create RAM disk in OS X

ramdisk.sh

#!/bin/bash
#
# Create a RAM Disk in Mac OS X 10.5, 10.6, 10.7 or later.
# To remove the RAM disk, simply eject it from the desktop
# as you would any other disk.
#
# http://osxdaily.com/2007/03/23/create-a-ram-disk-in-mac-os-x/

if [ -z "$1" ]; then
   echo Usage: $0 SIZE_IN_MB
   exit 1
fi

MB_SIZE=$1
# The `hdiutil` wants the number in form of 512K blocks.
# However, we'd like to use values in MB.
let "MB_SIZE *= 2048"

diskutil erasevolume HFS+ "ramdisk" `hdiutil attach -nomount ram://${MB_SIZE}`