STATFS(2)                 (2020-12-21)                  STATFS(2)

     NAME
          statfs, fstatfs - get filesystem 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 statfs() system call 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:

              struct statfs {
                  __fsword_t f_type;    /* Type of filesystem (see below) */
                  __fsword_t f_bsize;   /* Optimal transfer block size */
                  fsblkcnt_t f_blocks;  /* Total data blocks in filesystem */
                  fsblkcnt_t f_bfree;   /* Free blocks in filesystem */
                  fsblkcnt_t f_bavail;  /* Free blocks available to
                                           unprivileged user */
                  fsfilcnt_t f_files;   /* Total inodes in filesystem */
                  fsfilcnt_t f_ffree;   /* Free inodes in filesystem */
                  fsid_t     f_fsid;    /* Filesystem ID */
                  __fsword_t f_namelen; /* Maximum length of filenames */
                  __fsword_t f_frsize;  /* Fragment size (since Linux 2.6) */
                  __fsword_t f_flags;   /* Mount flags of filesystem
                                           (since Linux 2.6.36) */
                  __fsword_t f_spare[xxx];
                                  /* Padding bytes reserved for future use */
              };

          The following filesystem types may appear in f_type:

              ADFS_SUPER_MAGIC      0xadf5
              AFFS_SUPER_MAGIC      0xadff
              AFS_SUPER_MAGIC       0x5346414f
              ANON_INODE_FS_MAGIC   0x09041934 /* Anonymous inode FS (for
                                                  pseudofiles that have no name;
                                                  e.g., epoll, signalfd, bpf) */
              AUTOFS_SUPER_MAGIC    0x0187
              BDEVFS_MAGIC          0x62646576
              BEFS_SUPER_MAGIC      0x42465331
              BFS_MAGIC             0x1badface
              BINFMTFS_MAGIC        0x42494e4d
              BPF_FS_MAGIC          0xcafe4a11
              BTRFS_SUPER_MAGIC     0x9123683e
              BTRFS_TEST_MAGIC      0x73727279
              CGROUP_SUPER_MAGIC    0x27e0eb   /* Cgroup pseudo FS */

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              CGROUP2_SUPER_MAGIC   0x63677270 /* Cgroup v2 pseudo FS */
              CIFS_MAGIC_NUMBER     0xff534d42
              CODA_SUPER_MAGIC      0x73757245
              COH_SUPER_MAGIC       0x012ff7b7
              CRAMFS_MAGIC          0x28cd3d45
              DEBUGFS_MAGIC         0x64626720
              DEVFS_SUPER_MAGIC     0x1373     /* Linux 2.6.17 and earlier */
              DEVPTS_SUPER_MAGIC    0x1cd1
              ECRYPTFS_SUPER_MAGIC  0xf15f
              EFIVARFS_MAGIC        0xde5e81e4
              EFS_SUPER_MAGIC       0x00414a53
              EXT_SUPER_MAGIC       0x137d     /* Linux 2.0 and earlier */
              EXT2_OLD_SUPER_MAGIC  0xef51
              EXT2_SUPER_MAGIC      0xef53
              EXT3_SUPER_MAGIC      0xef53
              EXT4_SUPER_MAGIC      0xef53
              F2FS_SUPER_MAGIC      0xf2f52010
              FUSE_SUPER_MAGIC      0x65735546
              FUTEXFS_SUPER_MAGIC   0xbad1dea  /* Unused */
              HFS_SUPER_MAGIC       0x4244
              HOSTFS_SUPER_MAGIC    0x00c0ffee
              HPFS_SUPER_MAGIC      0xf995e849
              HUGETLBFS_MAGIC       0x958458f6
              ISOFS_SUPER_MAGIC     0x9660
              JFFS2_SUPER_MAGIC     0x72b6
              JFS_SUPER_MAGIC       0x3153464a
              MINIX_SUPER_MAGIC     0x137f     /* original minix FS */
              MINIX_SUPER_MAGIC2    0x138f     /* 30 char minix FS */
              MINIX2_SUPER_MAGIC    0x2468     /* minix V2 FS */
              MINIX2_SUPER_MAGIC2   0x2478     /* minix V2 FS, 30 char names */
              MINIX3_SUPER_MAGIC    0x4d5a     /* minix V3 FS, 60 char names */
              MQUEUE_MAGIC          0x19800202 /* POSIX message queue FS */
              MSDOS_SUPER_MAGIC     0x4d44
              MTD_INODE_FS_MAGIC    0x11307854
              NCP_SUPER_MAGIC       0x564c
              NFS_SUPER_MAGIC       0x6969
              NILFS_SUPER_MAGIC     0x3434
              NSFS_MAGIC            0x6e736673
              NTFS_SB_MAGIC         0x5346544e
              OCFS2_SUPER_MAGIC     0x7461636f
              OPENPROM_SUPER_MAGIC  0x9fa1
              OVERLAYFS_SUPER_MAGIC 0x794c7630
              PIPEFS_MAGIC          0x50495045
              PROC_SUPER_MAGIC      0x9fa0     /* /proc FS */
              PSTOREFS_MAGIC        0x6165676c
              QNX4_SUPER_MAGIC      0x002f
              QNX6_SUPER_MAGIC      0x68191122
              RAMFS_MAGIC           0x858458f6
              REISERFS_SUPER_MAGIC  0x52654973
              ROMFS_MAGIC           0x7275
              SECURITYFS_MAGIC      0x73636673
              SELINUX_MAGIC         0xf97cff8c

