Create ram disk on OS X

CreateRamDisk.sh

#!/bin/bash

LIMIT=8  #size limit

if [[ $# -eq 1 ]]; then
    if [[ ! $1 =~ ^[0-9]+$ ]]; then
        >&2 echo "Error: Invalid parameter: \"$1\""
        exit 1
    fi
    SIZE=$1
elif [[ $# -eq 0 ]]; then
    SIZE=1
else
    >&2 echo "Error: Too many parameters"
    exit 2
fi

if [[ $SIZE -gt $LIMIT ]]; then
    >&2 echo "Error: Should not allocate more than ${LIMIT} GB"
    exit 3
fi

if [[ ! -e /Volumes/RamDisk ]]; then
    echo "Allocating ${SIZE} GB of Ram Disk..."
    diskutil erasevolume HFS+ RamDisk `hdiutil attach -nomount ram://$((1000*1000*2*$SIZE))`
else
    >&2 echo "Error: Ram Disk is exsiting"
    exit 4
fi