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       statfs, fstatfs - get file system statistics


       #include <sys/vfs.h>    /* or <sys/statfs.h> */

       int statfs(const char *path, struct statfs *buf);
       int fstatfs(int fd, struct statfs *buf);


       The  function statfs() returns information about a mounted file system.
       path is the pathname of any file within the mounted file  system.   buf
       is a pointer to a statfs structure defined approximately as follows:

           struct statfs {
              long    f_type;     /* type of file system (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 unprivileged user */
              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.


       On  success,  zero is returned.  On error, -1 is returned, and errno is
       set appropriately.


       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.

              (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.

              (statfs()) A component of the path  prefix  of  path  is  not  a

              Some  values  were  too  large to be represented in the returned


       Linux-specific.  The Linux statfs() was inspired by the 4.4BSD one (but
       they do not use the same structure).


       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
       file-system 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 file system  when  NFS-exported,
       and giving it out is a security concern.

       Under  some OSes the fsid can be used as second argument to the sysfs()
       system call.


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


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