HP-UX Reference (11i v2 04/09) - 5 Miscellaneous Topics (vol 9)

mesg(5) mesg(5)

(Tunable Kernel Parameters)

NAME

mesg - enable or disable System V IPC messages at boot time

DESCRIPTION

The

mesg tunable is obsolete. The System V IPC message subsystem is always enabled.

Overview

A System V message is just a sequence of bytes that can be passed between cooperating processes via a

message queue. Messages can be of any length up to a tunable maximum. Messages larger than 64 bytes

(not tunable) are stored in one or more contiguous "segments" of reserved kernel memory and are

managed through the message segment map. Messages equal to or smaller than 64 bytes are allocated

with the message header and therefore do not consume a segment. Each message is "typed" with an

application-speciﬁc number. Each message queue is referenced by a unique ID, and can contain multiple

individual messages.

The process receiving a message can get the "ﬁrst" message (FIFO), the ﬁrst of a speciﬁed type, the ﬁrst of

a group of types, or wait for a speciﬁc type to appear.

WARNINGS

Installation of optional kernel software, from HP or other vendors, may cause changes to tunable parame-

ter values. After installation, some tunable parameters may no longer be at the default or recommended

values. For information about the effects of installation on tunable values, consult the documentation for

the kernel software being installed. For information about optional kernel software that was factory

installed on your system, see HP-UX Release Notes at

http://docs.hp.com

AUTHOR

mesg was developed by AT&T.