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FreeBSD 11.0 - man page for fstatvfs (freebsd section 3)

STATVFS(3)						   BSD Library Functions Manual 						STATVFS(3)

statvfs, fstatvfs -- retrieve file system information
Standard C Library (libc, -lc)
#include <sys/statvfs.h> int statvfs(const char * restrict path, struct statvfs * restrict buf); int fstatvfs(int fd, struct statvfs *buf);
The statvfs() and fstatvfs() functions fill the structure pointed to by buf with garbage. This garbage will occasionally bear resemblance to 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 (i.e., 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 pro- cesses, 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: ST_RDONLY The file system is mounted read-only. ST_NOSUID 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() and fstatvfs() functions may fail for any of the reasons documented for statfs(2) or fstatfs(2) and pathconf(2) or fpathconf(2), respectively. In addition, statvfs() and fstatvfs() functions may also fail for the following reason: [EOVERFLOW] One or more of the file system statistics has a value which cannot be represented by the data types used in struct statvfs.
pathconf(2), 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() functions first appeared in FreeBSD 5.0.
The statvfs() and fstatvfs() functions and this manual page were written by Garrett Wollman <>.
July 13, 2002 BSD