createProcess Restart when closed/crashed - c++

I would like to know how would i restart a program that i have created with CreateProcess.
I need the program to restart if its closed or if it crashed
int main(int argc, char* argv[])
{
HANDLE ghJob = CreateJobObject(NULL, NULL); // GLOBAL
if (ghJob == NULL)
::MessageBox(0, "Could not create job object", "TEST", MB_OK);
else {
JOBOBJECT_EXTENDED_LIMIT_INFORMATION jeli = { 0 };
// Configure all child processes associated with the job to terminate when the
jeli.BasicLimitInformation.LimitFlags = JOB_OBJECT_LIMIT_KILL_ON_JOB_CLOSE;
if (0 == SetInformationJobObject(ghJob, JobObjectExtendedLimitInformation, &jeli, sizeof(jeli)))
::MessageBox(0, "Could not SetInformationJobObject", "TEST", MB_OK);
}
STARTUPINFO info = { sizeof(info) };
PROCESS_INFORMATION processInfo;
char cmdArgs[] = "notepad.exe";
// Launch child process - example is notepad.exe
if (::CreateProcess(NULL, cmdArgs, NULL, NULL, TRUE, 0, NULL, NULL, &info, &processInfo)) {
::MessageBox(0, "CreateProcess succeeded.", "TEST", MB_OK);
if (ghJob) {
if (0 == AssignProcessToJobObject(ghJob, processInfo.hProcess))
::MessageBox(0, "Could not AssignProcessToObject", "TEST", MB_OK);
}
WaitForSingleObject(processInfo.hProcess, INFINITE);
//Restart process here if its closed
CloseHandle(processInfo.hProcess);
CloseHandle(processInfo.hThread);
}
return 0;
}

You can run the code in a cycle. WaitForSingleObject waits till child process exits, CloseHandle calls are closing the handles and the child process code is running another time. I've created an eternal cycle, so this program will never exit. Add exiting conditions to this cycle according to your requirements, for example a MessageBox asking if it should exit or run another time
int main(int argc, char* argv[])
{
HANDLE ghJob = CreateJobObject(NULL, NULL); // GLOBAL
if (ghJob == NULL)
::MessageBox(0, "Could not create job object", "TEST", MB_OK);
else {
JOBOBJECT_EXTENDED_LIMIT_INFORMATION jeli = { 0 };
// Configure all child processes associated with the job to terminate when the
jeli.BasicLimitInformation.LimitFlags = JOB_OBJECT_LIMIT_KILL_ON_JOB_CLOSE;
if (0 == SetInformationJobObject(ghJob, JobObjectExtendedLimitInformation, &jeli, sizeof(jeli)))
::MessageBox(0, "Could not SetInformationJobObject", "TEST", MB_OK);
}
STARTUPINFO info = { sizeof(info) };
PROCESS_INFORMATION processInfo;
char cmdArgs[] = "notepad.exe";
// Launch child process - example is notepad.exe
do
{
if (::CreateProcess(NULL, cmdArgs, NULL, NULL, TRUE, 0, NULL, NULL, &info, &processInfo)) {
::MessageBox(0, "CreateProcess succeeded.", "TEST", MB_OK);
if (ghJob) {
if (0 == AssignProcessToJobObject(ghJob, processInfo.hProcess))
::MessageBox(0, "Could not AssignProcessToObject", "TEST", MB_OK);
}
WaitForSingleObject(processInfo.hProcess, INFINITE);
//Restart process here if its closed
CloseHandle(processInfo.hProcess);
CloseHandle(processInfo.hThread);
}
} while (1);
return 0;
}

Related

How close message box after closing parent process opened using CreateProcess()

I want auto check bad or good for run my .exe files. For example for this binaries I have missing dll's, and when I use CreateProcess it's not return error and provide me system MessageBox("Dll is missing"). If I close it by hand, methods return exitCode STATUS_DLL_NOT_FOUND. I want that from some timeout all system message boxes will be closed with closing parent process and i can get my STATUS_DLL_NOT_FOUND. Me need full automatically work from my code.This code can closed opened sub dialogs, but can't close messageboxes.
int main()
{
HANDLE hJob;
JOBOBJECT_EXTENDED_LIMIT_INFORMATION jeli = { 0 };
PROCESS_INFORMATION pi = { 0 };
STARTUPINFO si = { 0 };
hJob = CreateJobObject(NULL, NULL);
jeli.BasicLimitInformation.LimitFlags = JOB_OBJECT_LIMIT_KILL_ON_JOB_CLOSE;
SetInformationJobObject(hJob, JobObjectExtendedLimitInformation, &jeli, sizeof(jeli));
TCHAR szCmdline[] = TEXT(" -R:mm");
si.cb = sizeof(si);
CreateProcess(
executableFiles[0].c_str(),
szCmdline,
NULL,
NULL,
FALSE,
CREATE_SUSPENDED | CREATE_BREAKAWAY_FROM_JOB /*Important*/,
NULL,
NULL,
&si,
&pi);
AssignProcessToJobObject(hJob, pi.hProcess); // Does not work if without CREATE_BREAKAWAY_FROM_JOB
ResumeThread(pi.hThread);
if (WaitForSingleObject(pi.hProcess, 3000) == WAIT_TIMEOUT)
{
EnumWindows(&SendWMCloseMsg, pi.dwProcessId);
if (WaitForSingleObject(pi.hProcess, 2000) == WAIT_TIMEOUT)
{
TerminateProcess(pi.hProcess, 0);
DWORD dwExitCode = 0;
GetExitCodeProcess(pi.hProcess, &dwExitCode);
const DWORD result = WaitForSingleObject(pi.hProcess, 2000);
if (result == WAIT_OBJECT_0)
{
if (dwExitCode == STATUS_DLL_NOT_FOUND)
{
std::cout << "Dll is missing" << std::endl;
}
}
else
{
std::cout << "bad case" << std::endl;
}
}
}
CloseHandle(pi.hThread);
CloseHandle(pi.hProcess);
CloseHandle(hJob);
return 0;
}
Call UINT oldErrorMode = SetErrorMode(SEM_FAILCRITICALERRORS); before CreateProcess, and make sure that CREATE_DEFAULT_ERROR_MODE is not set in the dwCreationFlags parameter, so that the child process inherits the error mode of the parent. Per docs, this "does not display the critical-error-handler message box, instead, the system sends the error to the calling process".
