documents: fstatvfs · statvfs
STATVFS(3) Library Functions Manual STATVFS(3)

fstatvfs, statvfs — retrieve file system information

Standard C Library (libc, -lc)

#include <sys/statvfs.h>

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

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

The () and () functions attempt to fill the structure pointed to by buf with file system statistics, but portable applications must not depend on this. Applications must pass a pathname or file descriptor which refers to a file on the file system in which they are interested.

The statvfs structure contains the following members:

f_namemax
The maximum length in bytes of a file name on this file system. Applications should use pathconf(2) instead.
f_fsid
Not meaningful in this implementation.
f_frsize
The size in bytes of the minimum unit of allocation on this file system. (This corresponds to the f_bsize member of struct statfs.)
f_bsize
The preferred length of I/O requests for files on this file system. (Corresponds to the f_iosize member of struct statfs.)
f_flag
Flags describing mount options for this file system; see below.

In addition, there are three members of type fsfilcnt_t, which represent counts of file serial numbers (, inodes); these are named f_files, f_favail, and f_ffree, and represent the number of file serial numbers which exist in total, are available to unprivileged processes, and are available to privileged processes, respectively. Likewise, the members f_blocks, f_bavail, and f_bfree (all of type fsblkcnt_t) represent the respective allocation-block counts.

There are two flags defined for the f_flag member:

The file system is mounted read-only.
The semantics of the S_ISUID and S_ISGID file mode bits are not supported by, or are disabled on, this file system.

The statvfs() and fstatvfs() functions are implemented as wrappers around the statfs() and fstatfs() functions, respectively. Not all the information provided by those functions is made available through this interface.

The statvfs() and fstatvfs() functions return the value 0 if successful; otherwise the value -1 is returned and the global variable errno is set to indicate the error.

The statvfs() function fails if one or more of the following are true:

[]
Search permission is denied for a component of the path prefix of path.
[]
Buf or path points to an invalid address.
[]
An I/O error occurred while reading from or writing to the file system.
[]
Too many symbolic links were encountered in translating path.
[]
The length of a component of path exceeds {NAME_MAX} characters, or the length of path exceeds {PATH_MAX} characters.
[]
The file referred to by path does not exist.
[]
A component of the path prefix of Path is not a directory.

The fstatvfs() functions fails if one or more of the following are true:

[]
fildes is not a valid open file descriptor.
[]
Buf points to an invalid address.
[]
An I/O error occurred while reading from or writing to the file system.

statfs(2)

The statvfs() and fstatvfs() functions conform to IEEE Std 1003.1-2001 (“POSIX.1”). As standardized, portable applications cannot depend on these functions returning any valid information at all. This implementation attempts to provide as much useful information as is provided by the underlying file system, subject to the limitations of the specified data types.

The statvfs() and fstatvfs() manual page was originally written by Garrett Wollman ⟨wollman@FreeBSD.org⟩.

July 13, 2002 macOS 26.4