'\" te
.\" Copyright (c) 2003, 2011, Oracle and/or its affiliates. All rights reserved.
.TH port_alert 3C "1 Oct 2003" "SunOS 5.11" "Standard C Library Functions"
.SH NAME
port_alert \- set a port in alert mode
.SH SYNOPSIS
.LP
.nf
#include <port.h>

\fBint\fR \fBport_alert\fR(\fBint\fR \fIport\fR, \fBint\fR \fIflags\fR, \fBint\fR \fIevents\fR, \fBvoid *\fR\fIuser\fR);
.fi

.SH DESCRIPTION
.sp
.LP
The \fBport_alert()\fR function transitions a port into or out of alert mode.  A port in alert mode immediately awakens all threads blocked in \fBport_get\fR(3C) or \fBport_getn\fR(3C). These threads return with an alert notification that consists of a single \fBport_event_t\fR structure with the source \fBPORT_SOURCE_ALERT\fR. Subsequent threads trying to retrieve events from a port that is in alert mode will return immediately with the alert notification.
.sp
.LP
A port is transitioned into alert mode by calling the \fBport_alert()\fR function with a non-zero \fIevents\fR parameter.  The specified \fIevents\fR and \fIuser\fR parameters will be made available in the \fBportev_events\fR and the \fBportev_user\fR members of the alert notification, respectively. The \fIflags\fR argument determines the mode of operation of the alert mode:
.RS +4
.TP
.ie t \(bu
.el o
If \fIflags\fR is set to \fBPORT_ALERT_SET\fR, \fBport_alert()\fR sets the port in alert mode independent of the current state of the port.  The \fBportev_events\fR and \fBportev_user\fR members are set or updated accordingly.
.RE
.RS +4
.TP
.ie t \(bu
.el o
If \fIflags\fR is set to \fBPORT_ALERT_UPDATE\fR and the port is not in alert mode, \fBport_alert()\fR transitions the port into alert mode.  The \fBportev_events\fR and \fBportev_user\fR members are set accordingly.
.RE
.RS +4
.TP
.ie t \(bu
.el o
If \fIflags\fR is set to \fBPORT_ALERT_UPDATE\fR and the port is already in alert mode, \fBport_alert()\fR returns with an error value of \fBEBUSY\fR.
.RE
.sp
.LP
\fBPORT_ALERT_SET\fR and \fBPORT_ALERT_UPDATE\fR are mutually exclusive.
.sp
.LP
A port is transitioned out of alert mode by calling the \fBport_alert()\fR function with a zero \fIevents\fR parameter.
.sp
.LP
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.
.SH RETURN VALUES
.sp
.LP
Upon successful completion, 0 is returned. Otherwise, -1 is returned and \fBerrno\fR is set to indicate the error.
.SH ERRORS
.sp
.LP
The \fBport_alert()\fR function will fail if:
.sp
.ne 2
.mk
.na
\fB\fBEBADF\fR\fR
.ad
.RS 10n
.rt  
The port identifier is not valid.
.RE

.sp
.ne 2
.mk
.na
\fB\fBEBADFD\fR\fR
.ad
.RS 10n
.rt  
The \fIport\fR argument is not an event port file descriptor.
.RE

.sp
.ne 2
.mk
.na
\fB\fBEBUSY\fR\fR
.ad
.RS 10n
.rt  
The port is already in alert mode.
.RE

.sp
.ne 2
.mk
.na
\fB\fBEINVAL\fR\fR
.ad
.RS 10n
.rt  
Mutually exclusive \fIflags\fR are set.
.RE

.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(5) for descriptions of the following attributes:
.sp

.sp
.TS
tab() box;
cw(2.75i) |cw(2.75i) 
lw(2.75i) |lw(2.75i) 
.
ATTRIBUTE TYPEATTRIBUTE VALUE
_
Architectureall
_
Availabilitysystem/core-os, system/header
_
Interface StabilityCommitted
_
MT-LevelSafe
.TE

.SH SEE ALSO
.sp
.LP
\fBport_associate\fR(3C), \fBport_create\fR(3C), \fBport_get\fR(3C), \fBport_send\fR(3C), \fBattributes\fR(5)