msgget(2) System Calls Manual msgget(2)
msgget - get message queue
int msgget (key, msgflg)
The system call returns the message queue identifier associated with key.
A message queue identifier and associated message queue and data structure are created for key if one of the following is true:
o The key is equal to IPC_PRIVATE
o The key does not already have a message queue identifier associated with it, and (msgflg & IPC_CREAT) is true. For further informa-
Upon creation, the data structure associated with the new message queue identifier is initialized as follows:
o The msg_perm.cuid, msg_perm.uid, msg_perm.cgid and msg_perm.gid members are set equal to the effective user ID and effective group ID,
respectively, of the calling process.
o The low-order nine bits of msg_perm.mode are set equal to the low-order nine bits of msgflg.
o The msg_qnum, msg_lspid, msg_lrpid, msg_stime, and mgs_rtime members are set equal to 0.
o The msg_ctime is set equal to the current time.
o The msg_qbytes is set equal to the system limit.
Upon successful completion, a non-negative integer, which is a message queue identifier, is returned. Otherwise, a value of -1 is
returned, and errno is set to indicate the error.
The system call fails under the following conditions:
[EACCES] A message queue identifier exists for key but operations permission, as specified by the low-order nine bits of msgflg,
would not be granted. For further information, see
[ENOENT] A message queue identifier does not exist for key and the logical operation (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 the logical operation ((msgflg & IPC_CREAT ) & (msgflg & IPC_EXCL )) is true.
msgctl(2), msgop(2), ftok(3)