Other Alias

statfs

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 statfs() system call 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:

struct statfs {
 __fsword_t f_type; /* Type of filesystem (see below) */
 __fsword_t f_bsize; /* Optimal transfer block size */
 fsblkcnt_t f_blocks; /* Total data blocks in filesystem */
 fsblkcnt_t f_bfree; /* Free blocks in filesystem */
 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 filesystem */
 fsid_t f_fsid; /* Filesystem ID */
 __fsword_t f_namelen; /* Maximum length of filenames */
 __fsword_t f_frsize; /* Fragment size (since Linux 2.6) */
 __fsword_t f_flags; /* Mount flags of filesystem
 (since Linux 2.6.36) */
 __fsword_t f_spare[xxx];
 /* Padding bytes reserved for future use */
};
Filesystem types:
 ADFS_SUPER_MAGIC 0xadf5
 AFFS_SUPER_MAGIC 0xadff
 BDEVFS_MAGIC 0x62646576
 BEFS_SUPER_MAGIC 0x42465331
 BFS_MAGIC 0x1badface
 BINFMTFS_MAGIC 0x42494e4d
 BTRFS_SUPER_MAGIC 0x9123683e
 CGROUP_SUPER_MAGIC 0x27e0eb
 CIFS_MAGIC_NUMBER 0xff534d42
 CODA_SUPER_MAGIC 0x73757245
 COH_SUPER_MAGIC 0x012ff7b7
 CRAMFS_MAGIC 0x28cd3d45
 DEBUGFS_MAGIC 0x64626720
 DEVFS_SUPER_MAGIC 0x1373
 DEVPTS_SUPER_MAGIC 0x1cd1
 EFIVARFS_MAGIC 0xde5e81e4
 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
 FUSE_SUPER_MAGIC 0x65735546
 FUTEXFS_SUPER_MAGIC 0xbad1dea
 HFS_SUPER_MAGIC 0x4244
 HOSTFS_SUPER_MAGIC 0x00c0ffee
 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 */
 MINIX3_SUPER_MAGIC 0x4d5a /* minix V3 fs, 60 char names */
 MQUEUE_MAGIC 0x19800202
 MSDOS_SUPER_MAGIC 0x4d44
 NCP_SUPER_MAGIC 0x564c
 NFS_SUPER_MAGIC 0x6969
 NILFS_SUPER_MAGIC 0x3434
 NTFS_SB_MAGIC 0x5346544e
 OCFS2_SUPER_MAGIC 0x7461636f
 OPENPROM_SUPER_MAGIC 0x9fa1
 PIPEFS_MAGIC 0x50495045
 PROC_SUPER_MAGIC 0x9fa0
 PSTOREFS_MAGIC 0x6165676c
 QNX4_SUPER_MAGIC 0x002f
 QNX6_SUPER_MAGIC 0x68191122
 RAMFS_MAGIC 0x858458f6
 REISERFS_SUPER_MAGIC 0x52654973
 ROMFS_MAGIC 0x7275
 SELINUX_MAGIC 0xf97cff8c
 SMACK_MAGIC 0x43415d53
 SMB_SUPER_MAGIC 0x517b
 SOCKFS_MAGIC 0x534f434b
 SQUASHFS_MAGIC 0x73717368
 SYSFS_MAGIC 0x62656572
 SYSV2_SUPER_MAGIC 0x012ff7b6
 SYSV4_SUPER_MAGIC 0x012ff7b5
 TMPFS_MAGIC 0x01021994
 UDF_SUPER_MAGIC 0x15013346
 UFS_MAGIC 0x00011954
 USBDEVICE_SUPER_MAGIC 0x9fa2
 V9FS_MAGIC 0x01021997
 VXFS_SUPER_MAGIC 0xa501fcf5
 XENFS_SUPER_MAGIC 0xabba1974
 XENIX_SUPER_MAGIC 0x012ff7b4
 XFS_SUPER_MAGIC 0x58465342
 _XIAFS_SUPER_MAGIC 0x012fd16d

Most of these MAGIC constants are defined in /usr/include/linux/magic.h, and some are hardcoded in kernel sources.

The f_flags is a bit mask indicating mount options for the file system. It contains zero or more of the following bits:

ST_MANDLOCK

Mandatory locking is permitted on the filesystem (see fcntl(2)).

ST_NOATIME

Do not update access times; see mount(2).

ST_NODEV

Disallow access to device special files on this filesystem.

ST_NODIRATIME

Do not update directory access times; see mount(2).

ST_NOEXEC

Execution of programs is disallowed on this filesystem.

ST_NOSUID

The set-user-ID and set-group-ID bits are ignored by exec(3) for executable files on this filesystem

ST_RDONLY

This filesystem is mounted read-only.

ST_RELATIME

Update atime relative to mtime/ctime; see mount(2).

ST_SYNCHRONOUS

Writes are synched to the filesystem immediately (see the description of O_SYNC in open(2)).

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; see signal(7).

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 __fsword_t type used for various fields in the statfs structure definition is a glibc internal type, not intended for public use. This leaves the programmer in a bit of a conundrum when trying to copy or compare these fields to local variables in a program. Using unsigned int for such variables suffices on most systems.

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 have only <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 operating systems 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 the second argument to the sysfs(2) system call.

BUGS

From Linux 2.6.38 up to and including Linux 3.1, fstatfs() failed with the error ENOSYS for file descriptors created by pipe(2).

COLOPHON

This page is part of release 4.06 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at https://www.kernel.org/doc/man-pages/.