Functions are much more flexible than aliases. The following would overload the usual ls with a version that always does ls -F (arguments are passed in $@, including any flags that you use), pretty much as the alias alias ls="ls -F" would do: ls () { command ls -F "$@" }

To understand this helper, you should understand that every step invocation calls Output() for you behind the scenes. The following DSL use is identical to the one [above]. class Execute < Trailblazer::Activity::Railway step :find_provider, Output(Trailblazer::Activity::Left, :failure) => Track(:failure), Output(Trailblazer::Activity::Right, :success) => Track(:success)