How to get current Debian/Ubuntu version name in a Bash script

Question

How to get in a Bash script the simple lowercase name of the current Debian or Ubuntu release, e.g. stretch, jessie, xenial, artful?

Answer 1

It's available in /etc/os-release, but it's inconsistent between Ubuntu and Debian. Documentation isn't very specific on how to use it.

. /etc/os-release
NAME=$VERSION_CODENAME
if [ -z "$NAME" ]; then
    NAME=$(echo $VERSION | sed -rn 's|.+\((.+)\).+|\1|p')
fi

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It's also available in the command lsb_release, which, when installed, needs no parsing:

NAME=$(lsb_release --codename --short)

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Finally, it can be obtained directly from the sources file with some heavy-ish parsing.

NAME=$(sed -rn 's|^deb\s+\S+\s+(\w+)\s+main.*$|\1|p' /etc/apt/sources.list | head -n 1)