Hi, There's probably a far better way that someone with some more experience will suggest, but the first thing that came to mind is to write a little program/script that does the following: - read all the files, into their own list of packages - combine the lists, filling a list of package names, sorted in alphabetical order and removing duplicates - iterate through the combined list, for each package check each of the four individual lists and if it is in there output it, otherwise leave a space That should achieve it in a fairly simple way, and can be done with any language. Best of luck, Joe <div class="gmail_quote">On 4 May 2014 13:29, "Mark Fraser" <<a href="mailto:mfraz74%2Bubuntu@gmail.com">mfraz74+ubuntu@gmail.com</a>> wrote: <blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"> I've got 4 computers here that I would like to compare the installed packages on each one together. I've done dpkg --get-selection > installed.txt on each computer, but now I'm trying to merge each one into a single file and leave a space where a package isn't installed. Instead of: Acpi-support acpi-support Acpi-support acpi-support adduser acroread adduser adduser Adobereader-enu acroread-bin adobereader-enu adobereader-enu I'd like: Acpi-support acpi-support Acpi-support acpi-support acroread acroread-bin adduser adduser adduser Adobereader-enu adobereader-enu adobereader-enu Any ideas how to achieve this? -- Registered Linux User #466407 <a href="http://counter.li.org" target="_blank">http://counter.li.org</a> -- <a href="mailto:ubuntu-uk@lists.ubuntu.com">ubuntu-uk@lists.ubuntu.com</a> <a href="https://lists.ubuntu.com/mailman/listinfo/ubuntu-uk" target="_blank">https://lists.ubuntu.com/mailman/listinfo/ubuntu-uk</a> <a href="https://wiki.ubuntu.com/UKTeam/" target="_blank">https://wiki.ubuntu.com/UKTeam/</a> </blockquote></div>