Imaging a USB flash drive from a Mac (suitable for making a bootable Ubuntu flash drive, for instance).

image.sh

#!/bin/bash

echo "Searching for available ISO..."
find ~ -name "*.iso" -type f -size +1048576 | xargs ls -l
read -e -p "Which ISO should be used? " ISO_FILE
if [ "${ISO_FILE}" == "" ] ; then
  echo "No ISO selected!"
  exit 1
fi
echo "Using ${ISO_FILE}"

ls ${ISO_FILE} 1>/dev/null 2>&1
EXISTENCE_CHECK=$?
if [ ! "${EXISTENCE_CHECK}" == "0" ] ; then
  echo  "ISO file does not exist: ${ISO_FILE}"
  exit 1
fi

df -h
read -e -p "Which device should we image? " DEVICE
echo "Imaging ${DEVICE}"

ls ${DEVICE} 1>/dev/null 2>&1
EXISTENCE_CHECK=$?
if [ ! "${EXISTENCE_CHECK}" == "0" ] ; then
  echo "Device does not exist: ${DEVICE}"
  exit 1
fi

# Convert /dev/disk1s1 to /dev/disk1 (the "parent device name")
# And thence to /dev/rdisk1 (the "raw device name")
PARENT_DEVICE=$(dirname ${DEVICE})/$(basename ${DEVICE} | grep -oE "^[a-zA-Z]+[0-9]*" | head -1)
RAW_DEVICE=$(dirname ${PARENT_DEVICE})/r$(basename ${PARENT_DEVICE})
  
ls ${RAW_DEVICE} 1>/dev/null 2>&1
EXISTENCE_CHECK=$?
if [ ! "${EXISTENCE_CHECK}" == "0" ] ; then
  echo "Raw device does not exist: ${RAW_DEVICE}"
  exit 1
fi

# Convert the ISO to a disk image file
IMG_FILE=${ISO_FILE%.*}.img
if [ -e "${IMG_FILE}" ] ; then
  echo "Disk image file already exists, not converting ISO"
else
  echo "Converting ISO file to disk image file"
  hdiutil convert -format UDRW -o ${IMG_FILE} ${ISO_FILE}
  # Damn you implicit defaults
  mv ${IMG_FILE}.dmg ${IMG_FILE}
fi

sudo diskutil unmountDisk ${PARENT_DEVICE}
if [ "$?" == "0" ] ; then
  sudo dd bs=1m if=${IMG_FILE} of=${RAW_DEVICE}
  # chug chug chug chug chugs
  
  if [ "$?" == "0" ] ; then
    # Done, now unmount so we can eject
    diskutil eject ${PARENT_DEVICE}
    
    if [ "$?" == "0" ] ; then
      echo "Done"
      exit 0
    fi
  fi
fi

echo "Writing ISO file to USB drive failed"
exit 1