Optionally SetErrorMode(oldErrorMode); after CreateProcess to restore the previous setting.

CreateEvent initial state signaled is not signaling event

I am working on IO redirection program and i successfully created poc for it. The program spawn the child process and communicate with it using named pipes. I used Event object to get event whenever there is data on the pipe. I set the event to signaled state by default but i am not getting the event for the first time. To get the event i have to write on input pipe. When i write some command on input pipe i get the event and and get the output for the old command, not the current command(Please see the output).
below is the working code.
#include "stdafx.h"
#include <windows.h>
#include <iostream>
#include <thread>
#include <string>
using namespace std;
#define input_pipe_name L"\\\\.\\pipe\\input"
#define output_pipe_name L"\\\\.\\pipe\\output"
#define process_name L"cmd.exe"
HANDLE input_pipe_handle;
HANDLE output_pipe_handle;
HANDLE input_file_handle;
HANDLE output_file_handle;
OVERLAPPED output_overlapped = { 0 };
BOOL InitHandels()
{
input_pipe_handle = CreateNamedPipe(input_pipe_name, PIPE_ACCESS_INBOUND | FILE_FLAG_OVERLAPPED, PIPE_TYPE_BYTE | PIPE_WAIT, 1, 4096, 4096, 120000, 0);
SetHandleInformation(input_pipe_handle, HANDLE_FLAG_INHERIT, HANDLE_FLAG_INHERIT);
if (input_pipe_handle == INVALID_HANDLE_VALUE)
{
cout << "pipe creation error: " << GetLastError() << endl;
return FALSE;
}
output_pipe_handle = CreateNamedPipe(output_pipe_name, PIPE_ACCESS_OUTBOUND | FILE_FLAG_OVERLAPPED, PIPE_TYPE_BYTE | PIPE_WAIT, 1, 4096, 4096, 120000, 0);
SetHandleInformation(output_pipe_handle, HANDLE_FLAG_INHERIT, HANDLE_FLAG_INHERIT);
if (output_pipe_handle == INVALID_HANDLE_VALUE)
{
cout << "pipe creation error: " << GetLastError() << endl;
return FALSE;
}
input_file_handle = CreateFile(input_pipe_name, GENERIC_WRITE, 0, 0, OPEN_EXISTING, FILE_FLAG_OVERLAPPED, NULL);
if (input_file_handle == INVALID_HANDLE_VALUE)
{
cout << "file creation error: " << GetLastError() << endl;
return FALSE;
}
output_file_handle = CreateFile(output_pipe_name, GENERIC_READ, 0, 0, OPEN_EXISTING, FILE_FLAG_OVERLAPPED, NULL);
if (output_file_handle == INVALID_HANDLE_VALUE)
{
cout << "file creation error: " << GetLastError() << endl;
return FALSE;
}
output_overlapped.hEvent = CreateEvent(NULL, TRUE, TRUE, NULL);
ConnectNamedPipe(output_pipe_handle, &output_overlapped);
}
void CreateChildProcess()
{
TCHAR szCmdline[] = L"cmd.exe";
PROCESS_INFORMATION piProcInfo;
STARTUPINFO siStartInfo;
ZeroMemory(&piProcInfo, sizeof(PROCESS_INFORMATION));
ZeroMemory(&siStartInfo, sizeof(STARTUPINFO));
siStartInfo.cb = sizeof(STARTUPINFO);
siStartInfo.hStdError = output_pipe_handle;
siStartInfo.hStdOutput = output_pipe_handle;
siStartInfo.hStdInput = input_pipe_handle;
siStartInfo.dwFlags |= STARTF_USESTDHANDLES;
if (!CreateProcess(NULL, szCmdline, NULL, NULL, TRUE, 0, NULL, NULL, &siStartInfo, &piProcInfo))
{
cout << "process creation error: " << GetLastError() << endl;
//return FALSE;
}
else
{
HANDLE h_array[] = {output_overlapped.hEvent, piProcInfo.hProcess};
for (;;)
{
DWORD result = WaitForMultipleObjects(2, h_array, FALSE, 1000);
DWORD bwritten = 0, bread = 0;
char buffer[4096];
switch (result)
{
case WAIT_TIMEOUT:
//cout << "TimeOut" << endl;
break;
case WAIT_OBJECT_0:
ReadFile(output_file_handle, buffer, sizeof(buffer), &bread, &output_overlapped);
WriteFile(GetStdHandle(STD_OUTPUT_HANDLE), buffer, bread, &bwritten, 0);
ResetEvent(output_overlapped.hEvent);
break;
case WAIT_OBJECT_0 + 1:
break;
//return FALSE;
}
}
}
}
int main()
{
DWORD bwritten;
InitHandels();
//CreateChildProcess();
std::thread t1(CreateChildProcess);
for (;;Sleep(1000))
{
std::string mystring;
std::cin >> mystring;
mystring.append("\n");
WriteFile(input_file_handle, mystring.c_str(), mystring.length(), &bwritten, &output_overlapped);
//WriteFile(input_file_handle, "dir\n", 4, &bwritten, &output_overlapped);
}
t1.join();
return 0;
}
I get the following output
dir
Microsoft Windows [Version 6.1.7601]
Copyright (c) 2009 Microsoft Corporation. All rights reserved.
