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 path_make_absolute(p, cwd);
 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 int path_is_mount_point(const char *t, bool allow_symlink) {
 439
 440         union file_handle_union h = {
 441                 .handle.handle_bytes = MAX_HANDLE_SZ
 442         };
 443
 444         int mount_id, mount_id_parent;
 445         char *parent;
 446         struct stat a, b;
 447         int r;
 448
 449         /* We are not actually interested in the file handles, but
 450          * name_to_handle_at() also passes us the mount ID, hence use
 451          * it but throw the handle away */
 452
 453         if (path_equal(t, "/"))
 454                 return 1;
 455
 456         r = name_to_handle_at(AT_FDCWD, t, &h.handle, &mount_id, allow_symlink ? AT_SYMLINK_FOLLOW : 0);
 457         if (r < 0) {
 458                 if (IN_SET(errno, ENOSYS, EOPNOTSUPP))
 459                         /* This kernel or file system does not support
 460                          * name_to_handle_at(), hence fallback to the
 461                          * traditional stat() logic */
 462                         goto fallback;
 463
 464                 if (errno == ENOENT)
 465                         return 0;
 466
 467                 return -errno;
 468         }
 469
 470         r = path_get_parent(t, &parent);
 471         if (r < 0)
 472                 return r;
 473
 474         h.handle.handle_bytes = MAX_HANDLE_SZ;
 475         r = name_to_handle_at(AT_FDCWD, parent, &h.handle, &mount_id_parent, 0);
 476         free(parent);
 477         if (r < 0) {
 478                 /* The parent can't do name_to_handle_at() but the
 479                  * directory we are interested in can? If so, it must
 480                  * be a mount point */
 481                 if (errno == EOPNOTSUPP)
 482                         return 1;
 483
 484                 return -errno;
 485         }
 486
 487         return mount_id != mount_id_parent;
 488
 489 fallback:
 490         if (allow_symlink)
 491                 r = stat(t, &a);
 492         else
 493                 r = lstat(t, &a);
 494
 495         if (r < 0) {
 496                 if (errno == ENOENT)
 497                         return 0;
 498
 499                 return -errno;
 500         }
 501
 502         r = path_get_parent(t, &parent);
 503         if (r < 0)
 504                 return r;
 505
 506         r = lstat(parent, &b);
 507         free(parent);
 508         if (r < 0)
 509                 return -errno;
 510
 511         return a.st_dev != b.st_dev;
 512 }
 513
 514 int path_is_read_only_fs(const char *path) {
 515         struct statvfs st;
 516
 517         assert(path);
 518
 519         if (statvfs(path, &st) < 0)
 520                 return -errno;
 521
 522         return !!(st.f_flag & ST_RDONLY);
 523 }
 524
 525 int path_is_os_tree(const char *path) {
 526         char *p;
 527         int r;
 528
 529         /* We use /usr/lib/os-release as flag file if something is an OS */
 530         p = strappenda(path, "/usr/lib/os-release");
 531         r = access(p, F_OK);
 532
 533         if (r >= 0)
 534                 return 1;
 535
 536         /* Also check for the old location in /etc, just in case. */
 537         p = strappenda(path, "/etc/os-release");
 538         r = access(p, F_OK);
 539
 540         return r >= 0;
 541 }
 542
 543 int find_binary(const char *name, char **filename) {
 544         assert(name);
 545
 546         if (strchr(name, '/')) {
 547                 if (access(name, X_OK) < 0)
 548                         return -errno;
 549
 550                 if (filename) {
 551                         char *p;
 552
 553                         p = path_make_absolute_cwd(name);
 554                         if (!p)
 555                                 return -ENOMEM;
 556
 557                         *filename = p;
 558                 }
 559
 560                 return 0;
 561         } else {
 562                 const char *path;
 563                 char *state, *w;
 564                 size_t l;
 565
 566                 /**
 567                  * Plain getenv, not secure_getenv, because we want
 568                  * to actually allow the user to pick the binary.
 569                  */
 570                 path = getenv("PATH");
 571                 if (!path)
 572                         path = DEFAULT_PATH;
 573
 574                 FOREACH_WORD_SEPARATOR(w, l, path, ":", state) {
 575                         _cleanup_free_ char *p = NULL;
 576
 577                         if (asprintf(&p, "%.*s/%s", (int) l, w, name) < 0)
 578                                 return -ENOMEM;
 579
 580                         if (access(p, X_OK) < 0)
 581                                 continue;
 582
 583                         if (filename) {
 584                                 *filename = path_kill_slashes(p);
 585                                 p = NULL;
 586                         }
 587
 588                         return 0;
 589                 }
 590
 591                 return -ENOENT;
 592         }
 593 }
 594
 595 bool paths_check_timestamp(const char* const* paths, usec_t *timestamp, bool update) {
 596         bool changed = false;
 597         const char* const* i;
 598
 599         assert(timestamp);
 600
 601         if (paths == NULL)
 602                 return false;
 603
 604         STRV_FOREACH(i, paths) {
 605                 struct stat stats;
 606                 usec_t u;
 607
 608                 if (stat(*i, &stats) < 0)
 609                         continue;
 610
 611                 u = timespec_load(&stats.st_mtim);
 612
 613                 /* first check */
 614                 if (*timestamp >= u)
 615                         continue;
 616
 617                 log_debug("timestamp of '%s' changed", *i);
 618
 619                 /* update timestamp */
 620                 if (update) {
 621                         *timestamp = u;
 622                         changed = true;
 623                 } else
 624                         return true;
 625         }
 626
 627         return changed;
 628 }
 629
 630 int fsck_exists(const char *fstype) {
 631         const char *checker;
 632
 633         checker = strappenda("fsck.", fstype);
 634         return find_binary(checker, NULL);
 635 }