create a ramdisk on OSX.

.bash_profile

# you can add this to your ~/.bash_profile
# based on: http://www.tekrevue.com/tip/how-to-create-a-4gbs-ram-disk-in-mac-os-x/

create_ramdisk() {
  # usage: create_ramdisk ramdisk_name size_in_kb
  # e.g. "create_ramdisk ramdisk 4096" will create a 4GB ramdisk.
  let ramsize=$2*2048;
  diskutil erasevolume HFS+ $1 `hdiutil attach -nomount ram://$ramsize`;
}