fstatvfs (3)

Leading comments

Copyright (C) 2003 Andries Brouwer (aeb@cwi.nl)

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Since the L...

(The comments found at the beginning of the groff file "man3/fstatvfs.3".)

NAME

statvfs, fstatvfs - get filesystem statistics

SYNOPSIS

#include <sys/statvfs.h>

int statvfs(const char *path, struct statvfs *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 appropriately.

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.

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
statvfs(), fstatvfs()	Thread safety	MT-Safe

CONFORMING TO

POSIX.1-2001, POSIX.1-2008.
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.
In glibc versions before 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 version 2.13, the statvfs() function will use information from that field rather than scanning /proc/mounts.
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.

SEE ALSO

statfs(2)

COLOPHON

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