man2/statfs.2

   1 .\" Copyright (C) 2003 Andries Brouwer (aeb@cwi.nl)
   2 .\"
   3 .\" SPDX-License-Identifier: Linux-man-pages-copyleft
   4 .\"
   5 .\" Modified 2003-08-17 by Walter Harms
   6 .\" Modified 2004-06-23 by Michael Kerrisk <mtk.manpages@gmail.com>
   7 .\"
   8 .TH STATFS 2 2021-03-22 "Linux" "Linux Programmer's Manual"
   9 .SH NAME
  10 statfs, fstatfs \- get filesystem statistics
  11 .SH LIBRARY
  12 Standard C library
  13 .RI ( libc ", " \-lc )
  14 .SH SYNOPSIS
  15 .nf
  16 .BR "#include <sys/vfs.h>    " "/* or <sys/statfs.h> */"
  17 .PP
  18 .BI "int statfs(const char *" path ", struct statfs *" buf );
  19 .BI "int fstatfs(int " fd ", struct statfs *" buf );
  20 .fi
  21 .SH DESCRIPTION
  22 The
  23 .BR statfs ()
  24 system call returns information about a mounted filesystem.
  25 .I path
  26 is the pathname of any file within the mounted filesystem.
  27 .I buf
  28 is a pointer to a
  29 .I statfs
  30 structure defined approximately as follows:
  31 .PP
  32 .in +4n
  33 .EX
  34 struct statfs {
  35     __fsword_t f_type;    /* Type of filesystem (see below) */
  36     __fsword_t f_bsize;   /* Optimal transfer block size */
  37     fsblkcnt_t f_blocks;  /* Total data blocks in filesystem */
  38     fsblkcnt_t f_bfree;   /* Free blocks in filesystem */
  39     fsblkcnt_t f_bavail;  /* Free blocks available to
  40                              unprivileged user */
  41     fsfilcnt_t f_files;   /* Total inodes in filesystem */
  42     fsfilcnt_t f_ffree;   /* Free inodes in filesystem */
  43     fsid_t     f_fsid;    /* Filesystem ID */
  44     __fsword_t f_namelen; /* Maximum length of filenames */
  45     __fsword_t f_frsize;  /* Fragment size (since Linux 2.6) */
  46     __fsword_t f_flags;   /* Mount flags of filesystem
  47                              (since Linux 2.6.36) */
  48     __fsword_t f_spare[xxx];
  49                     /* Padding bytes reserved for future use */
  50 };
  51 .EE
  52 .in
  53 .PP
  54 The following filesystem types may appear in
  55 .IR f_type :
  56 .PP
  57 .in +4n
  58 .EX
  59 ADFS_SUPER_MAGIC      0xadf5
  60 AFFS_SUPER_MAGIC      0xadff
  61 AFS_SUPER_MAGIC       0x5346414f
  62 ANON_INODE_FS_MAGIC   0x09041934 /* Anonymous inode FS (for
  63                                     pseudofiles that have no name;
  64                                     e.g., epoll, signalfd, bpf) */
  65 AUTOFS_SUPER_MAGIC    0x0187
  66 BDEVFS_MAGIC          0x62646576
  67 BEFS_SUPER_MAGIC      0x42465331
  68 BFS_MAGIC             0x1badface
  69 BINFMTFS_MAGIC        0x42494e4d
  70 BPF_FS_MAGIC          0xcafe4a11
  71 BTRFS_SUPER_MAGIC     0x9123683e
  72 BTRFS_TEST_MAGIC      0x73727279
  73 CGROUP_SUPER_MAGIC    0x27e0eb   /* Cgroup pseudo FS */
  74 CGROUP2_SUPER_MAGIC   0x63677270 /* Cgroup v2 pseudo FS */
  75 CIFS_MAGIC_NUMBER     0xff534d42
  76 CODA_SUPER_MAGIC      0x73757245
  77 COH_SUPER_MAGIC       0x012ff7b7
