How to test if package is installed?

Question

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How can I check if a package is installed (no superuser privileges)

I want a shell script method to test/report if a package is installed. I don't need details, only a yes/no.

I've come up with this method. Is there a more direct way?

is_installed=0
test_installed=( `apt-cache policy domy-ce | grep Installed: ` )
[ ! "${test_installed[1]}" == "(none)" ] && is_installed=1

Answer 1

You could use the output of dpkg -s <packagename> or dpkg-query -l <packagename>

in your script for the purpose.
Courtesy:https://stackoverflow.com/questions/1298066/check-if-a-package-is-installed-and-then-install-it-if-its-not

e.g.

#!/bin/sh

for P; do
    dpkg -s "$P" >/dev/null 2>&1 && {
        echo "$P is installed."
    } || {
        echo "$P is not installed."
    }
done

Usage: script.sh package1 package2 .... packageN

Courtesy:https://stackoverflow.com/a/10594734/749232