silent_which ()
{
        which $1 1>/dev/null 2>/dev/null || {
                echo "================================================="
                echo "================================================="
                echo "= WARNING: Package '$1' is required"
                echo "=          to build Xen documentation"
                echo "================================================="
                echo "================================================="
        }
        which $1 1>/dev/null 2>/dev/null
}

silent_which latex      || exit 1
silent_which dvips      || exit 1
silent_which ps2pdf     || exit 1
silent_which fig2dev    || exit 1

exit 0