src/shared/path-util.c

   1 /*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
   2
   3 /***
   4   This file is part of systemd.
   5
   6   Copyright 2010-2012 Lennart Poettering
   7
   8   systemd is free software; you can redistribute it and/or modify it
   9   under the terms of the GNU Lesser General Public License as published by
  10   the Free Software Foundation; either version 2.1 of the License, or
  11   (at your option) any later version.
  12
  13   systemd is distributed in the hope that it will be useful, but
  14   WITHOUT ANY WARRANTY; without even the implied warranty of
  15   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  16   Lesser General Public License for more details.
  17
  18   You should have received a copy of the GNU Lesser General Public License
  19   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  20 ***/
  21
  22 #include <assert.h>
  23 #include <string.h>
  24 #include <unistd.h>
  25 #include <errno.h>
  26 #include <stdlib.h>
  27 #include <signal.h>
  28 #include <stdio.h>
  29 #include <fcntl.h>
  30 #include <dirent.h>
  31 #include <sys/statvfs.h>
  32
  33 #include "macro.h"
  34 #include "util.h"
  35 #include "log.h"
  36 #include "strv.h"
  37 #include "path-util.h"
  38 #include "missing.h"
  39
  40 bool path_is_absolute(const char *p) {
  41         return p[0] == '/';
  42 }
  43
  44 bool is_path(const char *p) {
  45         return !!strchr(p, '/');
  46 }
  47
  48 int path_get_parent(const char *path, char **_r) {
  49         const char *e, *a = NULL, *b = NULL, *p;
  50         char *r;
  51         bool slash = false;
  52
  53         assert(path);
  54         assert(_r);
  55
  56         if (!*path)
  57                 return -EINVAL;
  58
  59         for (e = path; *e; e++) {
  60
  61                 if (!slash && *e == '/') {
  62                         a = b;
  63                         b = e;
  64                         slash = true;
  65                 } else if (slash && *e != '/')
  66                         slash = false;
  67         }
  68
  69         if (*(e-1) == '/')
  70                 p = a;
  71         else
  72                 p = b;
  73
  74         if (!p)
  75                 return -EINVAL;
  76
  77         if (p == path)
  78                 r = strdup("/");
  79         else
  80                 r = strndup(path, p-path);
  81
  82         if (!r)
  83                 return -ENOMEM;
  84
  85         *_r = r;
  86         return 0;
  87 }
  88
  89 char **path_split_and_make_absolute(const char *p) {
  90         char **l;
  91         assert(p);
  92
  93         l = strv_split(p, ":");
  94         if (!l)
  95                 return NULL;
  96
  97         if (!path_strv_make_absolute_cwd(l)) {
  98                 strv_free(l);
  99                 return NULL;
 100         }
 101
 102         return l;
 103 }
 104
 105 char *path_make_absolute(const char *p, const char *prefix) {
 106         assert(p);
 107
 108         /* Makes every item in the list an absolute path by prepending
 109          * the prefix, if specified and necessary */
 110
 111         if (path_is_absolute(p) || !prefix)
 112                 return strdup(p);
 113
 114         return strjoin(prefix, "/", p, NULL);
 115 }
 116
 117 char *path_make_absolute_cwd(const char *p) {
 118         _cleanup_free_ char *cwd = NULL;
 119
 120         assert(p);
 121
 122         /* Similar to path_make_absolute(), but prefixes with the
 123          * current working directory. */
 124
 125         if (path_is_absolute(p))
 126                 return strdup(p);
 127
 128         cwd = get_current_dir_name();
 129         if (!cwd)
 130                 return NULL;
 131
 132         return strjoin(cwd, "/", p, NULL);
 133 }
 134
 135 int path_make_relative(const char *from_dir, const char *to_path, char **_r) {
 136         char *r, *p;
 137         unsigned n_parents;
 138
 139         assert(from_dir);
 140         assert(to_path);
 141         assert(_r);
 142
 143         /* Strips the common part, and adds ".." elements as necessary. */
 144
 145         if (!path_is_absolute(from_dir))
 146                 return -EINVAL;
 147
 148         if (!path_is_absolute(to_path))
 149                 return -EINVAL;
 150
 151         /* Skip the common part. */
 152         for (;;) {
 153                 size_t a;
 154                 size_t b;
 155
 156                 from_dir += strspn(from_dir, "/");
 157                 to_path += strspn(to_path, "/");
 158
 159                 if (!*from_dir) {
 160                         if (!*to_path)
 161                                 /* from_dir equals to_path. */
 162                                 r = strdup(".");
 163                         else
 164                                 /* from_dir is a parent directory of to_path. */
 165                                 r = strdup(to_path);
 166
 167                         if (!r)
 168                                 return -ENOMEM;
 169
 170                         path_kill_slashes(r);
 171
 172                         *_r = r;
 173                         return 0;
 174                 }
 175
 176                 if (!*to_path)
 177                         break;
 178
 179                 a = strcspn(from_dir, "/");
 180                 b = strcspn(to_path, "/");
 181
