From: CSBVAX::MRGATE!postmaster@RITA.ACS.WASHINGTON.EDU@SMTP 27-JAN-1988 19:04 To: ARISIA::EVERHART Subj: Undeliverable mail Received: from oly.acs.washington.edu by KL.SRI.COM with TCP; Mon 25 Jan 88 14:19:58-PST Received: from UWAVM.ACS.WASHINGTON.EDU by oly.acs.washington.edu ; Mon, 25 Jan 88 14:19:27 PST P1-Message-Id: US**EDU;UWAVM.ACS.WASHINGTON.EDU:LDL@Sx$j Date: Mon, 25 Jan 88 14:15-0800 X400-Trace: US**EDU; arrival Mon, 25 Jan 88 14:15-0800 action Relayed X400-Trace: US**EDU; arrival Mon, 25 Jan 88 14:19-0800 action Relayed From: PMDF Mail Server To: Subject: Undeliverable mail Message-Id: The message could not be delivered to: Addressee: B8639 Reason: %MAIL-E-NOSUCHUSR, no such user B8639 at node RITA ---------------------------------------- Received: from JNET-DAEMON by RITA.ACS.WASHINGTON.EDU; Mon, 25 Jan 88 14:14 PST Received: From OREGON1(MAILER) by UWARITA with RSCS id 7768 for B8639@UWARITA; Mon, 25 Jan 88 14:14 PST Received: by OREGON1 (Mailer X1.25) id 7763; Mon, 25 Jan 88 14:14:43 PST Date: Thu, 21 Jan 88 15:16:44 CST From: John Hascall Subject: Re: WAIT ON FILE (possible in VMS?) Sender: INFO-VAX Discussion To: Pete Pulliam Reply-to: INFO-VAX@KL.SRI.COM Comments: To: info-vax@kl.sri.com > From: GRANT%LAUCOSC.BITNET@CUNYVM.CUNY.EDU > > Some recent experiences have led me to consider implementing > a new "feature" in my experimental/instructional operating system. > The idea, in brief, is to be able to "wait on a file". For example, > a process could wait on a given directory: whenever that directory > is written upon the process would be resumed and could deal with new > files found there. > > Some recent dialogue concerning the VMS SET WATCH command (which, though > related, is not quite what I have in mind) encouraged me to ask the > corporate experience of this list to comment. > > 1. Has anyone heard of any operating system including this idea ? > > 2. Clearly, I have some particular applications in mind. As a > "blue sky" exercise, what applications come to mind for this > facility ? > > 3. Do you perceive any obvious weaknesses in the basic idea ? > > 4. As far as I can tell, there is no efficient way to simulate this > idea on VMS. Can anybody contradict me ? > It seems to me that it should be possible in VMS. I did a little research with ANALYZE/SYSTEM and it appears that when you open a file RMS enqueues a lock. The lock name is: 'RMS$ffffffxvvvvvvvvvvvv', where ffffff is the file-id; x is a byte whose meaning I was unable to discover, (anyone?), but whose value appeared to be X02 consistently; and vvvvvvvvvvvv is the volume name (blank padded). For example I opened a file with: $ open/share=write/read log$name test.dat where the test.dat resided on volume ISU000 and had file-id (3353,132,0), the resource was RMS$ x19 x0D x84 x00 x00 x00 x02 ISU000 x20 x20 x20 x20 x20 x20. (note 3533 = x0D19, 132 = x0084). The lock had the following characteristics: VALBLK, CONVERT, SYNCSTS, SYSTEM, and was an exec-mode NL-lock. The upshot of this is that a suitably privileged program should be able to create its own lock (EX-mode?) on this resource and specify a blocking AST to be triggered when access to the file is attempted.... > The problems which gave rise to this idea concern VMS programs (which > can't be modified) that write on known files. A good example of such > a program is VMS MAIL. The system on which I propose to test this idea > is LUMOS-2, a "toy" OS written in Modula-2. > > I realise that this is not a VMS question, but any comments > would be appreciated. > > Thanks > > Grant Guenther Bitnet etc.: GRANT@LAUCOSC > > Department of Computer Science > Laurentian University > Sudbury, Ontario > CANADA P3E 2C6 = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = name: John Hascall = = employ: Iowa State University Computation Center = = USmail: Ames, IA 50010 = = bitnet: GGUUU@ISUMVS.BITNET = = internet: random!string!with!plenty!of!these%and!these!also@sometimes = = thought: "Sixty billion gigabytes can do much. They even do windows." = = -- F. Pohl ("Beyond the Blue Event Horizon") = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =