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 <string.h>
  23 #include <unistd.h>
  24 #include <errno.h>
  25 #include <stdlib.h>
  26 #include <stdio.h>
  27 #include <fcntl.h>
  28 #include <sys/statvfs.h>
  29
  30 #include "macro.h"
  31 #include "util.h"
  32 #include "log.h"
  33 #include "strv.h"
  34 #include "path-util.h"
  35 #include "missing.h"
  36
  37 bool path_is_absolute(const char *p) {
  38         return p[0] == '/';
  39 }
  40
  41 bool is_path(const char *p) {
  42         return !!strchr(p, '/');
  43 }
  44
  45 int path_get_parent(const char *path, char **_r) {
  46         const char *e, *a = NULL, *b = NULL, *p;
  47         char *r;
  48         bool slash = false;
  49
  50         assert(path);
  51         assert(_r);
  52
  53         if (!*path)
  54                 return -EINVAL;
  55
  56         for (e = path; *e; e++) {
  57
  58                 if (!slash && *e == '/') {
  59                         a = b;
  60                         b = e;
  61                         slash = true;
  62                 } else if (slash && *e != '/')
  63                         slash = false;
  64         }
  65
  66         if (*(e-1) == '/')
  67                 p = a;
  68         else
  69                 p = b;
  70
  71         if (!p)
  72                 return -EINVAL;
  73
  74         if (p == path)
  75                 r = strdup("/");
  76         else
  77                 r = strndup(path, p-path);
  78
  79         if (!r)
  80                 return -ENOMEM;
  81
  82         *_r = r;
  83         return 0;
  84 }
  85
  86 char **path_split_and_make_absolute(const char *p) {
  87         char **l;
  88         assert(p);
  89
  90         l = strv_split(p, ":");
  91         if (!l)
  92                 return NULL;
  93
  94         if (!path_strv_make_absolute_cwd(l)) {
  95                 strv_free(l);
  96                 return NULL;
  97         }
  98
  99         return l;
 100 }
 101
 102 char *path_make_absolute(const char *p, const char *prefix) {
 103         assert(p);
 104
 105         /* Makes every item in the list an absolute path by prepending
 106          * the prefix, if specified and necessary */
 107
 108         if (path_is_absolute(p) || !prefix)
 109                 return strdup(p);
 110
 111         return strjoin(prefix, "/", p, NULL);
 112 }
 113
 114 char *path_make_absolute_cwd(const char *p) {
 115         _cleanup_free_ char *cwd = NULL;
 116
 117         assert(p);
 118
 119         /* Similar to path_make_absolute(), but prefixes with the
 120          * current working directory. */
 121
 122         if (path_is_absolute(p))
 123                 return strdup(p);
 124
 125         cwd = get_current_dir_name();
 126         if (!cwd)
 127                 return NULL;
 128
 129         return strjoin(cwd, "/", p, NULL);
 130 }
 131
 132 int path_make_relative(const char *from_dir, const char *to_path, char **_r) {
 133         char *r, *p;
 134         unsigned n_parents;
 135
 136         assert(from_dir);
 137         assert(to_path);
 138         assert(_r);
 139
 140         /* Strips the common part, and adds ".." elements as necessary. */
 141
 142         if (!path_is_absolute(from_dir))
 143                 return -EINVAL;
 144
 145         if (!path_is_absolute(to_path))
 146                 return -EINVAL;
 147
 148         /* Skip the common part. */
 149         for (;;) {
 150                 size_t a;
 151                 size_t b;
 152
 153                 from_dir += strspn(from_dir, "/");
 154                 to_path += strspn(to_path, "/");
 155
 156                 if (!*from_dir) {
 157                         if (!*to_path)
 158                                 /* from_dir equals to_path. */
 159                                 r = strdup(".");
 160                         else
 161                                 /* from_dir is a parent directory of to_path. */
 162                                 r = strdup(to_path);
 163
 164                         if (!r)
 165                                 return -ENOMEM;
 166
 167                         path_kill_slashes(r);
 168
 169                         *_r = r;
 170                         return 0;
 171                 }
 172
 173                 if (!*to_path)
 174                         break;
 175
 176                 a = strcspn(from_dir, "/");
 177                 b = strcspn(to_path, "/");
 178
 179                 if (a != b)
 180                         break;
 181
 182                 if (memcmp(from_dir, to_path, a) != 0)
 183                         break;
 184
 185                 from_dir += a;
 186                 to_path += b;
 187         }
 188
 189         /* If we're here, then "from_dir" has one or more elements that need to
 190          * be replaced with "..". */
 191
 192         /* Count the number of necessary ".." elements. */
 193         for (n_parents = 0;;) {
