statfs

Sommaire

NAME

statfs, fstatfs - get file system 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 file system. 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 {

   long    f_type;     /* type of filesystem (see below) */

   long    f_bsize;    /* optimal transfer block size */

   long    f_blocks;   /* total data blocks in file system */

   long    f_bfree;    /* free blocks in fs */

   long    f_bavail;   /* free blocks avail to non-superuser */

   long    f_files;    /* total file nodes in file system */

   long    f_ffree;    /* free file nodes in fs */

   fsid_t  f_fsid;     /* file system id */

   long    f_namelen;  /* maximum length of filenames */

};



File system 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

   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 file system 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 file system.
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 file system 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 kernel has system calls statfs(), fstatfs(), statfs64(), and fstatfs64() to support this library call.

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 OSes 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 OSes the fsid can be used as second parameter to the sysfs() system call.

SEE ALSO

stat(2), statvfs(2), path_resolution(7)