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cd.c revision 1.47 
      1 /*	$NetBSD: cd.c,v 1.47 2016/12/26 02:27:57 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[] = "@(#)cd.c	8.2 (Berkeley) 5/4/95";
     39 #else
     40 __RCSID("$NetBSD: cd.c,v 1.47 2016/12/26 02:27:57 christos 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 "builtins.h"
     61 #include "output.h"
     62 #include "memalloc.h"
     63 #include "error.h"
     64 #include "exec.h"
     65 #include "redir.h"
     66 #include "mystring.h"
     67 #include "show.h"
     68 #include "cd.h"
     69 
     70 STATIC int docd(const char *, int);
     71 STATIC char *getcomponent(void);
     72 STATIC void updatepwd(const char *);
     73 STATIC void find_curdir(int noerror);
     74 
     75 char *curdir = NULL;		/* current working directory */
     76 char *prevdir;			/* previous working directory */
     77 STATIC char *cdcomppath;
     78 
     79 int
     80 cdcmd(int argc, char **argv)
     81 {
     82 	const char *dest;
     83 	const char *path, *p;
     84 	char *d;
     85 	struct stat statb;
     86 	int print = cdprint;	/* set -cdprint to enable */
     87 
     88 	while (nextopt("P") != '\0')
     89 		;
     90 
     91 	/*
     92 	 * Try (quite hard) to have 'curdir' defined, nothing has set
     93 	 * it on entry to the shell, but we want 'cd fred; cd -' to work.
     94 	 */
     95 	getpwd(1);
     96 	dest = *argptr;
     97 	if (dest == NULL) {
     98 		dest = bltinlookup("HOME", 1);
     99 		if (dest == NULL)
    100 			error("HOME not set");
    101 	} else {
    102 		if (argptr[1]) {
    103 			/* Do 'ksh' style substitution */
    104 			if (!curdir)
    105 				error("PWD not set");
    106 			p = strstr(curdir, dest);
    107 			if (!p)
    108 				error("bad substitution");
    109 			d = stalloc(strlen(curdir) + strlen(argptr[1]) + 1);
    110 			memcpy(d, curdir, p - curdir);
    111 			strcpy(d + (p - curdir), argptr[1]);
    112 			strcat(d, p + strlen(dest));
    113 			dest = d;
    114 			print = 1;
    115 		}
    116 	}
    117 
    118 	if (dest[0] == '-' && dest[1] == '\0') {
    119 		dest = prevdir ? prevdir : curdir;
    120 		print = 1;
    121 	}
    122 	if (*dest == '\0')
    123 	        dest = ".";
    124 	p = dest;
    125 	if (*p == '.' && *++p == '.')
    126 	    p++;
    127 	if (*p == 0 || *p == '/' || (path = bltinlookup("CDPATH", 1)) == NULL)
    128 		path = nullstr;
    129 	while ((p = padvance(&path, dest)) != NULL) {
    130 		if (stat(p, &statb) >= 0 && S_ISDIR(statb.st_mode)) {
    131 			if (!print) {
    132 				/*
    133 				 * XXX - rethink
    134 				 */
    135 				if (p[0] == '.' && p[1] == '/' && p[2] != '\0')
    136 					print = strcmp(p + 2, dest);
    137 				else
    138 					print = strcmp(p, dest);
    139 			}
    140 			if (docd(p, print) >= 0)
    141 				return 0;
    142 
    143 		}
    144 	}
    145 	error("can't cd to %s", dest);
    146 	/* NOTREACHED */
    147 }
    148 
    149 
    150 /*
    151  * Actually do the chdir.  In an interactive shell, print the
    152  * directory name if "print" is nonzero.
    153  */
    154 
    155 STATIC int
    156 docd(const char *dest, int print)
    157 {
    158 	char *p;
    159 	char *q;
    160 	char *component;
    161 	struct stat statb;
    162 	int first;
    163 	int badstat;
    164 
    165 	TRACE(("docd(\"%s\", %d) called\n", dest, print));
    166 
    167 	/*
    168 	 *  Check each component of the path. If we find a symlink or
    169 	 *  something we can't stat, clear curdir to force a getcwd()
    170 	 *  next time we get the value of the current directory.
    171 	 */
    172 	badstat = 0;
    173 	cdcomppath = stalloc(strlen(dest) + 1);
    174 	scopy(dest, cdcomppath);
    175 	STARTSTACKSTR(p);
    176 	if (*dest == '/') {
    177 		STPUTC('/', p);
    178 		cdcomppath++;
    179 	}
    180 	first = 1;
    181 	while ((q = getcomponent()) != NULL) {
    182 		if (q[0] == '\0' || (q[0] == '.' && q[1] == '\0'))
    183 			continue;
    184 		if (! first)
    185 			STPUTC('/', p);
    186 		first = 0;
    187 		component = q;
    188 		while (*q)
    189 			STPUTC(*q++, p);
    190 		if (equal(component, ".."))
