NAME
sys/msg.h — XSI
message queue structures
SYNOPSIS
DESCRIPTION
The <sys/msg.h> header shall define 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 a message queue.
These types shall be unsigned integer types that are able to store values at least as large as a type unsigned short.
The <sys/msg.h> header shall define the following symbolic constant as a message operation flag:
- MSG_NOERROR
- No error if big message.
The <sys/msg.h> header shall define the msqid_ds structure, which shall include 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 (). pid_t msg_lrpid Process ID of last msgrcv (). 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 <sys/msg.h> header shall define the pid_t, size_t, ssize_t, and time_t types as described in <sys/types.h>.
The following shall be declared as functions and may also be defined as macros. Function prototypes shall be provided.
int msgctl(int, int, struct msqid_ds *); int msgget(key_t, int); ssize_t msgrcv(int, void *, size_t, long, int); int msgsnd(int, const void *, size_t, int);
In addition, the <sys/msg.h> header shall include the <sys/ipc.h> header.
APPLICATION USAGE
None.
RATIONALE
None.
FUTURE DIRECTIONS
None.
SEE ALSO
CHANGE HISTORY
First released in Issue 2. Derived from System V Release 2.0.
Issue 7
Austin Group Interpretation 1003.1-2001 #179 is applied.
This reference page is clarified with respect to macros and symbolic constants.