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      1 /*	$NetBSD: cd.c,v 1.34 2003/11/14 20:00:28 dsl 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[] = "@(#)cd.c	8.2 (Berkeley) 5/4/95";
     39 #else
     40 __RCSID("$NetBSD: cd.c,v 1.34 2003/11/14 20:00:28 dsl Exp $");
     41 #endif
     42 #endif /* not lint */
     43 
     44 #include <sys/types.h>
     45 #include <sys/stat.h>
     46 #include <stdlib.h>
     47 #include <string.h>
     48 #include <unistd.h>
     49 #include <errno.h>
     50 
     51 /*
     52  * The cd and pwd commands.
     53  */
     54 
     55 #include "shell.h"
     56 #include "var.h"
     57 #include "nodes.h"	/* for jobs.h */
     58 #include "jobs.h"
     59 #include "options.h"
     60 #include "output.h"
     61 #include "memalloc.h"
     62 #include "error.h"
     63 #include "exec.h"
     64 #include "redir.h"
     65 #include "mystring.h"
     66 #include "show.h"
     67 #include "cd.h"
     68 
     69 STATIC int docd(char *, int);
     70 STATIC char *getcomponent(void);
     71 STATIC void updatepwd(char *);
     72 STATIC void find_curdir(int noerror);
     73 
     74 char *curdir = NULL;		/* current working directory */
     75 char *prevdir;			/* previous working directory */
     76 STATIC char *cdcomppath;
     77 
     78 int
     79 cdcmd(int argc, char **argv)
     80 {
     81 	const char *dest;
     82 	const char *path;
     83 	char *p, *d;
     84 	struct stat statb;
     85 	int print = cdprint;	/* set -cdprint to enable */
     86 
     87 	nextopt(nullstr);
     88 
     89 	/*
     90 	 * Try (quite hard) to have 'curdir' defined, nothing has set
     91 	 * it on entry to the shell, but we want 'cd fred; cd -' to work.
     92 	 */
     93 	getpwd(1);
     94 	dest = *argptr;
     95 	if (dest == NULL) {
     96 		dest = bltinlookup("HOME", 1);
     97 		if (dest == NULL)
     98 			error("HOME not set");
     99 	} else {
    100 		if (argptr[1]) {
    101 			/* Do 'ksh' style substitution */
    102 			if (!curdir)
    103 				error("PWD not set");
    104 			p = strstr(curdir, dest);
    105 			if (!p)
    106 				error("bad substitution");
    107 			d = stalloc(strlen(curdir) + strlen(argptr[1]) + 1);
    108 			memcpy(d, curdir, p - curdir);
    109 			strcpy(d + (p - curdir), argptr[1]);
    110 			strcat(d, p + strlen(dest));
    111 			dest = d;
    112 			print = 1;
    113 		}
    114 	}
    115 
    116 	if (dest[0] == '-' && dest[1] == '\0') {
    117 		dest = prevdir ? prevdir : curdir;
    118 		print = 1;
    119 	}
    120 	if (*dest == '\0')
    121 	        dest = ".";
    122 	if (*dest == '/' || (path = bltinlookup("CDPATH", 1)) == NULL)
    123 		path = nullstr;
    124 	while ((p = padvance(&path, dest)) != NULL) {
    125 		if (stat(p, &statb) >= 0 && S_ISDIR(statb.st_mode)) {
    126 			if (!print) {
    127 				/*
    128 				 * XXX - rethink
    129 				 */
    130 				if (p[0] == '.' && p[1] == '/' && p[2] != '\0')
    131 					p += 2;
    132 				print = strcmp(p, dest);
    133 			}
    134 			if (docd(p, print) >= 0)
    135 				return 0;
    136 
    137 		}
    138 	}
    139 	error("can't cd to %s", dest);
    140 	/* NOTREACHED */
    141 }
    142 
    143 
    144 /*
    145  * Actually do the chdir.  In an interactive shell, print the
    146  * directory name if "print" is nonzero.
    147  */
    148 
    149 STATIC int
    150 docd(char *dest, int print)
    151 {
    152 	char *p;
    153 	char *q;
    154 	char *component;
    155 	struct stat statb;
    156 	int first;
    157 	int badstat;
    158 
    159 	TRACE(("docd(\"%s\", %d) called\n", dest, print));
    160 
    161 	/*
    162 	 *  Check each component of the path. If we find a symlink or
    163 	 *  something we can't stat, clear curdir to force a getcwd()
    164 	 *  next time we get the value of the current directory.
