POSTIN

/bin/sh

update-alternatives --install /usr/bin/links links /usr/bin/links-text 10

POSTUN

/bin/sh

if [ "$1" = "0" ]; then
  update-alternatives --remove links /usr/bin/links-text || :
fi

Triggers

links

/bin/sh

if [ ! -e /usr/bin/links ]; then
  update-alternatives --auto links
fi