 194                 from_dir += strspn(from_dir, "/");
 195
 196                 if (!*from_dir)
 197                         break;
 198
 199                 from_dir += strcspn(from_dir, "/");
 200                 n_parents++;
 201         }
 202
 203         r = malloc(n_parents * 3 + strlen(to_path) + 1);
 204         if (!r)
 205                 return -ENOMEM;
 206
 207         for (p = r; n_parents > 0; n_parents--, p += 3)
 208                 memcpy(p, "../", 3);
 209
 210         strcpy(p, to_path);
 211         path_kill_slashes(r);
 212
 213         *_r = r;
 214         return 0;
 215 }
 216
 217 char **path_strv_make_absolute_cwd(char **l) {
 218         char **s;
 219
 220         /* Goes through every item in the string list and makes it
 221          * absolute. This works in place and won't rollback any
 222          * changes on failure. */
 223
 224         STRV_FOREACH(s, l) {
 225                 char *t;
 226
 227                 t = path_make_absolute_cwd(*s);
 228                 if (!t)
 229                         return NULL;
 230
 231                 free(*s);
 232                 *s = t;
 233         }
 234
 235         return l;
 236 }
 237
 238 char **path_strv_resolve(char **l, const char *prefix) {
 239         char **s;
 240         unsigned k = 0;
 241         bool enomem = false;
 242
 243         if (strv_isempty(l))
 244                 return l;
 245
 246         /* Goes through every item in the string list and canonicalize
 247          * the path. This works in place and won't rollback any
 248          * changes on failure. */
 249
 250         STRV_FOREACH(s, l) {
 251                 char *t, *u;
 252                 _cleanup_free_ char *orig = NULL;
 253
 254                 if (!path_is_absolute(*s)) {
 255                         free(*s);
 256                         continue;
 257                 }
 258
 259                 if (prefix) {
 260                         orig = *s;
 261                         t = strappend(prefix, orig);
 262                         if (!t) {
 263                                 enomem = true;
 264                                 continue;
 265                         }
 266                 } else
 267                         t = *s;
 268
 269                 errno = 0;
 270                 u = canonicalize_file_name(t);
 271                 if (!u) {
 272                         if (errno == ENOENT) {
 273                                 if (prefix) {
 274                                         u = orig;
 275                                         orig = NULL;
 276                                         free(t);
 277                                 } else
 278                                         u = t;
 279                         } else {
 280                                 free(t);
 281                                 if (errno == ENOMEM || errno == 0)
 282                                         enomem = true;
 283
 284                                 continue;
 285                         }
 286                 } else if (prefix) {
 287                         char *x;
 288
 289                         free(t);
 290                         x = path_startswith(u, prefix);
 291                         if (x) {
 292                                 /* restore the slash if it was lost */
 293                                 if (!startswith(x, "/"))
 294                                         *(--x) = '/';
 295
 296                                 t = strdup(x);
 297                                 free(u);
 298                                 if (!t) {
 299                                         enomem = true;
 300                                         continue;
 301                                 }
 302                                 u = t;
 303                         } else {
 304                                 /* canonicalized path goes outside of
 305                                  * prefix, keep the original path instead */
 306                                 free(u);
 307                                 u = orig;
 308                                 orig = NULL;
 309                         }
 310                 } else
 311                         free(t);
 312
 313                 l[k++] = u;
 314         }
 315
 316         l[k] = NULL;
 317
 318         if (enomem)
 319                 return NULL;
 320
 321         return l;
 322 }
 323
 324 char **path_strv_resolve_uniq(char **l, const char *prefix) {
 325
 326         if (strv_isempty(l))
 327                 return l;
 328
 329         if (!path_strv_resolve(l, prefix))
 330                 return NULL;
 331
 332         return strv_uniq(l);
 333 }
 334
 335 char *path_kill_slashes(char *path) {
 336         char *f, *t;
 337         bool slash = false;
 338
 339         /* Removes redundant inner and trailing slashes. Modifies the
 340          * passed string in-place.
