MirOS Manual: msgget(2)

MSGGET(2)                  BSD Programmer's Manual                   MSGGET(2)


     msgget - get message queue


     #include <sys/types.h>
     #include <sys/ipc.h>
     #include <sys/msg.h>

     msgget(key_t key, int msgflg);


     msgget() returns the message queue identifier associated with key. A mes-
     sage queue identifier is a unique integer greater than zero.

     A message queue is created if either key is equal to IPC_PRIVATE, or key
     does not have a message queue identifier associated with it, and the
     IPC_CREAT bit is set in msgflg.

     If a new message queue is created, the data structure associated with it
     (the msqid_ds structure, see msgctl(2)) is initialized as follows:

     •   msg_perm.cuid and msg_perm.uid are set to the effective UID of the
         calling process.

     •   msg_perm.gid and msg_perm.cgid are set to the effective GID of the
         calling process.

     •   msg_perm.mode is set to the lower 9 bits of msgflg.

     •   msg_cbytes, msg_qnum, msg_lspid, msg_lrpid, msg_rtime, and msg_stime
         are set to 0

     •   msg_qbytes is set to the system wide maximum value for the number of
         bytes in a queue (MSGMNB).

     •   msg_ctime is set to the current time.


     Upon successful completion a positive message queue identifier is re-
     turned. Otherwise, -1 is returned and the global variable errno is set to
     indicate the error.


     [EACCES]      A message queue is already associated with key and the
                   caller has no permission to access it.

     [EEXIST]      Both IPC_CREAT and IPC_EXCL are set in msgflg, and a mes-
                   sage queue is already associated with key.

     [ENOSPC]      A new message queue could not be created because the system
                   limit for the number of message queues has been reached.

     [ENOENT]      IPC_CREAT was not set in msgflg and no message queue asso-
                   ciated with key was found.


     msgctl(2), msgrcv(2), msgsnd(2), ftok(3)


     Message queues appeared in the first release of AT&T Unix System V.

MirOS BSD #10-current          August 17, 1995                               1

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