On Wed, Jul 27, 2016 at 04:35:32AM +0200, Torsten Bögershausen wrote:
> > + mkdir -p generated-test-data &&
> > + for i in $(test_seq 1 $T0021_LARGE_FILE_SIZE)
> > + do
> > + # Generate 1MB of empty data and 100 bytes of random characters
> > + printf "%1048576d" 1
> > + printf "$(LC_ALL=C tr -dc "A-Za-z0-9" </dev/urandom | dd
> > bs=$((RANDOM>>8)) count=1 2>/dev/null)"
> I'm not sure how portable /dev/urandom is.
> The other thing, that "really random" numbers are an overkill, and
> it may be easier to use pre-defined numbers,
Right, there are a few reasons not to use /dev/urandom:
- it's not portable
- if we have to generate a lot of numbers, it drains the system's
entropy pool, which is an unfriendly thing to do (and may also be
slow)
- it makes our tests random! This sounds like a good thing, but it
means that if some input happens to cause failure, you are unlikely
to be able to reproduce it.
Instead, use test-genrandom, which is an LCG that starts at a seed. So
you get a large amount of random-ish quickly and portably, and you get
the same data each time.
-Peff
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