POSTIN

/bin/sh

if [ ! -x /usr/bin/emacs -a ! -L /usr/bin/emacs ]; then
  ln -sf emacs-nox /usr/bin/emacs
fi

POSTUN

/bin/sh

[ $1 = 0 ] || exit 0
if [ -L /usr/bin/emacs ]; then
  rm /usr/bin/emacs
fi

Triggers

emacs-X11

/bin/sh

if [ -L /usr/bin/emacs ]; then
  rm /usr/bin/emacs
fi

emacs-X11

/bin/sh

[ $2 = 0 ] || exit 0
if [ ! -L /usr/bin/emacs ]; then
  ln -sf emacs-nox /usr/bin/emacs
fi