File Write Permission Rules

[David J. Camp]

We have a strange situation where a program can write to a file even
though it does not have write permission.  What it does is remove the
file and write a new one in its place.  It can do this because it has
write permission to the directory in which the file is contained.

My question is:  What is the (historical or otherwise) justification for
this rule?  It seems wrong.  I would have required write permission to
the file itself in order that it be removed.
-David-
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