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Path: utzoo!mnetor!seismo!munnari!goanna!ajk
From: ajk@goanna.oz (Alan Kent)
Newsgroups: comp.sys.amiga
Subject: AmigaDOS locks
Message-ID: <798@goanna.oz>
Date: Mon, 27-Apr-87 02:59:38 EDT
Article-I.D.: goanna.798
Posted: Mon Apr 27 02:59:38 1987
Date-Received: Tue, 28-Apr-87 01:18:13 EDT
Organization: Comp Sci, RMIT, Melbourne, Australia
Lines: 31
Keywords: locking files with amigados

Please Enlighten me.

I have been looking through all the manuals I can lay my hands on, but
nothing seems to help.

I want to lock a file so that no-one else will touch it while I do
I/O on the file (reads and possibly writes).

When I open it, it may only be for read access, but I might want to 
write to it later (to save a new version). I have tried Lock()ing
the file for exclusive access, but then Open() wont work (because
its locked). Doing the Open() first makes the Lock() fail. Is there
any way of using Lock() to give myself exclusive access to a file
and have it open at the same time for I/O?  I want to make sure I
dont allow the user to modify the memory version of a file if I cannot
save it later! (I am writing a sort of editor). Obviously I dont want
to write to the file if the user does not change it.

At present, I exclusive Lock() the file and if that works, I quickly
UnLock() and Open() it.  This is not perfect but its the best I can
think of. Anyone got any better ideas?

Thanks in advance


Alan Kent                     UUCP: {seismo,hplabs,mcvax,ukc,nttlab}
Dept of Computing                         !munnari!goanna.oz!ajk
Royal Melb. Inst. of Tech.    ACSnet: ajk@goanna.oz
124 La Trobe St               ARPA: munnari!goanna.oz!ajk@SEISMO.ARPA
Melbourne, Victoria 3000
AUSTRALIA