|MSGGET(3P)||POSIX Programmer's Manual||MSGGET(3P)|
int msgget(key_t key, int msgflg);
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 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 to the low-order 9 bits of msgflg.
- msg_qnum, msg_lspid, msg_lrpid, msg_stime, and msg_rtime shall be set to 0.
- msg_ctime shall be set to the current time, as described in Section 2.7.1, IPC General Description.
- msg_qbytes shall be set to the system limit.
- 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 Section 2.7, XSI Interprocess Communication.
- A message queue identifier exists for the argument key but ((msgflg & IPC_CREAT) && (msgflg & IPC_EXCL)) is non-zero.
- A message queue identifier does not exist for the argument key and (msgflg & IPC_CREAT) is 0.
- 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.
The Base Definitions volume of POSIX.1‐2008, Section 3.225, Message Queue, <sys_msg.h>
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 https://www.kernel.org/doc/man-pages/reporting_bugs.html .
|2013||IEEE/The Open Group|