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.
sys/msg.h — XSI message queue structures
header shall define the following data types
- Used for the number of messages in the message queue.
- 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
header shall define the following symbolic constant
as a message operation flag:
- No error if big message.
header shall define the msqid_ds
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.
header shall define the pid_t
, and time_t
types as described in
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
The following sections are informative.
The System Interfaces volume of POSIX.1‐2008, msgctl()
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 .
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