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#!/bin/bash
# Commands like `sort` and `shuf` have a "--random-source" argument, for
# generating a stable, reproducible output. However, they require an input
# that provides sufficiently many bytes (depending on the input).
#
# This script generates a stream that can be used like
#
# shuf --random-source=<($0 "$seed")
seed=""
for a; do
seed="$seed${#a}:$a\n"
done
if command -v openssl &>/dev/null ; then
# We have openssl. Use it.
# https://www.gnu.org/software/coreutils/manual/html_node/Random-sources.html#Random-sources
#
# Note that we don't care that different installations/architectures generate the
# same output.
openssl enc -aes-256-ctr -pass "pass:$seed" -nosalt </dev/zero 2>/dev/null
else
# Hack something. It's much slower.
idx=0
while : ; do
idx="$((idx++))"
seed="$(sha256sum <<<"$idx.$seed")"
echo ">>>$seed" >> a
seed="${seed%% *}"
LANG=C awk -v s="$seed" 'BEGIN{
for (i=1; i <= length(s); i+=2) {
xchar = substr(s, i, 2);
decnum = strtonum("0x"xchar);
printf("%c", decnum);
}
}' || break
done
fi
exit 0
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