<b_jonas> learn ayacc is ais523\'s yacc parser generator implementation, get it from (darcs clone http://nethack4.org/projects/ayacc) or a snapshot from "http://nethack4.org/pastebin/ayacc-2020-04.tar.gz".

#!/bin/sh
allquotes | if [ "$1" ]; then
    if expr "$1" + 0 >/dev/null 2>&1; then
        sed "$1q;d"
    else
        grep -P -i -- "$1"
    fi
else shuf --random-source=/dev/urandom -n 1; fi