man2/statfs.2

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  25 .\" Modified 2003-08-17 by Walter Harms
  26 .\" Modified 2004-06-23 by Michael Kerrisk <mtk.manpages@gmail.com>
  27 .\"
  28 .TH STATFS 2 2017-09-15 "Linux" "Linux Programmer's Manual"
  29 .SH NAME
  30 statfs, fstatfs \- get filesystem statistics
  31 .SH SYNOPSIS
  32 .BR "#include <sys/vfs.h>    " "/* or <sys/statfs.h> */"
  33 .PP
  34 .BI "int statfs(const char *" path ", struct statfs *" buf );
  35 .br
  36 .BI "int fstatfs(int " fd ", struct statfs *" buf );
  37 .SH DESCRIPTION
  38 The
  39 .BR statfs ()
  40 system call returns information about a mounted filesystem.
  41 .I path
  42 is the pathname of any file within the mounted filesystem.
  43 .I buf
  44 is a pointer to a
  45 .I statfs
  46 structure defined approximately as follows:
  47 .PP
  48 .in +4n
  49 .EX
  50 struct statfs {
  51     __fsword_t f_type;    /* Type of filesystem (see below) */
  52     __fsword_t f_bsize;   /* Optimal transfer block size */
  53     fsblkcnt_t f_blocks;  /* Total data blocks in filesystem */
  54     fsblkcnt_t f_bfree;   /* Free blocks in filesystem */
  55     fsblkcnt_t f_bavail;  /* Free blocks available to
  56                              unprivileged user */
  57     fsfilcnt_t f_files;   /* Total file nodes in filesystem */
  58     fsfilcnt_t f_ffree;   /* Free file nodes in filesystem */
  59     fsid_t     f_fsid;    /* Filesystem ID */
  60     __fsword_t f_namelen; /* Maximum length of filenames */
  61     __fsword_t f_frsize;  /* Fragment size (since Linux 2.6) */
  62     __fsword_t f_flags;   /* Mount flags of filesystem
  63                              (since Linux 2.6.36) */
  64     __fsword_t f_spare[xxx];
  65                     /* Padding bytes reserved for future use */
  66 };
  67 .EE
  68 .in
  69 .PP
  70 The following filesystem types may appear in
  71 .IR f_type :
  72 .PP
  73 .in +4n
  74 .EX
  75 ADFS_SUPER_MAGIC      0xadf5
  76 AFFS_SUPER_MAGIC      0xadff
  77 AFS_SUPER_MAGIC       0x5346414f
  78 ANON_INODE_FS_MAGIC   0x09041934 /* Anonymous inode FS (for
  79                                     pseudofiles that have no name;
  80                                     e.g., epoll, signalfd, bpf) */
  81 AUTOFS_SUPER_MAGIC    0x0187
  82 BDEVFS_MAGIC          0x62646576
  83 BEFS_SUPER_MAGIC      0x42465331
  84 BFS_MAGIC             0x1badface
  85 BINFMTFS_MAGIC        0x42494e4d
  86 BPF_FS_MAGIC          0xcafe4a11
  87 BTRFS_SUPER_MAGIC     0x9123683e
  88 BTRFS_TEST_MAGIC      0x73727279
  89 CGROUP_SUPER_MAGIC    0x27e0eb   /* Cgroup pseudo FS */
  90 CGROUP2_SUPER_MAGIC   0x63677270 /* Cgroup v2 pseudo FS */
  91 CIFS_MAGIC_NUMBER     0xff534d42
  92 CODA_SUPER_MAGIC      0x73757245
  93 COH_SUPER_MAGIC       0x012ff7b7
  94 CRAMFS_MAGIC          0x28cd3d45
