The <sys/msg.h> header defines the following data types through typedef:
used for the number of messages in the message queue
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:
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: