NAME    [Toc]    [Back]

     msgget -- get message queue

LIBRARY    [Toc]    [Back]

     Standard C Library (libc, -lc)

SYNOPSIS    [Toc]    [Back]

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

     int
     msgget(key_t key, int msgflg);

DESCRIPTION    [Toc]    [Back]

     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(3)) 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    [Toc]    [Back]

     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    [Toc]    [Back]

     [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    [Toc]    [Back]

     msgctl(3), msgrcv(3), msgsnd(3)

HISTORY    [Toc]    [Back]

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


FreeBSD 5.2.1			August 17, 1995 		 FreeBSD 5.2.1