Create bootable Windows installer drive from Linux

mkwinusb.sh

#!/bin/bash
die(){
 echo -e "\n$1"
 echo -e "\nUsage: $0 /path/to/windows.iso /path/to/usb [gpt|mbr] [full|quick]\n"
 exit
}
[ "$(id -u)" != "0" ] && die "You must be root to run this script"
[ -f "$1" ] && iso="$1" || die "Error: File $1 does not exist"
[ -e "$2" ] && usb="$2" || die "Error: Drive $2 not present"
[[ ${3,,} = "mbr" ]] && { mode=1; echo "Mode: MBR"; } || { mode=0; echo "Mode: GPT"; }
[[ ${4,,} = "full" ]] && { files=1; echo "Files: Full"; } || { files=0; echo "Files: Quick"; }
curl -LJO https://github.com/pbatard/rufus/raw/master/res/uefi/uefi-ntfs.img
umount "${usb}"?*
wipefs -fa "${usb}"
parted "${usb}" -s mklabel `[ $mode = 1 ] && echo msdos || echo gpt`
bs=`lsblk -bno log-sec "$usb" |head -1`
size=$(((`stat -c '%s' uefi-ntfs.img`+$bs-1)/$bs))
parted "${usb}" -s mkpart primary ntfs 4MiB -- -`[ $mode = 1 ] && echo $(($size+1)) || echo $(($size+1+33))`s
parted "${usb}" -a none -s mkpart primary fat16 -- -`[ $mode = 1 ] && echo $size || echo $(($size+33))`s -`[ $mode = 1 ] && echo 1 || echo $((1+33))`s
sync "${usb}"
mkntfs -v -Q -I -T -F -L "Windows_USB" "${usb}1"
tmpiso=$(mktemp /tmp/tmpisoXXXX -d)
tmpusb=$(mktemp /tmp/tmpusbXXXX -d)
mount --options loop,ro --types udf,iso9660 "${iso}" "${tmpiso}"
mount "${usb}1" "${tmpusb}"
if [ $files = 1 ]
then
rsync -aP "${tmpiso}"/ "${tmpusb}"
else
rsync -aP --exclude 'sources/install.wim' "${tmpiso}"/ "${tmpusb}"
touch "${tmpusb}"/sources/install.wim
fi
if [ $mode = 1 ]
then
 grub-install --target=i386-pc --boot-directory="${tmpusb}" --force "${usb}"
 echo -e "ntldr /bootmgr\nboot" > "${tmpusb}"/grub/grub.cfg
fi
umount "${tmpiso}" "${tmpusb}"
rm -rf "${tmpiso}" "${tmpusb}"
dd if=uefi-ntfs.img of="${usb}2"
unset -v iso usb mode bs size

Script has been updated, thank you @andrewdbate for testing and reporting back.

Changes:

• supports both gpt and mbr schemes via optional argument
• calculate offsets and sizes from downloaded uefi-ntfs.img file
• added reserved space at end of GPT drive as per feedback

This is still untested (due to lack of hardware) so any further feedback is welcome.