su: use correct option when cmd.exe is used as shell

Most Unix shells (and PowerShell) use the '-c' option to specify
commands to execute.  cmd.exe uses '/c' instead.

Detect when cmd.exe is the 'shell' being used with 'su -s' and
adjust the command option to suit.

Adds 48-56 bytes.

(GitHub issue #438)

1 files changed, 3 insertions, 1 deletions

diff --git a/loginutils/suw32.c b/loginutils/suw32.c
index cbe727969..821071388 100644
--- a/loginutils/suw32.c
+++ b/loginutils/suw32.c
@@ -111,7 +111,9 @@ int suw32_main(int argc UNUSED_PARAM, char **argv)
                 args = xappendword(args, "-N");
 
         if (opt_command) {
-                args = xappendword(args, "-c");
+                args = xappendword(args,
+                        (opt_shell && strcasecmp(bb_basename(bb_path), "cmd.exe") == 0) ?
+                        "/c" : "-c");
                 q = quote_arg(opt_command);
                 args = xappendword(args, q);
                 free(q);