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var.c revision 1.37 
      1 /*	$NetBSD: var.c,v 1.37 2006/04/24 19:00:30 snj 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 1.37 2006/04/24 19:00:30 snj 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 "mail.h"
     62 #include "var.h"
     63 #include "memalloc.h"
     64 #include "error.h"
     65 #include "mystring.h"
     66 #include "parser.h"
     67 #include "show.h"
     68 #ifndef SMALL
     69 #include "myhistedit.h"
     70 #endif
     71 
     72 #ifdef SMALL
     73 #define VTABSIZE 39
     74 #else
     75 #define VTABSIZE 517
     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 #if ATTY
     88 struct var vatty;
     89 #endif
     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 const struct varinit varinit[] = {
    105 #if ATTY
    106 	{ &vatty,	VSTRFIXED|VTEXTFIXED|VUNSET,	"ATTY=",
    107 	  NULL },
    108 #endif
    109 #ifndef SMALL
    110 	{ &vhistsize,	VSTRFIXED|VTEXTFIXED|VUNSET,	"HISTSIZE=",
    111 	  sethistsize },
    112 #endif
    113 	{ &vifs,	VSTRFIXED|VTEXTFIXED,		"IFS= \t\n",
    114 	  NULL },
    115 	{ &vmail,	VSTRFIXED|VTEXTFIXED|VUNSET,	"MAIL=",
    116 	  NULL },
    117 	{ &vmpath,	VSTRFIXED|VTEXTFIXED|VUNSET,	"MAILPATH=",
    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 "var.h"
    149 MKINIT char **environ;
    150 INIT {
    151 	char **envp;
    152 
    153 	initvar();
    154 	for (envp = environ ; *envp ; envp++) {
    155 		if (strchr(*envp, '=')) {
    156 			setvareq(*envp, VEXPORT|VTEXTFIXED);
    157 		}
    158 	}
    159 }
    160 #endif
    161 
    162 
    163 /*
    164  * This routine initializes the builtin variables.  It is called when the
    165  * shell is initialized and again when a shell procedure is spawned.
    166  */
    167 
    168 void
    169 initvar(void)
    170 {
    171 	const struct varinit *ip;
    172 	struct var *vp;
    173 	struct var **vpp;
    174 
    175 	for (ip = varinit ; (vp = ip->var) != NULL ; ip++) {
    176 		if (find_var(ip->text, &vpp, &vp->name_len) != NULL)
    177 			continue;
    178 		vp->next = *vpp;
    179 		*vpp = vp;
    180 		vp->text = strdup(ip->text);
    181 		vp->flags = ip->flags;
    182 		vp->func = ip->func;
    183 	}
    184 	/*
    185 	 * PS1 depends on uid
    186 	 */
    187 	if (find_var("PS1", &vpp, &vps1.name_len) == NULL) {
    188 		vps1.next = *vpp;
    189 		*vpp = &vps1;
    190 		vps1.text = strdup(geteuid() ? "PS1=$ " : "PS1=# ");
    191 		vps1.flags = VSTRFIXED|VTEXTFIXED;
    192 	}
    193 }
    194 
    195 /*
    196  * Safe version of setvar, returns 1 on success 0 on failure.
    197  */
    198 
    199 int
    200 setvarsafe(const char *name, const char *val, int flags)
    201 {
    202 	struct jmploc jmploc;
    203 	struct jmploc *volatile savehandler = handler;
    204 	int err = 0;
    205 #ifdef __GNUC__
    206 	(void) &err;
    207 #endif
    208 
    209 	if (setjmp(jmploc.loc))
    210 		err = 1;
    211 	else {
    212 		handler = &jmploc;
    213 		setvar(name, val, flags);
    214 	}
    215 	handler = savehandler;
    216 	return err;
    217 }
    218 
    219 /*
    220  * Set the value of a variable.  The flags argument is ored with the
    221  * flags of the variable.  If val is NULL, the variable is unset.
    222  */
    223 
    224 void
    225 setvar(const char *name, const char *val, int flags)
    226 {
    227 	const char *p;
    228 	const char *q;
    229 	char *d;
    230 	int len;
    231 	int namelen;
    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", namelen, name);
    251 	len = namelen + 2;		/* 2 is space for '=' and '\0' */
    252 	if (val == NULL) {
    253 		flags |= VUNSET;
    254 	} else {
    255 		len += strlen(val);
    256 	}
    257 	d = nameeq = ckmalloc(len);
    258 	q = name;
    259 	while (--namelen >= 0)
    260 		*d++ = *q++;
    261 	*d++ = '=';
    262 	*d = '\0';
    263 	if (val)
    264 		scopy(val, d);
    265 	setvareq(nameeq, flags);
    266 }
    267 
    268 
    269 
    270 /*
    271  * Same as setvar except that the variable and value are passed in
    272  * the first argument as name=value.  Since the first argument will
    273  * be actually stored in the table, it should not be a string that
    274  * will go away.