    165 	 */
    166 	badstat = 0;
    167 	cdcomppath = stalloc(strlen(dest) + 1);
    168 	scopy(dest, cdcomppath);
    169 	STARTSTACKSTR(p);
    170 	if (*dest == '/') {
    171 		STPUTC('/', p);
    172 		cdcomppath++;
    173 	}
    174 	first = 1;
    175 	while ((q = getcomponent()) != NULL) {
    176 		if (q[0] == '\0' || (q[0] == '.' && q[1] == '\0'))
    177 			continue;
    178 		if (! first)
    179 			STPUTC('/', p);
    180 		first = 0;
    181 		component = q;
    182 		while (*q)
    183 			STPUTC(*q++, p);
    184 		if (equal(component, ".."))
    185 			continue;
    186 		STACKSTRNUL(p);
    187 		if ((lstat(stackblock(), &statb) < 0)
    188 		    || (S_ISLNK(statb.st_mode)))  {
    189 			/* print = 1; */
    190 			badstat = 1;
    191 			break;
    192 		}
    193 	}
    194 
    195 	INTOFF;
    196 	if (chdir(dest) < 0) {
    197 		INTON;
    198 		return -1;
    199 	}
    200 	updatepwd(badstat ? NULL : dest);
    201 	INTON;
    202 	if (print && iflag && curdir)
    203 		out1fmt("%s\n", curdir);
    204 	return 0;
    205 }
    206 
    207 
    208 /*
    209  * Get the next component of the path name pointed to by cdcomppath.
    210  * This routine overwrites the string pointed to by cdcomppath.
    211  */
    212 
    213 STATIC char *
    214 getcomponent()
    215 {
    216 	char *p;
    217 	char *start;
    218 
    219 	if ((p = cdcomppath) == NULL)
    220 		return NULL;
    221 	start = cdcomppath;
    222 	while (*p != '/' && *p != '\0')
    223 		p++;
    224 	if (*p == '\0') {
    225 		cdcomppath = NULL;
    226 	} else {
    227 		*p++ = '\0';
    228 		cdcomppath = p;
    229 	}
    230 	return start;
    231 }
    232 
    233 
    234 
    235 /*
    236  * Update curdir (the name of the current directory) in response to a
    237  * cd command.  We also call hashcd to let the routines in exec.c know
    238  * that the current directory has changed.
    239  */
    240 
    241 STATIC void
    242 updatepwd(char *dir)
    243 {
    244 	char *new;
    245 	char *p;
    246 
    247 	hashcd();				/* update command hash table */
    248 
    249 	/*
    250 	 * If our argument is NULL, we don't know the current directory
    251 	 * any more because we traversed a symbolic link or something
    252 	 * we couldn't stat().
    253 	 */
    254 	if (dir == NULL || curdir == NULL)  {
    255 		if (prevdir)
    256 			ckfree(prevdir);
    257 		INTOFF;
    258 		prevdir = curdir;
    259 		curdir = NULL;
    260 		getpwd(1);
    261 		INTON;
    262 		if (curdir)
    263 			setvar("PWD", curdir, VEXPORT);
    264 		else
    265 			unsetvar("PWD", 0);
    266 		return;
    267 	}
    268 	cdcomppath = stalloc(strlen(dir) + 1);
    269 	scopy(dir, cdcomppath);
    270 	STARTSTACKSTR(new);
    271 	if (*dir != '/') {
    272 		p = curdir;
    273 		while (*p)
    274 			STPUTC(*p++, new);
    275 		if (p[-1] == '/')
    276 			STUNPUTC(new);
    277 	}
    278 	while ((p = getcomponent()) != NULL) {
    279 		if (equal(p, "..")) {
    280 			while (new > stackblock() && (STUNPUTC(new), *new) != '/');
    281 		} else if (*p != '\0' && ! equal(p, ".")) {
    282 			STPUTC('/', new);
    283 			while (*p)
    284 				STPUTC(*p++, new);
    285 		}
    286 	}
    287 	if (new == stackblock())
    288 		STPUTC('/', new);
    289 	STACKSTRNUL(new);
    290 	INTOFF;
    291 	if (prevdir)
    292 		ckfree(prevdir);
    293 	prevdir = curdir;
    294 	curdir = savestr(stackblock());
    295 	setvar("PWD", curdir, VEXPORT);
    296 	INTON;
    297 }
    298 
    299 /*
    300  * Posix says the default should be 'pwd -L' (as below), however
    301  * the 'cd' command (above) does something much nearer to the
    302  * posix 'cd -P' (not the posix default of 'cd -L').
    303  * If 'cd' is changed to support -P/L then the default here
    304  * needs to be revisited if the historic behaviour is to be kept.
