statvfs(3)

NAME
statvfs, fstatvfs - get filesystem statistics

LIBRARY
Standard C library (libc, -lc)

SYNOPSIS
#include <sys/statvfs.h>

int statvfs(const char *restrict path, struct statvfs *restrict buf);
int fstatvfs(int fd, struct statvfs *buf);

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

    struct statvfs {
        unsigned long  f_bsize;    /* Filesystem block size */
        unsigned long  f_frsize;   /* Fragment size */
        fsblkcnt_t     f_blocks;   /* Size of fs in f_frsize units */
        fsblkcnt_t     f_bfree;    /* Number of free blocks */
        fsblkcnt_t     f_bavail;   /* Number of free blocks for
                                      unprivileged users */
        fsfilcnt_t     f_files;    /* Number of inodes */
        fsfilcnt_t     f_ffree;    /* Number of free inodes */
        fsfilcnt_t     f_favail;   /* Number of free inodes for
                                      unprivileged users */
        unsigned long  f_fsid;     /* Filesystem ID */
        unsigned long  f_flag;     /* Mount flags */
        unsigned long  f_namemax;  /* Maximum filename length */
    };

Here the types fsblkcnt_t and fsfilcnt_t are defined in <sys/types.h>. Both used to be unsigned long.

The field f_flag is a bit mask indicating various options that were employed when mounting this filesystem. It contains zero or more of the following flags:

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.

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)).

It is unspecified whether all members of the returned struct have meaningful values on all filesystems.

fstatvfs() 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 to indicate the error.

ERRORS

EACCES
    (statvfs()) Search permission is denied for a component of the path prefix of path. (See also path_resolution(7).)

EBADF
    (fstatvfs()) 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; see signal(7).

EIO An I/O error occurred while reading from the filesystem.

ELOOP
    (statvfs()) Too many symbolic links were encountered in translating path.

ENAMETOOLONG
    (statvfs()) path is too long.

ENOENT
    (statvfs()) The file referred to by path does not exist.

ENOMEM
    Insufficient kernel memory was available.

ENOSYS
    The filesystem does not support this call.

ENOTDIR
    (statvfs()) 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.

ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7).
Interface | Attribute | Value
 | Thread safety | MT-Safe

VERSIONS
Only the ST_NOSUID and ST_RDONLY flags of the f_flag field are specified in POSIX.1. To obtain definitions of the remaining flags, one must define _GNU_SOURCE.

NOTES
The Linux kernel has system calls statfs(2) and fstatfs(2) to support this library call.

The glibc implementations of

    pathconf(path, _PC_REC_XFER_ALIGN);
    pathconf(path, _PC_ALLOC_SIZE_MIN);
    pathconf(path, _PC_REC_MIN_XFER_SIZE);

respectively use the f_frsize, f_frsize, and f_bsize fields returned by a call to statvfs() with the argument path.

Under Linux, f_favail is always the same as f_ffree, and there's no way for a filesystem to report otherwise. This is not an issue, since no filesystems with an inode root reservation exist.

STANDARDS
POSIX.1-2008.

HISTORY
POSIX.1-2001.

Before glibc 2.13, statvfs() populated the bits of the f_flag field by scanning the mount options shown in /proc/mounts. However, starting with Linux 2.6.36, the underlying statfs(2) system call provides the necessary information via the f_flags field, and since glibc 2.13, the statvfs() function will use information from that field rather than scanning /proc/mounts.

SEE ALSO
statfs(2)