postinst is in squid-common 3.5.27-1ubuntu1.
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 | #! /bin/sh
set -e
case "$1" in
	configure)
		#
		# Fix directory->link transition for /usr/share/squid3/errors in
		# 3.0.STABLE15-1: all has gone well, remove temporary directory
		#
		if (dpkg --compare-versions "$2" lt '3.0.STABLE15-1' &&
		   [ ! -h "/usr/share/squid3/errors" ] &&
		   [ -d "/usr/share/squid3/errors" ])
		then
			rm -rf /usr/share/squid3/errors
			ln -s /usr/share/squid-langpack /usr/share/squid/errors
		fi
		if (dpkg --compare-versions "$2" lt '3.0.STABLE15-1' &&
		   [ ! -h "/usr/share/squid/errors" ] &&
		   [ -d "/usr/share/squid/errors" ])
		then
			rm -rf /usr/share/squid/errors
			ln -s /usr/share/squid-langpack /usr/share/squid/errors
		fi
		;;
	abort-upgrade|abort-remove|abort-deconfigure)
		;;
	*)
		#
		#	Unknown action - do nothing.
		#
		exit 0
		;;
esac
# dh_installdeb will replace this with shell code automatically
# generated by other debhelper scripts.
exit 0
 |