sysfs man page
sysfs — get filesystem type information
int sysfs(int option, const char *fsname);
int sysfs(int option, unsigned int fs_index, char *buf);
int sysfs(int option);
Note: if you are looking for information about the sysfs filesystem that is normally mounted at /sys, see sysfs(5).
The (obsolete) sysfs() system call returns information about the filesystem 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 filesystem identifier string fsname into a filesystem type index.
Translate the filesystem type index fs_index into a null-terminated filesystem 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 filesystem types currently present in the kernel.
The numbering of the filesystem type indexes begins with zero.
On success, sysfs() returns the filesystem index for option 1, zero for option 2, and the number of currently configured filesystems for option 3. On error, -1 is returned, and errno is set appropriately.
Either fsname or buf is outside your accessible address space.
fsname is not a valid filesystem type identifier; fs_index is out-of-bounds; option is invalid.
This System-V derived system call is obsolete; don't use it. On systems with /proc, the same information can be obtained via /proc/filesystems; use that interface instead.
There is no libc or glibc support. There is no way to guess how large buf should be.
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