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var.c revision 1.40 
      1 /*	$NetBSD: var.c,v 1.40 2011/06/18 21:18:46 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 1.40 2011/06/18 21:18:46 christos Exp $");
     41 #endif
     42 #endif /* not lint */
     43 
     44 #include <unistd.h>
     45 #include <stdlib.h>
     46 #include <strings.h>
     47 #include <paths.h>
     48 
     49 /*
     50  * Shell variables.
     51  */
     52 
     53 #include "shell.h"
     54 #include "output.h"
     55 #include "expand.h"
     56 #include "nodes.h"	/* for other headers */
     57 #include "eval.h"	/* defines cmdenviron */
     58 #include "exec.h"
     59 #include "syntax.h"
     60 #include "options.h"
     61 #include "builtins.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 "show.h"
     69 #ifndef SMALL
     70 #include "myhistedit.h"
     71 #endif
     72 
     73 #ifdef SMALL
     74 #define VTABSIZE 39
     75 #else
     76 #define VTABSIZE 517
     77 #endif
     78 
     79 
     80 struct varinit {
     81 	struct var *var;
     82 	int flags;
     83 	const char *text;
     84 	void (*func)(const char *);
     85 };
     86 
     87 struct localvar *localvars;
     88 
     89 #if ATTY
     90 struct var vatty;
     91 #endif
     92 #ifndef SMALL
     93 struct var vhistsize;
     94 struct var vterm;
     95 #endif
     96 struct var vifs;
     97 struct var vmail;
     98 struct var vmpath;
     99 struct var vpath;
    100 struct var vps1;
    101 struct var vps2;
    102 struct var vps4;
    103 struct var vvers;
    104 struct var voptind;
    105 
    106 const struct varinit varinit[] = {
    107 #if ATTY
    108 	{ &vatty,	VSTRFIXED|VTEXTFIXED|VUNSET,	"ATTY=",
    109 	  NULL },
    110 #endif
    111 #ifndef SMALL
    112 	{ &vhistsize,	VSTRFIXED|VTEXTFIXED|VUNSET,	"HISTSIZE=",
    113 	  sethistsize },
    114 #endif
    115 	{ &vifs,	VSTRFIXED|VTEXTFIXED,		"IFS= \t\n",
    116 	  NULL },
    117 	{ &vmail,	VSTRFIXED|VTEXTFIXED|VUNSET,	"MAIL=",
    118 	  NULL },
    119 	{ &vmpath,	VSTRFIXED|VTEXTFIXED|VUNSET,	"MAILPATH=",
    120 	  NULL },
    121 	{ &vpath,	VSTRFIXED|VTEXTFIXED,		"PATH=" _PATH_DEFPATH,
    122 	  changepath },
    123 	/*
    124 	 * vps1 depends on uid
    125 	 */
    126 	{ &vps2,	VSTRFIXED|VTEXTFIXED,		"PS2=> ",
    127 	  NULL },
    128 	{ &vps4,	VSTRFIXED|VTEXTFIXED,		"PS4=+ ",
    129 	  NULL },
    130 #ifndef SMALL
    131 	{ &vterm,	VSTRFIXED|VTEXTFIXED|VUNSET,	"TERM=",
    132 	  setterm },
    133 #endif
    134 	{ &voptind,	VSTRFIXED|VTEXTFIXED|VNOFUNC,	"OPTIND=1",
    135 	  getoptsreset },
    136 	{ NULL,	0,				NULL,
    137 	  NULL }
    138 };
    139 
    140 struct var *vartab[VTABSIZE];
    141 
    142 STATIC int strequal(const char *, const char *);
    143 STATIC struct var *find_var(const char *, struct var ***, int *);
    144 
    145 /*
    146  * Initialize the varable symbol tables and import the environment
    147  */
    148 
    149 #ifdef mkinit
    150 INCLUDE "var.h"
    151 MKINIT char **environ;
    152 INIT {
    153 	char **envp;
    154 
    155 	initvar();
    156 	for (envp = environ ; *envp ; envp++) {
    157 		if (strchr(*envp, '=')) {
    158 			setvareq(*envp, VEXPORT|VTEXTFIXED);
    159 		}
    160 	}
    161 }
    162 #endif
    163 
    164 
    165 /*
    166  * This routine initializes the builtin variables.  It is called when the
    167  * shell is initialized and again when a shell procedure is spawned.
