#include <u.h>
#include <libc.h>

 int fversion(int fd, int bufsize, char *version, int nversion)
 DESCRIPTION

 Fversion is used to initialize the 9P connection represented by
 fd and to negotiate the version of the protocol to be used.

The
 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
 version is a text string that represents the highest version level the protocol will support.
The
 version will be overwritten with the negotiated, possibly lower, version of the protocol.
The return value of
 fversion is the length of the returned version string; the value of
 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.

Default values of zero for
 bufsize and the empty string for
 version will negotiate sensible defaults for the connection.
If
 version is the empty string,
 nversion must still be large enough to receive the returned version string.

The interpretation of the version strings is defined in
 version (5). 

It is rare to use
 fversion directly; usually the default negotiation performed
by the kernel during
 mount (see
 bind (2)) or even more commonly
 amount (see
 auth (2)) is sufficient.
 SOURCE
 /sys/src/libc/9syscall 
 SEE ALSO
 intro (5),  version (5),  fauth (2). 
 DIAGNOSTICS
Sets
 errstr .