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man pages section 3: Library Interfaces and Headers

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Updated: Thursday, June 13, 2019
 
 

msg(3HEAD)

Name

msg.h, msg - message queue structures

Synopsis

#include <sys/msg.h> 

Description

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).

Attributes

See attributes(7) for descriptions of the following attributes:

ATTRIBUTE TYPE
ATTRIBUTE VALUE
Interface Stability
Committed
Standard

See Also

msgctl(2), msgget(2), msgrcv(2), msgsnd(2), ipc.h(3HEAD), types.h(3HEAD), attributes(7), standards(7)