#!/bin/bash
CURRENT_KERNEL=`uname -r`
OLD_KERNELS=`ls /usr/src/ -l | grep -v ">"| awk '{print $9}' | grep linux | grep -v $CURRENT_KERNEL | sed -r 's/^.{6}//'`
AMOUNT_OF_OLD_KERNELS=`ls /usr/src/ -l | grep -v ">" | awk '{print $9}' | grep linux | grep -v $CURRENT_KERNEL | wc -l`
echo "Amount of kernels to get rid of: $AMOUNT_OF_OLD_KERNELS"
read -r -p "Are you sure? [y/N] " response
if [[ $response =~ ^([yY][eE][sS]|[yY])$ ]]
then
	for (( COUNTER=0; COUNTER<$AMOUNT_OF_OLD_KERNELS; COUNTER++ ))
	do
		HEAD=$((COUNTER+1))
		DIR=`ls /usr/src/ -l | grep -v ">" | awk '{print $9}' | grep linux | grep -v $CURRENT_KERNEL | head -n$HEAD | tail -n1`
		echo -ne "Fetching package name of kernel #$HEAD... "
		# Gentoo only
		PACKAGE=`equery b $DIR | head -n+1`
		echo "done!"
		echo "Kernel #$HEAD is currently known as $PACKAGE"
		echo -ne "Removing kernel #$HEAD ..."
		# Gentoo only
		emerge -Cq $PACKAGE
		echo "done!"
		echo -ne "Removing kernel #$HEAD source directory... "
		rm -rf /usr/src/$DIR
		echo "done!"
		# Truncating the "linux-" from directory name so that we can find it in /boot and /lib/modules
		KERNEL=`echo $DIR | sed -r 's/^.{6}//'`
		echo -ne "Removing kernel #$HEAD from /boot... "
		rm -f /boot/*$KERNEL*
		echo "done!"
		echo -ne "Removing kernel #$HEAD modules... "
		rm -rf /lib/modules/$KERNEL
		echo "done!"
		echo "$PACKAGE has been purged from the system."
	done
	echo "All your old kernels have been purged. Have a nice day and remember to install Gentoo!"
else
    echo "Quitting. No changes made."
fi