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To: Peter Chubb <peter@chubb.wattle.id.au>
Cc: rob@landley.net, linux-kernel@vger.kernel.org
Subject: Re: Is there a "make hole" (truncate in middle) syscall?
References: <200312041432.23907.rob@landley.net>
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From: Philippe Troin <phil@fifi.org>
Date: 04 Dec 2003 17:04:48 -0800
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Peter Chubb <peter@chubb.wattle.id.au> writes:

> >>>>> "Rob" == Rob Landley <rob@landley.net> writes:
> 
> Rob> You can make a file with a hole by seeking past it and never
> Rob> writing to that bit, but is there any way to punch a hole in a
> Rob> file after the fact?  (I mean other with lseek and write.  Having
> Rob> a sparse file as the result....)
> 
> SVr4 has fcntl(fd, F_FREESP, flock) that frees the space covered by
> the struct flock in the file.  Linux doesn't have this, at least in
> the baseline kernels.

However most SVr4 (at least Solaris and HP-UX) only implement FREESP
when the freed space is at the file's tail. In other words, FREESP can
only be used to implement ftruncate().

Phil.