You can write to a .bat file just like you can a .txt file using /write. Just make sure that what you write is valid for a .bat file. Then, you can /run the .bat file if that's what you want to do.
If you want to run a command directly in a command prompt, you can do what was suggesting using /run. I'm not sure what you're trying to "echo" to the command prompt or why you'd want to. You need to be more specific in what your goal is for people to be able to help you with specific information rather than general.
There really isn't any reason I can think of as to why you'd echo a message from chat to the command prompt. It doesn't make any sense to do so. The command prompt is for executing commands, not for logging chat. If there's a reason or you have a better example of what you want to happen and why, then it would really help.
