/dev/mem and /dev/shm

From: Captain Dondo (yan_at_NsOeSiPnAeMr.com)
Date: 10/29/05

  • Next message: Chris F.A. Johnson: "Re: Trim file with sed" 
    Date: Sat, 29 Oct 2005 14:05:08 -0700

    Could someone please point me at some docs or explain the difference
    betwen these two?

    >From the docs, I can do

    fd = shm_open("file",..,..);
    memptr = mmap(..,fd..,..,offset);

    and I can do

    fd = open("/dev/mem",...);
    memptr = mmap(..,fd,...,offset);

    What is the difference? If I set offset the same, will memptr point to
    the same block of memory?

    And what does tmpfs have to do with this? I've been through two posix
    books, googled all over the place, and I'm still confused. I have not
    found a single clear example of the use of shm_open and how it relates to
    a memory mapping.....

    (I think I understand the open/mmap; at least I can use it in my code and
    it works without errors.... :-) )

    --Yan 

    -- 
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