The Open Group Base Specifications Issue 6
IEEE Std 1003.1, 2004 Edition
Copyright © 2001-2004 The IEEE and The Open Group, All Rights reserved.
A newer edition of this document exists here


msgget - get the XSI message queue identifier


[XSI] [Option Start] #include <sys/msg.h>

int msgget(key_t
key, int msgflg); [Option End]


The msgget() function operates on XSI message queues (see the Base Definitions volume of IEEE Std 1003.1-2001, Section 3.224, Message Queue). It is unspecified whether this function interoperates with the realtime interprocess communication facilities defined in Realtime.

The msgget() function shall return the message queue identifier associated with the argument key.

A message queue identifier, associated message queue, and data structure (see <sys/msg.h>), shall be created for the argument key if one of the following is true:

Upon creation, the data structure associated with the new message queue identifier shall be initialized as follows:


Upon successful completion, msgget() shall return a non-negative integer, namely a message queue identifier. Otherwise, it shall return -1 and set errno to indicate the error.


The msgget() function shall fail if:

A message queue identifier exists for the argument key, but operation permission as specified by the low-order 9 bits of msgflg would not be granted; see XSI Interprocess Communication.
A message queue identifier exists for the argument key but ((msgflg & IPC_CREAT) && (msgflg & IPC_EXCL)) is non-zero.
A message queue identifier does not exist for the argument key and (msgflg & IPC_CREAT) is 0.
A message queue identifier is to be created but the system-imposed limit on the maximum number of allowed message queue identifiers system-wide would be exceeded.

The following sections are informative.




The POSIX Realtime Extension defines alternative interfaces for interprocess communication (IPC). Application developers who need to use IPC should design their applications so that modules using the IPC routines described in XSI Interprocess Communication can be easily modified to use the alternative interfaces.






XSI Interprocess Communication, Realtime, mq_close(), mq_getattr(), mq_notify(), mq_open(), mq_receive(), mq_send(), mq_setattr(), mq_unlink(), msgctl(), msgrcv(), msgsnd(), the Base Definitions volume of IEEE Std 1003.1-2001, <sys/msg.h>


First released in Issue 2. Derived from Issue 2 of the SVID.

Issue 5

The note about use of POSIX Realtime Extension IPC routines has been moved from FUTURE DIRECTIONS to a new APPLICATION USAGE section.

End of informative text.

UNIX ® is a registered Trademark of The Open Group.
POSIX ® is a registered Trademark of The IEEE.
[ Main Index | XBD | XCU | XSH | XRAT ]