    168  */
    169 
    170 void
    171 initvar(void)
    172 {
    173 	const struct varinit *ip;
    174 	struct var *vp;
    175 	struct var **vpp;
    176 
    177 	for (ip = varinit ; (vp = ip->var) != NULL ; ip++) {
    178 		if (find_var(ip->text, &vpp, &vp->name_len) != NULL)
    179 			continue;
    180 		vp->next = *vpp;
    181 		*vpp = vp;
    182 		vp->text = strdup(ip->text);
    183 		vp->flags = ip->flags;
    184 		vp->func = ip->func;
    185 	}
    186 	/*
    187 	 * PS1 depends on uid
    188 	 */
    189 	if (find_var("PS1", &vpp, &vps1.name_len) == NULL) {
    190 		vps1.next = *vpp;
    191 		*vpp = &vps1;
    192 		vps1.text = strdup(geteuid() ? "PS1=$ " : "PS1=# ");
    193 		vps1.flags = VSTRFIXED|VTEXTFIXED;
    194 	}
    195 }
    196 
    197 /*
    198  * Safe version of setvar, returns 1 on success 0 on failure.
    199  */
    200 
    201 int
    202 setvarsafe(const char *name, const char *val, int flags)
    203 {
    204 	struct jmploc jmploc;
    205 	struct jmploc *volatile savehandler = handler;
    206 	int volatile err = 0;
    207 
    208 	if (setjmp(jmploc.loc))
    209 		err = 1;
    210 	else {
    211 		handler = &jmploc;
    212 		setvar(name, val, flags);
    213 	}
    214 	handler = savehandler;
    215 	return err;
    216 }
    217 
    218 /*
    219  * Set the value of a variable.  The flags argument is ored with the
    220  * flags of the variable.  If val is NULL, the variable is unset.
    221  */
    222 
    223 void
    224 setvar(const char *name, const char *val, int flags)
    225 {
    226 	const char *p;
    227 	const char *q;
    228 	char *d;
    229 	int len;
    230 	int namelen;
    231 	char *nameeq;
    232 	int isbad;
    233 
    234 	isbad = 0;
    235 	p = name;
    236 	if (! is_name(*p))
    237 		isbad = 1;
    238 	p++;
    239 	for (;;) {
    240 		if (! is_in_name(*p)) {
    241 			if (*p == '\0' || *p == '=')
    242 				break;
    243 			isbad = 1;
    244 		}
    245 		p++;
    246 	}
    247 	namelen = p - name;
    248 	if (isbad)
    249 		error("%.*s: bad variable name", namelen, name);
    250 	len = namelen + 2;		/* 2 is space for '=' and '\0' */
    251 	if (val == NULL) {
    252 		flags |= VUNSET;
    253 	} else {
    254 		len += strlen(val);
    255 	}
    256 	d = nameeq = ckmalloc(len);
    257 	q = name;
    258 	while (--namelen >= 0)
    259 		*d++ = *q++;
    260 	*d++ = '=';
    261 	*d = '\0';
    262 	if (val)
    263 		scopy(val, d);
    264 	setvareq(nameeq, flags);
    265 }
    266 
    267 
    268 
    269 /*
    270  * Same as setvar except that the variable and value are passed in
    271  * the first argument as name=value.  Since the first argument will
    272  * be actually stored in the table, it should not be a string that
    273  * will go away.
    274  */
    275 
    276 void
    277 setvareq(char *s, int flags)
    278 {
    279 	struct var *vp, **vpp;
    280 	int nlen;
    281 
    282 	if (aflag)
    283 		flags |= VEXPORT;
    284 	vp = find_var(s, &vpp, &nlen);
    285 	if (vp != NULL) {
    286 		if (vp->flags & VREADONLY)
    287 			error("%.*s: is read only", vp->name_len, s);
    288 		if (flags & VNOSET)
    289 			return;
    290 		INTOFF;
    291 
    292 		if (vp->func && (flags & VNOFUNC) == 0)
    293 			(*vp->func)(s + vp->name_len + 1);
    294 
    295 		if ((vp->flags & (VTEXTFIXED|VSTACK)) == 0)
    296 			ckfree(vp->text);
    297 
    298 		vp->flags &= ~(VTEXTFIXED|VSTACK|VUNSET);
    299 		vp->flags |= flags & ~VNOFUNC;
    300 		vp->text = s;
    301 
    302 		/*
    303 		 * We could roll this to a function, to handle it as
    304 		 * a regular variable function callback, but why bother?