  95 DEBUGFS_MAGIC         0x64626720
  96 DEVFS_SUPER_MAGIC     0x1373     /* Linux 2.6.17 and earlier */
  97 DEVPTS_SUPER_MAGIC    0x1cd1
  98 ECRYPTFS_SUPER_MAGIC  0xf15f
  99 EFIVARFS_MAGIC        0xde5e81e4
 100 EFS_SUPER_MAGIC       0x00414a53
 101 EXT_SUPER_MAGIC       0x137d     /* Linux 2.0 and earlier */
 102 EXT2_OLD_SUPER_MAGIC  0xef51
 103 EXT2_SUPER_MAGIC      0xef53
 104 EXT3_SUPER_MAGIC      0xef53
 105 EXT4_SUPER_MAGIC      0xef53
 106 F2FS_SUPER_MAGIC      0xf2f52010
 107 FUSE_SUPER_MAGIC      0x65735546
 108 FUTEXFS_SUPER_MAGIC   0xbad1dea  /* Unused */
 109 HFS_SUPER_MAGIC       0x4244
 110 HOSTFS_SUPER_MAGIC    0x00c0ffee
 111 HPFS_SUPER_MAGIC      0xf995e849
 112 HUGETLBFS_MAGIC       0x958458f6
 113 ISOFS_SUPER_MAGIC     0x9660
 114 JFFS2_SUPER_MAGIC     0x72b6
 115 JFS_SUPER_MAGIC       0x3153464a
 116 MINIX_SUPER_MAGIC     0x137f     /* original minix FS */
 117 MINIX_SUPER_MAGIC2    0x138f     /* 30 char minix FS */
 118 MINIX2_SUPER_MAGIC    0x2468     /* minix V2 FS */
 119 MINIX2_SUPER_MAGIC2   0x2478     /* minix V2 FS, 30 char names */
 120 MINIX3_SUPER_MAGIC    0x4d5a     /* minix V3 FS, 60 char names */
 121 MQUEUE_MAGIC          0x19800202 /* POSIX message queue FS */
 122 MSDOS_SUPER_MAGIC     0x4d44
 123 MTD_INODE_FS_MAGIC    0x11307854
 124 NCP_SUPER_MAGIC       0x564c
 125 NFS_SUPER_MAGIC       0x6969
 126 NILFS_SUPER_MAGIC     0x3434
 127 NSFS_MAGIC            0x6e736673
 128 NTFS_SB_MAGIC         0x5346544e
 129 OCFS2_SUPER_MAGIC     0x7461636f
 130 OPENPROM_SUPER_MAGIC  0x9fa1
 131 OVERLAYFS_SUPER_MAGIC 0x794c7630
 132 PIPEFS_MAGIC          0x50495045
 133 PROC_SUPER_MAGIC      0x9fa0     /* /proc FS */
 134 PSTOREFS_MAGIC        0x6165676c
 135 QNX4_SUPER_MAGIC      0x002f
 136 QNX6_SUPER_MAGIC      0x68191122
 137 RAMFS_MAGIC           0x858458f6
 138 REISERFS_SUPER_MAGIC  0x52654973
 139 ROMFS_MAGIC           0x7275
 140 SECURITYFS_MAGIC      0x73636673
 141 SELINUX_MAGIC         0xf97cff8c
 142 SMACK_MAGIC           0x43415d53
 143 SMB_SUPER_MAGIC       0x517b
 144 SOCKFS_MAGIC          0x534f434b
 145 SQUASHFS_MAGIC        0x73717368
 146 SYSFS_MAGIC           0x62656572
 147 SYSV2_SUPER_MAGIC     0x012ff7b6
 148 SYSV4_SUPER_MAGIC     0x012ff7b5
 149 TMPFS_MAGIC           0x01021994
 150 TRACEFS_MAGIC         0x74726163
 151 UDF_SUPER_MAGIC       0x15013346
 152 UFS_MAGIC             0x00011954
 153 USBDEVICE_SUPER_MAGIC 0x9fa2
 154 V9FS_MAGIC            0x01021997
 155 VXFS_SUPER_MAGIC      0xa501fcf5
 156 XENFS_SUPER_MAGIC     0xabba1974
 157 XENIX_SUPER_MAGIC     0x012ff7b4
 158 XFS_SUPER_MAGIC       0x58465342
 159 _XIAFS_SUPER_MAGIC    0x012fd16d /* Linux 2.0 and earlier */
 160 .EE
 161 .in
 162 .PP
 163 Most of these MAGIC constants are defined in
 164 .IR /usr/include/linux/magic.h ,
 165 and some are hardcoded in kernel sources.
