The <sys/msg.h> header defines the following data types through typedef:
msgqnum_t used for the number of messages in the message queue
msglen_t used for the number of bytes allowed in the message queue
These types are unsigned integer types that are able to store values at least as large as a type unsigned short.
The <sys/msg.h> header defines the following constant as a message operation flag:
MSG_NOERROR no error if big message
The msqid_ds structure contains the following members:
struct ipc_perm msg_perm Operation permission structure. msgqnum_t msg_qnum Number of messages currently on queue. msglen_t msg_qbytes Maximum number of bytes allowed on queue. pid_t msg_lspid Process ID of last msgsnd(2). pid_t msg_lrpid Process ID of last msgrcv(2). time_t msg_stime Time of last msgsnd(). time_t msg_rtime Time of last msgrcv(). time_t msg_ctime Time of last change.
The pid_t, time_t, key_t, size_t, and ssize_t types are defined as described in <sys/types.h>. See types(3HEAD).
See attributes(5) for descriptions of the following attributes:
|ATTRIBUTE TYPE||ATTRIBUTE VALUE|
msgctl(2), msgget(2), msgrcv(2), msgsnd(2), ipc.h(3HEAD), types.h(3HEAD), attributes(5), standards(5)