 341          *
 342          * ///foo///bar/ becomes /foo/bar
 343          */
 344
 345         for (f = path, t = path; *f; f++) {
 346
 347                 if (*f == '/') {
 348                         slash = true;
 349                         continue;
 350                 }
 351
 352                 if (slash) {
 353                         slash = false;
 354                         *(t++) = '/';
 355                 }
 356
 357                 *(t++) = *f;
 358         }
 359
 360         /* Special rule, if we are talking of the root directory, a
 361         trailing slash is good */
 362
 363         if (t == path && slash)
 364                 *(t++) = '/';
 365
 366         *t = 0;
 367         return path;
 368 }
 369
 370 char* path_startswith(const char *path, const char *prefix) {
 371         assert(path);
 372         assert(prefix);
 373
 374         if ((path[0] == '/') != (prefix[0] == '/'))
 375                 return NULL;
 376
 377         for (;;) {
 378                 size_t a, b;
 379
 380                 path += strspn(path, "/");
 381                 prefix += strspn(prefix, "/");
 382
 383                 if (*prefix == 0)
 384                         return (char*) path;
 385
 386                 if (*path == 0)
 387                         return NULL;
 388
 389                 a = strcspn(path, "/");
 390                 b = strcspn(prefix, "/");
 391
 392                 if (a != b)
 393                         return NULL;
 394
 395                 if (memcmp(path, prefix, a) != 0)
 396                         return NULL;
 397
 398                 path += a;
 399                 prefix += b;
 400         }
 401 }
 402
 403 int path_compare(const char *a, const char *b) {
 404         int d;
 405
 406         assert(a);
 407         assert(b);
 408
 409         /* A relative path and an abolute path must not compare as equal.
 410          * Which one is sorted before the other does not really matter.
 411          * Here a relative path is ordered before an absolute path. */
 412         d = (a[0] == '/') - (b[0] == '/');
 413         if (d)
 414                 return d;
 415
 416         for (;;) {
 417                 size_t j, k;
 418
 419                 a += strspn(a, "/");
 420                 b += strspn(b, "/");
 421
 422                 if (*a == 0 && *b == 0)
 423                         return 0;
 424
 425                 /* Order prefixes first: "/foo" before "/foo/bar" */
 426                 if (*a == 0)
 427                         return -1;
 428                 if (*b == 0)
 429                         return 1;
 430
 431                 j = strcspn(a, "/");
 432                 k = strcspn(b, "/");
 433
 434                 /* Alphabetical sort: "/foo/aaa" before "/foo/b" */
 435                 d = memcmp(a, b, MIN(j, k));
 436                 if (d)
 437                         return (d > 0) - (d < 0); /* sign of d */
 438
 439                 /* Sort "/foo/a" before "/foo/aaa" */
 440                 d = (j > k) - (j < k);  /* sign of (j - k) */
 441                 if (d)
 442                         return d;
 443
 444                 a += j;
 445                 b += k;
 446         }
 447 }
 448
 449 bool path_equal(const char *a, const char *b) {
 450         return path_compare(a, b) == 0;
 451 }
 452
 453 bool path_equal_or_files_same(const char *a, const char *b) {
 454         return path_equal(a, b) || files_same(a, b) > 0;
 455 }
 456
 457 char* path_join(const char *root, const char *path, const char *rest) {
 458         assert(path);
 459
 460         if (!isempty(root))
 461                 return strjoin(root, endswith(root, "/") ? "" : "/",
 462                                path[0] == '/' ? path+1 : path,
 463                                rest ? (endswith(path, "/") ? "" : "/") : NULL,
 464                                rest && rest[0] == '/' ? rest+1 : rest,
 465                                NULL);
 466         else
 467                 return strjoin(path,
 468                                rest ? (endswith(path, "/") ? "" : "/") : NULL,
 469                                rest && rest[0] == '/' ? rest+1 : rest,
