.TH SYS-FAUTH 2.SH NAMEfauth \- set up authentication on a file descriptor to a file server.SH SYNOPSIS.EXinclude "sys.m";sys := load Sys Sys->PATH; fauth:  fn(fd: ref FD, aname: string): ref FD;.EE.SH DESCRIPTION.B Fauthprovides a means for the current user to authenticate to accessresources available through the Styx connection represented by.IR fd .The return value is a file descriptor, conventionally called.IR afd ,that is subsequently used to execute the authentication protocolfor the server.After successful authentication,.I afdmay be passed as the second argument to a subsequent.B mountcall (see.IR sys-bind (2)),with the same.IR aname,as a ticket-of-entry for the user..PPIf.B fauthreturns nil, the error case, that means the file server does not requireauthentication for the connection, and.I afdshould be nilin the call to.BR mount..ig.PPIt is rare to use.IR fauthdirectly; more commonly.I amount(see.IR auth (2))is used....SH SEE ALSO.IR attach (5),.IR security-auth (2).ig(particularly.BR amount ),.IR authsrv (6)...SH DIAGNOSTICSThe system error string is set on error,including the server not requiring authentication,and.B fauthreturns nil.