    305 		 */
    306 		if (vp == &vmpath || (vp == &vmail && ! mpathset()))
    307 			chkmail(1);
    308 		INTON;
    309 		return;
    310 	}
    311 	/* not found */
    312 	if (flags & VNOSET)
    313 		return;
    314 	vp = ckmalloc(sizeof (*vp));
    315 	vp->flags = flags & ~VNOFUNC;
    316 	vp->text = s;
    317 	vp->name_len = nlen;
    318 	vp->next = *vpp;
    319 	vp->func = NULL;
    320 	*vpp = vp;
    321 }
    322 
    323 
    324 
    325 /*
    326  * Process a linked list of variable assignments.
    327  */
    328 
    329 void
    330 listsetvar(struct strlist *list, int flags)
    331 {
    332 	struct strlist *lp;
    333 
    334 	INTOFF;
    335 	for (lp = list ; lp ; lp = lp->next) {
    336 		setvareq(savestr(lp->text), flags);
    337 	}
    338 	INTON;
    339 }
    340 
    341 void
    342 listmklocal(struct strlist *list, int flags)
    343 {
    344 	struct strlist *lp;
    345 
    346 	for (lp = list ; lp ; lp = lp->next)
    347 		mklocal(lp->text, flags);
    348 }
    349 
    350 
    351 /*
    352  * Find the value of a variable.  Returns NULL if not set.
    353  */
    354 
    355 char *
    356 lookupvar(const char *name)
    357 {
    358 	struct var *v;
    359 
    360 	v = find_var(name, NULL, NULL);
    361 	if (v == NULL || v->flags & VUNSET)
    362 		return NULL;
    363 	return v->text + v->name_len + 1;
    364 }
    365 
    366 
    367 
    368 /*
    369  * Search the environment of a builtin command.  If the second argument
    370  * is nonzero, return the value of a variable even if it hasn't been
    371  * exported.
    372  */
    373 
    374 char *
    375 bltinlookup(const char *name, int doall)
    376 {
    377 	struct strlist *sp;
    378 	struct var *v;
    379 
    380 	for (sp = cmdenviron ; sp ; sp = sp->next) {
    381 		if (strequal(sp->text, name))
    382 			return strchr(sp->text, '=') + 1;
    383 	}
    384 
    385 	v = find_var(name, NULL, NULL);
    386 
    387 	if (v == NULL || v->flags & VUNSET || (!doall && !(v->flags & VEXPORT)))
    388 		return NULL;
    389 	return v->text + v->name_len + 1;
    390 }
    391 
    392 
    393 
    394 /*
    395  * Generate a list of exported variables.  This routine is used to construct
    396  * the third argument to execve when executing a program.
    397  */
    398 
    399 char **
    400 environment(void)
    401 {
    402 	int nenv;
    403 	struct var **vpp;
    404 	struct var *vp;
    405 	char **env;
    406 	char **ep;
    407 
    408 	nenv = 0;
    409 	for (vpp = vartab ; vpp < vartab + VTABSIZE ; vpp++) {
    410 		for (vp = *vpp ; vp ; vp = vp->next)
    411 			if (vp->flags & VEXPORT)
    412 				nenv++;
    413 	}
    414 	ep = env = stalloc((nenv + 1) * sizeof *env);
    415 	for (vpp = vartab ; vpp < vartab + VTABSIZE ; vpp++) {
    416 		for (vp = *vpp ; vp ; vp = vp->next)
    417 			if (vp->flags & VEXPORT)
    418 				*ep++ = vp->text;
    419 	}
    420 	*ep = NULL;
    421 	return env;
    422 }
    423 
    424 
    425 /*
    426  * Called when a shell procedure is invoked to clear out nonexported
    427  * variables.  It is also necessary to reallocate variables of with
    428  * VSTACK set since these are currently allocated on the stack.
