ref: e1f02664d96e392a608d97c5bdd0c1c3c6a26c84
dir: /sys/lib/man/mksearchindex/
#!/bin/rc
awk '
{ if($2 in a) a[$2] = a[$2] " " $1; else a[$2] = $1; }
END { for(i in a) print " " a[i] " " i; }
'< /sys/lib/man/lookman/index |sed 's/ \/sys\/man\/(.*)\/(.*)/ \2 \1\/\2/' | sort