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NAME
statfs, fstatfs - get filesystem statistics
SYNOPSIS
#include <sys/vfs.h> /* or <sys/statfs.h> */
int statfs(const char *path, struct statfs *buf);
int fstatfs(int fd, struct statfs *buf);
DESCRIPTION
The function statfs() returns information about a mounted filesystem. path is the pathname of any file
within the mounted filesystem. buf is a pointer to a statfs structure defined approximately as follows:
#if __WORDSIZE == 32 /* System word size */
# define __SWORD_TYPE int
#else /* __WORDSIZE == 64 */
# define __SWORD_TYPE long int
#endif
struct statfs {
__SWORD_TYPE f_type; /* type of filesystem (see below) */
__SWORD_TYPE f_bsize; /* optimal transfer block size */
fsblkcnt_t f_blocks; /* total data blocks in filesystem */
fsblkcnt_t f_bfree; /* free blocks in fs */
fsblkcnt_t f_bavail; /* free blocks available to
unprivileged user */
fsfilcnt_t f_files; /* total file nodes in filesystem */
fsfilcnt_t f_ffree; /* free file nodes in fs */
fsid_t f_fsid; /* filesystem id */
__SWORD_TYPE f_namelen; /* maximum length of filenames */
__SWORD_TYPE f_frsize; /* fragment size (since Linux 2.6) */
__SWORD_TYPE f_spare[5];
};
Filesystem types:
ADFS_SUPER_MAGIC 0xadf5
AFFS_SUPER_MAGIC 0xADFF
BEFS_SUPER_MAGIC 0x42465331
BFS_MAGIC 0x1BADFACE
CIFS_MAGIC_NUMBER 0xFF534D42
CODA_SUPER_MAGIC 0x73757245
COH_SUPER_MAGIC 0x012FF7B7
CRAMFS_MAGIC 0x28cd3d45
DEVFS_SUPER_MAGIC 0x1373
EFS_SUPER_MAGIC 0x00414A53
EXT_SUPER_MAGIC 0x137D
EXT2_OLD_SUPER_MAGIC 0xEF51
EXT2_SUPER_MAGIC 0xEF53
EXT3_SUPER_MAGIC 0xEF53
EXT4_SUPER_MAGIC 0xEF53
HFS_SUPER_MAGIC 0x4244
HPFS_SUPER_MAGIC 0xF995E849
HUGETLBFS_MAGIC 0x958458f6
ISOFS_SUPER_MAGIC 0x9660
JFFS2_SUPER_MAGIC 0x72b6
JFS_SUPER_MAGIC 0x3153464a
MINIX_SUPER_MAGIC 0x137F /* orig. minix */
MINIX_SUPER_MAGIC2 0x138F /* 30 char minix */
MINIX2_SUPER_MAGIC 0x2468 /* minix V2 */
MINIX2_SUPER_MAGIC2 0x2478 /* minix V2, 30 char names */
MSDOS_SUPER_MAGIC 0x4d44
NCP_SUPER_MAGIC 0x564c
NFS_SUPER_MAGIC 0x6969
NTFS_SB_MAGIC 0x5346544e
OPENPROM_SUPER_MAGIC 0x9fa1
PROC_SUPER_MAGIC 0x9fa0
QNX4_SUPER_MAGIC 0x002f
REISERFS_SUPER_MAGIC 0x52654973
ROMFS_MAGIC 0x7275
SMB_SUPER_MAGIC 0x517B
SYSV2_SUPER_MAGIC 0x012FF7B6
SYSV4_SUPER_MAGIC 0x012FF7B5
TMPFS_MAGIC 0x01021994
UDF_SUPER_MAGIC 0x15013346
UFS_MAGIC 0x00011954
USBDEVICE_SUPER_MAGIC 0x9fa2
VXFS_SUPER_MAGIC 0xa501FCF5
XENIX_SUPER_MAGIC 0x012FF7B4
XFS_SUPER_MAGIC 0x58465342
_XIAFS_SUPER_MAGIC 0x012FD16D
Nobody knows what f_fsid is supposed to contain (but see below).
Fields that are undefined for a particular filesystem are set to 0. fstatfs() returns the same
information about an open file referenced by descriptor fd.
RETURN VALUE
On success, zero is returned. On error, -1 is returned, and errno is set appropriately.
ERRORS
EACCES (statfs()) Search permission is denied for a component of the path prefix of path. (See also
path_resolution(7).)
EBADF (fstatfs()) fd is not a valid open file descriptor.
EFAULT buf or path points to an invalid address.
EINTR This call was interrupted by a signal.
EIO An I/O error occurred while reading from the filesystem.
ELOOP (statfs()) Too many symbolic links were encountered in translating path.
ENAMETOOLONG
(statfs()) path is too long.
ENOENT (statfs()) The file referred to by path does not exist.
ENOMEM Insufficient kernel memory was available.
ENOSYS The filesystem does not support this call.
ENOTDIR
(statfs()) A component of the path prefix of path is not a directory.
EOVERFLOW
Some values were too large to be represented in the returned struct.
CONFORMING TO
Linux-specific. The Linux statfs() was inspired by the 4.4BSD one (but they do not use the same
structure).
NOTES
The original Linux statfs() and fstatfs() system calls were not designed with extremely large file sizes
in mind. Subsequently, Linux 2.6 added new statfs64() and fstatfs64() system calls that employ a new
structure, statfs64. The new structure contains the same fields as the original statfs structure, but
the sizes of various fields are increased, to accommodate large file sizes. The glibc statfs() and
fstatfs() wrapper functions transparently deal with the kernel differences.
Some systems only have <sys/vfs.h>, other systems also have <sys/statfs.h>, where the former includes the
latter. So it seems including the former is the best choice.
LSB has deprecated the library calls statfs() and fstatfs() and tells us to use statvfs(2) and
fstatvfs(2) instead.
The f_fsid field
Solaris, Irix and POSIX have a system call statvfs(2) that returns a struct statvfs (defined in
<sys/statvfs.h>) containing an unsigned long f_fsid. Linux, SunOS, HP-UX, 4.4BSD have a system call
statfs() that returns a struct statfs (defined in <sys/vfs.h>) containing a fsid_t f_fsid, where fsid_t
is defined as struct { int val[2]; }. The same holds for FreeBSD, except that it uses the include file
<sys/mount.h>.
The general idea is that f_fsid contains some random stuff such that the pair (f_fsid,ino) uniquely
determines a file. Some operating systems use (a variation on) the device number, or the device number
combined with the filesystem type. Several OSes restrict giving out the f_fsid field to the superuser
only (and zero it for unprivileged users), because this field is used in the filehandle of the filesystem
when NFS-exported, and giving it out is a security concern.
Under some operating systems the fsid can be used as second argument to the sysfs(2) system call.
SEE ALSO
stat(2), statvfs(2), path_resolution(7)
COLOPHON
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