 166 .PP
 167 The
 168 .IR f_flags
 169 field is a bit mask indicating mount options for the filesystem.
 170 It contains zero or more of the following bits:
 171 .\" XXX Keep this list in sync with statvfs(3)
 172 .TP
 173 .B ST_MANDLOCK
 174 Mandatory locking is permitted on the filesystem (see
 175 .BR fcntl (2)).
 176 .TP
 177 .B ST_NOATIME
 178 Do not update access times; see
 179 .BR mount (2).
 180 .TP
 181 .B ST_NODEV
 182 Disallow access to device special files on this filesystem.
 183 .TP
 184 .B ST_NODIRATIME
 185 Do not update directory access times; see
 186 .BR mount (2).
 187 .TP
 188 .B ST_NOEXEC
 189 Execution of programs is disallowed on this filesystem.
 190 .TP
 191 .B ST_NOSUID
 192 The set-user-ID and set-group-ID bits are ignored by
 193 .BR exec (3)
 194 for executable files on this filesystem
 195 .TP
 196 .B ST_RDONLY
 197 This filesystem is mounted read-only.
 198 .TP
 199 .B ST_RELATIME
 200 Update atime relative to mtime/ctime; see
 201 .BR mount (2).
 202 .TP
 203 .B ST_SYNCHRONOUS
 204 Writes are synched to the filesystem immediately (see the description of
 205 .B O_SYNC
 206 in
 207 .BR open (2)).
 208 .PP
 209 Nobody knows what
 210 .I f_fsid
 211 is supposed to contain (but see below).
 212 .PP
 213 Fields that are undefined for a particular filesystem are set to 0.
 214 .PP
 215 .BR fstatfs ()
 216 returns the same information about an open file referenced by descriptor
 217 .IR fd .
 218 .SH RETURN VALUE
 219 On success, zero is returned.
 220 On error, \-1 is returned, and
 221 .I errno
 222 is set appropriately.
 223 .SH ERRORS
 224 .TP
 225 .B EACCES
 226 .RB ( statfs ())
 227 Search permission is denied for a component of the path prefix of
 228 .IR path .
 229 (See also
 230 .BR path_resolution (7).)
 231 .TP
 232 .B EBADF
 233 .RB ( fstatfs ())
 234 .I fd
 235 is not a valid open file descriptor.
 236 .TP
 237 .B EFAULT
 238 .I buf
 239 or
 240 .I path
 241 points to an invalid address.
 242 .TP
 243 .B EINTR
 244 The call was interrupted by a signal; see
 245 .BR signal (7).
 246 .TP
 247 .B EIO
 248 An I/O error occurred while reading from the filesystem.
 249 .TP
 250 .B ELOOP
 251 .RB ( statfs ())
 252 Too many symbolic links were encountered in translating
 253 .IR path .
 254 .TP
 255 .B ENAMETOOLONG
 256 .RB ( statfs ())
 257 .I path
 258 is too long.
 259 .TP
 260 .B ENOENT
 261 .RB ( statfs ())
 262 The file referred to by
 263 .I path
 264 does not exist.
 265 .TP
 266 .B ENOMEM
 267 Insufficient kernel memory was available.
 268 .TP
 269 .B ENOSYS
 270 The filesystem does not support this call.
 271 .TP
 272 .B ENOTDIR
 273 .RB ( statfs ())
 274 A component of the path prefix of
 275 .I path
 276 is not a directory.
