src/basic/stat-util.c

   1 /***
   2   This file is part of systemd.
   3
   4   Copyright 2010-2012 Lennart Poettering
   5
   6   systemd is free software; you can redistribute it and/or modify it
   7   under the terms of the GNU Lesser General Public License as published by
   8   the Free Software Foundation; either version 2.1 of the License, or
   9   (at your option) any later version.
  10
  11   systemd is distributed in the hope that it will be useful, but
  12   WITHOUT ANY WARRANTY; without even the implied warranty of
  13   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  14   Lesser General Public License for more details.
  15
  16   You should have received a copy of the GNU Lesser General Public License
  17   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  18 ***/
  19
  20 #include <dirent.h>
  21 #include <errno.h>
  22 #include <fcntl.h>
  23 #include <sys/stat.h>
  24 #include <sys/types.h>
  25 #include <linux/magic.h>
  26 #include <sys/statvfs.h>
  27 #include <unistd.h>
  28
  29 #include "dirent-util.h"
  30 #include "fd-util.h"
  31 #include "fs-util.h"
  32 #include "macro.h"
  33 #include "missing.h"
  34 #include "stat-util.h"
  35 #include "string-util.h"
  36
  37 int is_symlink(const char *path) {
  38         struct stat info;
  39
  40         assert(path);
  41
  42         if (lstat(path, &info) < 0)
  43                 return -errno;
  44
  45         return !!S_ISLNK(info.st_mode);
  46 }
  47
  48 int is_dir(const char* path, bool follow) {
  49         struct stat st;
  50         int r;
  51
  52         assert(path);
  53
  54         if (follow)
  55                 r = stat(path, &st);
  56         else
  57                 r = lstat(path, &st);
  58         if (r < 0)
  59                 return -errno;
  60
  61         return !!S_ISDIR(st.st_mode);
  62 }
  63
  64 int is_device_node(const char *path) {
  65         struct stat info;
  66
  67         assert(path);
  68
  69         if (lstat(path, &info) < 0)
  70                 return -errno;
  71
  72         return !!(S_ISBLK(info.st_mode) || S_ISCHR(info.st_mode));
  73 }
  74
  75 int dir_is_empty(const char *path) {
  76         _cleanup_closedir_ DIR *d;
  77         struct dirent *de;
  78
  79         d = opendir(path);
  80         if (!d)
  81                 return -errno;
  82
  83         FOREACH_DIRENT(de, d, return -errno)
  84                 return 0;
  85
  86         return 1;
  87 }
  88
  89 bool null_or_empty(struct stat *st) {
  90         assert(st);
  91
  92         if (S_ISREG(st->st_mode) && st->st_size <= 0)
  93                 return true;
  94
  95         /* We don't want to hardcode the major/minor of /dev/null,
  96          * hence we do a simpler "is this a device node?" check. */
  97
  98         if (S_ISCHR(st->st_mode) || S_ISBLK(st->st_mode))
  99                 return true;
 100
 101         return false;
 102 }
 103
 104 int null_or_empty_path(const char *fn) {
 105         struct stat st;
 106
 107         assert(fn);
 108
 109         if (stat(fn, &st) < 0)
 110                 return -errno;
 111
 112         return null_or_empty(&st);
 113 }
 114
 115 int null_or_empty_fd(int fd) {
 116         struct stat st;
 117
 118         assert(fd >= 0);
 119
 120         if (fstat(fd, &st) < 0)
 121                 return -errno;
 122
 123         return null_or_empty(&st);
 124 }
 125
 126 int path_is_read_only_fs(const char *path) {
 127         struct statvfs st;
 128
 129         assert(path);
 130
 131         if (statvfs(path, &st) < 0)
 132                 return -errno;
 133
 134         if (st.f_flag & ST_RDONLY)
 135                 return true;
 136
 137         /* On NFS, statvfs() might not reflect whether we can actually
 138          * write to the remote share. Let's try again with
 139          * access(W_OK) which is more reliable, at least sometimes. */
 140         if (access(path, W_OK) < 0 && errno == EROFS)
 141                 return true;
 142
 143         return false;
 144 }
 145
 146 int path_is_os_tree(const char *path) {
 147         int r;
 148
 149         assert(path);
 150
 151         /* Does the path exist at all? If not, generate an error immediately. This is useful so that a missing root dir
 152          * always results in -ENOENT, and we can properly distuingish the case where the whole root doesn't exist from
 153          * the case where just the os-release file is missing. */
 154         if (laccess(path, F_OK) < 0)
 155                 return -errno;
 156
 157         /* We use /usr/lib/os-release as flag file if something is an OS */
 158         r = chase_symlinks("/usr/lib/os-release", path, CHASE_PREFIX_ROOT, NULL);
 159         if (r == -ENOENT) {
 160
 161                 /* Also check for the old location in /etc, just in case. */
 162                 r = chase_symlinks("/etc/os-release", path, CHASE_PREFIX_ROOT, NULL);
 163                 if (r == -ENOENT)
 164                         return 0; /* We got nothing */
 165         }
 166         if (r < 0)
 167                 return r;
 168
 169         return 1;
 170 }
 171
 172 int files_same(const char *filea, const char *fileb, int flags) {
 173         struct stat a, b;
 174
 175         assert(filea);
 176         assert(fileb);
 177
 178         if (fstatat(AT_FDCWD, filea, &a, flags) < 0)
 179                 return -errno;
 180
 181         if (fstatat(AT_FDCWD, fileb, &b, flags) < 0)
 182                 return -errno;
 183
 184         return a.st_dev == b.st_dev &&
 185                a.st_ino == b.st_ino;
 186 }
 187
 188 bool is_fs_type(const struct statfs *s, statfs_f_type_t magic_value) {
 189         assert(s);
 190         assert_cc(sizeof(statfs_f_type_t) >= sizeof(s->f_type));
 191
 192         return F_TYPE_EQUAL(s->f_type, magic_value);
 193 }
 194
 195 int fd_check_fstype(int fd, statfs_f_type_t magic_value) {
 196         struct statfs s;
 197
 198         if (fstatfs(fd, &s) < 0)
 199                 return -errno;
 200
 201         return is_fs_type(&s, magic_value);
 202 }
 203
 204 int path_check_fstype(const char *path, statfs_f_type_t magic_value) {
 205         _cleanup_close_ int fd = -1;
 206
 207         fd = open(path, O_RDONLY|O_CLOEXEC|O_NOCTTY|O_PATH);
 208         if (fd < 0)
 209                 return -errno;
 210
 211         return fd_check_fstype(fd, magic_value);
 212 }
 213
 214 bool is_temporary_fs(const struct statfs *s) {
 215     return is_fs_type(s, TMPFS_MAGIC) ||
 216            is_fs_type(s, RAMFS_MAGIC);
 217 }
 218
 219 int fd_is_temporary_fs(int fd) {
 220         struct statfs s;
 221
 222         if (fstatfs(fd, &s) < 0)
 223                 return -errno;
 224
 225         return is_temporary_fs(&s);
 226 }
 227
 228 int path_is_temporary_fs(const char *path) {
 229         _cleanup_close_ int fd = -1;
 230
 231         fd = open(path, O_RDONLY|O_CLOEXEC|O_NOCTTY|O_PATH);
 232         if (fd < 0)
 233                 return -errno;
 234
 235         return fd_is_temporary_fs(fd);
 236 }