2:fstatfs

From Linux Man Pages

      statfs, fstatfs - get file system statistics
      

Contents 1 SYNOPSIS 2 DESCRIPTION 3 RETURN VALUE 4 ERRORS 5 CONFORMING TO 6 NOTES 7 The f_fsid field 7.1 RELATED 7.2 CATEGORY

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_resolu-
             tion(2).)
 
      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

      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() and fstatvfs() 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.

RELATED

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

CATEGORY