Get list of installed packages? [duplicate]

You have to run the same command (there's no need to run it as root)

dpkg --get-selections > ~/InstalledPackages.list

Then you can

cat ~/InstalledPackages.list

to see the content.

Now, if you are not sure how's ~ been processed, you can

cd ~
pwd

And that's it.

Use dpkg-query, this command is precisely intended to what you need: request on packages data‑base. A quick man dpkg-query will tell you more, however, you may try dpkg-query --list or dpkg-query -- show.

You said you've looked in the root folder, but with the "~" you are clearly pointing to the home folder. The root would be /Package.list, or -/Package.list. Check in the home folder.

EDIT: As I can see now, even though my answer was correct, it might have been unclear to a fresh user. I'm sorry for introducing additional confusion. @0R10N thanks for good example :)

What's with these answers lol all this question is asking is a simple dpkg output list,

 dpkg --list | less

 dpkg -l | more 

 dpkg-query -l | tail

 dpkg-query --list | head

 diff <(ps aux| grep x) <(pgrep x)

 apt-file list "package"