Download and install a raspbian image on a SD card for a Raspberry Pi 3 on OSX. Use "chmod +x setup_raspbian_osx.sh" to make it executable.

setup_raspbian_osx.sh

#!/usr/bin/env bash

# download and write image to sd card
image() {
    read -p "Enter raspbian image download link: " link
    if [ -n "$link" ]; then
        echo "Download latest raspbian image from:" $link
    else
        link=https://downloads.raspberrypi.org/raspbian_lite_latest
        echo "No link provided. Using default link:" $link
    fi
    
    zip="${link##*/}"
    curl -L $link > $zip && unzip $zip -d .
    img=$(ls -t -U *-raspbian-*-lite.img)
    
    echo "Write" $img "with dd to" /dev/$disk
    sudo dd bs=1m if=$img of=/dev/$disk conv=sync

    echo "dd finished, eject sd card now"
    sudo diskutil eject /dev/$disk

    # remove artifacts after setup
    rm -f $zip && echo "rm" $zip
    rm -f $img && echo "rm" $img
}

# discover disk of sd card and unmount sd card
diskutil list
echo "Identify the disk (not the partition) of your SD card, e.g. disk4, not  disk4s1"
read -p "Enter disk identifier to be unmounted: " disk
if [ -n $disk ]; then
    diskutil unmountDisk /dev/$disk
    image "$disk"
fi