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              SMACK_MAGIC           0x43415d53
              SMB_SUPER_MAGIC       0x517b
              SMB2_MAGIC_NUMBER     0xfe534d42
              SOCKFS_MAGIC          0x534f434b
              SQUASHFS_MAGIC        0x73717368
              SYSFS_MAGIC           0x62656572
              SYSV2_SUPER_MAGIC     0x012ff7b6
              SYSV4_SUPER_MAGIC     0x012ff7b5
              TMPFS_MAGIC           0x01021994
              TRACEFS_MAGIC         0x74726163
              UDF_SUPER_MAGIC       0x15013346
              UFS_MAGIC             0x00011954
              USBDEVICE_SUPER_MAGIC 0x9fa2
              V9FS_MAGIC            0x01021997
              VXFS_SUPER_MAGIC      0xa501fcf5
              XENFS_SUPER_MAGIC     0xabba1974
              XENIX_SUPER_MAGIC     0x012ff7b4
              XFS_SUPER_MAGIC       0x58465342
              _XIAFS_SUPER_MAGIC    0x012fd16d /* Linux 2.0 and earlier */

          Most of these MAGIC constants are defined in
          /usr/include/linux/magic.h, and some are hardcoded in kernel
          sources.

          The f_flags field is a bit mask indicating mount options for
          the filesystem.  It contains zero or more of the following
          bits:

          ST_MANDLOCK
               Mandatory locking is permitted on the filesystem (see
               fcntl(2)).

          ST_NOATIME
               Do not update access times; see mount(2).

          ST_NODEV
               Disallow access to device special files on this
               filesystem.

          ST_NODIRATIME
               Do not update directory access times; see mount(2).

          ST_NOEXEC
               Execution of programs is disallowed on this filesystem.

          ST_NOSUID
               The set-user-ID and set-group-ID bits are ignored by
               exec(3) for executable files on this filesystem

          ST_RDONLY
               This filesystem is mounted read-only.

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          ST_RELATIME
               Update atime relative to mtime/ctime; see mount(2).

          ST_SYNCHRONOUS
               Writes are synched to the filesystem immediately (see
               the description of O_SYNC in open(2)).

          ST_NOSYMFOLLOW (since Linux 5.10)
               Symbolic links are not followed when resolving paths;
               see mount(2).

          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.

     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
               The call was interrupted by a signal; see signal(7).

          EIO  An I/O error occurred while reading from the filesys-
               tem.

          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.

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          ENOMEM
               Insufficient kernel memory was available.

          ENOSYS
               The filesystem 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 __fsword_t type used for various fields in the statfs
          structure definition is a glibc internal type, not intended
          for public use.  This leaves the programmer in a bit of a
          conundrum when trying to copy or compare these fields to
          local variables in a program.  Using unsigned int for such
          variables suffices on most systems.

          The original Linux statfs() and fstatfs() system calls were
          not designed with extremely large file sizes in mind.  Sub-
          sequently, 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 ker-
          nel differences.

          Some systems have only <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>) con-
          taining 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>.

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          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 num-
          ber, or the device number combined with the filesystem type.
          Several operating systems 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 secu-
          rity concern.

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

     BUGS
          From Linux 2.6.38 up to and including Linux 3.1, fstatfs()
          failed with the error ENOSYS for file descriptors created by
          pipe(2).

     SEE ALSO
          stat(2), statvfs(3), path_resolution(7)

     COLOPHON
          This page is part of release 5.10 of the Linux man-pages
          project.  A description of the project, information about
          reporting bugs, and the latest version of this page, can be
          found at https://www.kernel.org/doc/man-pages/.

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