    429  */
    430 
    431 #ifdef mkinit
    432 void shprocvar(void);
    433 
    434 SHELLPROC {
    435 	shprocvar();
    436 }
    437 #endif
    438 
    439 void
    440 shprocvar(void)
    441 {
    442 	struct var **vpp;
    443 	struct var *vp, **prev;
    444 
    445 	for (vpp = vartab ; vpp < vartab + VTABSIZE ; vpp++) {
    446 		for (prev = vpp ; (vp = *prev) != NULL ; ) {
    447 			if ((vp->flags & VEXPORT) == 0) {
    448 				*prev = vp->next;
    449 				if ((vp->flags & VTEXTFIXED) == 0)
    450 					ckfree(vp->text);
    451 				if ((vp->flags & VSTRFIXED) == 0)
    452 					ckfree(vp);
    453 			} else {
    454 				if (vp->flags & VSTACK) {
    455 					vp->text = savestr(vp->text);
    456 					vp->flags &=~ VSTACK;
    457 				}
    458 				prev = &vp->next;
    459 			}
    460 		}
    461 	}
    462 	initvar();
    463 }
    464 
    465 
    466 
    467 /*
    468  * Command to list all variables which are set.  Currently this command
    469  * is invoked from the set command when the set command is called without
    470  * any variables.
    471  */
    472 
    473 void
    474 print_quoted(const char *p)
    475 {
    476 	const char *q;
    477 
    478 	if (strcspn(p, "|&;<>()$`\\\"' \t\n*?[]#~=%") == strlen(p)) {
    479 		out1fmt("%s", p);
    480 		return;
    481 	}
    482 	while (*p) {
    483 		if (*p == '\'') {
    484 			out1fmt("\\'");
    485 			p++;
    486 			continue;
    487 		}
    488 		q = index(p, '\'');
    489 		if (!q) {
    490 			out1fmt("'%s'", p );
    491 			return;
    492 		}
    493 		out1fmt("'%.*s'", (int)(q - p), p );
    494 		p = q;
    495 	}
    496 }
    497 
    498 static int
    499 sort_var(const void *v_v1, const void *v_v2)
    500 {
    501 	const struct var * const *v1 = v_v1;
    502 	const struct var * const *v2 = v_v2;
    503 
    504 	/* XXX Will anyone notice we include the '=' of the shorter name? */
    505 	return strcoll((*v1)->text, (*v2)->text);
    506 }
    507 
    508 /*
    509  * POSIX requires that 'set' (but not export or readonly) output the
    510  * variables in lexicographic order - by the locale's collating order (sigh).
    511  * Maybe we could keep them in an ordered balanced binary tree
    512  * instead of hashed lists.
    513  * For now just roll 'em through qsort for printing...
    514  */
    515 
    516 int
    517 showvars(const char *name, int flag, int show_value)
    518 {
    519 	struct var **vpp;
    520 	struct var *vp;
    521 	const char *p;
    522 
    523 	static struct var **list;	/* static in case we are interrupted */
    524 	static int list_len;
    525 	int count = 0;
    526 
    527 	if (!list) {
    528 		list_len = 32;
    529 		list = ckmalloc(list_len * sizeof *list);
    530 	}
    531 
    532 	for (vpp = vartab ; vpp < vartab + VTABSIZE ; vpp++) {
    533 		for (vp = *vpp ; vp ; vp = vp->next) {
    534 			if (flag && !(vp->flags & flag))
    535 				continue;
    536 			if (vp->flags & VUNSET && !(show_value & 2))
    537 				continue;
    538 			if (count >= list_len) {
    539 				list = ckrealloc(list,
    540 					(list_len << 1) * sizeof *list);
    541 				list_len <<= 1;
    542 			}
    543 			list[count++] = vp;
    544 		}
    545 	}
    546 
    547 	qsort(list, count, sizeof *list, sort_var);
    548 
    549 	for (vpp = list; count--; vpp++) {
    550 		vp = *vpp;
    551 		if (name)
    552 			out1fmt("%s ", name);
    553 		for (p = vp->text ; *p != '=' ; p++)
    554 			out1c(*p);
    555 		if (!(vp->flags & VUNSET) && show_value) {
    556 			out1fmt("=");
    557 			print_quoted(++p);
    558 		}
    559 		out1c('\n');
    560 	}
    561 	return 0;
    562 }
    563 
    564 
    565 
    566 /*
    567  * The export and readonly commands.
