bin/sh/cd.c

   1 /*      $NetBSD: cd.c,v 1.39 2006/05/04 11:16:53 simonb 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 1.39 2006/05/04 11:16:53 simonb 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(const char *, int);
  70 STATIC char *getcomponent(void);
  71 STATIC void updatepwd(const 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, *p;
  83         char *d;
  84         struct stat statb;
  85         int print = cdprint;    /* set -cdprint to enable */
  86
  87         while (nextopt("P") != '\0')
  88                 ;
  89
  90         /*
  91          * Try (quite hard) to have 'curdir' defined, nothing has set
  92          * it on entry to the shell, but we want 'cd fred; cd -' to work.
  93          */
  94         getpwd(1);
  95         dest = *argptr;
  96         if (dest == NULL) {
  97                 dest = bltinlookup("HOME", 1);
  98                 if (dest == NULL)
  99                         error("HOME not set");
 100         } else {
 101                 if (argptr[1]) {
 102                         /* Do 'ksh' style substitution */
 103                         if (!curdir)
 104                                 error("PWD not set");
 105                         p = strstr(curdir, dest);
 106                         if (!p)
 107                                 error("bad substitution");
 108                         d = stalloc(strlen(curdir) + strlen(argptr[1]) + 1);
 109                         memcpy(d, curdir, p - curdir);
 110                         strcpy(d + (p - curdir), argptr[1]);
 111                         strcat(d, p + strlen(dest));
 112                         dest = d;
 113                         print = 1;
 114                 }
 115         }
 116
 117         if (dest[0] == '-' && dest[1] == '\0') {
 118                 dest = prevdir ? prevdir : curdir;
 119                 print = 1;
 120         }
 121         if (*dest == '\0')
 122                 dest = ".";
 123         p = dest;
 124         if (*p == '.' && *++p == '.')
 125             p++;
 126         if (*p == 0 || *p == '/' || (path = bltinlookup("CDPATH", 1)) == NULL)
 127                 path = nullstr;
 128         while ((p = padvance(&path, dest)) != NULL) {
 129                 if (stat(p, &statb) >= 0 && S_ISDIR(statb.st_mode)) {
 130                         if (!print) {
 131                                 /*
 132                                  * XXX - rethink
 133                                  */
 134                                 if (p[0] == '.' && p[1] == '/' && p[2] != '\0')
 135                                         print = strcmp(p + 2, dest);
 136                                 else
 137                                         print = strcmp(p, dest);
 138                         }
 139                         if (docd(p, print) >= 0)
 140                                 return 0;
 141
 142                 }
 143         }
 144         error("can't cd to %s", dest);
 145         /* NOTREACHED */
 146 }
 147
 148
 149 /*
 150  * Actually do the chdir.  In an interactive shell, print the
 151  * directory name if "print" is nonzero.
 152  */
 153
 154 STATIC int
 155 docd(const char *dest, int print)
 156 {
 157         char *p;
 158         char *q;
 159         char *component;
 160         struct stat statb;
 161         int first;
 162         int badstat;
 163
 164         TRACE(("docd(\"%s\", %d) called\n", dest, print));
 165
 166         /*
 167          *  Check each component of the path. If we find a symlink or
 168          *  something we can't stat, clear curdir to force a getcwd()
 169          *  next time we get the value of the current directory.
 170          */
 171         badstat = 0;
 172         cdcomppath = stalloc(strlen(dest) + 1);
 173         scopy(dest, cdcomppath);
 174         STARTSTACKSTR(p);
 175         if (*dest == '/') {
 176                 STPUTC('/', p);
 177                 cdcomppath++;
 178         }
 179         first = 1;
 180         while ((q = getcomponent()) != NULL) {
 181                 if (q[0] == '\0' || (q[0] == '.' && q[1] == '\0'))
 182                         continue;
 183                 if (! first)
 184                         STPUTC('/', p);
 185                 first = 0;
 186                 component = q;
 187                 while (*q)
 188                         STPUTC(*q++, p);
 189                 if (equal(component, ".."))
 190                         continue;
 191                 STACKSTRNUL(p);
 192                 if ((lstat(stackblock(), &statb) < 0)
 193                     || (S_ISLNK(statb.st_mode)))  {
 194                         /* print = 1; */
 195                         badstat = 1;
 196                         break;
 197                 }
 198         }
 199
 200         INTOFF;
 201         if (chdir(dest) < 0) {
 202                 INTON;
 203                 return -1;
 204         }
 205         updatepwd(badstat ? NULL : dest);
 206         INTON;
 207         if (print && iflag == 1 && curdir)
 208                 out1fmt("%s\n", curdir);
 209         return 0;
 210 }
 211
 212
 213 /*
 214  * Get the next component of the path name pointed to by cdcomppath.
 215  * This routine overwrites the string pointed to by cdcomppath.
 216  */
 217
 218 STATIC char *
 219 getcomponent(void)
 220 {
 221         char *p;
 222         char *start;
 223
 224         if ((p = cdcomppath) == NULL)
 225                 return NULL;
 226         start = cdcomppath;
 227         while (*p != '/' && *p != '\0')
 228                 p++;
 229         if (*p == '\0') {
 230                 cdcomppath = NULL;
 231         } else {
 232                 *p++ = '\0';
 233                 cdcomppath = p;
 234         }
 235         return start;
 236 }
 237
 238
 239
 240 /*
 241  * Update curdir (the name of the current directory) in response to a
 242  * cd command.  We also call hashcd to let the routines in exec.c know
 243  * that the current directory has changed.
