This manual page is part of the POSIX Programmer's Manual. The Linux
implementation of this interface may differ (consult the
corresponding Linux manual page for details of Linux behavior), or
the interface may not be implemented on Linux.
The <sys/msg.h> header shall define the following data types through
msgqnum_t Used for the number of messages in the message queue.
msglen_t Used for the number of bytes allowed in a message
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>
The following sections are informative.
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information
Technology -- Portable Operating System Interface (POSIX), The Open
Group Base Specifications Issue 7, Copyright (C) 2013 by the
Institute of Electrical and Electronics Engineers, Inc and The Open
Group. (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1
applied.) In the event of any discrepancy between this version and
the original IEEE and The Open Group Standard, the original IEEE and
The Open Group Standard is the referee document. The original
Standard can be obtained online at http://www.unix.org/online.html .
Any typographical or formatting errors that appear in this page are
most likely to have been introduced during the conversion of the
source files to man page format. To report such errors, see
IEEE/The Open Group 2013 sys_msg.h(0P)