flash.sh script to flash Raspberry Pi SD card image on a Mac

flash.sh

#!/bin/bash
# Flash Raspberry Pi SD card images on your Mac
# Stefan Scherer - scherer_stefan@icloud.com
# MIT License

function usage {
  echo "Usage: $0 name-of-rpi.img [name-of-occidentalis.txt]"
  echo ""
  echo "Flash a local or remote Raspberry Pi SD card image on your Mac."
  echo ""
  echo "Optionally customize your Pi image with a hostname and your WiFi settings."
  echo "Example for the occidentalis.txt file:"
  echo ""
  echo "# hostname for your Hypriot Raspberry Pi:
hostname=your-pi-hostname

#
# basic wireless networking options:
# wifi_ssid=your-wifi-ssid
# wifi_password=your-wifi-preshared-key
"
  exit 1
}

beginswith() { case $2 in $1*) true;; *) false;; esac; }
endswith() { case $2 in *$1) true;; *) false;; esac; }

if [ "$1" == "" ]; then
  usage
fi
if [ "$1" == "--help" ]; then
  usage
fi

image=$1

occi=$2

if [ "$1" == "--help" ]; then
  usage
fi

if beginswith http:// "$image"; then
  echo "Downloading $image ..."
  curl -L -o /tmp/image.img.zip "$image"
  image=/tmp/image.img.zip
fi

if beginswith s3:// "$image"; then
  echo "Downloading $image ..."
  aws s3 cp "$image" /tmp/image.img.zip
  image=/tmp/image.img.zip
fi

if [ ! -f "$image" ]; then
  echo "File not found."
  exit 10
fi

if endswith .zip "$image"; then
  echo "Uncompressing $image ..."
  unzip -o "$image" -d /tmp
  image=$(unzip -l "$image" | grep -v Archive: | grep img | cut -c 30-)
  image="/tmp/$image"
  echo "Use $image"
fi

if [[ "$OSTYPE" != "darwin"*  ]]; then
  echo "Only Mac OSX supported"
  exit 11
fi

# try to find the correct disk of the inserted SD card
disk=`df | grep -e "disk[0-9]s1" | grep Volumes | cut -c 6-10`
if [ "$disk" == "" ]; then
  echo "No SD card found. Please insert SD card, I'll wait for it..."
  while [ "$disk" == "" ]; do
    sleep 1
    disk=`df | grep -e "disk[0-9]s1" | grep Volumes | cut -c 6-10`
  done
fi

df
while true; do
  echo ""
  read -p "Is /dev/${disk}s1 correct? " yn
  case $yn in
    [Yy]* ) break;;
    [Nn]* ) exit;;
    * ) echo "Please answer yes or no.";;
  esac
done

echo "Unmounting ${disk} ..."
diskutil unmountDisk /dev/${disk}s1
diskutil unmountDisk /dev/${disk}
echo "Flashing $image to ${disk} ..."
pv=`which pv 2>/dev/null`
if [ $? -eq 0 ]; then
  # this sudo here is used for a login without pv's progress bar
  # hiding the password prompt
  size=`sudo stat -f %z $image`
  cat $image | pv -s $size | sudo dd bs=1m of=/dev/r${disk}
else
  echo "No `pv` command found, so no progress available."
  echo "Press CTRL+T if you want to see the current info of dd command."
  sudo dd bs=1m if=$image of=/dev/r${disk}
fi

if [ -f "$occi" ]; then
  # try to find the correct disk again
  boot=$(df | grep /dev/${disk}s1 | sed 's,.*/Volumes,/Volumes,')
  if [ "$boot" == "" ]; then
    while [ "$boot" == "" ]; do
      sleep 1
      boot=$(df | grep /dev/${disk}s1 | sed 's,.*/Volumes,/Volumes,')
    done
  fi

  echo "Copying $occi to ${boot}/occidentalis.txt ..."
  cp "$occi"  "${boot}/occidentalis.txt"
fi

echo "Unmounting and ejecting ${disk} ..."
sleep 1
diskutil unmountDisk /dev/${disk}s1
diskutil unmountDisk /dev/${disk}s2
diskutil eject /dev/${disk}
if [ $? -eq 0 ]; then
  afplay /System/Library/Sounds/Bottle.aiff
  echo "🍺  Finished."
else
  afplay /System/Library/Sounds/Basso.aiff
  echo "👎  Someting went wrong."
fi

I'm not familiar with OSX, nor the details of diskutil unmountDisk (and the man page doesn't specify :-/), but you might consider a couple explicit sync's prior to unmounting -- that way you know that the data is flushed to disk.