Make Windows USB Installer on Mac

make_windows_usb.sh

#!/bin/bash
# Installs Homebrew and Wimlib if not already installed,
# then formats and prepares an external USB device as
# a bootable Windows installer from your Windows ISO.
#
# Usage: ./make_windows_usb.sh windows_installer.iso
# (first make executable with: chmod u+x ./make_windows_usb.sh)
#
# Insert a single external USB target device before running.
# Do not use blindly – bad things can happen.

#######################################################################################
# Colours
BoldRed='\033[1;31m'     # Critical Errors
BoldGreen='\033[1;32m'   # Success Messages
BoldYellow='\033[1;33m'  # Warnings or User Prompts
BoldBlue='\033[1;34m'    # Information or Status Messages
NoColour='\033[0m'       # Reset Colour

#######################################################################################
# Errors
# Using an array to store error messages
errors[0]="${BoldRed}No ISO image specified.${NoColour}\nUsage: ./make_windows_usb.sh windows_installer.iso"
errors[1]="${BoldRed}Please make sure you have exactly one USB storage device attached.${NoColour}\nusb_disk_count devices found"
errors[2]="${BoldRed}Fatal Error:${NoColour} There was a problem formatting the disk."
errors[3]="${BoldRed}Fatal Error:${NoColour} There was a problem rsyncing the files."
errors[4]="${BoldRed}Fatal Error:${NoColour} There was a problem creating the installation files."
errors[5]="${BoldRed}Error:${NoColour} There was a problem ejecting the USB device."
errors[6]="${BoldRed}Error:${NoColour} There was a problem unmounting the ISO."

#######################################################################################
# Sanity Check
if [ $# -eq 0 ]; then
    echo -e ${errors[0]}
    exit 1
fi

usb_disk_count=$(diskutil list | grep "external" | awk 'END {print NR}')

if [ ! $usb_disk_count -eq 1 ]; then
    echo -e ${errors[1]} | sed "s/usb_disk_count/$usb_disk_count/g"
    exit 1
fi

#######################################################################################
# Homebrew
echo -e "${BoldBlue}Preparing Homebrew.${NoColour}"

which -s brew
if [[ $? != 0 ]] ; then
    echo -e "${BoldYellow}Installing Homebrew.${NoColour}"
    /bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install.sh)"
else
    echo -e "${BoldBlue}Making sure Homebrew is up-to-date.${NoColour}"
    brew update &>/dev/null
fi

#######################################################################################
# Wimlib
echo -e "${BoldBlue}Preparing Wimlib.${NoColour}"

lib="wimlib"
lib_exec="wimlib-imagex"

which -s $lib_exec
if [[ $? != 0 ]] ; then
    echo -e "${BoldYellow}Installing Wimlib.${NoColour}"
    brew install $lib
else
    echo -e "${BoldBlue}Making sure Wimlib is up-to-date.${NoColour}"
    brew outdated $lib  &>/dev/null || brew install $lib
fi

#######################################################################################
# ISO Disc Image
echo -e "${BoldBlue}Preparing ISO.${NoColour}"

image_file="$1"

IFS=$'\n' read -d'\n' iso_dev_entry iso_mount_point < <(
    hdiutil mount "${image_file}" | awk '{print $1; print $2}'
)

echo -e "${BoldBlue}ISO mounted at ${iso_mount_point}.${NoColour}"

#######################################################################################
# USB Drive File Copy
echo -e "${BoldBlue}Preparing USB.${NoColour}"

usb_disk=$(diskutil list | grep "external" | head -n 1 | awk '{print $1}')
usb_label="WINDOWS"
usb_mount_point="/Volumes/$usb_label"

echo -e "${BoldYellow}Ready to format $usb_disk.${NoColour}"
read -p "Press any key to continue or ctrl-c to abort."

# Format USB drive
diskutil eraseDisk MS-DOS "${usb_label}" MBR ${usb_disk} || { echo -e ${errors[2]}; exit 1; }

echo -e "${BoldBlue}USB formatted. Checking mount status...${NoColour}"
diskutil list # Debugging output to check mount status

# Rsync - Copy files to USB
echo -e "${BoldYellow}Ready to start writing contents of $image_file to $usb_disk.${NoColour}"
read -p "Press any key to copy source files to USB (step 1)."

rsync -avh --progress --exclude=sources/install.wim ${iso_mount_point}/ ${usb_mount_point} || { echo -e ${errors[3]}; exit 1; }

echo -e "${BoldBlue}Rsync complete. Ready to split install.wim...${NoColour}"

# Wimlib - Split install.wim into smaller files
read -p "Press any key to copy files to USB (step 2)."
wimlib-imagex split "$iso_mount_point/sources/install.wim" "$usb_mount_point/sources/install.swm" 3800 || { echo -e ${errors[4]}; exit 1; }

# Eject the mounted volumes
echo -e "${BoldBlue}All done.${NoColour}"
read -p "Press any key to eject mounted volumes or ctrl-c to abort."

hdiutil eject ${usb_mount_point} || { echo -e ${errors[5]}; }
hdiutil eject ${iso_mount_point} || { echo -e ${errors[6]}; }

echo -e "${BoldGreen}All done!${NoColour}"
echo "You can unplug the USB drive now."