Ian Nelson writes:
> I think I know the answer to this first question already. Is there a
> head trunc function? I don't think there is but you never know. The
> situation is like this: we've got a large file (multiple gigs) and at
> some point while still writing data to it we realize that we don't want
> the first 500MB so we want to trunc it off the front of the file will
> keeping it open and keep writing to it. Anyone want head trunc if I get
> strapped in to writing it?
We have written such a function (called "punch") which can arbitrarily
zero/remove data at the beginning/middle/end of a file. It is a superset
of normal truncate and the head truncate function you describe. The punch
code itself is complete and has been used in an application for a long
time, but there is a little work to do to get it up-to-speed for the
newer kernels, namely vmpunch() (which will be a superset of vmtruncate).
If you are interested in the current code, let me know.
Cheers, Andreas
--
Andreas Dilger \ "If a man ate a pound of pasta and a pound of antipasto,
\ would they cancel out, leaving him still hungry?"
http://www-mddsp.enel.ucalgary.ca/People/adilger/ -- Dogbert
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