    305  */
    306 
    307 int
    308 pwdcmd(int argc, char **argv)
    309 {
    310 	int i;
    311 	char opt = 'L';
    312 
    313 	while ((i = nextopt("LP")) != '\0')
    314 		opt = i;
    315 	if (*argptr)
    316 		error("unexpected argument");
    317 
    318 	if (opt == 'L')
    319 		getpwd(0);
    320 	else
    321 		find_curdir(0);
    322 
    323 	setvar("PWD", curdir, VEXPORT);
    324 	out1str(curdir);
    325 	out1c('\n');
    326 	return 0;
    327 }
    328 
    329 
    330 
    331 
    332 #define MAXPWD 256
    333 
    334 /*
    335  * Find out what the current directory is. If we already know the current
    336  * directory, this routine returns immediately.
    337  */
    338 void
    339 getpwd(int noerror)
    340 {
    341 	char *pwd;
    342 	struct stat stdot, stpwd;
    343 	static int first = 1;
    344 
    345 	if (curdir)
    346 		return;
    347 
    348 	if (first) {
    349 		first = 0;
    350 		pwd = getenv("PWD");
    351 		if (pwd && *pwd == '/' && stat(".", &stdot) != -1 &&
    352 		    stat(pwd, &stpwd) != -1 &&
    353 		    stdot.st_dev == stpwd.st_dev &&
    354 		    stdot.st_ino == stpwd.st_ino) {
    355 			curdir = savestr(pwd);
    356 			return;
    357 		}
    358 	}
    359 
    360 	find_curdir(noerror);
    361 
    362 	return;
    363 }
    364 
    365 STATIC void
    366 find_curdir(int noerror)
    367 {
    368 	int i;
    369 	char *pwd;
    370 
    371 	/*
    372 	 * Things are a bit complicated here; we could have just used
    373 	 * getcwd, but traditionally getcwd is implemented using popen
    374 	 * to /bin/pwd. This creates a problem for us, since we cannot
    375 	 * keep track of the job if it is being ran behind our backs.
    376 	 * So we re-implement getcwd(), and we suppress interrupts
    377 	 * throughout the process. This is not completely safe, since
    378 	 * the user can still break out of it by killing the pwd program.
    379 	 * We still try to use getcwd for systems that we know have a
    380 	 * c implementation of getcwd, that does not open a pipe to
    381 	 * /bin/pwd.
    382 	 */
    383 #if defined(__NetBSD__) || defined(__SVR4) || defined(__linux__)
    384 	for (i = MAXPWD;; i *= 2) {
    385 		pwd = stalloc(i);
    386 		if (getcwd(pwd, i) != NULL) {
    387 			curdir = savestr(pwd);
    388 			return;
    389 		}
    390 		stunalloc(pwd);
    391 		if (errno == ERANGE)
    392 			continue;
    393 		if (!noerror)
    394 			error("getcwd() failed: %s", strerror(errno));
    395 		return;
    396 	}
    397 #else
    398 	{
    399 		char *p;
    400 		int status;
    401 		struct job *jp;
    402 		int pip[2];
    403 
    404 		pwd = stalloc(MAXPWD);
    405 		INTOFF;
    406 		if (pipe(pip) < 0)
    407 			error("Pipe call failed");
    408 		jp = makejob((union node *)NULL, 1);
    409 		if (forkshell(jp, (union node *)NULL, FORK_NOJOB) == 0) {
    410 			(void) close(pip[0]);
    411 			if (pip[1] != 1) {
    412 				close(1);
    413 				copyfd(pip[1], 1);
    414 				close(pip[1]);
    415 			}
    416 			(void) execl("/bin/pwd", "pwd", (char *)0);
    417 			sh_warn("Cannot exec /bin/pwd");
    418 			exit(1);
    419 		}
    420 		(void) close(pip[1]);
    421 		pip[1] = -1;
    422 		p = pwd;
    423 		while ((i = read(pip[0], p, pwd + MAXPWD - p)) > 0
    424 		     || (i == -1 && errno == EINTR)) {
    425 			if (i > 0)
    426 				p += i;
    427 		}
    428 		(void) close(pip[0]);
    429 		pip[0] = -1;
    430 		status = waitforjob(jp);
    431 		if (status != 0)
    432 			error((char *)0);
    433 		if (i < 0 || p == pwd || p[-1] != '\n') {
    434 			if (noerror) {
    435 				INTON;
    436 				return;
    437 			}
    438 			error("pwd command failed");
    439 		}
    440 		p[-1] = '\0';
    441 		INTON;
    442 		curdir = savestr(pwd);
    443 		return;
    444 	}
    445 #endif
    446 }
    447