 182                 if (a != b)
 183                         break;
 184
 185                 if (memcmp(from_dir, to_path, a) != 0)
 186                         break;
 187
 188                 from_dir += a;
 189                 to_path += b;
 190         }
 191
 192         /* If we're here, then "from_dir" has one or more elements that need to
 193          * be replaced with "..". */
 194
 195         /* Count the number of necessary ".." elements. */
 196         for (n_parents = 0;;) {
 197                 from_dir += strspn(from_dir, "/");
 198
 199                 if (!*from_dir)
 200                         break;
 201
 202                 from_dir += strcspn(from_dir, "/");
 203                 n_parents++;
 204         }
 205
 206         r = malloc(n_parents * 3 + strlen(to_path) + 1);
 207         if (!r)
 208                 return -ENOMEM;
 209
 210         for (p = r; n_parents > 0; n_parents--, p += 3)
 211                 memcpy(p, "../", 3);
 212
 213         strcpy(p, to_path);
 214         path_kill_slashes(r);
 215
 216         *_r = r;
 217         return 0;
 218 }
 219
 220 char **path_strv_make_absolute_cwd(char **l) {
 221         char **s;
 222
 223         /* Goes through every item in the string list and makes it
 224          * absolute. This works in place and won't rollback any
 225          * changes on failure. */
 226
 227         STRV_FOREACH(s, l) {
 228                 char *t;
 229
 230                 t = path_make_absolute_cwd(*s);
 231                 if (!t)
 232                         return NULL;
 233
 234                 free(*s);
 235                 *s = t;
 236         }
 237
 238         return l;
 239 }
 240
 241 char **path_strv_resolve(char **l, const char *prefix) {
 242         char **s;
 243         unsigned k = 0;
 244         bool enomem = false;
 245
 246         if (strv_isempty(l))
 247                 return l;
 248
 249         /* Goes through every item in the string list and canonicalize
 250          * the path. This works in place and won't rollback any
 251          * changes on failure. */
 252
 253         STRV_FOREACH(s, l) {
 254                 char *t, *u;
 255                 _cleanup_free_ char *orig = NULL;
 256
 257                 if (!path_is_absolute(*s)) {
 258                         free(*s);
 259                         continue;
 260                 }
 261
 262                 if (prefix) {
 263                         orig = *s;
 264                         t = strappend(prefix, orig);
 265                         if (!t) {
 266                                 enomem = true;
 267                                 continue;
 268                         }
 269                 } else
 270                         t = *s;
 271
 272                 errno = 0;
 273                 u = canonicalize_file_name(t);
 274                 if (!u) {
 275                         if (errno == ENOENT) {
 276                                 if (prefix) {
 277                                         u = orig;
 278                                         orig = NULL;
 279                                         free(t);
 280                                 } else
 281                                         u = t;
 282                         } else {
 283                                 free(t);
 284                                 if (errno == ENOMEM || errno == 0)
 285                                         enomem = true;
 286
 287                                 continue;
 288                         }
 289                 } else if (prefix) {
 290                         char *x;
 291
 292                         free(t);
 293                         x = path_startswith(u, prefix);
 294                         if (x) {
 295                                 /* restore the slash if it was lost */
 296                                 if (!startswith(x, "/"))
 297                                         *(--x) = '/';
 298
 299                                 t = strdup(x);
 300                                 free(u);
 301                                 if (!t) {
 302                                         enomem = true;
 303                                         continue;
 304                                 }
 305                                 u = t;
 306                         } else {
 307                                 /* canonicalized path goes outside of
 308                                  * prefix, keep the original path instead */
 309                                 u = orig;
 310                                 orig = NULL;
 311                         }
 312                 } else
 313                         free(t);
 314
 315                 l[k++] = u;
 316         }
 317
 318         l[k] = NULL;
 319
 320         if (enomem)
 321                 return NULL;
 322
 323         return l;
 324 }
 325
 326 char **path_strv_resolve_uniq(char **l, const char *prefix) {
 327
 328         if (strv_isempty(l))
 329                 return l;
 330
 331         if (!path_strv_resolve(l, prefix))
 332                 return NULL;
 333
 334         return strv_uniq(l);
 335 }
 336
 337 char *path_kill_slashes(char *path) {
 338         char *f, *t;
 339         bool slash = false;
 340
 341         /* Removes redundant inner and trailing slashes. Modifies the
 342          * passed string in-place.
