RunProcess doesn't list files on Windows

Question

I am using Windows 10, Mathematica version 11.0.1.

SetDirectory["C:\\"];
RunProcess[$SystemShell, All, "dir"]

I found that SystemShell doesn't work on my computer, the above gives

<|"ExitCode" -> 0, 
 "StandardOutput" -> 
  "Microsoft Windows [\[Degree]æ\[PlusMinus]¾ 10.0.15063]

  (c) 2017 Microsoft Corporation¡£\[PlusMinus]£ÁôËùÓÐȨÀû¡£



  C:\\>More? ", "StandardError" -> ""|>

What is wrong? How to fix this?

Answer 1

It will work if you send a newline at the end of dir:

RunProcess[$SystemShell, All, "dir\n"] (* note the \n *)

What I do not understand is why this newline is not necessary when running the equivalent command on Unix-like systems. On OS X, the following works:

RunProcess[$SystemShell, All, "ls"] (* no \n needed *)

Update: As pointed out by Itai, the difference in behaviour between Windows and Unix is normal.

Answer 2

Actually, poking at this some I believe this is correct behavior based on platform differences between cmd.exe and bash (and other Unix shells).

On a Unix system, create a file containing "ls" with no newline. For example, WriteString["test_file","ls"]. Now execute bash < test_file. You'll see the contents of the current directory (or technically, whatever directory bash is in after processing your non-login init files).

On Windows, create a file containing "dir" with no new line by replacing "ls" with "dir" in the above command. Now execute cmd.exe < test_file. You'll see the output More? in your shell, just as in the output given in the question above.

So basically, bash considers an end-of-file with no newline to be valid input, but cmd.exe does not. Which is surely one reason why all the examples in the documentation end with newlines. I'm therefore inclined to consider the current behavior correct and desirable--if the program being called operated at a byte level, we surely wouldn't want to throw an extra 10 byte (or 10 13 bytes on Windows) at it.