Empty Swap. Can be put into ~/.bashrc or similar and then called with stopswap.

stopswap

mem_stat() {
    mem_total="$(free | head -2 | tail -1 | awk '{print $2}')"
    mem_free="$(free | head -2 | tail -1 | awk '{print $4}')"
    mem_percentage=$((mem_free * 100 / $mem_total))
    swap_total="$(free | tail -1 | awk '{print $2}')"
    swap_used="$(free | tail -1 | awk '{print $3}')"
    swap_percentage=$(($swap_used * 100 / $swap_total))

    echo -e "Free memory:\t$((mem_free / 1024))/$((mem_total / 1024)) MB\t($mem_percentage%)"
    echo -e "Used swap:\t$((swap_used / 1024))/$((swap_total / 1024)) MB\t($swap_percentage%)"
}

stopswap() {
	mem_stat
	if (( $swap_used == 0 ))
	then echo "No swap is in use."
	elif (( $swap_used + 100000 < mem_free ))
	then echo "Freeing swap..."
		sudo swapoff -a
		sudo swapon -a
		mem_stat
	else
		echo "Not enough free memory!"
	fi
}

Scripts is a little incorrect and doesn't always work with low RAM size.
mem_free="$(free | head -2 | tail -1 | awk '{print $4}')"
With 2GB RAM and ~580MB used (according to htop) command shows that I have only 94MB of free memory so script refuses to clear swap.

I guess it's better to print "available" memory (like in Jekis version)
mem_free="$(free | head -2 | tail -1 | awk '{print $7}')"