sysfs returns information about the file system types currently present
in the kernel. The specific form of the sysfs call and the information
returned depends on the option in effect:
Translate the file-system identifier string fsname
into a file-system type index.
Translate the file-system type index fs_index into a
NUL-terminated file-system identifier string. This string will be written
to the buffer pointed to by buf. Make sure that buf has
enough space to accept the string.
Return the total number of file system types currently
present in the kernel.
The numbering of the file-system type indexes begins with zero.
On success, sysfs returns the file-system index for option 1, zero
for option 2, and the number of currently configured file systems for
option 3. On error, -1 is returned, and errno is set