How to start cmd.exe using CreateProcess() without exiting cmd.exe immediately? - winapi

Question

I want to execute Windows' cmd.exe via CreateProcess() from my own command-line program. I redirect its input/output to another program I have written, which needs to have access to cmd.exe. But cmd.exe terminates immediately. I want to run cmd.exe until it receives "exit" from the other program communicating with it via the redirected stdin/stdout. I have tried no parameter, and the parameters /C and /K.
Here is my code:
ZeroMemory( &StartupInfo, sizeof(StartupInfo) );
StartupInfo.cb = sizeof(StartupInfo);
ZeroMemory( &ProcessInformation, sizeof(ProcessInformation) );
StartupInfo.hStdOutput = &cmd_stdout;
StartupInfo.hStdInput = &cmd_stdin;
StartupInfo.hStdError = &cmd_stderr;
//https://stackoverflow.com/questions/4380575/how-to-launch-console-application-using-createprocess-with-minimized-main-window
StartupInfo.dwFlags = STARTF_USESTDHANDLES | STARTF_USESHOWWINDOW;
StartupInfo.wShowWindow = SW_SHOWNOACTIVATE;//SW_SHOWNORMAL also tried;
pprogstr = "C:\\WINDOWS\\system32\\cmd.exe"; //gets substituted by GetSystemDirectory...
pargstr = '\0';//"/K";
LastError = 0;
OK = CreateProcess (
pprogstr, // pointer to name of executable module
pargstr, // pointer to command line string: full progname + parameters
NULL, // pointer to process security attributes
NULL, // pointer to thread security attributes
TRUE, // handle inheritance flag
NORMAL_PRIORITY_CLASS,// | DETACHED_PROCESS, // creation flags
NULL, // pointer to new environment block
NULL, // pointer to current directory name
&StartupInfo, // pointer to STARTUPINFO
&ProcessInformation // pointer to PROCESS_INFORMATION
);
LastError = GetLastError();
pidProcess = ProcessInformation.hProcess;
What do I have to change so cmd.exe does not terminate immediately?
Now I have written an executable sample program:
/* a Win32 test program starting cmd.exe via CreateProcess */
#include <windows.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define logwrite dat = fopen ("cmdtest.log", "at"); fprintf
#define logend; fclose (dat);
int main(int argc, char* argv[])
{
STARTUPINFO StartupInfo; // pointer to STARTUPINFO
PROCESS_INFORMATION ProcessInformation; // pointer to PROCESS_INFORMATION
char *pargstr, *pargstr2, *pprogstr;
DWORD LastError, WaitResult, exit_code;
FILE *dat;
BOOL OK;
ZeroMemory( &StartupInfo, sizeof(StartupInfo) );
StartupInfo.cb = sizeof(StartupInfo);
ZeroMemory( &ProcessInformation, sizeof(ProcessInformation) );
//StartupInfo.hStdOutput = cmd_stdout;
//StartupInfo.hStdInput = cmd_stdin;
//StartupInfo.hStdError = cmd_stderr;
//https://stackoverflow.com/questions/4380575/how-to-launch-console-application-using-createprocess-with-minimized-main-window
StartupInfo.dwFlags = STARTF_USESTDHANDLES | STARTF_USESHOWWINDOW;
StartupInfo.wShowWindow = SW_SHOWNOACTIVATE;//SW_SHOWNORMAL;
//please adapt the string
pprogstr = "C:\\WINDOWS\\system32\\cmd.exe";
pargstr = "/K"; //"\0";
logwrite (dat, "\n"); logend;
logwrite (dat, "Trying CreateProcess pprogstr: %s; pargstr: %s;\n", pprogstr, pargstr); logend;
LastError = 0;
OK = CreateProcess (
pprogstr, // pointer to name of executable module
pargstr, // pointer to command line string: full progname + parameters
NULL, // pointer to process security attributes
NULL, // pointer to thread security attributes
TRUE, // handle inheritance flag
NORMAL_PRIORITY_CLASS,//0,//DETACHED_PROCESS | NORMAL_PRIORITY_CLASS, // creation flags
NULL, // pointer to new environment block
NULL, // pointer to current directory name
&StartupInfo, // pointer to STARTUPINFO
&ProcessInformation // pointer to PROCESS_INFORMATION
);
LastError = GetLastError();
logwrite (dat, "CreateProcess cmd.exe returns OK %i Processhandle %i LastError %i \n", OK, ProcessInformation.hProcess, LastError); logend;
GetExitCodeProcess(ProcessInformation.hProcess, &exit_code);
if (exit_code == STILL_ACTIVE) {
logwrite (dat, "After 0 seconds, cmd.exe process is still active\n"); logend;
}
else {
logwrite (dat, "After 0 seconds, cmd.exe process is no more active\n"); logend;
}
Sleep (2000);
if (exit_code == STILL_ACTIVE) {
logwrite (dat, "After 2 seconds, cmd.exe process is still active\n"); logend;
}
else {
logwrite (dat, "After 2 seconds, cmd.exe process is no more active\n"); logend;
}
Sleep (8000);
WaitResult = WaitForSingleObject (ProcessInformation.hProcess, INFINITE);
LastError = GetLastError();
if (WaitResult == WAIT_FAILED)
{
logwrite (dat, "WaitForSingleObject error: return code = %u Processhandle %i LastError %i\n", WaitResult, ProcessInformation.hProcess, LastError); logend;
}
else
{
logwrite (dat, "cmd.exe complete.\n"); logend;
}
}
The log file shows:
Trying CreateProcess pprogstr: C:\WINDOWS\system32\cmd.exe; pargstr: /K;
CreateProcess cmd.exe returns OK 1 Processhandle 252 LastError 183
After 0 seconds, cmd.exe process is still active
After 2 seconds, cmd.exe process is still active
cmd.exe complete.
This is a strange behaviour:
GetExitCodeProcess returns STILL_ACTIVE
the Task Manager detail view shows no cmd.exe while pausing the program with Sleep
WaitForSingleObject immediately exits cmd.exe.
The behaviour I want is that cmd.exe still runs and does not terminate (so my program should "hang").