msgget(2)                                                            msgget(2)


NAME
     msgget - get message queue

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

     int msgget(key_t key, int msgflg);

DESCRIPTION
     msgget returns the message queue identifier associated with key.

     A message queue identifier and associated message queue and data
     structure [see intro(2)] are created for key if one of the following are
     true:

          key is IPC_PRIVATE.

          key does not already have a message queue identifier associated with
          it, and (msgflg&IPC_CREAT) is true.

     On creation, the data structure associated with the new message queue
     identifier is initialized as follows:

          msg_perm.cuid, msg_perm.uid, msg_perm.cgid, and msg_perm.gid are set
          to the effective user ID and effective group ID, respectively, of
          the calling process.

          The low-order 9 bits of msg_perm.mode are set to the low-order 9
          bits of msgflg.

          msg_qnum, msg_lspid, msg_lrpid, msg_stime, and msg_rtime are set to
          0.

          msg_ctime is set to the current time.

          msg_qbytes is set to the system limit.


     msgget fails if one or more of the following are true:

     EACCES         A message queue identifier exists for key, but operation
                    permission [see intro(2)] as specified by the low-order 9
                    bits of msgflg would not be granted.

     ENOENT         A message queue identifier does not exist for key and
                    (msgflg&IPC_CREAT) is false.


     ENOSPC         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.

     EEXIST         A message queue identifier exists for key but
                    (msgflg&IPC_CREAT) and (msgflg&IPC_EXCL) are both true.

SEE ALSO
     intro(2), msgctl(2), msgop(2), stdipc(3C).

DIAGNOSTICS
     Upon successful completion, a non-negative integer, namely a message
     queue identifier, is returned.  Otherwise, a value of -1 is returned and
     errno is set to indicate the error.


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