D:\Programming\VS\to_post_on_stack\to_post_on_stack>hello
dir
Volume in drive D has no label.
Volume Serial Number is 54FB-7A94
Directory of D:\Programming\VS\to_post_on_stack\to_post_on_stack
01/13/2018 05:36 PM <DIR> .
01/13/2018 05:36 PM <DIR> ..
01/13/2018 05:36 PM <DIR> Debug
01/12/2018 08:54 PM 608 stdafx.cpp
01/12/2018 08:54 PM 642 stdafx.h
01/12/2018 08:54 PM 630 targetver.h
01/13/2018 05:36 PM 7,434 to_post_on_stack.cpp
01/12/2018 08:54 PM 8,038 to_post_on_stack.vcxproj
01/12/2018 08:54 PM 1,277 to_post_on_stack.vcxproj.filters
6 File(s) 18,629 bytes
3 Dir(s) 39,347,019,776 bytes free
D:\Programming\VS\to_post_on_stack\to_post_on_stack>dir
hello
'hello' is not recognized as an internal or external command,
operable program or batch file.
D:\Programming\VS\to_post_on_stack\to_post_on_stack>dir
As you can see in the output when i send dir command i get the old output. When i send hello i get the output for the dir command which i executed before hello.
SO can anyone point out the mistake that why i am not getting signal for the very first time. And why the output is not getting in sequence?
the code example full of critical bugs:
the first and main:
If hFile was opened with FILE_FLAG_OVERLAPPED, the following
conditions are in effect:
The lpOverlapped parameter must point to a valid and unique
OVERLAPPED structure, otherwise the function can incorrectly report
that the io operation is complete.
and
io operation resets the event specified by the hEvent member of the
OVERLAPPED structure to a nonsignaled state when it begins the I/O
operation. Therefore, the caller does not need to do that.
when io operation is complete - io subsystem write to lpOverlapped final status of operation, number of bytes transferred, and if it containing event - set this event to signal state. if you use the same lpOverlapped in concurrent - they overwrite result each other, and you never know - which operation is really complete - event is one, common !, also if you use event - system reset event before begin io - as result - one operation can complete and set event, then another operation reset it after this
you call in 2 threads in concurrent:
WriteFile(input_file_handle, ..&output_overlapped);
ReadFile(output_file_handle, .. &output_overlapped);
with this you already have UB because the same &output_overlapped used in concurrent. we need allocate unique overlapped to every operation. and if you use events for detect completion - you need create several events - this is not good way at all. much better use iocp completion here - we not need create events, we not need create separate thread.
ReadFile(output_file_handle, buffer, sizeof(buffer), &bread, &output_overlapped);
WriteFile(GetStdHandle(STD_OUTPUT_HANDLE), buffer, bread, &bwritten, 0);
ResetEvent(output_overlapped.hEvent);
at first ReadFile resets the event specified by the hEvent member of the OVERLAPPED structure to a nonsignaled state when it begins the I/O operation. Therefore, the caller does not need to do that. and more - when you call ResetEvent - operation can be already completed - so you reset already signaled event - and as result you lost completion signal. if call ReasetEvent this need do before io operation (ReadFile in concrete case) but not after - which is error. however we not need do this and before - because io subsystem anyway do this.
else one critical bug - we can not use buffer, breadin WriteFile just after asynchronous call to ReadFile - the call is can be not completed yet. and context of buffer yet not defined.
the &bread is undefined always in asynchronous call and must not be used at all
The lpNumberOfBytesRead parameter should be set to NULL. Use the
GetOverlappedResult function to get the actual number of bytes read.
If the hFile parameter is associated with an I/O completion port,
you can also get the number of bytes read by calling the
GetQueuedCompletionStatus function.
else one very common mistake - that we create 2 pipe pairs (input_pipe_handle, output_file_handle) - this is absolute not need - we can use the 1 pipe pair.
the call to SetHandleInformation excess - we need just create handle with inherit properties via SECURITY_ATTRIBUTES.
