Messages in this thread | | | Date | Wed, 23 Dec 1998 03:25:51 -0500 | From | Dave Cinege <> | Subject | device: /dev/repeat |
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Jason Burrell wrote: > > > There are problems in multi-process setups. Say I have one process > which wants to have /dev/repeat return 01010101. I have another > process which wants 00000000, and another which wants 11111111. The > first process writes 01010101 to /dev/repeat. The second writes > 00000000. Then the first finally gets around to reading > /dev/repeat. Then the third process writes 11111111, and the second > process reads. Oops. :)
Unlike the blabering in the rest of this thread, this is actually a real problem.
I guess the same this exists with serial ports, an that is 'solved' (somewhat) with lock files. /dev/repeat0-9 could also be available to help this. Any better ideas?
> I could be wrong, but it seems that one of the primary uses of > /dev/zero are to mmap it and get copy-on-write pages. Adding different > device objects for different bit patterns doesn't seem too useful to > me.
Well sure. Example: In the 'wipe' thread it was brought up that random and urandom are too slow.
dd if=/dev/random of=/dev/repeat bs=512 count=1. cat /dev/repeat Very fast, and refilled several times over the operation, random enough.
> If you want a particular repeated pattern, use a function like > memfill() from Lars Wirzenius's 'publib' library.
IMO you should be able to accomplish this without resorting to C.
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