Re: Is there a "make hole" (truncate in middle) syscall?

From: Måns Rullgård
Date: Thu Dec 04 2003 - 15:57:58 EST

Rob Landley <rob@xxxxxxxxxxx> writes:

> You can make a file with a hole by seeking past it and never writing to that
> bit, but is there any way to punch a hole in a file after the fact? (I mean
> other with lseek and write. Having a sparse file as the result....)

I've never heard of one.

> What are the downsides of holes? (How big do they have to be to
> actually save space, is there a performance penalty to having a file
> with 1000 4k holes in it, etc...)

A hole has to be at least the size of one block in the filesystem,
typically 4k, to save any space. Regarding performance, I would
expect it to improve for reads.

Måns Rullgård

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