 470                                NULL);
 471 }
 472
 473 int fd_is_mount_point(int fd) {
 474         union file_handle_union h = FILE_HANDLE_INIT;
 475         int mount_id = -1, mount_id_parent = -1;
 476         bool nosupp = false;
 477         struct stat a, b;
 478         int r;
 479
 480         /* We are not actually interested in the file handles, but
 481          * name_to_handle_at() also passes us the mount ID, hence use
 482          * it but throw the handle away */
 483
 484         r = name_to_handle_at(fd, "", &h.handle, &mount_id, AT_EMPTY_PATH);
 485         if (r < 0) {
 486                 if (errno == ENOSYS)
 487                         /* This kernel does not support name_to_handle_at()
 488                          * fall back to the traditional stat() logic. */
 489                         goto fallback;
 490                 else if (errno == EOPNOTSUPP)
 491                         /* This kernel or file system does not support
 492                          * name_to_handle_at(), hence let's see if the
 493                          * upper fs supports it (in which case it is a
 494                          * mount point), otherwise fallback to the
 495                          * traditional stat() logic */
 496                         nosupp = true;
 497                 else if (errno == ENOENT)
 498                         return 0;
 499                 else
 500                         return -errno;
 501         }
 502
 503         h.handle.handle_bytes = MAX_HANDLE_SZ;
 504         r = name_to_handle_at(fd, "..", &h.handle, &mount_id_parent, 0);
 505         if (r < 0) {
 506                 if (errno == EOPNOTSUPP) {
 507                         if (nosupp)
 508                                 /* Neither parent nor child do name_to_handle_at()?
 509                                    We have no choice but to fall back. */
 510                                 goto fallback;
 511                         else
 512                                 /* The parent can't do name_to_handle_at() but the
 513                                  * directory we are interested in can?
 514                                  * If so, it must be a mount point. */
 515                                 return 1;
 516                 } else
 517                         return -errno;
 518         } else if (nosupp)
 519                 /* The parent can do name_to_handle_at() but the
 520                  * directory we are interested in can't? If so, it
 521                  * must be a mount point. */
 522                 return 1;
 523         else
 524                 return mount_id != mount_id_parent;
 525
 526 fallback:
 527         r = fstatat(fd, "", &a, AT_EMPTY_PATH);
 528         if (r < 0) {
 529                 if (errno == ENOENT)
 530                         return 0;
 531
 532                 return -errno;
 533         }
 534
 535         r = fstatat(fd, "..", &b, 0);
 536         if (r < 0)
 537                 return -errno;
 538
 539         return a.st_dev != b.st_dev;
 540 }
 541
 542 int path_is_mount_point(const char *t, bool allow_symlink) {
 543         _cleanup_close_ int fd = -1;
 544         assert(t);
 545
 546         if (path_equal(t, "/"))
 547                 return 1;
 548
 549         fd = openat(AT_FDCWD, t, O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC|(allow_symlink ? 0 : O_PATH));
 550         if (fd < 0) {
 551                 if (errno == ENOENT)
 552                         return 0;
 553
 554                 return -errno;
 555         }
 556
 557         return fd_is_mount_point(fd);
 558 }
 559
 560 int path_is_read_only_fs(const char *path) {
 561         struct statvfs st;
 562
 563         assert(path);
 564
 565         if (statvfs(path, &st) < 0)
 566                 return -errno;
 567
 568         if (st.f_flag & ST_RDONLY)
 569                 return true;
 570
 571         /* On NFS, statvfs() might not reflect whether we can actually
 572          * write to the remote share. Let's try again with
 573          * access(W_OK) which is more reliable, at least sometimes. */