 277 .TP
 278 .B EOVERFLOW
 279 Some values were too large to be represented in the returned struct.
 280 .SH CONFORMING TO
 281 Linux-specific.
 282 The Linux
 283 .BR statfs ()
 284 was inspired by the 4.4BSD one
 285 (but they do not use the same structure).
 286 .SH NOTES
 287 The
 288 .I __fsword_t
 289 type used for various fields in the
 290 .I statfs
 291 structure definition is a glibc internal type,
 292 not intended for public use.
 293 This leaves the programmer in a bit of a conundrum when trying to copy
 294 or compare these fields to local variables in a program.
 295 Using
 296 .I "unsigned\ int"
 297 for such variables suffices on most systems.
 298 .PP
 299 The original Linux
 300 .BR statfs ()
 301 and
 302 .BR fstatfs ()
 303 system calls were not designed with extremely large file sizes in mind.
 304 Subsequently, Linux 2.6
 305 added new
 306 .BR statfs64 ()
 307 and
 308 .BR fstatfs64 ()
 309 system calls that employ a new structure,
 310 .IR statfs64 .
 311 The new structure contains the same fields as the original
 312 .I statfs
 313 structure, but the sizes of various fields are increased,
 314 to accommodate large file sizes.
 315 The glibc
 316 .BR statfs ()
 317 and
 318 .BR fstatfs ()
 319 wrapper functions transparently deal with the kernel differences.
 320 .PP
 321 Some systems have only \fI<sys/vfs.h>\fP, other systems also have
 322 \fI<sys/statfs.h>\fP, where the former includes the latter.
 323 So it seems
 324 including the former is the best choice.
 325 .PP
 326 LSB has deprecated the library calls
 327 .BR statfs ()
 328 and
 329 .BR fstatfs ()
 330 and tells us to use
 331 .BR statvfs (2)
 332 and
 333 .BR fstatvfs (2)
 334 instead.
 335 .SS The f_fsid field
 336 Solaris, Irix and POSIX have a system call
 337 .BR statvfs (2)
 338 that returns a
 339 .I "struct statvfs"
 340 (defined in
 341 .IR <sys/statvfs.h> )
 342 containing an
 343 .I "unsigned long"
 344 .IR f_fsid .
 345 Linux, SunOS, HP-UX, 4.4BSD have a system call
 346 .BR statfs ()
 347 that returns a
 348 .I "struct statfs"
 349 (defined in
 350 .IR <sys/vfs.h> )
 351 containing a
 352 .I fsid_t
 353 .IR f_fsid ,
 354 where
 355 .I fsid_t
 356 is defined as
 357 .IR "struct { int val[2]; }" .
 358 The same holds for FreeBSD, except that it uses the include file
 359 .IR <sys/mount.h> .
 360 .PP
 361 The general idea is that
 362 .I f_fsid
 363 contains some random stuff such that the pair
 364 .RI ( f_fsid , ino )
 365 uniquely determines a file.
 366 Some operating systems use (a variation on) the device number,
 367 or the device number combined with the filesystem type.
 368 Several operating systems restrict giving out the
 369 .I f_fsid
 370 field to the superuser only (and zero it for unprivileged users),
 371 because this field is used in the filehandle of the filesystem
 372 when NFS-exported, and giving it out is a security concern.
 373 .PP
 374 Under some operating systems, the
 375 .I fsid
 376 can be used as the second argument to the
 377 .BR sysfs (2)
 378 system call.
 379 .SH BUGS
 380 From Linux 2.6.38 up to and including Linux 3.1,
 381 .\" broken in commit ff0c7d15f9787b7e8c601533c015295cc68329f8
 382 .\" fixed in commit d70ef97baf048412c395bb5d65791d8fe133a52b
 383 .BR fstatfs ()
 384 failed with the error
 385 .B ENOSYS
 386 for file descriptors created by
 387 .BR pipe (2).
 388 .SH SEE ALSO
 389 .BR stat (2),
 390 .BR statvfs (3),
 391 .BR path_resolution (7)