    191 			continue;
    192 		STACKSTRNUL(p);
    193 		if (lstat(stackblock(), &statb) < 0) {
    194 			badstat = 1;
    195 			break;
    196 		}
    197 	}
    198 
    199 	INTOFF;
    200 	if (chdir(dest) < 0) {
    201 		INTON;
    202 		return -1;
    203 	}
    204 	updatepwd(badstat ? NULL : dest);
    205 	INTON;
    206 	if (print && iflag == 1 && curdir)
    207 		out1fmt("%s\n", curdir);
    208 	return 0;
    209 }
    210 
    211 
    212 /*
    213  * Get the next component of the path name pointed to by cdcomppath.
    214  * This routine overwrites the string pointed to by cdcomppath.
    215  */
    216 
    217 STATIC char *
    218 getcomponent(void)
    219 {
    220 	char *p;
    221 	char *start;
    222 
    223 	if ((p = cdcomppath) == NULL)
    224 		return NULL;
    225 	start = cdcomppath;
    226 	while (*p != '/' && *p != '\0')
    227 		p++;
    228 	if (*p == '\0') {
    229 		cdcomppath = NULL;
    230 	} else {
    231 		*p++ = '\0';
    232 		cdcomppath = p;
    233 	}
    234 	return start;
    235 }
    236 
    237 
    238 
    239 /*
    240  * Update curdir (the name of the current directory) in response to a
    241  * cd command.  We also call hashcd to let the routines in exec.c know
    242  * that the current directory has changed.
    243  */
    244 
    245 STATIC void
    246 updatepwd(const char *dir)
    247 {
    248 	char *new;
    249 	char *p;
    250 
    251 	hashcd();				/* update command hash table */
    252 
    253 	/*
    254 	 * If our argument is NULL, we don't know the current directory
    255 	 * any more because we traversed a symbolic link or something
    256 	 * we couldn't stat().
    257 	 */
    258 	if (dir == NULL || curdir == NULL)  {
    259 		if (prevdir)
    260 			ckfree(prevdir);
    261 		INTOFF;
    262 		prevdir = curdir;
    263 		curdir = NULL;
    264 		getpwd(1);
    265 		INTON;
    266 		if (curdir) {
    267 			setvar("OLDPWD", prevdir, VEXPORT);
    268 			setvar("PWD", curdir, VEXPORT);
    269 		} else
    270 			unsetvar("PWD", 0);
    271 		return;
    272 	}
    273 	cdcomppath = stalloc(strlen(dir) + 1);
    274 	scopy(dir, cdcomppath);
    275 	STARTSTACKSTR(new);
    276 	if (*dir != '/') {
    277 		p = curdir;
    278 		while (*p)
    279 			STPUTC(*p++, new);
    280 		if (p[-1] == '/')
    281 			STUNPUTC(new);
    282 	}
    283 	while ((p = getcomponent()) != NULL) {
    284 		if (equal(p, "..")) {
    285 			while (new > stackblock() && (STUNPUTC(new), *new) != '/');
    286 		} else if (*p != '\0' && ! equal(p, ".")) {
    287 			STPUTC('/', new);
    288 			while (*p)
    289 				STPUTC(*p++, new);
    290 		}
    291 	}
    292 	if (new == stackblock())
    293 		STPUTC('/', new);
    294 	STACKSTRNUL(new);
    295 	INTOFF;
    296 	if (prevdir)
    297 		ckfree(prevdir);
    298 	prevdir = curdir;
    299 	curdir = savestr(stackblock());
    300 	setvar("OLDPWD", prevdir, VEXPORT);
    301 	setvar("PWD", curdir, VEXPORT);
    302 	INTON;
    303 }
    304 
    305 /*
    306  * Posix says the default should be 'pwd -L' (as below), however
    307  * the 'cd' command (above) does something much nearer to the
    308  * posix 'cd -P' (not the posix default of 'cd -L').
    309  * If 'cd' is changed to support -P/L then the default here
    310  * needs to be revisited if the historic behaviour is to be kept.
