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From: nather@utastro.UUCP (Ed Nather)
Newsgroups: net.micro.pc
Subject: Re: How does a program know when a disk is changed.
Message-ID: <12@utastro.UUCP>
Date: Thu, 28-Mar-85 11:52:10 EST
Article-I.D.: utastro.12
Posted: Thu Mar 28 11:52:10 1985
Date-Received: Sun, 31-Mar-85 03:13:52 EST
References: <131@creed.UUCP>
Organization: U. Texas, Astronomy, Austin, TX
Lines: 23

> I have a program that needs to keep a file open for a long time.  
> How can I be sure that someone hasn't changed the disk since I 
> opened the file?  
> 
> Bruce Arden
> ..!mcvax!ukc!stc-a!creed!arden

If the disk in question has a file on it you can be sure has a unique
name (perhaps you could write one on it you're sure would be unique)
then you can search the disk for its existence.

In a .bat file, the "If exist filename ..." does that job.

Apparently DOS does it that way -- you can swap disks around if they have
the same directory names, and are "in" a subdirectory -- and DOS will leave
you there, on the new disk, if it hasn't seen you refer to that drive
and been unable to find the path it last saw.


-- 
Ed Nather
Astronony Dept, U of Texas @ Austin
{allegra,ihnp4}!{noao,ut-sally}!utastro!nather