Sometimes I type a command in linux and it's not found. I try to install it and it's not found.

> foo
  (not found)

> apt install -y foo
  (no install candidate)

Often it will say what package you need to install, but when it doesn't it's usually something like "archery-tools2" or something you'd never guess and if you did you'd wished you'd gone to Vegas instead. You'd have to be pretty lucky.

Googling said I could do: dpkg -S /usr/bin/top which is cool but that means it is already installed and so... moot.

# (For the record, ^^^ command to find out where a specific command comes from:)
> root@5e60afe003a9:/# dpkg -S /usr/bin/top
  coreutils: /usr/bin/top

But, apt-file to the rescue!

Oh, but you have to install it. Sigh. At least it's the same name as the package.

> apt update -y && apt install -y apt-file && apt-file update

Okay, now you can search. Easy as pi. Say you want to install 'top':

> apt-file search top

Er...

eg: apt-file search top

apt-file search --regex "\btop$"

apt-file search --regex "\/top$" # <<< wow, you REALLY gotta want it!!