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Re: Measuring (or calculating) how many bytes are actually written to disk when I repeatedly save a file





On Sat, Apr 6, 2019, 4:44 PM Stefan Monnier <monnier@xxxxxxxxxxxxxxxx> wrote:

> 2. A lot of my editing involves editing near (but not at) the end of
> a file.  I assume (I know) that the software that saves the file is
> smart enough not to rewrite the entire file but instead to preserve
> the beginning of the file and just rewrite the changed part of the
> file (or from there to the end of the file).

Not completely sure if "you assume" or "you know" it to be the case.
Especially given that you then add:

> Can anyone confirm that,

which suggest you're not really sure (unless it referred to something else).

Let's say you are using vi. Last I heard, it will buffer the entire file contents on the initial open (unless you use the right option etc). How about on file write?
I don't know. 
I submit that rather than try to figure out each app, just install sar and related utilities and view the aggregate throughput. Maybe use cacti for quicker-to-screen graphics if you want.


        Stefan