.\"
.\" $Id: procsend.2,v 1.1 1997/02/27 07:32:15 gdr Exp $
.\"
.\" .TH "MESSAGE IPC" 2 GNO "System Calls" "16 December 1996"
.TH "MESSAGE IPC" 2 "16 December 1996" GNO "System Calls"
.SH NAME
.BR procreceive ,
.BR procsend ,
.BR procrecvclr ,
.BR procrecvtim
\- GNO message passing IPC system
.SH SYNOPSIS
.nf
#include <gno/gno.h>

int procsend (pid_t \fIpid\fR, unsigned long \fImsg\fR);
unsigned long procreceive (void);
unsigned long procrecvtim (short \fItimeout\fR);
unsigned long procrecvclr (void);
.fi
.SH DESCRIPTION
These kernel traps comprise GNO's message passing IPC (interprocess
communication) system.  Messages are unsigned 32-bit data values.  A
process sends a message to another by using the
.BR procsend
call.  You must specify the process ID of the recipient and the message
to pass.
.LP
The
.BR procreceive
trap receives a message.  If no message has been sent to the process, the
process sleeps until a message arrives.  A
.BR procreceive
that is interrupted by a signal will abort and return -1, with
.BR errno
set to 
.BR EINTR .
.LP
.BR procrecvclr
is used to clear any pending message a process may have waiting.
.LP
.BR procrecvtim
is similar to
.BR procreceive ,
but takes a 
.IR timeout
argument, specified in 1/10ths of a second.  If no message has been
received in 
.IR timeout
seconds, 
.BR procrecvtim
fails and returns -1.  The message buffer for a process is only one message
deep; any attempt to 
.BR procsend
a message to a process that already has one queued will result in an error.
.LP
For an IPC system with a deeper queue, see the Ports IPC man page, 
.BR ports (2).
.SH "SEE ALSO"
.BR ports (2).