.TH FVERSION 2
.SH NAME
fversion \- initialize 9P connection and negotiate version
.SH SYNOPSIS
.nf
.PP
.ft L
#include <u.h>
#include <libc.h>
.PP
.ft P
.B
int   fversion(int fd, int bufsize, char *version, int nversion)
.SH DESCRIPTION
.PP
.I Fversion
is used to initialize the 9P connection represented by
.I fd
and to negotiate the version of the protocol to be used.
.PP
The
.I bufsize
determines the size of the I/O buffer used to stage 9P requests to the server,
subject to the constraints of the server itself.
The
.I version
is a text string that represents the highest version level the protocol will support.
The
.I version
will be overwritten with the negotiated, possibly lower, version of the protocol.
The return value of
.I fversion
is the length of the returned version string; the value of
.I nversion
is therefore not the length of the version string presented to the system call,
but the total length of the buffer to accept the final result, in the manner of a read system call.
.PP
Default values of zero for
.I bufsize
and the empty string for
.I version
will negotiate sensible defaults for the connection.
If
.I version
is the empty string,
.I nversion
must still be large enough to receive the returned version string.
.PP
The interpretation of the version strings is defined in
.IR version (5).
.PP
It is rare to use
.IR fversion
directly; usually the default negotiation performed
by the kernel during
.B mount
(see
.IR bind (2))
or even more commonly
.B amount
(see
.IR auth (2))
is sufficient.
.SH SOURCE
.B /sys/src/libc/9syscall
.SH SEE ALSO
.IR intro (5),
.IR version (5),
.IR fauth (2).
.SH DIAGNOSTICS
Sets
.IR errstr .