What is `cmd /s` for?

Question

The Windows command prompt (cmd.exe) has an optional /s parameter, which modifies the behavior of /c (run a particular command and then exit) or

Answer 1

Here's an example of how it can make a difference.

Suppose you have two executables: c:\Program.exe and c:\Program Files\foo.exe.

If you say

cmd /c "c:\Program Files\foo"

you'll run foo.exe (with no arguments) whereas if you say

cmd /s /c "c:\Program Files\foo"

you'll run Program.exe with Files\foo as the argument.

(Oddly enough, in the first example, if foo.exe didn't exist, Program.exe would run instead.)

Addendum: if you were to type

 c:\Program Files\foo

at the command prompt, you would run Program.exe (as happens with cmd /s /c) rather than foo.exe (as happens with just cmd /c). So one reason for using /s would be if you want to make sure a command is parsed in exactly the same way as if it were being typed at the command prompt. This is probably more likely to be desirable in the scenario in the question Michael Burr linked to, where cmd.exe is being launched by CreateProcess rather than from a batch file or the command line itself..

That is, if you say

CreateProcess("cmd.exe", "cmd /s /c \"" MY_COMMAND "\"", ...)

then the string MY_COMMAND will be parsed exactly as if it were typed at the command prompt. If you're taking command-line input from the user, or if you're a library processing a command line provided by an application, that's probably a good idea. For example, the C runtime library system() function might be implemented in this way.