    275  */
    276 
    277 void
    278 setvareq(char *s, int flags)
    279 {
    280 	struct var *vp, **vpp;
    281 	int nlen;
    282 
    283 	if (aflag)
    284 		flags |= VEXPORT;
    285 	vp = find_var(s, &vpp, &nlen);
    286 	if (vp != NULL) {
    287 		if (vp->flags & VREADONLY)
    288 			error("%.*s: is read only", vp->name_len, s);
    289 		if (flags & VNOSET)
    290 			return;
    291 		INTOFF;
    292 
    293 		if (vp->func && (flags & VNOFUNC) == 0)
    294 			(*vp->func)(s + vp->name_len + 1);
    295 
    296 		if ((vp->flags & (VTEXTFIXED|VSTACK)) == 0)
    297 			ckfree(vp->text);
    298 
    299 		vp->flags &= ~(VTEXTFIXED|VSTACK|VUNSET);
    300 		vp->flags |= flags & ~VNOFUNC;
    301 		vp->text = s;
    302 
    303 		/*
    304 		 * We could roll this to a function, to handle it as
    305 		 * a regular variable function callback, but why bother?
    306 		 */
    307 		if (vp == &vmpath || (vp == &vmail && ! mpathset()))
    308 			chkmail(1);
    309 		INTON;
    310 		return;
    311 	}
    312 	/* not found */
    313 	if (flags & VNOSET)
    314 		return;
    315 	vp = ckmalloc(sizeof (*vp));
    316 	vp->flags = flags & ~VNOFUNC;
    317 	vp->text = s;
    318 	vp->name_len = nlen;
    319 	vp->next = *vpp;
    320 	vp->func = NULL;
    321 	*vpp = vp;
    322 }
    323 
    324 
    325 
    326 /*
    327  * Process a linked list of variable assignments.
    328  */
    329 
    330 void
    331 listsetvar(struct strlist *list, int flags)
    332 {
    333 	struct strlist *lp;
    334 
    335 	INTOFF;
    336 	for (lp = list ; lp ; lp = lp->next) {
    337 		setvareq(savestr(lp->text), flags);
    338 	}
    339 	INTON;
    340 }
    341 
    342 void
    343 listmklocal(struct strlist *list, int flags)
    344 {
    345 	struct strlist *lp;
    346 
    347 	for (lp = list ; lp ; lp = lp->next)
    348 		mklocal(lp->text, flags);
    349 }
    350 
    351 
    352 /*
    353  * Find the value of a variable.  Returns NULL if not set.
    354  */
    355 
    356 char *
    357 lookupvar(const char *name)
    358 {
    359 	struct var *v;
    360 
    361 	v = find_var(name, NULL, NULL);
    362 	if (v == NULL || v->flags & VUNSET)
    363 		return NULL;
    364 	return v->text + v->name_len + 1;
    365 }
    366 
    367 
    368 
    369 /*
    370  * Search the environment of a builtin command.  If the second argument
    371  * is nonzero, return the value of a variable even if it hasn't been
    372  * exported.
    373  */
    374 
    375 char *
    376 bltinlookup(const char *name, int doall)
    377 {
    378 	struct strlist *sp;
    379 	struct var *v;
    380 
    381 	for (sp = cmdenviron ; sp ; sp = sp->next) {
    382 		if (strequal(sp->text, name))
    383 			return strchr(sp->text, '=') + 1;
    384 	}
    385 
    386 	v = find_var(name, NULL, NULL);
    387 
    388 	if (v == NULL || v->flags & VUNSET || (!doall && !(v->flags & VEXPORT)))
    389 		return NULL;
    390 	return v->text + v->name_len + 1;
    391 }
    392 
    393 
    394 
    395 /*
    396  * Generate a list of exported variables.  This routine is used to construct
    397  * the third argument to execve when executing a program.
