We need to standardize the output of the commands. Currently, they return a whole bunch of things. (See the shx output section).

I think that @nfischer is working on a standardized ShellString for all commands to return. I'm not sure about the details.

At bear minimum, I think that all commands need to return something with stdout and stderr properties. This will allow #269 to simply have error() return the exit code of the previous command (equivalent to $?). It will also greatly simplify shx.