How to tell Bash multiple values are success?

[Jeffrey Walton]

Hi Everyone,

I have a systemd service that automatically applies updates. Looking
at the service history, the service reports failure when it installs
updates due to this:

    if dnf -y update &>/dev/null
    then
        echo "Upgraded system"
    else
        echo "Failed to upgrade system"
        exit 1
    fi

The problems seems to be 0, 100 and 200 are success. When updates are
installed either 100 or 200 is returned. Confer,
https://dnf.readthedocs.io/en/latest/command_ref.html .

I looked through Bash Variables, but I did not see a way to signal the
information to Bash. Confer,
https://www.gnu.org/software/bash/manual/html_node/Bash-Variables.html
.

How do I tell Bash 0, 100 and 200 are success? (Or, how to tell Bash 1
is the only failure?)

Thanks in advance