  78 CRAMFS_MAGIC          0x28cd3d45
  79 DEBUGFS_MAGIC         0x64626720
  80 DEVFS_SUPER_MAGIC     0x1373     /* Linux 2.6.17 and earlier */
  81 DEVPTS_SUPER_MAGIC    0x1cd1
  82 ECRYPTFS_SUPER_MAGIC  0xf15f
  83 EFIVARFS_MAGIC        0xde5e81e4
  84 EFS_SUPER_MAGIC       0x00414a53
  85 EXT_SUPER_MAGIC       0x137d     /* Linux 2.0 and earlier */
  86 EXT2_OLD_SUPER_MAGIC  0xef51
  87 EXT2_SUPER_MAGIC      0xef53
  88 EXT3_SUPER_MAGIC      0xef53
  89 EXT4_SUPER_MAGIC      0xef53
  90 F2FS_SUPER_MAGIC      0xf2f52010
  91 FUSE_SUPER_MAGIC      0x65735546
  92 FUTEXFS_SUPER_MAGIC   0xbad1dea  /* Unused */
  93 HFS_SUPER_MAGIC       0x4244
  94 HOSTFS_SUPER_MAGIC    0x00c0ffee
  95 HPFS_SUPER_MAGIC      0xf995e849
  96 HUGETLBFS_MAGIC       0x958458f6
  97 ISOFS_SUPER_MAGIC     0x9660
  98 JFFS2_SUPER_MAGIC     0x72b6
  99 JFS_SUPER_MAGIC       0x3153464a
 100 MINIX_SUPER_MAGIC     0x137f     /* original minix FS */
 101 MINIX_SUPER_MAGIC2    0x138f     /* 30 char minix FS */
 102 MINIX2_SUPER_MAGIC    0x2468     /* minix V2 FS */
 103 MINIX2_SUPER_MAGIC2   0x2478     /* minix V2 FS, 30 char names */
 104 MINIX3_SUPER_MAGIC    0x4d5a     /* minix V3 FS, 60 char names */
 105 MQUEUE_MAGIC          0x19800202 /* POSIX message queue FS */
 106 MSDOS_SUPER_MAGIC     0x4d44
 107 MTD_INODE_FS_MAGIC    0x11307854
 108 NCP_SUPER_MAGIC       0x564c
 109 NFS_SUPER_MAGIC       0x6969
 110 NILFS_SUPER_MAGIC     0x3434
 111 NSFS_MAGIC            0x6e736673
 112 NTFS_SB_MAGIC         0x5346544e
 113 OCFS2_SUPER_MAGIC     0x7461636f
 114 OPENPROM_SUPER_MAGIC  0x9fa1
 115 OVERLAYFS_SUPER_MAGIC 0x794c7630
 116 PIPEFS_MAGIC          0x50495045
 117 PROC_SUPER_MAGIC      0x9fa0     /* /proc FS */
 118 PSTOREFS_MAGIC        0x6165676c
 119 QNX4_SUPER_MAGIC      0x002f
 120 QNX6_SUPER_MAGIC      0x68191122
 121 RAMFS_MAGIC           0x858458f6
 122 REISERFS_SUPER_MAGIC  0x52654973
 123 ROMFS_MAGIC           0x7275
 124 SECURITYFS_MAGIC      0x73636673
 125 SELINUX_MAGIC         0xf97cff8c
 126 SMACK_MAGIC           0x43415d53
 127 SMB_SUPER_MAGIC       0x517b
 128 SMB2_MAGIC_NUMBER     0xfe534d42
 129 SOCKFS_MAGIC          0x534f434b
 130 SQUASHFS_MAGIC        0x73717368
 131 SYSFS_MAGIC           0x62656572
 132 SYSV2_SUPER_MAGIC     0x012ff7b6
 133 SYSV4_SUPER_MAGIC     0x012ff7b5
 134 TMPFS_MAGIC           0x01021994
 135 TRACEFS_MAGIC         0x74726163
 136 UDF_SUPER_MAGIC       0x15013346
 137 UFS_MAGIC             0x00011954
 138 USBDEVICE_SUPER_MAGIC 0x9fa2
 139 V9FS_MAGIC            0x01021997
 140 VXFS_SUPER_MAGIC      0xa501fcf5
 141 XENFS_SUPER_MAGIC     0xabba1974
 142 XENIX_SUPER_MAGIC     0x012ff7b4
 143 XFS_SUPER_MAGIC       0x58465342
 144 _XIAFS_SUPER_MAGIC    0x012fd16d /* Linux 2.0 and earlier */
 145 .EE
 146 .in
 147 .PP
 148 Most of these MAGIC constants are defined in
 149 .IR /usr/include/linux/magic.h ,
 150 and some are hardcoded in kernel sources.