 343          *
 344          * ///foo///bar/ becomes /foo/bar
 345          */
 346
 347         for (f = path, t = path; *f; f++) {
 348
 349                 if (*f == '/') {
 350                         slash = true;
 351                         continue;
 352                 }
 353
 354                 if (slash) {
 355                         slash = false;
 356                         *(t++) = '/';
 357                 }
 358
 359                 *(t++) = *f;
 360         }
 361
 362         /* Special rule, if we are talking of the root directory, a
 363         trailing slash is good */
 364
 365         if (t == path && slash)
 366                 *(t++) = '/';
 367
 368         *t = 0;
 369         return path;
 370 }
 371
 372 char* path_startswith(const char *path, const char *prefix) {
 373         assert(path);
 374         assert(prefix);
 375
 376         if ((path[0] == '/') != (prefix[0] == '/'))
 377                 return NULL;
 378
 379         for (;;) {
 380                 size_t a, b;
 381
 382                 path += strspn(path, "/");
 383                 prefix += strspn(prefix, "/");
 384
 385                 if (*prefix == 0)
 386                         return (char*) path;
 387
 388                 if (*path == 0)
 389                         return NULL;
 390
 391                 a = strcspn(path, "/");
 392                 b = strcspn(prefix, "/");
 393
 394                 if (a != b)
 395                         return NULL;
 396
 397                 if (memcmp(path, prefix, a) != 0)
 398                         return NULL;
 399
 400                 path += a;
 401                 prefix += b;
 402         }
 403 }
 404
 405 bool path_equal(const char *a, const char *b) {
 406         assert(a);
 407         assert(b);
 408
 409         if ((a[0] == '/') != (b[0] == '/'))
 410                 return false;
 411
 412         for (;;) {
 413                 size_t j, k;
 414
 415                 a += strspn(a, "/");
 416                 b += strspn(b, "/");
 417
 418                 if (*a == 0 && *b == 0)
 419                         return true;
 420
 421                 if (*a == 0 || *b == 0)
 422                         return false;
 423
 424                 j = strcspn(a, "/");
 425                 k = strcspn(b, "/");
 426
 427                 if (j != k)
 428                         return false;
 429
 430                 if (memcmp(a, b, j) != 0)
 431                         return false;
 432
 433                 a += j;
 434                 b += k;
 435         }
 436 }
 437
 438 char* path_join(const char *root, const char *path, const char *rest) {
 439         assert(path);
 440
 441         if (!isempty(root))
 442                 return strjoin(root, endswith(root, "/") ? "" : "/",
 443                                path[0] == '/' ? path+1 : path,
 444                                rest ? (endswith(path, "/") ? "" : "/") : NULL,
 445                                rest && rest[0] == '/' ? rest+1 : rest,
 446                                NULL);
 447         else
 448                 return strjoin(path,
 449                                rest ? (endswith(path, "/") ? "" : "/") : NULL,
 450                                rest && rest[0] == '/' ? rest+1 : rest,
 451                                NULL);
 452 }
 453
 454 int path_is_mount_point(const char *t, bool allow_symlink) {
 455
 456         union file_handle_union h = {
 457                 .handle.handle_bytes = MAX_HANDLE_SZ
 458         };
 459
 460         int mount_id, mount_id_parent;
 461         _cleanup_free_ char *parent = NULL;
 462         struct stat a, b;
 463         int r;
 464
 465         /* We are not actually interested in the file handles, but
 466          * name_to_handle_at() also passes us the mount ID, hence use
 467          * it but throw the handle away */
 468
 469         if (path_equal(t, "/"))
 470                 return 1;
 471
 472         r = name_to_handle_at(AT_FDCWD, t, &h.handle, &mount_id, allow_symlink ? AT_SYMLINK_FOLLOW : 0);
 473         if (r < 0) {
 474                 if (IN_SET(errno, ENOSYS, EOPNOTSUPP))
 475                         /* This kernel or file system does not support
 476                          * name_to_handle_at(), hence fallback to the
 477                          * traditional stat() logic */
 478                         goto fallback;
 479
 480                 if (errno == ENOENT)
 481                         return 0;
 482
 483                 return -errno;
 484         }
 485
 486         r = path_get_parent(t, &parent);
 487         if (r < 0)
 488                 return r;
 489
 490         h.handle.handle_bytes = MAX_HANDLE_SZ;
 491         r = name_to_handle_at(AT_FDCWD, parent, &h.handle, &mount_id_parent, 0);
 492         if (r < 0) {
 493                 /* The parent can't do name_to_handle_at() but the
 494                  * directory we are interested in can? If so, it must
 495                  * be a mount point */
 496                 if (errno == EOPNOTSUPP)
 497                         return 1;
 498
 499                 return -errno;
 500         }
 501
 502         return mount_id != mount_id_parent;
 503
 504 fallback:
 505         if (allow_symlink)
 506                 r = stat(t, &a);
 507         else
 508                 r = lstat(t, &a);
 509
 510         if (r < 0) {
 511                 if (errno == ENOENT)
 512                         return 0;
 513
 514                 return -errno;
 515         }
 516
 517         r = path_get_parent(t, &parent);
 518         if (r < 0)
 519                 return r;
 520
 521         r = lstat(parent, &b);
 522         if (r < 0)
 523                 return -errno;
 524
 525         return a.st_dev != b.st_dev;
 526 }
 527
 528 int path_is_read_only_fs(const char *path) {
 529         struct statvfs st;
 530
 531         assert(path);
 532
 533         if (statvfs(path, &st) < 0)
 534                 return -errno;
 535
 536         if (st.f_flag & ST_RDONLY)
 537                 return true;
 538
 539         /* On NFS, statvfs() might not reflect whether we can actually
 540          * write to the remote share. Let's try again with
 541          * access(W_OK) which is more reliable, at least sometimes. */
 542         if (access(path, W_OK) < 0 && errno == EROFS)
 543                 return true;
 544
 545         return false;
 546 }
 547
 548 int path_is_os_tree(const char *path) {
 549         char *p;
 550         int r;
 551
 552         /* We use /usr/lib/os-release as flag file if something is an OS */
 553         p = strappenda(path, "/usr/lib/os-release");
 554         r = access(p, F_OK);
 555
 556         if (r >= 0)
 557                 return 1;
 558
 559         /* Also check for the old location in /etc, just in case. */
 560         p = strappenda(path, "/etc/os-release");
 561         r = access(p, F_OK);
 562
 563         return r >= 0;
 564 }
 565
 566 int find_binary(const char *name, bool local, char **filename) {
 567         assert(name);
 568
 569         if (is_path(name)) {
 570                 if (local && access(name, X_OK) < 0)
 571                         return -errno;
 572
 573                 if (filename) {
 574                         char *p;
 575
 576                         p = path_make_absolute_cwd(name);
 577                         if (!p)
 578                                 return -ENOMEM;
 579
 580                         *filename = p;
 581                 }
 582
 583                 return 0;
 584         } else {
 585                 const char *path;
 586                 const char *word, *state;
 587                 size_t l;
 588
 589                 /**
 590                  * Plain getenv, not secure_getenv, because we want
 591                  * to actually allow the user to pick the binary.
 592                  */
 593                 path = getenv("PATH");
 594                 if (!path)
 595                         path = DEFAULT_PATH;
 596
 597                 FOREACH_WORD_SEPARATOR(word, l, path, ":", state) {
 598                         _cleanup_free_ char *p = NULL;
 599
 600                         if (asprintf(&p, "%.*s/%s", (int) l, word, name) < 0)
 601                                 return -ENOMEM;
 602
 603                         if (access(p, X_OK) < 0)
 604                                 continue;
 605
 606                         if (filename) {
 607                                 *filename = path_kill_slashes(p);
 608                                 p = NULL;
 609                         }
 610
 611                         return 0;
 612                 }
 613
 614                 return -ENOENT;
 615         }
 616 }
 617
 618 bool paths_check_timestamp(const char* const* paths, usec_t *timestamp, bool update) {
 619         bool changed = false;
 620         const char* const* i;
 621
 622         assert(timestamp);
 623
 624         if (paths == NULL)
 625                 return false;
 626
 627         STRV_FOREACH(i, paths) {
 628                 struct stat stats;
 629                 usec_t u;
 630
 631                 if (stat(*i, &stats) < 0)
 632                         continue;
 633
 634                 u = timespec_load(&stats.st_mtim);
 635
 636                 /* first check */
 637                 if (*timestamp >= u)
 638                         continue;
 639
 640                 log_debug("timestamp of '%s' changed", *i);
 641
 642                 /* update timestamp */
 643                 if (update) {
 644                         *timestamp = u;
 645                         changed = true;
 646                 } else
 647                         return true;
 648         }
 649
 650         return changed;
 651 }
 652
 653 int fsck_exists(const char *fstype) {
 654         _cleanup_free_ char *p = NULL, *d = NULL;
 655         const char *checker;
 656         int r;
 657
 658         checker = strappenda("fsck.", fstype);
 659
 660         r = find_binary(checker, true, &p);
 661         if (r < 0)
 662                 return r;
 663
 664         /* An fsck that is linked to /bin/true is a non-existent
 665          * fsck */
 666
 667         r = readlink_malloc(p, &d);
 668         if (r >= 0 &&
 669             (path_equal(d, "/bin/true") ||
 670              path_equal(d, "/usr/bin/true") ||
 671              path_equal(d, "/dev/null")))
 672                 return -ENOENT;
 673
 674         return 0;
 675 }