The dpkg and apt-get commands are pretty useful and provide a lot of functionality. Here's some common things that you may want to do:

Search for the package that installed the file diff.info.gz

$ dpkg --search diff.info.gz [alternative is -S]

List all packages installed (one line per package)

$ dpkg --list [alternative is -l] $ dpkg --get-selections

What is the (one-line) status of the diff package?

$ dpkg --list diff

List the information for any package with diff in its name

$ dpkg --list *diff*

List files associated with the package diff

$ dpkg --listfiles diff [alternative dpkg -L diff]

What packages mention diff?

$ apt-cache search diff

Display information about a package

$ apt-cache show diff [alternative is dpkg --print-avail]

What packages depend on diff?

$ apt-cache showpkg diff $ apt-cache depends diff

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