 151 .PP
 152 The
 153 .IR f_flags
 154 field is a bit mask indicating mount options for the filesystem.
 155 It contains zero or more of the following bits:
 156 .\" XXX Keep this list in sync with statvfs(3)
 157 .TP
 158 .B ST_MANDLOCK
 159 Mandatory locking is permitted on the filesystem (see
 160 .BR fcntl (2)).
 161 .TP
 162 .B ST_NOATIME
 163 Do not update access times; see
 164 .BR mount (2).
 165 .TP
 166 .B ST_NODEV
 167 Disallow access to device special files on this filesystem.
 168 .TP
 169 .B ST_NODIRATIME
 170 Do not update directory access times; see
 171 .BR mount (2).
 172 .TP
 173 .B ST_NOEXEC
 174 Execution of programs is disallowed on this filesystem.
 175 .TP
 176 .B ST_NOSUID
 177 The set-user-ID and set-group-ID bits are ignored by
 178 .BR exec (3)
 179 for executable files on this filesystem
 180 .TP
 181 .B ST_RDONLY
 182 This filesystem is mounted read-only.
 183 .TP
 184 .B ST_RELATIME
 185 Update atime relative to mtime/ctime; see
 186 .BR mount (2).
 187 .TP
 188 .B ST_SYNCHRONOUS
 189 Writes are synched to the filesystem immediately (see the description of
 190 .B O_SYNC
 191 in
 192 .BR open (2)).
 193 .TP
 194 .BR ST_NOSYMFOLLOW " (since Linux 5.10)"
 195 .\" dab741e0e02bd3c4f5e2e97be74b39df2523fc6e
 196 Symbolic links are not followed when resolving paths; see
 197 .BR mount (2).
 198 .PP
 199 Nobody knows what
 200 .I f_fsid
 201 is supposed to contain (but see below).
 202 .PP
 203 Fields that are undefined for a particular filesystem are set to 0.
 204 .PP
 205 .BR fstatfs ()
 206 returns the same information about an open file referenced by descriptor
 207 .IR fd .
 208 .SH RETURN VALUE
 209 On success, zero is returned.
 210 On error, \-1 is returned, and
 211 .I errno
 212 is set to indicate the error.
 213 .SH ERRORS
 214 .TP
 215 .B EACCES
 216 .RB ( statfs ())
 217 Search permission is denied for a component of the path prefix of
 218 .IR path .
 219 (See also
 220 .BR path_resolution (7).)
 221 .TP
 222 .B EBADF
 223 .RB ( fstatfs ())
 224 .I fd
 225 is not a valid open file descriptor.
 226 .TP
 227 .B EFAULT
 228 .I buf
 229 or
 230 .I path
 231 points to an invalid address.
 232 .TP
 233 .B EINTR
 234 The call was interrupted by a signal; see
 235 .BR signal (7).
 236 .TP
 237 .B EIO
 238 An I/O error occurred while reading from the filesystem.
 239 .TP
 240 .B ELOOP
 241 .RB ( statfs ())
 242 Too many symbolic links were encountered in translating
 243 .IR path .
 244 .TP
 245 .B ENAMETOOLONG
 246 .RB ( statfs ())
 247 .I path
 248 is too long.
 249 .TP
 250 .B ENOENT
 251 .RB ( statfs ())
 252 The file referred to by
 253 .I path
 254 does not exist.
 255 .TP
 256 .B ENOMEM
 257 Insufficient kernel memory was available.
 258 .TP
 259 .B ENOSYS
 260 The filesystem does not support this call.
 261 .TP
 262 .B ENOTDIR
 263 .RB ( statfs ())
 264 A component of the path prefix of
 265 .I path
 266 is not a directory.
