msgget(2) [ultrix man page]

msgget(2)							System Calls Manual							 msgget(2)

Name
       msgget - get message queue

Syntax
       #include <sys/types.h>
       #include <sys/ipc.h>
       #include <sys/msg.h>

       int msgget (key, msgflg)
       key_t key;
       int msgflg;

Description
       The system call returns the message queue identifier associated with key.

       A message queue identifier and associated message queue and data structure are created for key if one of the following is true:

       o    The key is equal to IPC_PRIVATE

       o    The  key  does not already have a message queue identifier associated with it, and (msgflg & IPC_CREAT) is true.  For further informa-
	    tion, see

       Upon creation, the data structure associated with the new message queue identifier is initialized as follows:

       o    The msg_perm.cuid, msg_perm.uid, msg_perm.cgid and msg_perm.gid members are set equal to the effective user ID and effective group ID,
	    respectively, of the calling process.

       o    The low-order nine bits of msg_perm.mode are set equal to the low-order nine bits of msgflg.

       o    The msg_qnum, msg_lspid, msg_lrpid, msg_stime, and mgs_rtime members are set equal to 0.

       o    The msg_ctime is set equal to the current time.

       o    The msg_qbytes is set equal to the system limit.

Return Values
       Upon  successful  completion,  a  non-negative  integer,  which	is  a  message queue identifier, is returned.  Otherwise, a value of -1 is
       returned, and errno is set to indicate the error.

Diagnostics
       The system call fails under the following conditions:

       [EACCES]       A message queue identifier exists for key but operations permission, as specified by the	low-order  nine  bits  of  msgflg,
		      would not be granted.  For further information, see

       [ENOENT]       A message queue identifier does not exist for key and the logical operation (msgflg & IPC_CREAT) is false.

       [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.

       [EEXIST]       A message queue identifier exists for key but the logical operation ((msgflg & IPC_CREAT ) & (msgflg & IPC_EXCL )) is true.

See Also
       msgctl(2), msgop(2), ftok(3)

																	 msgget(2)

Check Out this Related Man Page

MSGGET(2)						      BSD System Calls Manual							 MSGGET(2)

NAME

     msgget -- get message queue

LIBRARY

     Standard C Library (libc, -lc)

SYNOPSIS

     #include <sys/types.h>
     #include <sys/ipc.h>
     #include <sys/msg.h>

     int
     msgget(key_t key, int msgflg);

DESCRIPTION

     The msgget() function returns the message queue identifier associated with key.  A message queue identifier is a unique integer greater than
     zero.

     A message queue is created if either key is equal to IPC_PRIVATE, or key does not have a message queue identifier associated with it, and the
     IPC_CREAT bit is set in msgflg.

     If a new message queue is created, the data structure associated with it (the msqid_ds structure, see msgctl(2)) is initialized as follows:

     o	 msg_perm.cuid and msg_perm.uid are set to the effective uid of the calling process.

     o	 msg_perm.gid and msg_perm.cgid are set to the effective gid of the calling process.

     o	 msg_perm.mode is set to the lower 9 bits of msgflg.

     o	 msg_cbytes, msg_qnum, msg_lspid, msg_lrpid, msg_rtime, and msg_stime are set to 0.

     o	 msg_qbytes is set to the system wide maximum value for the number of bytes in a queue (MSGMNB).

     o	 msg_ctime is set to the current time.

RETURN VALUES

     Upon successful completion a positive message queue identifier is returned.  Otherwise, -1 is returned and the global variable errno is set
     to indicate the error.

ERRORS

     [EACCES]		A message queue is already associated with key and the caller has no permission to access it.

     [EEXIST]		Both IPC_CREAT and IPC_EXCL are set in msgflg, and a message queue is already associated with key.

     [ENOSPC]		A new message queue could not be created because the system limit for the number of message queues has been reached.

     [ENOENT]		IPC_CREAT was not set in msgflg and no message queue associated with key was found.

SEE ALSO

     msgctl(2), msgrcv(2), msgsnd(2)

HISTORY

     Message queues appeared in the first release of AT&T System V UNIX.

BSD
								   July 9, 2009 							       BSD

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msgget(2) [ultrix man page]

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