The fstatfs64() function returns information about a mounted file system. The file system is identified by fd, a file descriptor of an open file within the mounted filesystem. The results are placed in the structure pointed to by buf.
Fields that are undefined for a particular file system shall be set to 0.
fstatfs64() is the 64-bit version of fstatfs().
Note: Application developers should use the fstatvfs64() function to obtain general file system information. Applications should only use the fstatfs64() function if they must determine the file system type, which need not be provided by fstatvfs64().
On success, the fstatfs64() function shall
return 0 and set the fields of the
structure idenfitied by buf accordingly.
On error, the fstatfs64() function shall
return -1 and set