t_look - look at the current event on a transport endpoint
t_look() returns the current event on the transport endpoint specified
by fd. This function enables a transport provider to notify a trans-
port 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.
This function also enables a transport user to poll(2) a transport end-
point periodically for asynchronous events.
Upon success, 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:
T_LISTEN Connection indication received
T_CONNECT Connect confirmation received
T_DATA Normal data received
T_EXDATA Expedited data received
T_DISCONNECT Disconnect received
T_ERROR Fatal error indication
T_UDERR Datagram error indication
T_ORDREL Orderly release indication
On failure, -1 is returned and t_errno is set to indicate the error.
TBADF The specified file descriptor does not refer to a trans-
TSYSERR The function failed due to a system error and set errno
to indicate the error.
21 January 1990 T_LOOK(3N)