 244  */
 245
 246 STATIC void
 247 updatepwd(const char *dir)
 248 {
 249         char *new;
 250         char *p;
 251
 252         hashcd();                               /* update command hash table */
 253
 254         /*
 255          * If our argument is NULL, we don't know the current directory
 256          * any more because we traversed a symbolic link or something
 257          * we couldn't stat().
 258          */
 259         if (dir == NULL || curdir == NULL)  {
 260                 if (prevdir)
 261                         ckfree(prevdir);
 262                 INTOFF;
 263                 prevdir = curdir;
 264                 curdir = NULL;
 265                 getpwd(1);
 266                 INTON;
 267                 if (curdir)
 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("PWD", curdir, VEXPORT);
 301         INTON;
 302 }
 303
 304 /*
 305  * Posix says the default should be 'pwd -L' (as below), however
 306  * the 'cd' command (above) does something much nearer to the
 307  * posix 'cd -P' (not the posix default of 'cd -L').
 308  * If 'cd' is changed to support -P/L then the default here
 309  * needs to be revisited if the historic behaviour is to be kept.
 310  */
 311
 312 int
 313 pwdcmd(int argc, char **argv)
 314 {
 315         int i;
 316         char opt = 'L';
 317
 318         while ((i = nextopt("LP")) != '\0')
 319                 opt = i;
 320         if (*argptr)
 321                 error("unexpected argument");
 322
 323         if (opt == 'L')
 324                 getpwd(0);
 325         else
 326                 find_curdir(0);
 327
 328         setvar("PWD", curdir, VEXPORT);
 329         out1str(curdir);
 330         out1c('\n');
 331         return 0;
 332 }
 333
 334
 335
 336 void
 337 initpwd(void)
 338 {
 339         getpwd(1);
 340         if (curdir)
 341                 setvar("PWD", curdir, VEXPORT);
 342         else
 343                 sh_warnx("Cannot determine current working directory");
 344 }
 345
 346 #define MAXPWD 256
 347
 348 /*
 349  * Find out what the current directory is. If we already know the current
 350  * directory, this routine returns immediately.
 351  */
 352 void
 353 getpwd(int noerror)
 354 {
 355         char *pwd;
 356         struct stat stdot, stpwd;
 357         static int first = 1;
 358
 359         if (curdir)
 360                 return;
 361
 362         if (first) {
 363                 first = 0;
 364                 pwd = getenv("PWD");
 365                 if (pwd && *pwd == '/' && stat(".", &stdot) != -1 &&
 366                     stat(pwd, &stpwd) != -1 &&
 367                     stdot.st_dev == stpwd.st_dev &&
 368                     stdot.st_ino == stpwd.st_ino) {
 369                         curdir = savestr(pwd);
 370                         return;
 371                 }
 372         }
 373
 374         find_curdir(noerror);
 375
 376         return;
 377 }
 378
 379 STATIC void
 380 find_curdir(int noerror)
 381 {
 382         int i;
 383         char *pwd;
 384
 385         /*
 386          * Things are a bit complicated here; we could have just used
 387          * getcwd, but traditionally getcwd is implemented using popen
 388          * to /bin/pwd. This creates a problem for us, since we cannot
 389          * keep track of the job if it is being ran behind our backs.
 390          * So we re-implement getcwd(), and we suppress interrupts
 391          * throughout the process. This is not completely safe, since
 392          * the user can still break out of it by killing the pwd program.
 393          * We still try to use getcwd for systems that we know have a
 394          * c implementation of getcwd, that does not open a pipe to
 395          * /bin/pwd.
 396          */
 397 #if defined(__NetBSD__) || defined(__SVR4)
 398
 399         for (i = MAXPWD;; i *= 2) {
 400                 pwd = stalloc(i);
 401                 if (getcwd(pwd, i) != NULL) {
 402                         curdir = savestr(pwd);
 403                         return;
 404                 }
 405                 stunalloc(pwd);
 406                 if (errno == ERANGE)
 407                         continue;
 408                 if (!noerror)
 409                         error("getcwd() failed: %s", strerror(errno));
 410                 return;
 411         }
 412 #else
 413         {
 414                 char *p;
 415                 int status;
 416                 struct job *jp;
 417                 int pip[2];
 418
 419                 pwd = stalloc(MAXPWD);
 420                 INTOFF;
 421                 if (pipe(pip) < 0)
 422                         error("Pipe call failed");
 423                 jp = makejob((union node *)NULL, 1);
 424                 if (forkshell(jp, (union node *)NULL, FORK_NOJOB) == 0) {
 425                         (void) close(pip[0]);
 426                         if (pip[1] != 1) {
 427                                 close(1);
 428                                 copyfd(pip[1], 1);
 429                                 close(pip[1]);
 430                         }
 431                         (void) execl("/bin/pwd", "pwd", (char *)0);
 432                         error("Cannot exec /bin/pwd");
 433                 }
 434                 (void) close(pip[1]);
 435                 pip[1] = -1;
 436                 p = pwd;
 437                 while ((i = read(pip[0], p, pwd + MAXPWD - p)) > 0
 438                      || (i == -1 && errno == EINTR)) {
 439                         if (i > 0)
 440                                 p += i;
 441                 }
 442                 (void) close(pip[0]);
 443                 pip[0] = -1;
 444                 status = waitforjob(jp);
 445                 if (status != 0)
 446                         error((char *)0);
 447                 if (i < 0 || p == pwd || p[-1] != '\n') {
 448                         if (noerror) {
 449                                 INTON;
 450                                 return;
 451                         }
 452                         error("pwd command failed");
 453                 }
 454                 p[-1] = '\0';
 455                 INTON;
 456                 curdir = savestr(pwd);
 457                 return;
 458         }
 459 #endif
 460 }