The Single UNIX ® Specification, Version 2
Copyright © 1997 The Open Group


msgget - get the message queue identifier


#include <sys/msg.h>

int msgget(key_t key, int msgflg);


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

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

Upon creation, the data structure associated with the new message queue identifier is initialised as follows:


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


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




mq_close(), mq_getattr(), mq_notify(), mq_open(), mq_receive(), mq_send(), mq_setattr(), mq_unlink(), msgctl(), msgrcv(), msgsnd(), <sys/msg.h>, IPC.


Derived from Issue 2 of the SVID.

UNIX ® is a registered Trademark of The Open Group.
Copyright © 1997 The Open Group
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