Skip site navigation (1)Skip section navigation (2)

FreeBSD Manual Pages

  
 
  

home | help 
MSGGET(2)		       System Calls Manual		       MSGGET(2)

NAME
     msgget -- get message queue

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #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:

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

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

     *	 msg_perm.mode is set to the lower 9 bits of msgflg which are set by OR-
	 ing these constants:

	 0400
	   Read access for user.

	 0200
	   Write access for user.

	 0040
	   Read access for group.

	 0020
	   Write access for group.

	 0004
	   Read access for other.

	 0002
	   Write access for other.

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

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

     *	 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 as-
			sociated 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.

FreeBSD ports 15.quarterly	  March 4, 2018 		       MSGGET(2)

Want to link to this manual page? Use this URL:
<https://man.freebsd.org/cgi/man.cgi?query=msgget&sektion=2&manpath=FreeBSD+15.1-RELEASE+and+Ports.quarterly>

home | help