    311  */
    312 
    313 int
    314 pwdcmd(int argc, char **argv)
    315 {
    316 	int i;
    317 	char opt = 'L';
    318 
    319 	while ((i = nextopt("LP")) != '\0')
    320 		opt = i;
    321 	if (*argptr)
    322 		error("unexpected argument");
    323 
    324 	if (opt == 'L')
    325 		getpwd(0);
    326 	else
    327 		find_curdir(0);
    328 
    329 	setvar("OLDPWD", prevdir, VEXPORT);
    330 	setvar("PWD", curdir, VEXPORT);
    331 	out1str(curdir);
    332 	out1c('\n');
    333 	return 0;
    334 }
    335 
    336 
    337 
    338 void
    339 initpwd(void)
    340 {
    341 	getpwd(1);
    342 	if (curdir)
    343 		setvar("PWD", curdir, VEXPORT);
    344 	else
    345 		sh_warnx("Cannot determine current working directory");
    346 }
    347 
    348 #define MAXPWD 256
    349 
    350 /*
    351  * Find out what the current directory is. If we already know the current
    352  * directory, this routine returns immediately.
    353  */
    354 void
    355 getpwd(int noerror)
    356 {
    357 	char *pwd;
    358 	struct stat stdot, stpwd;
    359 	static int first = 1;
    360 
    361 	if (curdir)
    362 		return;
    363 
    364 	if (first) {
    365 		first = 0;
    366 		pwd = getenv("PWD");
    367 		if (pwd && *pwd == '/' && stat(".", &stdot) != -1 &&
    368 		    stat(pwd, &stpwd) != -1 &&
    369 		    stdot.st_dev == stpwd.st_dev &&
    370 		    stdot.st_ino == stpwd.st_ino) {
    371 			curdir = savestr(pwd);
    372 			return;
    373 		}
    374 	}
    375 
    376 	find_curdir(noerror);
    377 
    378 	return;
    379 }
    380 
    381 STATIC void
    382 find_curdir(int noerror)
    383 {
    384 	int i;
    385 	char *pwd;
    386 
    387 	/*
    388 	 * Things are a bit complicated here; we could have just used
    389 	 * getcwd, but traditionally getcwd is implemented using popen
    390 	 * to /bin/pwd. This creates a problem for us, since we cannot
    391 	 * keep track of the job if it is being ran behind our backs.
    392 	 * So we re-implement getcwd(), and we suppress interrupts
    393 	 * throughout the process. This is not completely safe, since
    394 	 * the user can still break out of it by killing the pwd program.
    395 	 * We still try to use getcwd for systems that we know have a
    396 	 * c implementation of getcwd, that does not open a pipe to
    397 	 * /bin/pwd.
    398 	 */
    399 #if defined(__NetBSD__) || defined(__SVR4)
    400 
    401 	for (i = MAXPWD;; i *= 2) {
    402 		pwd = stalloc(i);
    403 		if (getcwd(pwd, i) != NULL) {
    404 			curdir = savestr(pwd);
    405 			return;
    406 		}
    407 		stunalloc(pwd);
    408 		if (errno == ERANGE)
    409 			continue;
    410 		if (!noerror)
    411 			error("getcwd() failed: %s", strerror(errno));
    412 		return;
    413 	}
    414 #else
    415 	{
    416 		char *p;
    417 		int status;
    418 		struct job *jp;
    419 		int pip[2];
    420 
    421 		pwd = stalloc(MAXPWD);
    422 		INTOFF;
    423 		if (pipe(pip) < 0)
    424 			error("Pipe call failed");
    425 		jp = makejob(NULL, 1);
    426 		if (forkshell(jp, NULL, FORK_NOJOB) == 0) {
    427 			(void) close(pip[0]);
    428 			movefd(pip[1], 1);
    429 			(void) execl("/bin/pwd", "pwd", (char *)0);
    430 			error("Cannot exec /bin/pwd");
    431 		}
    432 		(void) close(pip[1]);
    433 		pip[1] = -1;
    434 		p = pwd;
    435 		while ((i = read(pip[0], p, pwd + MAXPWD - p)) > 0
    436 		     || (i == -1 && errno == EINTR)) {
    437 			if (i > 0)
    438 				p += i;
    439 		}
    440 		(void) close(pip[0]);
    441 		pip[0] = -1;
    442 		status = waitforjob(jp);
    443 		if (status != 0)
    444 			error((char *)0);
    445 		if (i < 0 || p == pwd || p[-1] != '\n') {
    446 			if (noerror) {
    447 				INTON;
    448 				return;
    449 			}
    450 			error("pwd command failed");
    451 		}
    452 		p[-1] = '\0';
    453 		INTON;
    454 		curdir = savestr(pwd);
    455 		return;
    456 	}
    457 #endif
    458 }
    459