    398  */
    399 
    400 char **
    401 environment(void)
    402 {
    403 	int nenv;
    404 	struct var **vpp;
    405 	struct var *vp;
    406 	char **env;
    407 	char **ep;
    408 
    409 	nenv = 0;
    410 	for (vpp = vartab ; vpp < vartab + VTABSIZE ; vpp++) {
    411 		for (vp = *vpp ; vp ; vp = vp->next)
    412 			if (vp->flags & VEXPORT)
    413 				nenv++;
    414 	}
    415 	ep = env = stalloc((nenv + 1) * sizeof *env);
    416 	for (vpp = vartab ; vpp < vartab + VTABSIZE ; vpp++) {
    417 		for (vp = *vpp ; vp ; vp = vp->next)
    418 			if (vp->flags & VEXPORT)
    419 				*ep++ = vp->text;
    420 	}
    421 	*ep = NULL;
    422 	return env;
    423 }
    424 
    425 
    426 /*
    427  * Called when a shell procedure is invoked to clear out nonexported
    428  * variables.  It is also necessary to reallocate variables of with
    429  * VSTACK set since these are currently allocated on the stack.
    430  */
    431 
    432 #ifdef mkinit
    433 void shprocvar(void);
    434 
    435 SHELLPROC {
    436 	shprocvar();
    437 }
    438 #endif
    439 
    440 void
    441 shprocvar(void)
    442 {
    443 	struct var **vpp;
    444 	struct var *vp, **prev;
    445 
    446 	for (vpp = vartab ; vpp < vartab + VTABSIZE ; vpp++) {
    447 		for (prev = vpp ; (vp = *prev) != NULL ; ) {
    448 			if ((vp->flags & VEXPORT) == 0) {
    449 				*prev = vp->next;
    450 				if ((vp->flags & VTEXTFIXED) == 0)
    451 					ckfree(vp->text);
    452 				if ((vp->flags & VSTRFIXED) == 0)
    453 					ckfree(vp);
    454 			} else {
    455 				if (vp->flags & VSTACK) {
    456 					vp->text = savestr(vp->text);
    457 					vp->flags &=~ VSTACK;
    458 				}
    459 				prev = &vp->next;
    460 			}
    461 		}
    462 	}
    463 	initvar();
    464 }
    465 
    466 
    467 
    468 /*
    469  * Command to list all variables which are set.  Currently this command
    470  * is invoked from the set command when the set command is called without
    471  * any variables.
    472  */
    473 
    474 void
    475 print_quoted(const char *p)
    476 {
    477 	const char *q;
    478 
    479 	if (strcspn(p, "|&;<>()$`\\\"' \t\n*?[]#~=%") == strlen(p)) {
    480 		out1fmt("%s", p);
    481 		return;
    482 	}
    483 	while (*p) {
    484 		if (*p == '\'') {
    485 			out1fmt("\\'");
    486 			p++;
    487 			continue;
    488 		}
    489 		q = index(p, '\'');
    490 		if (!q) {
    491 			out1fmt("'%s'", p );
    492 			return;
    493 		}
    494 		out1fmt("'%.*s'", (int)(q - p), p );
    495 		p = q;
    496 	}
    497 }
    498 
    499 static int
    500 sort_var(const void *v_v1, const void *v_v2)
    501 {
    502 	const struct var * const *v1 = v_v1;
    503 	const struct var * const *v2 = v_v2;
    504 
    505 	/* XXX Will anyone notice we include the '=' of the shorter name? */
    506 	return strcoll((*v1)->text, (*v2)->text);
    507 }
    508 
    509 /*
    510  * POSIX requires that 'set' (but not export or readonly) output the
    511  * variables in lexicographic order - by the locale's collating order (sigh).
    512  * Maybe we could keep them in an ordered balanced binary tree
    513  * instead of hashed lists.
    514  * For now just roll 'em through qsort for printing...
    515  */
    516 
    517 int
    518 showvars(const char *name, int flag, int show_value)
    519 {
    520 	struct var **vpp;
    521 	struct var *vp;
    522 	const char *p;
    523 
    524 	static struct var **list;	/* static in case we are interrupted */
    525 	static int list_len;
    526 	int count = 0;
    527 
    528 	if (!list) {
    529 		list_len = 32;
    530 		list = ckmalloc(list_len * sizeof *list);
    531 	}
    532 
    533 	for (vpp = vartab ; vpp < vartab + VTABSIZE ; vpp++) {
    534 		for (vp = *vpp ; vp ; vp = vp->next) {
    535 			if (flag && !(vp->flags & flag))
    536 				continue;
    537 			if (vp->flags & VUNSET && !(show_value & 2))
    538 				continue;
    539 			if (count >= list_len) {
    540 				list = ckrealloc(list,
    541 					(list_len << 1) * sizeof *list);
    542 				list_len <<= 1;
    543 			}
    544 			list[count++] = vp;
    545 		}
    546 	}
    547 
    548 	qsort(list, count, sizeof *list, sort_var);
    549 
    550 	for (vpp = list; count--; vpp++) {
    551 		vp = *vpp;
    552 		if (name)
    553 			out1fmt("%s ", name);
    554 		for (p = vp->text ; *p != '=' ; p++)
    555 			out1c(*p);
    556 		if (!(vp->flags & VUNSET) && show_value) {
    557 			out1fmt("=");
    558 			print_quoted(++p);
    559 		}
    560 		out1c('\n');
    561 	}
    562 	return 0;
    563 }
    564 
    565 
    566 
    567 /*
    568  * The export and readonly commands.