    568  */
    569 
    570 int
    571 exportcmd(int argc, char **argv)
    572 {
    573 	struct var *vp;
    574 	char *name;
    575 	const char *p;
    576 	int flag = argv[0][0] == 'r'? VREADONLY : VEXPORT;
    577 	int pflag;
    578 
    579 	pflag = nextopt("p") == 'p' ? 3 : 0;
    580 	if (argc <= 1 || pflag) {
    581 		showvars( pflag ? argv[0] : 0, flag, pflag );
    582 		return 0;
    583 	}
    584 
    585 	while ((name = *argptr++) != NULL) {
    586 		if ((p = strchr(name, '=')) != NULL) {
    587 			p++;
    588 		} else {
    589 			vp = find_var(name, NULL, NULL);
    590 			if (vp != NULL) {
    591 				vp->flags |= flag;
    592 				continue;
    593 			}
    594 		}
    595 		setvar(name, p, flag);
    596 	}
    597 	return 0;
    598 }
    599 
    600 
    601 /*
    602  * The "local" command.
    603  */
    604 
    605 int
    606 localcmd(int argc, char **argv)
    607 {
    608 	char *name;
    609 
    610 	if (! in_function())
    611 		error("Not in a function");
    612 	while ((name = *argptr++) != NULL) {
    613 		mklocal(name, 0);
    614 	}
    615 	return 0;
    616 }
    617 
    618 
    619 /*
    620  * Make a variable a local variable.  When a variable is made local, its
    621  * value and flags are saved in a localvar structure.  The saved values
    622  * will be restored when the shell function returns.  We handle the name
    623  * "-" as a special case.
    624  */
    625 
    626 void
    627 mklocal(const char *name, int flags)
    628 {
    629 	struct localvar *lvp;
    630 	struct var **vpp;
    631 	struct var *vp;
    632 
    633 	INTOFF;
    634 	lvp = ckmalloc(sizeof (struct localvar));
    635 	if (name[0] == '-' && name[1] == '\0') {
    636 		char *p;
    637 		p = ckmalloc(sizeof_optlist);
    638 		lvp->text = memcpy(p, optlist, sizeof_optlist);
    639 		vp = NULL;
    640 	} else {
    641 		vp = find_var(name, &vpp, NULL);
    642 		if (vp == NULL) {
    643 			if (strchr(name, '='))
    644 				setvareq(savestr(name), VSTRFIXED|flags);
    645 			else
    646 				setvar(name, NULL, VSTRFIXED|flags);
    647 			vp = *vpp;	/* the new variable */
    648 			lvp->text = NULL;
    649 			lvp->flags = VUNSET;
    650 		} else {
    651 			lvp->text = vp->text;
    652 			lvp->flags = vp->flags;
    653 			vp->flags |= VSTRFIXED|VTEXTFIXED;
    654 			if (name[vp->name_len] == '=')
    655 				setvareq(savestr(name), flags);
    656 		}
    657 	}
    658 	lvp->vp = vp;
    659 	lvp->next = localvars;
    660 	localvars = lvp;
    661 	INTON;
    662 }
    663 
    664 
    665 /*
    666  * Called after a function returns.
    667  */
    668 
    669 void
    670 poplocalvars(void)
    671 {
    672 	struct localvar *lvp;
    673 	struct var *vp;
    674 
    675 	while ((lvp = localvars) != NULL) {
    676 		localvars = lvp->next;
    677 		vp = lvp->vp;
    678 		TRACE(("poplocalvar %s", vp ? vp->text : "-"));
    679 		if (vp == NULL) {	/* $- saved */
    680 			memcpy(optlist, lvp->text, sizeof_optlist);
    681 			ckfree(lvp->text);
    682 		} else if ((lvp->flags & (VUNSET|VSTRFIXED)) == VUNSET) {
    683 			(void)unsetvar(vp->text, 0);
    684 		} else {
    685 			if (vp->func && (vp->flags & VNOFUNC) == 0)
    686 				(*vp->func)(lvp->text + vp->name_len + 1);
    687 			if ((vp->flags & VTEXTFIXED) == 0)
    688 				ckfree(vp->text);
    689 			vp->flags = lvp->flags;
    690 			vp->text = lvp->text;
    691 		}
    692 		ckfree(lvp);
    693 	}
    694 }
    695 
    696 
    697 int
    698 setvarcmd(int argc, char **argv)
    699 {
    700 	if (argc <= 2)
    701 		return unsetcmd(argc, argv);
    702 	else if (argc == 3)
    703 		setvar(argv[1], argv[2], 0);
    704 	else
    705 		error("List assignment not implemented");
    706 	return 0;
    707 }
    708 
    709 
    710 /*
    711  * The unset builtin command.  We unset the function before we unset the
    712  * variable to allow a function to be unset when there is a readonly variable
    713  * with the same name.