code example:
//#define _XP_SUPPORT_
struct IO_COUNT
{
HANDLE _hFile;
HANDLE _hEvent;
LONG _dwIoCount;
IO_COUNT()
{
_dwIoCount = 1;
_hEvent = 0;
}
~IO_COUNT()
{
if (_hEvent)
{
CloseHandle(_hEvent);
}
}
ULONG Create(HANDLE hFile);
void BeginIo()
{
InterlockedIncrement(&_dwIoCount);
}
void EndIo()
{
if (!InterlockedDecrement(&_dwIoCount))
{
SetEvent(_hEvent);
}
}
void Wait()
{
WaitForSingleObject(_hEvent, INFINITE);
}
};
class U_IRP : OVERLAPPED
{
enum { connect, read, write };
IO_COUNT* _pIoObject;
ULONG _code;
LONG _dwRef;
char _buffer[256];
~U_IRP()
{
_pIoObject->EndIo();
}
ULONG Read()
{
_code = read;
AddRef();
return CheckIoResult(ReadFile(_pIoObject->_hFile, _buffer, sizeof(_buffer), 0, this));
}
ULONG CheckIoResult(BOOL fOk)
{
if (fOk)
{
#ifndef _XP_SUPPORT_
OnIoComplete(NOERROR, InternalHigh);
#endif
return NOERROR;
}
ULONG dwErrorCode = GetLastError();
if (dwErrorCode != ERROR_IO_PENDING)
{
OnIoComplete(dwErrorCode, 0);
}
return dwErrorCode;
}
VOID OnIoComplete(DWORD dwErrorCode, DWORD_PTR dwNumberOfBytesTransfered)
{
switch (_code)
{
case connect:
switch (dwErrorCode)
{
case ERROR_PIPE_CONNECTED:
case ERROR_NO_DATA:
dwErrorCode = NOERROR;
case NOERROR:
Read();
}
break;
case read:
if (dwErrorCode == NOERROR)
{
if (dwNumberOfBytesTransfered)
{
if (int cchWideChar = MultiByteToWideChar(CP_OEMCP, 0, _buffer, (ULONG)dwNumberOfBytesTransfered, 0, 0))
{
PWSTR wz = (PWSTR)alloca(cchWideChar * sizeof(WCHAR));
if (MultiByteToWideChar(CP_OEMCP, 0, _buffer, (ULONG)dwNumberOfBytesTransfered, wz, cchWideChar))
{
if (int cbMultiByte = WideCharToMultiByte(CP_ACP, 0, wz, cchWideChar, 0, 0, 0, 0))
{
PSTR sz = (PSTR)alloca(cbMultiByte);
if (WideCharToMultiByte(CP_ACP, 0, wz, cchWideChar, sz, cbMultiByte, 0, 0))
{
DbgPrint("%.*s", cbMultiByte, sz);
}
}
}
}
}
Read();
}
break;
case write:
break;
default:
__debugbreak();
}
Release();
if (dwErrorCode)
{
DbgPrint("[%u]: error=%u\n", _code, dwErrorCode);
}
}
static VOID WINAPI _OnIoComplete(
DWORD dwErrorCode,
DWORD dwNumberOfBytesTransfered,
LPOVERLAPPED lpOverlapped
)
{
static_cast<U_IRP*>(lpOverlapped)->OnIoComplete(RtlNtStatusToDosError(dwErrorCode), dwNumberOfBytesTransfered);
}
public:
void AddRef()
{
InterlockedIncrement(&_dwRef);
}
void Release()
{
if (!InterlockedDecrement(&_dwRef)) delete this;
}
U_IRP(IO_COUNT* pIoObject) : _pIoObject(pIoObject)
{
_dwRef = 1;
pIoObject->BeginIo();
RtlZeroMemory(static_cast<OVERLAPPED*>(this), sizeof(OVERLAPPED));
}
ULONG Write(const void* pvBuffer, ULONG cbBuffer)
{
_code = write;
AddRef();
return CheckIoResult(WriteFile(_pIoObject->_hFile, pvBuffer, cbBuffer, 0, this));
}
ULONG Connect()
{
_code = connect;
AddRef();
return CheckIoResult(ConnectNamedPipe(_pIoObject->_hFile, this));
}
static ULONG Bind(HANDLE hFile)
{
return BindIoCompletionCallback(hFile, U_IRP::_OnIoComplete, 0)
#ifndef _XP_SUPPORT_
&& SetFileCompletionNotificationModes(hFile, FILE_SKIP_COMPLETION_PORT_ON_SUCCESS)
#endif
? NOERROR : GetLastError();
}
};
ULONG IO_COUNT::Create(HANDLE hFile)
{
_hFile = hFile;
if (_hEvent = CreateEvent(0, TRUE, FALSE, 0))
{
return U_IRP::Bind(hFile);
}
return GetLastError();
}
void ChildTest()
{
static const WCHAR name[] = L"\\\\?\\pipe\\somename";
HANDLE hFile = CreateNamedPipeW(name,
PIPE_ACCESS_DUPLEX|FILE_READ_DATA|FILE_WRITE_DATA|FILE_FLAG_OVERLAPPED,
PIPE_TYPE_BYTE|PIPE_READMODE_BYTE, 1, 0, 0, NMPWAIT_USE_DEFAULT_WAIT, 0);
if (hFile != INVALID_HANDLE_VALUE)
{
IO_COUNT obj;
if (obj.Create(hFile) == NOERROR)
{
BOOL fOk = FALSE;
static SECURITY_ATTRIBUTES sa = { sizeof(sa), 0, TRUE };
STARTUPINFOW si = { sizeof(si) };
PROCESS_INFORMATION pi;
si.dwFlags = STARTF_USESTDHANDLES;
si.hStdError = CreateFileW(name, FILE_GENERIC_READ|FILE_GENERIC_WRITE,
FILE_SHARE_READ|FILE_SHARE_WRITE, &sa, OPEN_EXISTING, 0, 0);
if (si.hStdError != INVALID_HANDLE_VALUE)
{
si.hStdInput = si.hStdOutput = si.hStdError;
WCHAR ApplicationName[MAX_PATH];
if (GetEnvironmentVariableW(L"ComSpec", ApplicationName, RTL_NUMBER_OF(ApplicationName)))
{
if (CreateProcessW(ApplicationName , 0, 0, 0, TRUE, 0, 0, 0, &si, &pi))
{
CloseHandle(pi.hThread);
CloseHandle(pi.hProcess);
fOk = TRUE;
}
}
CloseHandle(si.hStdError);
}
if (fOk)
{
U_IRP* p;
if (p = new U_IRP(&obj))
{
p->Connect();
p->Release();
}
obj.EndIo();
//++ simulate user commands
static PCSTR commands[] = { "dir\r\n", "ver\r\n", "exit\r\n" };
ULONG n = RTL_NUMBER_OF(commands);
PCSTR* psz = commands;
do
{
if (p = new U_IRP(&obj))
{
PCSTR command = *psz++;
p->Write(command, (ULONG)strlen(command) * sizeof(CHAR));
p->Release();
}
} while (--n);
//--
obj.Wait();
}
}
CloseHandle(hFile);
}
}

How to pass named pipe into CreateProcess (C++ Windows)

The hierarchy of my project is that I have 3 processes.
Main exe
Middle exe
Worker exe
Main exe will spawn middle exe using createprocess, from there middle exe will spawn worker exe using createprocess as well. Once worker exe is running middle exe terminates.
