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fstatvfs(), fstatvfs64()

Get filesystem information, given a file descriptor

Synopsis:

#include <sys/statvfs.h>

int fstatvfs( int fildes, 
              struct statvfs *buf );

int fstatvfs64( int fildes,
                struct statvfs64 *buf );

Arguments:

fildes: The descriptor for a file that resides on the filesystem that you want to get information about.
buf: A pointer to a buffer where the function can store information about the filesystem; see below.

Library:

libc

Use the -l c option to qcc to link against this library. This library is usually included automatically.

The fstatvfs() function returns a "generic superblock" describing a filesystem; you can use it to get information about mounted filesystems. The fstatvfs64() function is a 64-bit version of fstatvfs().

The fildes argument is an open file descriptor, obtained from a successful call to open(), creat(), dup(), fcntl(), or pipe(), for a file that resides on that filesystem. The filesystem type is known to the operating system. Read, write, or execute permission for the named file isn't required.

The buf argument is a pointer to a statvfs or statvfs64 structure that's filled by the function. It contains at least:

unsigned long f_bsize

The preferred filesystem blocksize.

unsigned long f_frsize

The fundamental filesystem blocksize (if supported)

fsblkcnt_t f_blocks

The total number of blocks on the filesystem, in units of f_frsize.

fsblkcnt_t f_bfree

The total number of free blocks.

fsblkcnt_t f_bavail

The number of free blocks available to a nonsuperuser.

fsfilcnt_t f_files

The total number of file nodes (inodes).

fsfilcnt_t f_ffree

The total number of free file nodes.

fsfilcnt_t f_favail

The number of inodes available to a nonsuperuser.

unsigned long f_fsid

The filesystem ID (dev for now).

char f_basetype[16]

The type of the target filesystem, as a null-terminated string.

unsigned long f_flag

A bitmask of flags; the function can set these flags:

ST_RDONLY -- read-only filesystem.
ST_NOSUID -- the filesystem doesn't support setuid/setgid semantics.

unsigned long f_namemax

The maximum filename length.

Returns:

0: Success.
-1: An error occurred (errno is set).

Errors:

EBADF: The fildes argument isn't an open file descriptor.
EFAULT: The buf argument points to an illegal address.
EINTR: A signal was caught during execution.
EIO: An I/O error occurred while reading the filesystem.
EOVERFLOW: One of the values to be returned can't be represented correctly in the structure pointed to by buf.

Classification:

fstatvfs() is POSIX 1003.1 XSI; fstatvfs64() is Large-file support

Safety:
Cancellation point	No
Interrupt handler	No
Signal handler	Yes
Thread	Yes

Caveats:

The values returned for f_files, f_ffree, and f_favail might not be valid for NFS-mounted filesystems.