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NAME

       sys/msg.h - XSI message queue structures

SYNOPSIS

       #include <sys/msg.h>

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 constant as a message
       operation flag:

       MSG_NOERROR
              No error if big message.

       The msqid_ds structure shall contain 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, size_t, and ssize_t types shall be defined 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, all of the symbols from <sys/ipc.h> shall be defined  when
       this header is included.

       The following sections are informative.

APPLICATION USAGE

       None.

RATIONALE

       None.

FUTURE DIRECTIONS

       None.

SEE ALSO

       <sys/ipc.h> , <sys/types.h> , msgctl(), msgget(), msgrcv(), msgsnd()

COPYRIGHT

       Portions  of  this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
       --  Portable  Operating  System  Interface (POSIX), The Open Group Base
       Specifications Issue 6, Copyright (C) 2001-2003  by  the  Institute  of
       Electrical  and  Electronics  Engineers, Inc and The Open Group. 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.opengroup.org/unix/online.html .