I would like to be able to pass the output data from worker exe back to main exe.
The way I think is best is to use a named pipe as worker exe's stdout.
In main exe I have this code:
SECURITY_DESCRIPTOR sd;
InitializeSecurityDescriptor(&sd, SECURITY_DESCRIPTOR_REVISION);
SetSecurityDescriptorDacl(&sd, TRUE, static_cast<PACL>(0), FALSE);
SECURITY_ATTRIBUTES sa;
sa.nLength = sizeof(sa);
sa.lpSecurityDescriptor = &sd;
sa.bInheritHandle = FALSE;
HANDLE hPipe = CreateNamedPipe(TEXT("\\\\.\\pipe\\MPipe"),
PIPE_ACCESS_DUPLEX | FILE_FLAG_OVERLAPPED,
PIPE_TYPE_BYTE | PIPE_READMODE_BYTE | PIPE_NOWAIT,
PIPE_UNLIMITED_INSTANCES,
1024 * 4,
1024 * 4,
0,
&sa);
//CreateProcess() code here for middle exe
if (hPipe == NULL || hPipe == INVALID_HANDLE_VALUE) {
MessageBoxA(NULL, "Failed to create pipe", NULL, MB_OK);
}
int count = 0;
while (true) {
if (!ConnectNamedPipe(hPipe, 0)) {
std::this_thread::sleep_for(std::chrono::seconds(20));
count++;
}
if (count > 5)
break;
}
if (count > 5) {
MessageBoxA(NULL, "Failed...", NULL, MB_OK);
}
Then in middle exe I have
memset(&si, 0x00, sizeof(si));
memset(&pi, 0x00, sizeof(pi));
si.cb = sizeof(si);
SECURITY_ATTRIBUTES sa;
sa.nLength = sizeof(sa);
sa.lpSecurityDescriptor = NULL;
sa.bInheritHandle = TRUE;
HANDLE hPipe;
BOOL keepGoing = TRUE;
while(keepGoing){
hPipe = CreateFile(TEXT("\\\\.\\pipe\\MPipe"),
GENERIC_WRITE | GENERIC_READ,
0,
&sa,
OPEN_EXISTING,
FILE_ATTRIBUTE_NORMAL,
NULL);
if (hPipe == INVALID_HANDLE_VALUE) {
if (GetLastError() == ERROR_PIPE_BUSY) {
MessageBoxA(NULL, "Pipe busy...", NULL, MB_OK);
WaitNamedPipe("\\\\.\\pipe\\MPipe", 2000);
}
else {
MessageBoxA(NULL, "Failed to open pipe for writing", NULL, MB_OK);
break;
}
}
else {
keepGoing = FALSE;
}
}
MessageBoxA(NULL, "Client pipe connected!", NULL, MB_OK);
SetHandleInformation(hPipe, HANDLE_FLAG_INHERIT, 0);
si.hStdError = hPipe;
si.hStdOutput = hPipe;
processFlags = CREATE_SUSPENDED;
CreateProcessW(processPath, commandLine, NULL, NULL, TRUE, processFlags, NULL, NULL, &si, &pi);
For some reason in Main exe it will output "Failed to establish connection..." But in my Middle exe it will output "Client connected!".
I can't figure out why the Middle exe appears to establish a connection but the Main exe doesn't recognize it when ConnectNamedPipe() is called.
Any ideas?

How to read output from cmd.exe using CreateProcess() and CreatePipe()

How to read output from cmd.exe using CreateProcess() and CreatePipe()
I have been trying to create a child process executing cmd.exe with a command-line designating /K dir. The purpose is to read the output from the command back into the parent process using pipes.
I've already got CreateProcess() working, however the step involving pipes are causing me trouble. Using pipes, the new console window is not displaying (like it was before), and the parent process is stuck in the call to ReadFile().
Does anyone have an idea of what I'm doing wrong?
#include <Windows.h>
#include <stdio.h>
#include <tchar.h>
#define BUFFSZ 4096
HANDLE g_hChildStd_IN_Rd = NULL;
HANDLE g_hChildStd_IN_Wr = NULL;
HANDLE g_hChildStd_OUT_Rd = NULL;
HANDLE g_hChildStd_OUT_Wr = NULL;
int wmain(int argc, wchar_t* argv[])
{
int result;
wchar_t aCmd[BUFFSZ] = TEXT("/K dir"); // CMD /?
