postinst is in w3c-markup-validator 1.3+dfsg-3.
This file is a maintainer script. It is executed when installing (*inst) or removing (*rm) the package.
The actual contents of the file can be viewed below.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 | #! /bin/sh
# postinst script for w3c-markup-validator
#
# see: dh_installdeb(1)
set -e
# summary of how this script can be called:
#        * <postinst> `configure' <most-recently-configured-version>
#        * <old-postinst> `abort-upgrade' <new version>
#        * <conflictor's-postinst> `abort-remove' `in-favour' <package>
#          <new-version>
#        * <deconfigured's-postinst> `abort-deconfigure' `in-favour'
#          <failed-install-package> <version> `removing'
#          <conflicting-package> <version>
# for details, see http://www.debian.org/doc/debian-policy/ or
# the debian-policy package
#
# quoting from the policy:
#     Any necessary prompting should almost always be confined to the
#     post-installation script, and should be protected with a conditional
#     so that unnecessary prompting doesn't happen if a package's
#     installation fails and the `postinst' is called with `abort-upgrade',
#     `abort-remove' or `abort-deconfigure'.
case "$1" in
    configure|reconfigure)
        # Old versions stored config files here
        # We won't delete the old config file in case there are
        # customizations. However we must delete the link pointing to it
        # so that the upgrade can proceed.
        for old in apache2 apache apache-ssl apache-perl; do
            if [ -s /etc/$old/w3c-markup-validator.conf ]; then
                rm /etc/$old/w3c-markup-validator.conf
            fi
        done
	rm -f /etc/apache2/conf.d/w3c-markup-validator.conf
        if [ -e /usr/share/apache2/apache2-maintscript-helper ] ; then
            . /usr/share/apache2/apache2-maintscript-helper
            if ! a2query -qm include ; then
                apache2_invoke enmod include || exit $?
            fi
            if ! a2query -qm rewrite ; then
                apache2_invoke enmod rewrite || exit $?
            fi
            if ! a2query -qm cgi ; then
                apache2_invoke enmod cgi || exit $?
            fi
            apache2_invoke enconf w3c-markup-validator || exit $?
        fi
    ;;
    abort-upgrade|abort-remove|abort-deconfigure)
    ;;
    *)
        echo "postinst called with unknown argument \`$1'" >&2
        exit 1
    ;;
esac
# dh_installdeb will replace this with shell code automatically
# generated by other debhelper scripts.
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