port_alert(3C)						   Standard C Library Functions 					    port_alert(3C)

NAME

       port_alert - set a port in alert mode

SYNOPSIS

       #include <port.h>

       int port_alert(int port, int flags, int events, void *user);

DESCRIPTION

       The  port_alert()  function  transitions a port into or out of alert mode.  A port in alert mode immediately awakens all threads blocked in
       port_get(3C) or port_getn(3C). These threads return with an alert notification that consists of a single port_event_t  structure  with  the
       source  PORT_SOURCE_ALERT.  Subsequent threads trying to retrieve events from a port that is in alert mode will return immediately with the
       alert notification.

       A port is transitioned into alert mode by calling the port_alert() function with a non-zero events parameter.   The  specified  events  and
       user  parameters will be made available in the portev_events and the portev_user members of the alert notification, respectively. The flags
       argument determines the mode of operation of the alert mode:

	 o  If flags is set to PORT_ALERT_SET, port_alert() sets the port in alert mode independent  of  the  current  state  of  the  port.   The
	    portev_events and portev_user members are set or updated accordingly.

	 o  If	flags  is  set	to  PORT_ALERT_UPDATE  and  the port is not in alert mode, port_alert() transitions the port into alert mode.  The
	    portev_events and portev_user members are set accordingly.

	 o  If flags is set to PORT_ALERT_UPDATE and the port is already in alert mode, port_alert() returns with an error value of EBUSY.

       PORT_ALERT_SET and PORT_ALERT_UPDATE are mutually exclusive.

       A port is transitioned out of alert mode by calling the port_alert() function with a zero events parameter.

       Events can be queued to a port that is in alert mode, but they will not be retrievable until the port is transitioned out of alert mode.

RETURN VALUES

       Upon succesful completion, 0 is returned. Otherwise, -1 is returned and errno is set to indicate the error.

ERRORS

       The port_alert() function will fail if:

       EBADF	       The port identifier is not valid.

       EBADFD	       The port argument is not an event port file descriptor.

       EBUSY	       The port is already in alert mode.

       EINVAL	       Mutually exclusive flags are set.

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Architecture		     |all			   |
       +-----------------------------+-----------------------------+
       |Availability		     |SUNWcsr, SUNWhea		   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Evolving			   |
       +-----------------------------+-----------------------------+
       |MT-Level		     |Safe			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       port_associate(3C), port_create(3C), port_get(3C), port_send(3C), attributes(5)

SunOS 5.10							    1 Oct 2003							    port_alert(3C)