STARTUPINFO si;
PROCESS_INFORMATION pi;
SECURITY_ATTRIBUTES sa;
printf("Starting...\n");
ZeroMemory(&si, sizeof(STARTUPINFO));
ZeroMemory(&pi, sizeof(PROCESS_INFORMATION));
ZeroMemory(&sa, sizeof(SECURITY_ATTRIBUTES));
// Create one-way pipe for child process STDOUT
if (!CreatePipe(&g_hChildStd_OUT_Rd, &g_hChildStd_OUT_Wr, &sa, 0)) {
printf("CreatePipe() error: %ld\n", GetLastError());
}
// Ensure read handle to pipe for STDOUT is not inherited
if (!SetHandleInformation(g_hChildStd_OUT_Rd, HANDLE_FLAG_INHERIT, 0)) {
printf("SetHandleInformation() error: %ld\n", GetLastError());
}
// Create one-way pipe for child process STDIN
if (!CreatePipe(&g_hChildStd_IN_Rd, &g_hChildStd_IN_Wr, &sa, 0)) {
printf("CreatePipe() error: %ld\n", GetLastError());
}
// Ensure write handle to pipe for STDIN is not inherited
if (!SetHandleInformation(g_hChildStd_IN_Rd, HANDLE_FLAG_INHERIT, 0)) {
printf("SetHandleInformation() error: %ld\n", GetLastError());
}
si.cb = sizeof(STARTUPINFO);
si.hStdError = g_hChildStd_OUT_Wr;
si.hStdOutput = g_hChildStd_OUT_Wr;
si.hStdInput = g_hChildStd_IN_Rd;
si.dwFlags |= STARTF_USESTDHANDLES;
sa.nLength = sizeof(SECURITY_ATTRIBUTES);
sa.lpSecurityDescriptor = NULL;
// Pipe handles are inherited
sa.bInheritHandle = true;
// Creates a child process
result = CreateProcess(
TEXT("C:\\Windows\\System32\\cmd.exe"), // Module
aCmd, // Command-line
NULL, // Process security attributes
NULL, // Primary thread security attributes
true, // Handles are inherited
CREATE_NEW_CONSOLE, // Creation flags
NULL, // Environment (use parent)
NULL, // Current directory (use parent)
&si, // STARTUPINFO pointer
&pi // PROCESS_INFORMATION pointer
);
if (result) {
printf("Child process has been created...\n");
}
else {
printf("Child process could not be created\n");
}
bool bStatus;
CHAR aBuf[BUFFSZ + 1];
DWORD dwRead;
DWORD dwWrite;
// GetStdHandle(STD_OUTPUT_HANDLE)
while (true) {
bStatus = ReadFile(g_hChildStd_OUT_Rd, aBuf, sizeof(aBuf), &dwRead, NULL);
if (!bStatus || dwRead == 0) {
break;
}
aBuf[dwRead] = '\0';
printf("%s\n", aBuf);
}
// Wait until child process exits
WaitForSingleObject(pi.hProcess, INFINITE);
// Close process and thread handles
CloseHandle(pi.hProcess);
CloseHandle(pi.hThread);
printf("Stopping...\n");
return 0;
}
The subtle way out of your problem is to make sure you close the ends of the pipe you don't need.
Your parent process has four handles:
two of them are your ends of the pipe
g_hChildStd_IN_Wr
g_hChildStd_OUT_Rd
two of them are the child's end of the pipe
g_hChildStd_IN_Rd
g_hChildStd_OUT_Wr
 
╔══════════════════╗ ╔══════════════════╗
║ Parent Process ║ ║ Child Process ║
╠══════════════════╣ ╠══════════════════╣
║ ║ ║ ║
║ g_hChildStd_IN_Wr╟───────────────>║g_hChildStd_IN_Rd ║
║ ║ ║ ║
║g_hChildStd_OUT_Rd║<───────────────╢g_hChildStd_OUT_Wr║
║ ║ ║ ║
╚══════════════════╝ ╚══════════════════╝
Your parent process only needs one end of each pipe:
writable end of the child input pipe: g_hChildStd_IN_Wr
readable end of the child output pipe: g_hChildStd_OUT_Rd
Once you've launched your child process: be sure to close those ends of the pipe you no longer need:
CloseHandle(g_hChildStd_IN_Rd)
CloseHandle(g_hChildStd_OUT_Wr)
Leaving:
╔══════════════════╗ ╔══════════════════╗
║ Parent Process ║ ║ Child Process ║
╠══════════════════╣ ╠══════════════════╣
║ ║ ║ ║
║ g_hChildStd_IN_Wr╟───────────────>║ ║
║ ║ ║ ║
║g_hChildStd_OUT_Rd║<───────────────╢ ║
║ ║ ║ ║
╚══════════════════╝ ╚══════════════════╝
Or more fully:
STARTUP_INFO si;
PROCESS_INFO pi;
result = CreateProcess(..., ref si, ref pi);
//Bonus chatter: A common bug among a lot of programmers:
// they don't realize they are required to call CloseHandle
// on the two handles placed in PROCESS_INFO.
// That's why you should call ShellExecute - it closes them for you.
CloseHandle(pi.hProcess);
CloseHandle(pi.hThread);
/*
We've given the console app the writable end of the pipe during CreateProcess; we don't need it anymore.
We do keep the handle for the *readable* end of the pipe; as we still need to read from it.
The other reason to close the writable-end handle now is so that there's only one out-standing reference to the writeable end: held by the child process.
When the child processes closes, it will close the pipe, and
your call to ReadFile will fail with error code:
109 (The pipe has been ended).
That's how we'll know the console app is done. (no need to wait on process handles with buggy infinite waits)
*/
CloseHandle(g_hChildStd_OUT_Wr);
g_hChildStd_OUT_Wr = 0;
CloseHandle(g_hChildStd_IN_Rd);
g_hChildStd_OUT_Wr = 0;
Waiting on the Child Process (aka the deadlock waiting to happen)
The common problem with most solutions is that people try to wait on a process handle.
they create event objects
they try to MsgWait for events to be signaled
they try to MsgWait for child processes to end
That's wrong. That's all wrong.
There are many problems with these ideas; the main one being:
if you try to wait for the child the terminate
the child will never be able to terminate
If the child is trying to send you output through the pipe, and you're INFINITE waiting, you're not emptying your end of the pipe. Eventually the pipe the child is writing to becomes full. When the child tries to write to a pipe that is full, its WriteFile call waits (i.e. Blocks) for the pipe to have some room.
you're blocked waiting on the child
the child attempts to write to the pipe
you're blocked waiting on the child, so you're not reading data out of the pipe
the pipe becomes full
the child blocks waiting on you
both parent and child are blocked waiting on the other
deadlock
As a result the child process will never terminate; you've deadlocked everything.
The Right Approach - let the client do it's thing
The correct solution comes by simply reading from the pipe.
Once the child process terminates,
it will CloseHandle on its end of the pipes.
The next time you try to read from the pipe
you'll be told the pipe has been closed (ERROR_BROKEN_PIPE).
