[Info-vax] Unix fork, was: Re: New OpenSSL update from HP

[Simon Clubley]

On 2015-06-16, David Froble <davef at tsoft-inc.com> wrote:
>
> My understanding, and I'm not claiming it's complete, is that a whole 
> 'nother copy of everything in the "process" (don't know what *ix calls 
> them) with the program already running, files open, and some things 
> (like memory?) are shared.  Sounds rather dangerous to me.  Not sure how 
> I'd use such anyway ...

For memory accesses, Unix uses a copy on write model. When any process
tries to modify a shared memory page, the modifying process gets a
private copy of the original memory page:

	https://en.wikipedia.org/wiki/Copy-on-write

Simon.

-- 
Simon Clubley, clubley at remove_me.eisner.decus.org-Earth.UFP
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