<b_jonas> learn The hydra is at http://www.madore.org/~david/math/hydra0.xhtml , the dire hydra at http://www.madore.org/~david/math/hydra.xhtml , theory at http://www.madore.org/~david/weblog/d.2008-03-27.1537.html http://www.madore.org/~david/weblog/d.2008-03-16.1534.ordinaux-et-hydres.html http://math.andrej.com/2008/02/02/the-hydra-game/ https://en.wikipedia.org/wiki/Goodstein%27s_theorem

#!/bin/bash
[[ "$1" = */* ]] || exit
topic=$(echo "$1" | lowercase | cut -d / -f 1)
[ -z "$topic" ] && exit 1
stuff=$(echo "$1" | cut -d / -f 2-)
perl -i -p -e 's/\n/ /' "wisdom/$topic"
echo "$stuff" >>"wisdom/$topic"
echo -n "Learned '$topic': "
cat "wisdom/$topic"