Re: Alias Files
Re: Alias Files
- Subject: Re: Alias Files
- From: Doug McNutt <email@hidden>
- Date: Fri, 1 Aug 2008 14:42:14 -0600
At 12:47 -0700 8/1/08, Michelle Steiner wrote:
>On Aug 1, 2008, at 12:37 PM, Mark J. Reed wrote:
>
>> I could be way off base here, but I thought aliases didn't actually
>> store the path to the target, but rather a numeric identifier that
>> doesn't change when the file gets moved around (or the volume mounted
>> somewhere else)? You sure the ones that show the path in the info
>> window are actually aliases and not symbolic links?
>
>
>Yes, I'm sure. Move the file, and the information in the info window changes.
Early HFS had "catalog" memory assigned for "directory ID" which was a 32 bit number that was never re-used. Somewhere around OS-7 that was extended to include such a number "File-ID" for every file on a volume.
The File-ID became the basis for the concept of an alias file and the result was that one could rename a file or move it around in a file system without the alias being affected.
There were problems though with moving or copying files to removable media or even to another named hard disk. Does the alias follow the copy if you don't delete the original? What if you edit the original and then delete the copy? The result was that aliases and alias files needed more information. As of the last "Inside Macintosh" on my bookshelf the actual format of an alias resource or an alias file had never been disclosed by Apple.
And actually, moving a file from a local disk to a server or removable medium presents a real question regarding what to do to an alias file that might not even be mounted when the move occurs. Apple tries hard and I have been told to "please insert a floppy" by name but it can't ever be perfect. It was possible to put alias files on a floppy and they were pretty much usable even if you inserted the floppy on another Mac on a network. Disclosing the formats would help us understand the problems.
UNIX folks have real fun trying to fix alias files while writing to a CD-ROM. Just try replacing aliases with symbolic links that point to the correct place on a CD being cut with a UNIX or High Sierra file system. It would be a useful AppleScript for an interested guru.
--
--> From the U S of A, the only socialist country that refuses to admit it. <--
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