create-ram-disk

#!/bin/bash
# create a RAMDISK like so `create-ram-disk 6` to create a 6Gb ramdisk.
# diagnostic information is written to STDERR: the name of the newly-created disk is written to STDOUT

# from https://stackoverflow.com/a/47354885/6722
set -e

FILEPATH="${BASH_SOURCE[0]}"
FILE=$(basename "${FILEPATH}")
DIR="$(cd "$(dirname "${FILEPATH}")" && pwd)"

SECTOR_SIZE=512
FILE_SYSTEM="APFS"
VOLUME_NAME="RAMDISK"
VOLUME_PATH="/Volumes/${VOLUME_NAME}/"

# grab the command line arg
SIZE_IN_GB=$1; shift || true
SYMLINK_POINT=$1; shift || true

function show_help {
cat <<EOF1
Name

  $FILE

Synposis

    $FILE <size-in-gb>

Description

    creates a ramdisk on macos, and prints the file path of the new volume to 
    STDOUT.

    diagnostic info is written to STDERR.

Examples

    $FILE 5

Options

    <size-in-gb>      size in gigabytes of the disk.

EOF1
}

if [[ "" == "${SIZE_IN_GB}" ]]; then
	show_help
	exit 2
fi

if [[ "" == "${SYMLINK_POINT}" ]]; then
	show_help
	exit 2
fi

# calculate the number of sectors by calculating the bytes in SIZE_IN_GB bytes and dividing by sector size
NUM_SECTORS=$(perl -e "print $SIZE_IN_GB*1024*1024*1024/$SECTOR_SIZE")
IMAGE="ram://${NUM_SECTORS}"
cat <<EOF 1>&2 

$FILE

  ramdisk size       - ${SIZE_IN_GB} Gigabytes
  sector size        - ${SECTOR_SIZE} bytes 
  number of sectors  - $NUM_SECTORS
  image              - $IMAGE

EOF

DEVICE=$(hdiutil attach -nomount "${IMAGE}" | xargs)
echo "Device: $DEVICE"

1>&2 diskutil partitionDisk "${DEVICE}" 1 GPTFormat "${FILE_SYSTEM}" "${VOLUME_NAME}" '100%'
1>&2 hdiutil imageinfo "${DEVICE}"
echo "Volume: ${VOLUME_PATH}"

ln -s "${VOLUME_PATH}" "${SYMLINK_POINT}"
echo "Symlinked: ${SYMLINK_POINT}"