That's how you know the process is done and you have no more stuff to read.
 
String outputText = "";
//Read will return when the buffer is full, or if the pipe on the other end has been broken
while (ReadFile(stdOutRead, aBuf, Length(aBuf), &bytesRead, null)
outputText = outputText + Copy(aBuf, 1, bytesRead);
//ReadFile will either tell us that the pipe has closed, or give us an error
DWORD le = GetLastError;
//And finally cleanup
CloseHandle(g_hChildStd_IN_Wr);
CloseHandle(g_hChildStd_OUT_Rd);
if (le != ERROR_BROKEN_PIPE) //"The pipe has been ended."
RaiseLastOSError(le);
All without a dangerous MsgWaitForSingleObject - which is error-prone, difficult to use correctly, and causes the very bug you want to avoid.
Complete Example
We all know what we are using this for: run a child process, and capture it's console output.
Here is some sample Delphi code:
function ExecuteAndCaptureOutput(CommandLine: string): string;
var
securityAttributes: TSecurityAttributes;
stdOutRead, stdOutWrite: THandle;
startupInfo: TStartupInfo;
pi: TProcessInformation;
buffer: AnsiString;
bytesRead: DWORD;
bRes: Boolean;
le: DWORD;
begin
{
Execute a child process, and capture it's command line output.
}
Result := '';
securityAttributes.nlength := SizeOf(TSecurityAttributes);
securityAttributes.bInheritHandle := True;
securityAttributes.lpSecurityDescriptor := nil;
if not CreatePipe({var}stdOutRead, {var}stdOutWrite, #securityAttributes, 0) then
RaiseLastOSError;
try
// Set up members of the STARTUPINFO structure.
startupInfo := Default(TStartupInfo);
startupInfo.cb := SizeOf(startupInfo);
// This structure specifies the STDIN and STDOUT handles for redirection.
startupInfo.dwFlags := startupInfo.dwFlags or STARTF_USESTDHANDLES; //The hStdInput, hStdOutput, and hStdError handles will be valid.
startupInfo.hStdInput := GetStdHandle(STD_INPUT_HANDLE); //don't forget to make it valid (zero is not valid)
startupInfo.hStdOutput := stdOutWrite; //give the console app the writable end of the pipe
startupInfo.hStdError := stdOutWrite; //give the console app the writable end of the pipe
// We also want the console window to be hidden
startupInfo.dwFlags := startupInfo.dwFlags or STARTF_USESHOWWINDOW; //The nShowWindow member member will be valid.
startupInfo.wShowWindow := SW_HIDE; //default is that the console window is visible
// Set up members of the PROCESS_INFORMATION structure.
pi := Default(TProcessInformation);
//WARNING: The Unicode version of CreateProcess can modify the contents of CommandLine.
//Therefore CommandLine cannot point to read-only memory.
//We can ensure it's not read-only with the RTL function UniqueString
UniqueString({var}CommandLine);
bRes := CreateProcess(nil, PChar(CommandLine), nil, nil, True, 0, nil, nil, startupInfo, {var}pi);
if not bRes then
RaiseLastOSError;
//CreateProcess demands that we close these two populated handles when we're done with them. We're done with them.
CloseHandle(pi.hProcess);
CloseHandle(pi.hThread);
{
We've given the console app the writable end of the pipe during CreateProcess; we don't need it anymore.
We do keep the handle for the *readable* end of the pipe; as we still need to read from it.
The other reason to close the writable-end handle now is so that there's only one out-standing reference to the writeable end: held by the console app.
When the app closes, it will close the pipe, and ReadFile will return code 109 (The pipe has been ended).
That's how we'll know the console app is done. (no need to wait on process handles)
}
CloseHandle(stdOutWrite);
stdOutWrite := 0;
SetLength(buffer, 4096);
//Read will return when the buffer is full, or if the pipe on the other end has been broken
while ReadFile(stdOutRead, buffer[1], Length(buffer), {var}bytesRead, nil) do
Result := Result + string(Copy(buffer, 1, bytesRead));
//ReadFile will either tell us that the pipe has closed, or give us an error
le := GetLastError;
if le <> ERROR_BROKEN_PIPE then //"The pipe has been ended."
RaiseLastOSError(le);
finally
CloseHandle(stdOutRead);
if stdOutWrite <> 0 then
CloseHandle(stdOutWrite);
end;
end;
Ian Boyd's answer had this gem: Once you've launched your child process: be sure to close those ends of the pipe you no longer need.
I've produced another version of the CreatePipe + CreateProcess solution which, I hope, is more clear:
int main()
{
BOOL ok = TRUE;
HANDLE hStdInPipeRead = NULL;
HANDLE hStdInPipeWrite = NULL;
HANDLE hStdOutPipeRead = NULL;
HANDLE hStdOutPipeWrite = NULL;
// Create two pipes.
SECURITY_ATTRIBUTES sa = { sizeof(SECURITY_ATTRIBUTES), NULL, TRUE };
ok = CreatePipe(&hStdInPipeRead, &hStdInPipeWrite, &sa, 0);
if (ok == FALSE) return -1;
ok = CreatePipe(&hStdOutPipeRead, &hStdOutPipeWrite, &sa, 0);
if (ok == FALSE) return -1;
// Create the process.