    569  */
    570 
    571 int
    572 exportcmd(int argc, char **argv)
    573 {
    574 	struct var *vp;
    575 	char *name;
    576 	const char *p;
    577 	int flag = argv[0][0] == 'r'? VREADONLY : VEXPORT;
    578 	int pflag;
    579 
    580 	pflag = nextopt("p") == 'p' ? 3 : 0;
    581 	if (argc <= 1 || pflag) {
    582 		showvars( pflag ? argv[0] : 0, flag, pflag );
    583 		return 0;
    584 	}
    585 
    586 	while ((name = *argptr++) != NULL) {
    587 		if ((p = strchr(name, '=')) != NULL) {
    588 			p++;
    589 		} else {
    590 			vp = find_var(name, NULL, NULL);
    591 			if (vp != NULL) {
    592 				vp->flags |= flag;
    593 				continue;
    594 			}
    595 		}
    596 		setvar(name, p, flag);
    597 	}
    598 	return 0;
    599 }
    600 
    601 
    602 /*
    603  * The "local" command.
    604  */
    605 
    606 int
    607 localcmd(int argc, char **argv)
    608 {
    609 	char *name;
    610 
    611 	if (! in_function())
    612 		error("Not in a function");
    613 	while ((name = *argptr++) != NULL) {
    614 		mklocal(name, 0);
    615 	}
    616 	return 0;
    617 }
    618 
    619 
    620 /*
    621  * Make a variable a local variable.  When a variable is made local, its
    622  * value and flags are saved in a localvar structure.  The saved values
    623  * will be restored when the shell function returns.  We handle the name
    624  * "-" as a special case.
    625  */
    626 
    627 void
    628 mklocal(const char *name, int flags)
    629 {
    630 	struct localvar *lvp;
    631 	struct var **vpp;
    632 	struct var *vp;
    633 
    634 	INTOFF;
    635 	lvp = ckmalloc(sizeof (struct localvar));
    636 	if (name[0] == '-' && name[1] == '\0') {
    637 		char *p;
    638 		p = ckmalloc(sizeof_optlist);
    639 		lvp->text = memcpy(p, optlist, sizeof_optlist);
    640 		vp = NULL;
    641 	} else {
    642 		vp = find_var(name, &vpp, NULL);
    643 		if (vp == NULL) {
    644 			if (strchr(name, '='))
    645 				setvareq(savestr(name), VSTRFIXED|flags);
    646 			else
    647 				setvar(name, NULL, VSTRFIXED|flags);
    648 			vp = *vpp;	/* the new variable */
    649 			lvp->text = NULL;
    650 			lvp->flags = VUNSET;
    651 		} else {
    652 			lvp->text = vp->text;
    653 			lvp->flags = vp->flags;
    654 			vp->flags |= VSTRFIXED|VTEXTFIXED;
    655 			if (name[vp->name_len] == '=')
    656 				setvareq(savestr(name), flags);
    657 		}
    658 	}
    659 	lvp->vp = vp;
    660 	lvp->next = localvars;
    661 	localvars = lvp;
    662 	INTON;
    663 }
    664 
    665 
    666 /*
    667  * Called after a function returns.
    668  */
    669 
    670 void
    671 poplocalvars(void)
    672 {
    673 	struct localvar *lvp;
    674 	struct var *vp;
    675 
    676 	while ((lvp = localvars) != NULL) {
    677 		localvars = lvp->next;
    678 		vp = lvp->vp;
    679 		TRACE(("poplocalvar %s", vp ? vp->text : "-"));
    680 		if (vp == NULL) {	/* $- saved */
    681 			memcpy(optlist, lvp->text, sizeof_optlist);
    682 			ckfree(lvp->text);
    683 		} else if ((lvp->flags & (VUNSET|VSTRFIXED)) == VUNSET) {
    684 			(void)unsetvar(vp->text, 0);
    685 		} else {
    686 			if (vp->func && (vp->flags & VNOFUNC) == 0)
    687 				(*vp->func)(lvp->text + vp->name_len + 1);
    688 			if ((vp->flags & VTEXTFIXED) == 0)
    689 				ckfree(vp->text);
    690 			vp->flags = lvp->flags;
    691 			vp->text = lvp->text;
    692 		}
    693 		ckfree(lvp);
    694 	}
    695 }
    696 
    697 
    698 int
    699 setvarcmd(int argc, char **argv)
    700 {
    701 	if (argc <= 2)
    702 		return unsetcmd(argc, argv);
    703 	else if (argc == 3)
    704 		setvar(argv[1], argv[2], 0);
    705 	else
    706 		error("List assignment not implemented");
    707 	return 0;
    708 }
    709 
    710 
    711 /*
    712  * The unset builtin command.  We unset the function before we unset the
    713  * variable to allow a function to be unset when there is a readonly variable
    714  * with the same name.
