https://www.debian.org/doc/debian-policy/ap-pkg-conffiles.html : "Note that a package should not **modify** a dpkg-handled conffile in its maintainer scripts. Doing this will lead to dpkg giving the user confusing and possibly dangerous options for conffile update when the package is upgraded."
>> $ stat /etc/exim4/update-exim4.conf.conf >> Modify: 2019-04-18 01:32:53.473019451 +0800 <------------THIS Modified! Anyway to compare two things one could use $ test "$THING!" = "$THING2" No need to worry about accidentally leaving temp files on disk, which is a must less risk than failed unnecessary writes to a file that you won't end up changing anyway. You might argue that well, the md5sum doesn't change. But then I will argue back that what if I updated the modification dates of all the files in your home directory? That would make the whole concept of the date stamp of a file meaningless.