t_look.3xti

来自「<B>Digital的Unix操作系统VAX 4.2源码</B>」· 3XTI 代码 · 共 84 行

.TH t_look 3xti
.SH Name
t_look \- look at the current event on a transport endpoint
.SH Syntax
.B #include <xti.h>
.br
.sp 1
.B int t_look(\fIfd\fB)
.br
.B int \fIfd\fB;
.SH Arguments
.IP \fIfd\fR 10
Identifies the transport endpoint where the current event is returned.
.SH Description
This function returns the current event on the transport endpoint
specified by \fIfd\fR. This function enables a transport provider to
notify a transport user of an asynchronous event when the user is
issuing functions in synchronous mode. Certain events require immediate
notification of the user and are indicated by a specific error,
[TLOOK], on the current or next function to be executed.
.NXR "t_look system call" 
.NXR "transport endpoint" "returning current event"
.NXR "transport endpoint" "polling for asynchronous events"
.PP
This function also enables a transport user to poll a transport endpoint
periodically for asynchronous events.
.PP
.TS
tab(@);
lfHB lfHB lfHB
lfR  lfR  lfR .
_
.sp 6p
Parameters@Before Call@After Call
.sp 6p
_
.sp 6p
fd@x@/
.sp 6p
_
.TE
.PP
.sp 12p
.SH Return Values
Upon successful completion, 
.PN t_look() 
returns a value that indicates
which of the allowable events has occurred or returns zero if no event
exists. One of the following events is returned:
.RS 10
.IP T_LISTEN 18 
Connection indication received
.IP T_CONNECT 18
Connect confirmation received
.IP T_DATA 18
Normal data received
.IP T_EXDATA 18
Expedited data received
.IP T_DISCONNECT 18
Disconnect received
.IP T_UDERR 18
Datagram error indication
.IP T_ORDREL 18
Orderly release indication
.IP T_GODATA 18
Flow control restrictions on normal data flow have been lifted. Normal data can be sent again.
.IP T_GOEXDATA 18
Flow control restrictions on expedited data flow have been lifted. Expedited data can be sent again.
.RE
.PP
On failure, \-1 is returned, and \fBt_errno\fR is set to indicate the error.
.SH Diagnostics
On failure, \fBt_errno \fR is set to one of the following:
.TP 20
[TBADF]
The specified file descriptor does not refer to a transport endpoint.
.TP 20
[TSYSERR]
A system error has occurred during execution of this function.
.SH See Also
t_open(3xti),
t_snd(3xti), 
t_sndudata(3xti)