    715  */
    716 
    717 int
    718 unsetcmd(int argc, char **argv)
    719 {
    720 	char **ap;
    721 	int i;
    722 	int flg_func = 0;
    723 	int flg_var = 0;
    724 	int ret = 0;
    725 
    726 	while ((i = nextopt("evf")) != '\0') {
    727 		if (i == 'f')
    728 			flg_func = 1;
    729 		else
    730 			flg_var = i;
    731 	}
    732 	if (flg_func == 0 && flg_var == 0)
    733 		flg_var = 1;
    734 
    735 	for (ap = argptr; *ap ; ap++) {
    736 		if (flg_func)
    737 			ret |= unsetfunc(*ap);
    738 		if (flg_var)
    739 			ret |= unsetvar(*ap, flg_var == 'e');
    740 	}
    741 	return ret;
    742 }
    743 
    744 
    745 /*
    746  * Unset the specified variable.
    747  */
    748 
    749 int
    750 unsetvar(const char *s, int unexport)
    751 {
    752 	struct var **vpp;
    753 	struct var *vp;
    754 
    755 	vp = find_var(s, &vpp, NULL);
    756 	if (vp == NULL)
    757 		return 1;
    758 
    759 	if (vp->flags & VREADONLY)
    760 		return (1);
    761 
    762 	INTOFF;
    763 	if (unexport) {
    764 		vp->flags &= ~VEXPORT;
    765 	} else {
    766 		if (vp->text[vp->name_len + 1] != '\0')
    767 			setvar(s, nullstr, 0);
    768 		vp->flags &= ~VEXPORT;
    769 		vp->flags |= VUNSET;
    770 		if ((vp->flags & VSTRFIXED) == 0) {
    771 			if ((vp->flags & VTEXTFIXED) == 0)
    772 				ckfree(vp->text);
    773 			*vpp = vp->next;
    774 			ckfree(vp);
    775 		}
    776 	}
    777 	INTON;
    778 	return 0;
    779 }
    780 
    781 
    782 /*
    783  * Returns true if the two strings specify the same varable.  The first
    784  * variable name is terminated by '='; the second may be terminated by
    785  * either '=' or '\0'.
    786  */
    787 
    788 STATIC int
    789 strequal(const char *p, const char *q)
    790 {
    791 	while (*p == *q++) {
    792 		if (*p++ == '=')
    793 			return 1;
    794 	}
    795 	if (*p == '=' && *(q - 1) == '\0')
    796 		return 1;
    797 	return 0;
    798 }
    799 
    800 /*
    801  * Search for a variable.
    802  * 'name' may be terminated by '=' or a NUL.
    803  * vppp is set to the pointer to vp, or the list head if vp isn't found
    804  * lenp is set to the number of charactets in 'name'
    805  */
    806 
    807 STATIC struct var *
    808 find_var(const char *name, struct var ***vppp, int *lenp)
    809 {
    810 	unsigned int hashval;
    811 	int len;
    812 	struct var *vp, **vpp;
    813 	const char *p = name;
    814 
    815 	hashval = 0;
    816 	while (*p && *p != '=')
    817 		hashval = 2 * hashval + (unsigned char)*p++;
    818 	len = p - name;
    819 
    820 	if (lenp)
    821 		*lenp = len;
    822 	vpp = &vartab[hashval % VTABSIZE];
    823 	if (vppp)
    824 		*vppp = vpp;
    825 
    826 	for (vp = *vpp ; vp ; vpp = &vp->next, vp = *vpp) {
    827 		if (vp->name_len != len)
    828 			continue;
    829 		if (memcmp(vp->text, name, len) != 0)
    830 			continue;
    831 		if (vppp)
    832 			*vppp = vpp;
    833 		return vp;
    834 	}
    835 	return NULL;
    836 }
    837