.\" Copyright (C) 2003 Andries Brouwer (aeb@cwi.nl)
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.\" Modified 2003-08-17 by Walter Harms
.\" Modified 2004-06-23 by Michael Kerrisk <mtk.manpages@gmail.com>
.\"
.TH STATFS 2 2010-11-21 "Linux" "Linux Programmer's Manual"
.SH NAME
statfs, fstatfs \- get file system statistics
.SH SYNOPSIS
.BR "#include <sys/vfs.h>    " "/* or <sys/statfs.h> */"
.sp
.BI "int statfs(const char *" path ", struct statfs *" buf );
.br
.BI "int fstatfs(int " fd ", struct statfs *" buf );
.SH DESCRIPTION
The function
.BR statfs ()
returns information about a mounted file system.
.I path
is the pathname of any file within the mounted file system.
.I buf
is a pointer to a
.I statfs
structure defined approximately as follows:

.in +4n
.nf
#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 file system (see below) */
    __SWORD_TYPE f_bsize;   /* optimal transfer block size */
    fsblkcnt_t   f_blocks;  /* total data blocks in file system */
    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 file system */
    fsfilcnt_t   f_ffree;   /* free file nodes in fs */
    fsid_t       f_fsid;    /* file system id */
    __SWORD_TYPE f_namelen; /* maximum length of filenames */
    __SWORD_TYPE f_frsize;  /* fragment size (since Linux 2.6) */
    __SWORD_TYPE f_spare[5];
};

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
   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
.fi
.in
.PP
Nobody knows what
.I f_fsid
is supposed to contain (but see below).
.PP
Fields that are undefined for a particular file system are set to 0.
.BR fstatfs ()
returns the same information about an open file referenced by descriptor
.IR fd .
.SH "RETURN VALUE"
On success, zero is returned.
On error, \-1 is returned, and
.I errno
is set appropriately.
.SH ERRORS
.TP
.B EACCES
.RB ( statfs ())
Search permission is denied for a component of the path prefix of
.IR path .
(See also
.BR path_resolution (7).)
.TP
.B EBADF
.RB ( fstatfs ())
.I fd
is not a valid open file descriptor.
.TP
.B EFAULT
.I buf
or
.I path
points to an invalid address.
.TP
.B EINTR
This call was interrupted by a signal.
.TP
.B EIO
An I/O error occurred while reading from the file system.
.TP
.B ELOOP
.RB ( statfs ())
Too many symbolic links were encountered in translating
.IR path .
.TP
.B ENAMETOOLONG
.RB ( statfs ())
.I path
is too long.
.TP
.B ENOENT
.RB ( statfs ())
The file referred to by
.I path
does not exist.
.TP
.B ENOMEM
Insufficient kernel memory was available.
.TP
.B ENOSYS
The file system does not support this call.
.TP
.B ENOTDIR
.RB ( statfs ())
A component of the path prefix of
.I path
is not a directory.
.TP
.B EOVERFLOW
Some values were too large to be represented in the returned struct.
.SH "CONFORMING TO"
Linux-specific.
The Linux
.BR statfs ()
was inspired by the 4.4BSD one
(but they do not use the same structure).
.SH NOTES
The original Linux
.BR statfs ()
and
.BR fstatfs ()
system calls were not designed with extremely large file sizes in mind.
Subsequently, Linux 2.6
added new
.BR statfs64 ()
and
.BR fstatfs64 ()
system calls that employ a new structure,
.IR statfs64 .
The new structure contains the same fields as the original
.I statfs
structure, but the sizes of various fields are increased,
to accommodate large file sizes.
The glibc
.BR statfs ()
and
.BR fstatfs ()
wrapper functions transparently deal with the kernel differences.

Some systems only have \fI<sys/vfs.h>\fP, other systems also have
\fI<sys/statfs.h>\fP, where the former includes the latter.
So it seems
including the former is the best choice.

LSB has deprecated the library calls
.BR statfs ()
and
.BR fstatfs ()
and tells us to use
.BR statvfs (2)
and
.BR fstatvfs (2)
instead.
.SS The f_fsid field
Solaris, Irix and POSIX have a system call
.BR statvfs (2)
that returns a
.I "struct statvfs"
(defined in
.IR <sys/statvfs.h> )
containing an
.I "unsigned long"
.IR f_fsid .
Linux, SunOS, HP-UX, 4.4BSD have a system call
.BR statfs ()
that returns a
.I "struct statfs"
(defined in
.IR <sys/vfs.h> )
containing a
.I fsid_t
.IR f_fsid ,
where
.I fsid_t
is defined as
.IR "struct { int val[2]; }" .
The same holds for FreeBSD, except that it uses the include file
.IR <sys/mount.h> .

The general idea is that
.I f_fsid
contains some random stuff such that the pair
.RI ( f_fsid , ino )
uniquely determines a file.
Some operating systems use (a variation on) the device number, or the device number
combined with the file-system type.
Several OSes restrict giving out the
.I f_fsid
field to the superuser only (and zero it for unprivileged users),
because this field is used in the filehandle of the file system
when NFS-exported, and giving it out is a security concern.
.LP
Under some operating systems the
.I fsid
can be used as second argument to the
.BR sysfs (2)
system call.
.SH "SEE ALSO"
.BR stat (2),
.BR statvfs (2),
.BR path_resolution (7)