man2/sysfs.2

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.\" Created   Wed Aug  9 1995     Thomas K. Dyas <tdyas@eden.rutgers.edu>
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.TH SYSFS 2 2017-09-15 "Linux" "Linux Programmer's Manual"
.SH NAME
sysfs \- get filesystem type information
.SH SYNOPSIS
.BI "int sysfs(int " option ", const char *" fsname );
.PP
.BI "int sysfs(int " option ", unsigned int " fs_index ", char *" buf );
.PP
.BI "int sysfs(int " option );
.SH DESCRIPTION
.BR "Note" :
if you are looking for information about the
.B sysfs
filesystem that is normally mounted at
.IR /sys ,
see
.BR sysfs (5).
.PP
The (obsolete)
.BR sysfs ()
system call returns information about the filesystem types
currently present in the kernel.
The specific form of the
.BR sysfs ()
call and the information returned depends on the
.I option
in effect:
.TP 3
.B 1
Translate the filesystem identifier string
.I fsname
into a filesystem type index.
.TP
.B 2
Translate the filesystem type index
.I fs_index
into a null-terminated filesystem identifier string.
This string will
be written to the buffer pointed to by
.IR buf .
Make sure that
.I buf
has enough space to accept the string.
.TP
.B 3
Return the total number of filesystem types currently present in the
kernel.
.PP
The numbering of the filesystem type indexes begins with zero.
.SH RETURN VALUE
On success,
.BR sysfs ()
returns the filesystem index for option
.BR 1 ,
zero for option
.BR 2 ,
and the number of currently configured filesystems for option
.BR 3 .
On error, \-1 is returned, and
.I errno
is set appropriately.
.SH ERRORS
.TP
.B EFAULT
.RI "Either " fsname " or " buf
is outside your accessible address space.
.TP
.B EINVAL
.I fsname
is not a valid filesystem type identifier;
.I fs_index
is out-of-bounds;
.I option
is invalid.
.SH CONFORMING TO
SVr4.
.SH NOTES
This System-V derived system call is obsolete; don't use it.
On systems with
.IR /proc ,
the same information can be obtained via
.IR /proc/filesystems ;
use that interface instead.
.SH BUGS
There is no libc or glibc support.
There is no way to guess how large \fIbuf\fP should be.