<sys/msg.h>(P) POSIX Programmer's Manual <sys/msg.h>(P)
sys/msg.h - XSI message queue structures
The <sys/msg.h> header shall define the following data types through typedef:
Used for the number of messages in the message queue.
Used for the number of bytes allowed in a message queue.
These types shall be unsigned integer types that are able to store values at least as
large as a type unsigned short.
The <sys/msg.h> header shall define the following constant as a message operation flag:
No error if big message.
The msqid_ds structure shall contain the following members:
struct ipc_perm msg_perm Operation permission structure.
msgqnum_t msg_qnum Number of messages currently on queue.
msglen_t msg_qbytes Maximum number of bytes allowed on queue.
pid_t msg_lspid Process ID of last msgsnd
pid_t msg_lrpid Process ID of last msgrcv
time_t msg_stime Time of last msgsnd
time_t msg_rtime Time of last msgrcv
time_t msg_ctime Time of last change.
The pid_t, time_t, key_t, size_t, and ssize_t types shall be defined as described in
The following shall be declared as functions and may also be defined as macros. Function
prototypes shall be provided.
int msgctl(int, int, struct msqid_ds *);
int msgget(key_t, int);
ssize_t msgrcv(int, void *, size_t, long, int);
int msgsnd(int, const void *, size_t, int);
In addition, all of the symbols from <sys/ipc.h> shall be defined when this header is
The following sections are informative.
<sys/ipc.h> , <sys/types.h> , msgctl(), msgget(), msgrcv(), msgsnd()
Portions of this text are reprinted and reproduced in electronic form from IEEE Std
1003.1, 2003 Edition, Standard for Information Technology -- Portable Operating System
Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by
the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the
event of any discrepancy between this version and the original IEEE and The Open Group
Standard, the original IEEE and The Open Group Standard is the referee document. The orig-
inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .
IEEE/The Open Group 2003 <sys/msg.h>(P)