Search the environment of a builtin command.  If the second argument
437 * is nonzero, return the value of a variable even if it hasn't been
438 * exported.
439 */
440
441char *
442bltinlookup(const char *name, int doall)
443{
444	struct var *v;
445	char *result;
446	int i;
447
448	result = NULL;
449	if (cmdenviron) for (i = 0; i < cmdenviron->count; i++) {
450		if (varequal(cmdenviron->args[i], name))
451			result = strchr(cmdenviron->args[i], '=') + 1;
452	}
453	if (result != NULL)
454		return result;
455
456	v = find_var(name, NULL, NULL);
457	if (v == NULL || v->flags & VUNSET ||
458	    (!doall && (v->flags & VEXPORT) == 0))
459		return NULL;
460	return v->text + v->name_len + 1;
461}
462
463
464/*
465 * Set up locale for a builtin (LANG/LC_* assignments).
466 */
467void
468bltinsetlocale(void)
469{
470	int act = 0;
471	char *loc, *locdef;
472	int i;
473
474	if (cmdenviron) for (i = 0; i < cmdenviron->count; i++) {
475		if (localevar(cmdenviron->args[i])) {
476			act = 1;
477			break;
478		}
479	}
480	if (!act)
481		return;
482	loc = bltinlookup("LC_ALL", 0);
483	INTOFF;
484	if (loc != NULL) {
485		setlocale(LC_ALL, loc);
486		INTON;
487		updatecharset();
488		return;
489	}
490	locdef = bltinlookup("LANG", 0);
491	for (i = 0; locale_names[i] != NULL; i++) {
492		loc = bltinlookup(locale_names[i], 0);
493		if (loc == NULL)
494			loc = locdef;
495		if (loc != NULL)
496			setlocale(locale_categories[i], loc);
497	}
498	INTON;
499	updatecharset();
500}
501
502/*
503 * Undo the effect of bltinlocaleset().
504 */
505void
506bltinunsetlocale(void)
507{
508	int i;
509
510	INTOFF;
511	if (cmdenviron) for (i = 0; i < cmdenviron->count; i++) {
512		if (localevar(cmdenviron->args[i])) {
513			setlocale(LC_ALL, "");
514			updatecharset();
515			return;
516		}
517	}
518	INTON;
519}
520
521/*
522 * Update the localeisutf8 flag.
523 */
524void
525updatecharset(void)
526{
527	char *charset;
528
529	charset = nl_langinfo(CODESET);
530	localeisutf8 = !strcmp(charset, "UTF-8");
531}
532
533void
534initcharset(void)
535{
536	updatecharset();
537	initial_localeisutf8 = localeisutf8;
538}
539
540/*
541 * Generate a list of exported variables.  This routine is used to construct
542 * the third argument to execve when executing a program.
543 */
544
545char **
546environment(void)
547{
548	int nenv;
549	struct var **vpp;
550	struct var *vp;
551	char **env, **ep;
552
553	nenv = 0;
554	for (vpp = vartab ; vpp < vartab + VTABSIZE ; vpp++) {
555		for (vp = *vpp ; vp ; vp = vp->next)
556			if (vp->flags & VEXPORT)
557				nenv++;
558	}
559	ep = env = stalloc((nenv + 1) * sizeof *env);
560	for (vpp = vartab ; vpp < vartab + VTABSIZE ; vpp++) {
561		for (vp = *vpp ; vp ; vp = vp->next)
562			if (vp->flags & VEXPORT)
563				*ep++ = vp->text;
564	}
565	*ep = NULL;
566	return env;
567}
568
569
570static int
571var_compare(const void *a, const void *b)
572{
573	const char *const *sa, *const *sb;
574
575	sa = a;
576	sb = b;
577	/*
578	 * This compares two var=value strings which creates a different
579	 * order from what you would probably expect.  POSIX is somewhat
580	 * ambiguous on what should be sorted exactly.
581	 */
582	return strcoll(*sa, *sb);
583}
584
585
586/*
587 * Command to list all variables which are set.  This is invoked from the
588 * set command when it is called without any options or operands.
589 */
590
591int
592showvarscmd(int argc __unused, char **argv __unused)
593{
594	struct var **vpp;
595	struct var *vp;
596	const char *s;
597	const char **vars;
598	int i, n;
599
600	/*
601	 * POSIX requires us to sort the variables.
602	 */
603	n = 0;
604	for (vpp = vartab; vpp < vartab + VTABSIZE; vpp++) {
605		for (vp = *vpp; vp; vp = vp->next) {
606			if (!(vp->flags & VUNSET))
607				n++;
608		}
609	}
610
611	INTOFF;
612	vars = ckmalloc(n * sizeof(*vars));
613	i = 0;
614	for (vpp = vartab; vpp < vartab + VTABSIZE; vpp++) {
615		for (vp = *vpp; vp; vp = vp->next) {
616			if (!(vp->flags & VUNSET))
617				vars[i++] = vp->text;
618		}
619	}
620
621	qsort(vars, n, sizeof(*vars), var_compare);
622	for (i = 0; i < n; i++) {
623		/*
624		 * Skip improper variable names so the output remains usable as
625		 * shell input.
