A few years ago this saved my bacon when we had a piece of lab equipment that booted DOS (5.0-ish, I think) from a CF card. There was some problem with it and I fixed it by remembering how to copy console input into a file. Input was terminated with ^Z, which I also managed to remember.
It takes text input from the terminal quite literally. No backspacing, no editing. You'll just get control characters in the resulting file.
Type it right the first time or start over. Brutal.
But it works from a disk that has only IO.SYS, MSDOS.SYS, and COMMAND.COM.