    714  */
    715 
    716 int
    717 unsetcmd(int argc, char **argv)
    718 {
    719 	char **ap;
    720 	int i;
    721 	int flg_func = 0;
    722 	int flg_var = 0;
    723 	int ret = 0;
    724 
    725 	while ((i = nextopt("evf")) != '\0') {
    726 		if (i == 'f')
    727 			flg_func = 1;
    728 		else
    729 			flg_var = i;
    730 	}
    731 	if (flg_func == 0 && flg_var == 0)
    732 		flg_var = 1;
    733 
    734 	for (ap = argptr; *ap ; ap++) {
    735 		if (flg_func)
    736 			ret |= unsetfunc(*ap);
    737 		if (flg_var)
    738 			ret |= unsetvar(*ap, flg_var == 'e');
    739 	}
    740 	return ret;
    741 }
    742 
    743 
    744 /*
    745  * Unset the specified variable.
    746  */
    747 
    748 int
    749 unsetvar(const char *s, int unexport)
    750 {
    751 	struct var **vpp;
    752 	struct var *vp;
    753 
    754 	vp = find_var(s, &vpp, NULL);
    755 	if (vp == NULL)
    756 		return 1;
    757 
    758 	if (vp->flags & VREADONLY)
    759 		return (1);
    760 
    761 	INTOFF;
    762 	if (unexport) {
    763 		vp->flags &= ~VEXPORT;
    764 	} else {
    765 		if (vp->text[vp->name_len + 1] != '\0')
    766 			setvar(s, nullstr, 0);
    767 		vp->flags &= ~VEXPORT;
    768 		vp->flags |= VUNSET;
    769 		if ((vp->flags & VSTRFIXED) == 0) {
    770 			if ((vp->flags & VTEXTFIXED) == 0)
    771 				ckfree(vp->text);
    772 			*vpp = vp->next;
    773 			ckfree(vp);
    774 		}
    775 	}
    776 	INTON;
    777 	return 0;
    778 }
    779 
    780 
    781 /*
    782  * Returns true if the two strings specify the same varable.  The first
    783  * variable name is terminated by '='; the second may be terminated by
    784  * either '=' or '\0'.
    785  */
    786 
    787 STATIC int
    788 strequal(const char *p, const char *q)
    789 {
    790 	while (*p == *q++) {
    791 		if (*p++ == '=')
    792 			return 1;
    793 	}
    794 	if (*p == '=' && *(q - 1) == '\0')
    795 		return 1;
    796 	return 0;
    797 }
    798 
    799 /*
    800  * Search for a variable.
    801  * 'name' may be terminated by '=' or a NUL.
    802  * vppp is set to the pointer to vp, or the list head if vp isn't found
    803  * lenp is set to the number of charactets in 'name'
    804  */
    805 
    806 STATIC struct var *
    807 find_var(const char *name, struct var ***vppp, int *lenp)
    808 {
    809 	unsigned int hashval;
    810 	int len;
    811 	struct var *vp, **vpp;
    812 	const char *p = name;
    813 
    814 	hashval = 0;
    815 	while (*p && *p != '=')
    816 		hashval = 2 * hashval + (unsigned char)*p++;
    817 	len = p - name;
    818 
    819 	if (lenp)
    820 		*lenp = len;
    821 	vpp = &vartab[hashval % VTABSIZE];
    822 	if (vppp)
    823 		*vppp = vpp;
    824 
    825 	for (vp = *vpp ; vp ; vpp = &vp->next, vp = *vpp) {
    826 		if (vp->name_len != len)
    827 			continue;
    828 		if (memcmp(vp->text, name, len) != 0)
    829 			continue;
    830 		if (vppp)
    831 			*vppp = vpp;
    832 		return vp;
    833 	}
    834 	return NULL;
    835 }
    836