626		 */
627		if (!isassignment(vars[i]))
628			continue;
629		s = strchr(vars[i], '=');
630		s++;
631		outbin(vars[i], s - vars[i], out1);
632		out1qstr(s);
633		out1c('\n');
634	}
635	ckfree(vars);
636	INTON;
637
638	return 0;
639}
640
641
642
643/*
644 * The export and readonly commands.
645 */
646
647int
648exportcmd(int argc __unused, char **argv)
649{
650	struct var **vpp;
651	struct var *vp;
652	char **ap;
653	char *name;
654	char *p;
655	char *cmdname;
656	int ch, values;
657	int flag = argv[0][0] == 'r'? VREADONLY : VEXPORT;
658
659	cmdname = argv[0];
660	values = 0;
661	while ((ch = nextopt("p")) != '\0') {
662		switch (ch) {
663		case 'p':
664			values = 1;
665			break;
666		}
667	}
668
669	if (values && *argptr != NULL)
670		error("-p requires no arguments");
671	if (*argptr != NULL) {
672		for (ap = argptr; (name = *ap) != NULL; ap++) {
673			if ((p = strchr(name, '=')) != NULL) {
674				p++;
675			} else {
676				vp = find_var(name, NULL, NULL);
677				if (vp != NULL) {
678					vp->flags |= flag;
679					if ((vp->flags & VEXPORT) && localevar(vp->text)) {
680						change_env(vp->text, 1);
681						(void) setlocale(LC_ALL, "");
682						updatecharset();
683					}
684					continue;
685				}
686			}
687			setvar(name, p, flag);
688		}
689	} else {
690		for (vpp = vartab ; vpp < vartab + VTABSIZE ; vpp++) {
691			for (vp = *vpp ; vp ; vp = vp->next) {
692				if (vp->flags & flag) {
693					if (values) {
694						/*
695						 * Skip improper variable names
696						 * so the output remains usable
697						 * as shell input.
698						 */
699						if (!isassignment(vp->text))
700							continue;
701						out1str(cmdname);
702						out1c(' ');
703					}
704					if (values && !(vp->flags & VUNSET)) {
705						outbin(vp->text,
706						    vp->name_len + 1, out1);
707						out1qstr(vp->text +
708						    vp->name_len + 1);
709					} else
710						outbin(vp->text, vp->name_len,
711						    out1);
712					out1c('\n');
713				}
714			}
715		}
716	}
717	return 0;
718}
719
720
721/*
722 * The "local" command.
723 */
724
725int
726localcmd(int argc __unused, char **argv __unused)
727{
728	char *name;
729
730	nextopt("");
731	if (! in_function())
732		error("Not in a function");
733	while ((name = *argptr++) != NULL) {
734		mklocal(name);
735	}
736	return 0;
737}
738
739
740/*
741 * Make a variable a local variable.  When a variable is made local, it's
742 * value and flags are saved in a localvar structure.  The saved values
743 * will be restored when the shell function returns.  We handle the name
744 * "-" as a special case.
745 */
746
747void
748mklocal(char *name)
749{
750	struct localvar *lvp;
751	struct var **vpp;
752	struct var *vp;
753
754	INTOFF;
755	lvp = ckmalloc(sizeof (struct localvar));
756	if (name[0] == '-' && name[1] == '\0') {
757		lvp->text = ckmalloc(sizeof optval);
758		memcpy(lvp->text, optval, sizeof optval);
759		vp = NULL;
760	} else {
761		vp = find_var(name, &vpp, NULL);
762		if (vp == NULL) {
763			if (strchr(name, '='))
764				setvareq(savestr(name), VSTRFIXED | VNOLOCAL);
765			else
766				setvar(name, NULL, VSTRFIXED | VNOLOCAL);
767			vp = *vpp;	/* the new variable */
768			lvp->text = NULL;
769			lvp->flags = VUNSET;
770		} else {
771			lvp->text = vp->text;
772			lvp->flags = vp->flags;
773			vp->flags |= VSTRFIXED|VTEXTFIXED;
774			if (name[vp->name_len] == '=')
775				setvareq(savestr(name), VNOLOCAL);
776		}
777	}
778	lvp->vp = vp;
779	lvp->next = localvars;
780	localvars = lvp;
781	INTON;
782}
783
784
785/*
786 * Called after a function returns.
