Starting the Command Promt from a program using 'system(...)' - c

Question

If I start the Command Prompt the Standard" way, go to 'C:\Windows\System32' and do "dir m*.exe", I get "several screensful" of listing. Among others 'msg.exe' is there. And if I do 'msg /?' :
C:\WINDOWS\system32>msg /?
MSG {username | sessionname | sessionid | #filename | *}
[/SERVER:servername] [/TIME:seconds] [/V] [/W] [message]
e
tc.
And the 'msg' command works as expected.
But if I start the Command Prompt from a program, with the 'system(...)' function, i.e. like this (Console application in Visual Studio):
#include "stdafx.h"
#include <stdlib.h>
int _tmain(int argc, _TCHAR* argv[])
{
system("cmd") ;
return 0;
}
'msg' does not work:
C:\WINDOWS\system32>msg /?
'msg' is not recognized as an internal or external command,
operable program or batch file.
And dir m*.exe in this Command Prompt gives only half a screen of listing. Especially, msg.exe is not there.
Somebody who can explain why? Somebody who knows a walk-around? Or (even better) how I can do 'msg' from a program? I.e.
system("msg * /server:undis "Directory 'expenses' synced") ;
I would embed it in a program run via "Program after / When changes are made" in SyncBack Pro (2BrightSparks).

Answer 1

As n.m. comments, most likely the problem is that you're building a 32-bit program so the cmd you run with system is the 32-bit cmd emulator and not the nomral win64 cmd program.
This is what leads to your problem -- whenever you try to access C:\WINDOWS\system32 in 32-bit mode, the system silently sends you to C:\WINDOWS\sysWOW64 instead. That's because on win64, system32 actually contains 64-bit programs and dlls, not 32-bit ones. The 32-bit ones are in sysWOW64.
Now normally this isn't an issue -- most of what you want in the 32-bit program is in sysWOW64, so everything is fine. The problem is that msg is not. So to get around that, you need to "escape" from the 32-bit sandbox. To do that, you need to go to C:\WINDOWS\sysnative. This directory (which is only available/visible in 32-bit mode) silently redirects to the (real, 64-bit) C:\WINDOWS\system32 directory. If you cd to that directory, you should see msg.exe and be able to run it. Or just run it directly from your system command:
system("C:\\WINDOWS\\sysnative\\msg * /server:undis "Directory 'expenses' synced") ;