In a new folder completely empty :
composer init
i have :
Welcome to the Composer config generator
This command will guide you through creating your composer.json config.
Package name (<vendor>/<name>) [slordef/test-composer]:
[Symfony\Component\Console\Exception\RuntimeException]
Aborted
init [--name NAME] [--description DESCRIPTION] [--author AUTHOR] [--type [TYPE]] [--homepage HOMEPAGE] [--require REQUIRE] [--require-dev REQUIRE-DEV] [-s|--stability STABILITY] [-l|--license LICENSE] [--repository REPOSITORY]
Composer is up to date... Dont know how it append
-vvvto get debug output e.g:composer init -vvv