 267 .TP
 268 .B EOVERFLOW
 269 Some values were too large to be represented in the returned struct.
 270 .SH CONFORMING TO
 271 Linux-specific.
 272 The Linux
 273 .BR statfs ()
 274 was inspired by the 4.4BSD one
 275 (but they do not use the same structure).
 276 .SH NOTES
 277 The
 278 .I __fsword_t
 279 type used for various fields in the
 280 .I statfs
 281 structure definition is a glibc internal type,
 282 not intended for public use.
 283 This leaves the programmer in a bit of a conundrum when trying to copy
 284 or compare these fields to local variables in a program.
 285 Using
 286 .I "unsigned\ int"
 287 for such variables suffices on most systems.
 288 .PP
 289 The original Linux
 290 .BR statfs ()
 291 and
 292 .BR fstatfs ()
 293 system calls were not designed with extremely large file sizes in mind.
 294 Subsequently, Linux 2.6
 295 added new
 296 .BR statfs64 ()
 297 and
 298 .BR fstatfs64 ()
 299 system calls that employ a new structure,
 300 .IR statfs64 .
 301 The new structure contains the same fields as the original
 302 .I statfs
 303 structure, but the sizes of various fields are increased,
 304 to accommodate large file sizes.
 305 The glibc
 306 .BR statfs ()
 307 and
 308 .BR fstatfs ()
 309 wrapper functions transparently deal with the kernel differences.
 310 .PP
 311 Some systems have only \fI<sys/vfs.h>\fP, other systems also have
 312 \fI<sys/statfs.h>\fP, where the former includes the latter.
 313 So it seems
 314 including the former is the best choice.
 315 .PP
 316 LSB has deprecated the library calls
 317 .BR statfs ()
 318 and
 319 .BR fstatfs ()
 320 and tells us to use
 321 .BR statvfs (3)
 322 and
 323 .BR fstatvfs (3)
 324 instead.
 325 .SS The f_fsid field
 326 Solaris, Irix, and POSIX have a system call
 327 .BR statvfs (2)
 328 that returns a
 329 .I "struct statvfs"
 330 (defined in
 331 .IR <sys/statvfs.h> )
 332 containing an
 333 .I "unsigned long"
 334 .IR f_fsid .
 335 Linux, SunOS, HP-UX, 4.4BSD have a system call
 336 .BR statfs ()
 337 that returns a
 338 .I "struct statfs"
 339 (defined in
 340 .IR <sys/vfs.h> )
 341 containing a
 342 .I fsid_t
 343 .IR f_fsid ,
 344 where
 345 .I fsid_t
 346 is defined as
 347 .IR "struct { int val[2]; }" .
 348 The same holds for FreeBSD, except that it uses the include file
 349 .IR <sys/mount.h> .
 350 .PP
 351 The general idea is that
 352 .I f_fsid
 353 contains some random stuff such that the pair
 354 .RI ( f_fsid , ino )
 355 uniquely determines a file.
 356 Some operating systems use (a variation on) the device number,
 357 or the device number combined with the filesystem type.
 358 Several operating systems restrict giving out the
 359 .I f_fsid
 360 field to the superuser only (and zero it for unprivileged users),
 361 because this field is used in the filehandle of the filesystem
 362 when NFS-exported, and giving it out is a security concern.
 363 .PP
 364 Under some operating systems, the
 365 .I fsid
 366 can be used as the second argument to the
 367 .BR sysfs (2)
 368 system call.
 369 .SH BUGS
 370 From Linux 2.6.38 up to and including Linux 3.1,
 371 .\" broken in commit ff0c7d15f9787b7e8c601533c015295cc68329f8
 372 .\" fixed in commit d70ef97baf048412c395bb5d65791d8fe133a52b
 373 .BR fstatfs ()
 374 failed with the error
 375 .B ENOSYS
 376 for file descriptors created by
 377 .BR pipe (2).
 378 .SH SEE ALSO
 379 .BR stat (2),
 380 .BR statvfs (3),
 381 .BR path_resolution (7)