code: 9ferno

ref: b502a62da2ec6058923db94f87ecc2d29db2fa77
dir: /man/2/sys-fversion/

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.TH SYS-FVERSION 2
.SH NAME
fversion \- initialize 9P connection and negotiate version
.SH SYNOPSIS
.EX
include "sys.m";
sys := load Sys Sys->PATH;

fversion: fn(fd: ref FD, bufsize: int, version: string): (int, string);
.EE
.SH DESCRIPTION
.B Fversion
initialises the 9P connection represented by
.I fd
and negotiates the maximum message size and 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.
.PP
.B Fversion
returns a tuple
.RI ( n , useversion )
where
.I n
is -1 if the request was rejected, and otherwise
.I n
is
.I bufsize
and
.I useversion
is a string representing the negotiated, possibly lower, version of the protocol.
.PP
Default values of zero for
.I bufsize
and the empty string for
.I version
will negotiate sensible defaults for the connection.
.PP
The interpretation of the version strings is defined in
.IR version (5).
.PP
It is rare to use
.BR fversion
directly; usually the default negotiation performed
by the kernel during
.B mount
(see
.IR sys-bind (2))
is sufficient.
.SH SEE ALSO
.IR sys-fauth (2),
.IR intro (5),
.IR version (5).
.SH DIAGNOSTICS
.B Fversion
returns a value of -1 for
.I n
on error, including failure to negotiate acceptable values,
and sets the system error string.
.SH BUGS
The returned value of
.I n
when no error occurs should be the negotiated message size
but is currently the original
.I bufsize
parameter.