PREUN

/bin/sh

if [ $1 -eq 0 ]; then
 if [ "$(readlink /usr/lib/firebird/bin 2> /dev/null)" = "/usr/lib/firebird/bin-classic" ]; then
  rm -f /usr/lib/firebird/bin
 fi
fi

POSTIN

/bin/sh

if [ "$(readlink /usr/lib/firebird/bin 2> /dev/null)" \!= "/usr/lib/firebird/bin-classic" ]; then 
 [ -e /usr/lib/firebird/bin ] && rm -f /usr/lib/firebird/bin
 ln -s /usr/lib/firebird/bin{-classic,}
fi