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       statfs, fstatfs - get filesystem 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  filesystem.  path is the
       pathname of any file within the  mounted  filesystem.   buf  is  a  pointer  to  a  statfs
       structure defined approximately as follows:

           #if __WORDSIZE == 32          /* System word size */
           # define __SWORD_TYPE           int
           #else /* __WORDSIZE == 64 */
           # define __SWORD_TYPE         long int

           struct statfs {
               __SWORD_TYPE f_type;    /* type of filesystem (see below) */
               __SWORD_TYPE f_bsize;   /* optimal transfer block size */
               fsblkcnt_t   f_blocks;  /* total data blocks in filesystem */
               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 filesystem */
               fsfilcnt_t   f_ffree;   /* free file nodes in fs */
               fsid_t       f_fsid;    /* filesystem id */
               __SWORD_TYPE f_namelen; /* maximum length of filenames */
               __SWORD_TYPE f_frsize;  /* fragment size (since Linux 2.6) */
               __SWORD_TYPE f_spare[5];

           Filesystem 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

       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.


       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 filesystem.

       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 filesystem does not support this call.

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

              Some values were too large to be represented in the returned struct.


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


       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  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 operating  systems  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 operating systems the fsid can be used  as  second  argument  to  the  sysfs(2)
       system call.


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


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