#!/bin/sh
# Print a random line from input
td=
cleanup() {
    rm -fr -- "$td"
}
for sig in EXIT HUP INT TERM ; do
    trap cleanup "$sig"
done
if [ "$#" -eq 0 ] ; then
    td=$(mktd rndl) || exit
    set -- "$td"/stdin
    cat >"$td"/stdin
fi
lc=$(sed -- '$=;d' "$@") || exit
ri=$(rndi 1 "$lc") || exit
sed -- "$ri"'!d' "$@"