msgctl(2)							System Calls Manual							 msgctl(2)

NAME

       msgctl() - message control operations

SYNOPSIS

DESCRIPTION

       provides a variety of message control operations as specified by cmd.  The following cmds are available:

	      Place the current value of each member of the data structure associated with
			     msqid into the structure pointed to by buf.  The contents of this structure are defined in glossary(9).  This command
			     requres the privilege to operate on a message queue not permitted by access modes. This command requires  the  privi-
			     lege to operate on a message queue in a different compartment.

	      Set the value of the following members of the data structure associated with
			     msqid to the corresponding value found in the structure pointed to by buf:

			     This  cmd	can only be executed by a process that has the privilege or has an effective user ID equal to the value of
			     either or in the data structure associated with msqid.  Only a user with the privilege can raise the value of

			     WARNING: Programs compiled on HP-UX revisions prior to  HP-UX  11i  v1  use  old  16-bit  msqid_ds  structure  fields
			     (obtained	via  which can describe queue sizes only up to 64 KBytes.  Care must be taken such that queues shared with
			     such programs are not made larger than 64 KBytes(65535).	Or, those existing programs should be recompiled.  Or, the
			     system administrator should restrict the kernel tunable parameter to 64 KBytes or less.

	      Remove the message queue identifier specified by
			     msqid from the system and destroy the message queue and data structure associated with it.  This cmd can only be exe-
			     cuted by a process that has the privilege or has an effective user ID equal to the value of either  or  in  the  data
			     structure associated with msqid.

   Security Restrictions
       Some  or all of the actions associated with this system call are subject to compartmental restrictions. See compartments(5) for more infor-
       mation about compartmentalization on systems that support that feature.

       Compartmental restrictions can be overridden if the process possesses the privilege (PRIV_COMMALLOWED).	Processes owned by  the  superuser
       may not have this privilege.  Processes owned by any user may have this privilege, depending on system configuration.

       Some  or all of the actions associated with this system call require the or privileges (PRIV_DACREAD, PRIV_LIMIT or PRIV_OWNER).  Processes
       owned by the superuser have these privileges.  Processes owned by other users may have one or more of these privileges, depending on system
       configuration.

       See privileges(5) for more information about privileged access on systems that support fine-grained privileges.

RETURN VALUE

       Upon successful completion, a value of 0 is returned.  Otherwise, a value of -1 is returned and is set to indicate the error.

ERRORS

       fails if one or more of the following is true:

       msqid	      is not a valid message queue identifier.

       cmd	      is not a valid command, or the command contains invalid parameters.

       cmd	      is  equal  to  and  Read	operation  permission is denied to the calling process (see message operation permissions in glos-
		      sary(9)).

       cmd	      is equal to or and the calling process does not have the privilege or the effective user ID of the calling  process  is  not
		      equal to the value of either or in the data structure associated with msqid.

       cmd	      is equal to an attempt is being made to increase to the value of and the user does not have the privilege.

       buf	      points to an illegal address.  Reliable detection of this error is implementation dependent.

SEE ALSO

       ipcrm(1), ipcs(1), msgget(2), msgop(2), ftok(3C), privileges(5).

STANDARDS CONFORMANCE

																	 msgctl(2)