pre_install() {
	:
}

post_install() {
	for _ksh in ksh ksh93 rksh rksh93; do
		grep -qle "^/bin/${_ksh}$" /etc/shells || echo "/bin/${_ksh}" >> '/etc/shells'
		grep -qle "^/usr/bin/${_ksh}$" /etc/shells || echo "/usr/bin/${_ksh}" >> '/etc/shells'
	done
}

pre_upgrade() {
	:
}

post_upgrade() {
	post_install
}

pre_remove() {
	for _ksh in ksh ksh93 rksh rksh93; do
		if getent passwd root | cut -d: -f7 | grep -qle "/bin/${_ksh}"; then
			echo "**************************************************"
			echo "*** Warning: root has ${_ksh} as the login shell."
			echo "*** Shell changed to sh to prevent loss of access."
			echo "**************************************************"
			chsh -s '/bin/sh'
		fi
		sed -i -e '/^\/bin\/'"${_ksh}"'$/d' -e '/^\/usr\/bin\/'"${_ksh}"'$/d' '/etc/shells'
	done
}

post_remove() {
	# /usr/bin/${_ksh} is also detected
	for _ksh in ksh ksh93 rksh rksh93; do
		if getent passwd | cut -d: -f7 | grep -qle "/bin/${_ksh}"; then
			echo "*** Warning: Some users have ${_ksh} as their login shell."
			echo "*** Fix promptly to restore access."
		fi
	done
}