msg (0p) - Linux Manuals

msg: XSI message queue structures

NAME

sys/msg.h - XSI message queue structures

SYNOPSIS

#include <sys/msg.h>

DESCRIPTION

The <sys/msg.h> header shall define the following data types through typedef:

msgqnum_t

Used for the number of messages in the message queue.

msglen_t

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:

MSG_NOERROR

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 <sys/types.h> .

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 included.

The following sections are informative.

APPLICATION USAGE

None.

RATIONALE

None.

FUTURE DIRECTIONS

None.

COPYRIGHT

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 original Standard can be obtained online at http://www.opengroup.org/unix/online.html .