Originální popis anglicky:
msgget - get the XSI message queue identifier
Návod, kniha: POSIX Programmer's Manual
#include <sys/msg.h>
int msgget(key_t
key, int
msgflg );
The
msgget() function operates on XSI message queues (see the Base
Definitions volume of IEEE Std 1003.1-2001, Section 3.224,
Message Queue). It is unspecified whether this function interoperates with the
realtime interprocess communication facilities defined in
Realtime .
The
msgget() function shall return the message queue identifier
associated with the argument
key.
A message queue identifier, associated message queue, and data structure (see
<sys/msg.h>), shall be created for the argument
key if one
of the following is true:
- *
- The argument key is equal to IPC_PRIVATE.
- *
- The argument key does not already have a message
queue identifier associated with it, and ( msgflg & IPC_CREAT)
is non-zero.
Upon creation, the data structure associated with the new message queue
identifier shall be initialized as follows:
- *
- msg_perm.cuid, msg_perm.uid,
msg_perm.cgid, and msg_perm.gid shall be set equal to the
effective user ID and effective group ID, respectively, of the calling
process.
- *
- The low-order 9 bits of msg_perm.mode shall be set
equal to the low-order 9 bits of msgflg.
- *
- msg_qnum, msg_lspid, msg_lrpid,
msg_stime, and msg_rtime shall be set equal to 0.
- *
- msg_ctime shall be set equal to the current
time.
- *
- msg_qbytes shall be set equal to the system
limit.
Upon successful completion,
msgget() shall return a non-negative integer,
namely a message queue identifier. Otherwise, it shall return -1 and set
errno to indicate the error.
The
msgget() function shall fail if:
- EACCES
- A message queue identifier exists for the argument
key, but operation permission as specified by the low-order 9 bits
of msgflg would not be granted; see XSI Interprocess
Communication .
- EEXIST
- A message queue identifier exists for the argument
key but (( msgflg & IPC_CREAT) && (
msgflg & IPC_EXCL)) is non-zero.
- ENOENT
- A message queue identifier does not exist for the argument
key and ( msgflg & IPC_CREAT) is 0.
- ENOSPC
- A message queue identifier is to be created but the
system-imposed limit on the maximum number of allowed message queue
identifiers system-wide would be exceeded.
The following sections are informative.
None.
The POSIX Realtime Extension defines alternative interfaces for interprocess
communication (IPC). Application developers who need to use IPC should design
their applications so that modules using the IPC routines described in
XSI
Interprocess Communication can be easily modified to use the alternative
interfaces.
None.
None.
XSI Interprocess Communication ,
Realtime ,
mq_close() ,
mq_getattr() ,
mq_notify() ,
mq_open() ,
mq_receive() ,
mq_send() ,
mq_setattr() ,
mq_unlink() ,
msgctl() ,
msgrcv() ,
msgsnd() , the
Base Definitions volume of IEEE Std 1003.1-2001,
<sys/msg.h>
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
.