 574         if (access(path, W_OK) < 0 && errno == EROFS)
 575                 return true;
 576
 577         return false;
 578 }
 579
 580 int path_is_os_tree(const char *path) {
 581         char *p;
 582         int r;
 583
 584         /* We use /usr/lib/os-release as flag file if something is an OS */
 585         p = strjoina(path, "/usr/lib/os-release");
 586         r = access(p, F_OK);
 587
 588         if (r >= 0)
 589                 return 1;
 590
 591         /* Also check for the old location in /etc, just in case. */
 592         p = strjoina(path, "/etc/os-release");
 593         r = access(p, F_OK);
 594
 595         return r >= 0;
 596 }
 597
 598 int find_binary(const char *name, bool local, char **filename) {
 599         assert(name);
 600
 601         if (is_path(name)) {
 602                 if (local && access(name, X_OK) < 0)
 603                         return -errno;
 604
 605                 if (filename) {
 606                         char *p;
 607
 608                         p = path_make_absolute_cwd(name);
 609                         if (!p)
 610                                 return -ENOMEM;
 611
 612                         *filename = p;
 613                 }
 614
 615                 return 0;
 616         } else {
 617                 const char *path;
 618                 const char *word, *state;
 619                 size_t l;
 620
 621                 /**
 622                  * Plain getenv, not secure_getenv, because we want
 623                  * to actually allow the user to pick the binary.
 624                  */
 625                 path = getenv("PATH");
 626                 if (!path)
 627                         path = DEFAULT_PATH;
 628
 629                 FOREACH_WORD_SEPARATOR(word, l, path, ":", state) {
 630                         _cleanup_free_ char *p = NULL;
 631
 632                         if (asprintf(&p, "%.*s/%s", (int) l, word, name) < 0)
 633                                 return -ENOMEM;
 634
 635                         if (access(p, X_OK) < 0)
 636                                 continue;
 637
 638                         if (filename) {
 639                                 *filename = path_kill_slashes(p);
 640                                 p = NULL;
 641                         }
 642
 643                         return 0;
 644                 }
 645
 646                 return -ENOENT;
 647         }
 648 }
 649
 650 bool paths_check_timestamp(const char* const* paths, usec_t *timestamp, bool update) {
 651         bool changed = false;
 652         const char* const* i;
 653
 654         assert(timestamp);
 655
 656         if (paths == NULL)
 657                 return false;
 658
 659         STRV_FOREACH(i, paths) {
 660                 struct stat stats;
 661                 usec_t u;
 662
 663                 if (stat(*i, &stats) < 0)
 664                         continue;
 665
 666                 u = timespec_load(&stats.st_mtim);
 667
 668                 /* first check */
 669                 if (*timestamp >= u)
 670                         continue;
 671
 672                 log_debug("timestamp of '%s' changed", *i);
 673
 674                 /* update timestamp */
 675                 if (update) {
 676                         *timestamp = u;
 677                         changed = true;
 678                 } else
 679                         return true;
 680         }
 681
 682         return changed;
 683 }
 684
 685 int fsck_exists(const char *fstype) {
 686         _cleanup_free_ char *p = NULL, *d = NULL;
 687         const char *checker;
 688         int r;
 689
 690         checker = strjoina("fsck.", fstype);
 691
 692         r = find_binary(checker, true, &p);
 693         if (r < 0)
 694                 return r;
 695
 696         /* An fsck that is linked to /bin/true is a non-existent
 697          * fsck */
 698
 699         r = readlink_malloc(p, &d);
 700         if (r >= 0 &&
 701             (path_equal(d, "/bin/true") ||
 702              path_equal(d, "/usr/bin/true") ||
 703              path_equal(d, "/dev/null")))
 704                 return -ENOENT;
 705
 706         return 0;
 707 }