postrm_upgrade.sh.erb

#!/bin/sh

<% if attributes[:deb_maintainerscripts_force_errorchecks?] -%>
set -e
<% end -%>

after_remove() {
<%# Making sure that at least one command is in the function -%>
<%# avoids a lot of potential errors, including the case that -%>
<%# the script is non-empty, but just whitespace and/or comments -%>
    :
<% if script?(:after_remove) -%>
<%=  script(:after_remove) %>
<% end -%>
}

after_purge() {
<%# Making sure that at least one command is in the function -%>
<%# avoids a lot of potential errors, including the case that -%>
<%# the script is non-empty, but just whitespace and/or comments -%>
    :
<% if script?(:after_purge) -%>
<%=  script(:after_purge) %>
<% end -%>
}

dummy() {
    :
}


if [ "${1}" = "remove" -o "${1}" = "abort-install" ]
then
    # "after remove" goes here
    # "abort-install" happens when the pre-installation script failed.
    #   In that case, this script, which should be idemptoent, is run
    #   to ensure a clean roll-back of the installation.
    after_remove
elif [ "${1}" = "purge" -a -z "${2}" ]
then
    # like "on remove", but executes after dpkg deletes config files
    # 'apt-get purge' runs 'on remove' section, then this section.
    # There is no equivalent in RPM or ARCH.
    after_purge
elif [ "${1}" = "upgrade" -o "${1}" = "abort-upgrade" ]
then
    # This represents the case where the old package's postrm is called after
    # the 'preinst' script is called.
    # We should ignore this and just use 'preinst upgrade' and
    # 'postinst configure'. The newly installed package should do the
    # upgrade, not the uninstalled one, since it can't anticipate what new
    # things it will have to do to upgrade for the new version.
    dummy
elif echo "${1}" | grep -E -q '(fail|abort)'
then
    echo "Failed to install before the post-removal script was run." >&2
    exit 1
fi