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NetBSD 6.1.5 - man page for msgget (netbsd section 2)

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

NAME
     msgget -- get message queue identifier

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <sys/msg.h>

     int
     msgget(key_t key, int msgflg);

DESCRIPTION
     The msgget() system call returns the message queue identifier associated with key.  A mes-
     sage 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 both
     the IPC_CREAT bit and the IPC_EXCL bit are set in msgflg, and key has a message queue iden-
     tifier associated with it already, the operation will fail.

     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_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 per-
			mission 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 is not set in msgflg and no message queue associated with key
			was found.

SEE ALSO
     msgctl(2), msgrcv(2), msgsnd(2), ftok(3)

STANDARDS
     The msgget system call conforms to X/Open System Interfaces and Headers Issue 5 (``XSH5'').

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

BSD					   May 13, 2004 				      BSD


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