Peter Seebach <seebs@solon.com> wrote:
> Has anyone implemented a filesystem with copy-on-write semantics?  I'd like
> to be able to, for instance, have a file which will be a link to another file,
> until it gets written to, at which point, it becomes a new file, containing
> whatever new data.  Is this monumentally stupid for a reason which will
> become apparent before this message makes it back to me, and/or is it
> implemented already?

Such a thing has once been implemented in the Eumel programming
environment.  (Eumel is based around the Elan languague, which is Algol
68 simplified and then extended differently). User accounts are based on
a sort of inheritance of properties and files from its parent, wich are
shared on a copy-on-write basis. Interestingly, the file data is grouped
in lines and only modified lines are un-shared. Uninterestingly, FILE
was defined as something like array of array of characters, with fixed
upper limits, which made the whole thing useless.

> -s
-Olaf.
--
___ Olaf 'Rhialto' Seibert      D787B44DFC896063 4CBB95A5BD1DAA96 
\X/ Ceci n'est pas un Magritte          rhialto@polder.ubc.kun.nl