simple way to test authentication in scripts

[ktdreyer]

I have seen several bash scripts that test authentication to a registry ahead of launching into larger build processes. The idea is to fail fast with a friendly error if it appears that authentication will not work later on. Example:

if ! grep -q registry.redhat.io ${XDG_RUNTIME_DIR}/containers/auth.json ; then
	echo "No credentials found for registry.redhat.io."
	exit 1
fi

# ... run larger code here that assumes valid registry.redhat.io access towards the end...

An implementation like this assumes that podman will always use ${XDG_RUNTIME_DIR}/containers/auth.json. There are plenty of nuances to podman and skopeo's default behavior! (Eg. REGISTRY_AUTH_FILE always takes precedence, or several CI or containerized environments never set XDG_RUNTIME_DIR, etc.)

What if there was a simple podman has-login registry.redhat.io or something to test that our credential exists in whatever auth JSON podman would normally use? And print a friendly error to the user with a non-zero exit code?

[Luap99]

$ podman login --get-login quay.io
Error: not logged into quay.io

[ktdreyer]

Thanks, I never saw the --get-login option before! This is the answer I'm looking for.