NAME
sys/msg.h —
message queue structures
SYNOPSIS
#include <sys/msg.h>
DESCRIPTION
The < sys/msg.h > header defines the following constant and members of the structure msqid_ds .
The following data types are defined 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 are unsigned integer types that are able to store values at least as large as a type unsigned short.
Message operation flag:
- MSG_NOERROR
- No error if big message.
The structure
msqid_ds
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() 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 pid_t, time_t, key_t and size_t types are defined as described in <sys/types.h>.
The following are declared as functions and may also be defined as
macros. Function prototypes must be provided for use with an ISO C compiler.
int msgctl(int, int, struct msqid_ds *); int msgget(key_t,
int); ssize_t msgrcv(int, void *, size_t, long int, int); int msgsnd(int,
const void *, size_t, int);
In addition, all of the symbols from <sys/ipc.h> will be defined when this header is included.
APPLICATION USAGE
None.
FUTURE DIRECTIONS
None.
SEE ALSO
msgctl(3) , msgget(3) , msgrcv(3) , msgsnd(3) , <sys/types.h> .