contrib-munin/plugins/bsd/openbsd-memory

#!/bin/sh
if [ "$1" = "config" ]; then
  echo "graph_title Memory usage (in MB)"
  echo 'graph_category system'
  echo "acti.label Active"
  echo "used.label Used"
  echo "total.label Total"
  echo "free.label Free"
  exit 0
fi

# Memory: Real: 14M/69M act/tot  Free: 173M  Swap: 0K/612M used/tot

top -un | nawk '
function scale(v) {
  if (v ~ /G$/) { sub("G", "", v);v *= 1024 }
  else if (v ~ /M$/) sub("M", "", v)
  else if (v ~ /K$/) { sub("K", "", v);v /= 1024 }
  else v /= 1024 * 1024;
  return v;
}
function spliter(v, i) {
  split(v, a, "/");
  return(a[i]);
}
/^Memory/ {
  acti  = scale(spliter($3,1));
  used  = scale(spliter($3,2));
  free  = scale($6);
  total = used + free;

  print "acti.value", acti
  print "used.value", used
  print "total.value", total
  print "free.value", free
}'