787 */
788
789void
790poplocalvars(void)
791{
792	struct localvar *lvp;
793	struct var *vp;
794	int islocalevar;
795
796	INTOFF;
797	while ((lvp = localvars) != NULL) {
798		localvars = lvp->next;
799		vp = lvp->vp;
800		if (vp == NULL) {	/* $- saved */
801			memcpy(optval, lvp->text, sizeof optval);
802			ckfree(lvp->text);
803			optschanged();
804		} else if ((lvp->flags & (VUNSET|VSTRFIXED)) == VUNSET) {
805			(void)unsetvar(vp->text);
806		} else {
807			islocalevar = (vp->flags | lvp->flags) & VEXPORT &&
808			    localevar(lvp->text);
809			if ((vp->flags & VTEXTFIXED) == 0)
810				ckfree(vp->text);
811			vp->flags = lvp->flags;
812			vp->text = lvp->text;
813			if (vp->func)
814				(*vp->func)(vp->text + vp->name_len + 1);
815			if (islocalevar) {
816				change_env(vp->text, vp->flags & VEXPORT &&
817				    (vp->flags & VUNSET) == 0);
818				setlocale(LC_ALL, "");
819				updatecharset();
820			}
821		}
822		ckfree(lvp);
823	}
824	INTON;
825}
826
827
828int
829setvarcmd(int argc, char **argv)
830{
831	if (argc <= 2)
832		return unsetcmd(argc, argv);
833	else if (argc == 3)
834		setvar(argv[1], argv[2], 0);
835	else
836		error("too many arguments");
837	return 0;
838}
839
840
841/*
842 * The unset builtin command.
843 */
844
845int
846unsetcmd(int argc __unused, char **argv __unused)
847{
848	char **ap;
849	int i;
850	int flg_func = 0;
851	int flg_var = 0;
852	int ret = 0;
853
854	while ((i = nextopt("vf")) != '\0') {
855		if (i == 'f')
856			flg_func = 1;
857		else
858			flg_var = 1;
859	}
860	if (flg_func == 0 && flg_var == 0)
861		flg_var = 1;
862
863	INTOFF;
864	for (ap = argptr; *ap ; ap++) {
865		if (flg_func)
866			ret |= unsetfunc(*ap);
867		if (flg_var)
868			ret |= unsetvar(*ap);
869	}
870	INTON;
871	return ret;
872}
873
874
875/*
876 * Unset the specified variable.
877 * Called with interrupts off.
878 */
879
880int
881unsetvar(const char *s)
882{
883	struct var **vpp;
884	struct var *vp;
885
886	vp = find_var(s, &vpp, NULL);
887	if (vp == NULL)
888		return (0);
889	if (vp->flags & VREADONLY)
890		return (1);
891	if (vp->text[vp->name_len + 1] != '\0')
892		setvar(s, "", 0);
893	if ((vp->flags & VEXPORT) && localevar(vp->text)) {
894		change_env(s, 0);
895		setlocale(LC_ALL, "");
896		updatecharset();
897	}
898	vp->flags &= ~VEXPORT;
899	vp->flags |= VUNSET;
900	if ((vp->flags & VSTRFIXED) == 0) {
901		if ((vp->flags & VTEXTFIXED) == 0)
902			ckfree(vp->text);
903		*vpp = vp->next;
904		ckfree(vp);
905	}
906	return (0);
907}
908
909
910
911/*
912 * Returns true if the two strings specify the same variable.  The first
913 * variable name is terminated by '='; the second may be terminated by
914 * either '=' or '\0'.
915 */
916
917static int
918varequal(const char *p, const char *q)
919{
920	while (*p == *q++) {
921		if (*p++ == '=')
922			return 1;
923	}
924	if (*p == '=' && *(q - 1) == '\0')
925		return 1;
926	return 0;
927}
928
929/*
930 * Search for a variable.
931 * 'name' may be terminated by '=' or a NUL.
932 * vppp is set to the pointer to vp, or the list head if vp isn't found
933 * lenp is set to the number of characters in 'name'
934 */
935
936static struct var *
937find_var(const char *name, struct var ***vppp, int *lenp)
938{
939	unsigned int hashval;
940	int len;
941	struct var *vp, **vpp;
942	const char *p = name;
943
944	hashval = 0;
945	while (*p && *p != '=')
946		hashval = 2 * hashval + (unsigned char)*p++;
947	len = p - name;
948
949	if (lenp)
950		*lenp = len;
951	vpp = &vartab[hashval % VTABSIZE];
952	if (vppp)
953		*vppp = vpp;
954
955	for (vp = *vpp ; vp ; vpp = &vp->next, vp = *vpp) {
956		if (vp->name_len != len)
957			continue;
958		if (memcmp(vp->text, name, len) != 0)
959			continue;
960		if (vppp)
961			*vppp = vpp;
962		return vp;
963	}
964	return NULL;
965}
966