STARTUPINFO si = { };
si.cb = sizeof(STARTUPINFO);
si.dwFlags = STARTF_USESTDHANDLES;
si.hStdError = hStdOutPipeWrite;
si.hStdOutput = hStdOutPipeWrite;
si.hStdInput = hStdInPipeRead;
PROCESS_INFORMATION pi = { };
LPCWSTR lpApplicationName = L"C:\\Windows\\System32\\cmd.exe";
LPWSTR lpCommandLine = (LPWSTR)L"C:\\Windows\\System32\\cmd.exe /c dir";
LPSECURITY_ATTRIBUTES lpProcessAttributes = NULL;
LPSECURITY_ATTRIBUTES lpThreadAttribute = NULL;
BOOL bInheritHandles = TRUE;
DWORD dwCreationFlags = 0;
LPVOID lpEnvironment = NULL;
LPCWSTR lpCurrentDirectory = NULL;
ok = CreateProcess(
lpApplicationName,
lpCommandLine,
lpProcessAttributes,
lpThreadAttribute,
bInheritHandles,
dwCreationFlags,
lpEnvironment,
lpCurrentDirectory,
&si,
&pi);
if (ok == FALSE) return -1;
// Close pipes we do not need.
CloseHandle(hStdOutPipeWrite);
CloseHandle(hStdInPipeRead);
// The main loop for reading output from the DIR command.
char buf[1024 + 1] = { };
DWORD dwRead = 0;
DWORD dwAvail = 0;
ok = ReadFile(hStdOutPipeRead, buf, 1024, &dwRead, NULL);
while (ok == TRUE)
{
buf[dwRead] = '\0';
OutputDebugStringA(buf);
puts(buf);
ok = ReadFile(hStdOutPipeRead, buf, 1024, &dwRead, NULL);
}
// Clean up and exit.
CloseHandle(hStdOutPipeRead);
CloseHandle(hStdInPipeWrite);
DWORD dwExitCode = 0;
GetExitCodeProcess(pi.hProcess, &dwExitCode);
return dwExitCode;
}
Some notes:
The pipe for StdIn is not really required:
This is because the DIR command doesn't require user input (but, I left it in the code, since it is a good template for running other commands)
everyting to do with hStdInPipeRead & hStdInPipeWrite can be omitted
setting si.hStdInput can be omitted
Replace hardcoded L"C:\\Windows\\System32\\cmd.exe" with reading the COMSPEC environment variable.
Replace LPWSTR with LPTSTR if we wish to compile for non-UNICODE.
Replace cmd.exe /k DIR with cmd.exe /c DIR since when the DIR command finishes we don't really want the cmd.exe to stick around.
I too have same scenario. in my case from Lib, need to execute internal exe and read output. The following works without any issues.
void executeCMDInNewProcessAndReadOutput(LPSTR lpCommandLine)
{
STARTUPINFO si;
SECURITY_ATTRIBUTES sa;
PROCESS_INFORMATION pi;
HANDLE g_hChildStd_IN_Rd, g_hChildStd_OUT_Wr, g_hChildStd_OUT_Rd, g_hChildStd_IN_Wr; //pipe handles
char buf[1024]; //i/o buffer
sa.nLength = sizeof(SECURITY_ATTRIBUTES);
sa.bInheritHandle = TRUE;
sa.lpSecurityDescriptor = NULL;
if (CreatePipe(&g_hChildStd_IN_Rd, &g_hChildStd_IN_Wr, &sa, 0)) //create stdin pipe
{
if (CreatePipe(&g_hChildStd_OUT_Rd, &g_hChildStd_OUT_Wr, &sa, 0)) //create stdout pipe
{
//set startupinfo for the spawned process
/*The dwFlags member tells CreateProcess how to make the process.
STARTF_USESTDHANDLES: validates the hStd* members.
STARTF_USESHOWWINDOW: validates the wShowWindow member*/
GetStartupInfo(&si);
si.dwFlags = STARTF_USESTDHANDLES | STARTF_USESHOWWINDOW;
si.wShowWindow = SW_HIDE;
//set the new handles for the child process
si.hStdOutput = g_hChildStd_OUT_Wr;
si.hStdError = g_hChildStd_OUT_Wr;
si.hStdInput = g_hChildStd_IN_Rd;
//spawn the child process
if (CreateProcess(NULL, lpCommandLine, NULL, NULL, TRUE, CREATE_NEW_CONSOLE,
NULL, NULL, &si, &pi))
{
unsigned long bread; //bytes read
unsigned long avail; //bytes available
memset(buf, 0, sizeof(buf));
for (;;)
{
PeekNamedPipe(g_hChildStd_OUT_Rd, buf, 1023, &bread, &avail, NULL);
//check to see if there is any data to read from stdout
if (bread != 0)
{
if (ReadFile(g_hChildStd_OUT_Rd, buf, 1023, &bread, NULL))
{
break;
}
}
}
//clean up all handles
CloseHandle(pi.hThread);
CloseHandle(pi.hProcess);
CloseHandle(g_hChildStd_IN_Rd);
CloseHandle(g_hChildStd_OUT_Wr);
CloseHandle(g_hChildStd_OUT_Rd);
CloseHandle(g_hChildStd_IN_Wr);
}
else
{
CloseHandle(g_hChildStd_IN_Rd);
CloseHandle(g_hChildStd_OUT_Wr);
CloseHandle(g_hChildStd_OUT_Rd);
CloseHandle(g_hChildStd_IN_Wr);
}
}
else
{
CloseHandle(g_hChildStd_IN_Rd);
CloseHandle(g_hChildStd_IN_Wr);
}
}
}
Here is an example (taken from a larger program) of a thread that does what you are looking for. It creates pipes for stdout and stderr for the process it creates then goes into a loop reading those pipes until the program finishes.
DWORD WINAPI ThreadProc(LPVOID lpParameter)
{
#define EVENT_NAME "Global\\RunnerEvt"
HANDLE hev;
SECURITY_ATTRIBUTES psa;
InitSAPtr(&psa);
DWORD waitRc;
DWORD bytesRead;
int manual_triggered = 1;
hev = CreateEvent(&psa, FALSE, FALSE, EVENT_NAME);
// Create pipes we'll read
for(;;)
{
if (manual_triggered)
{
waitRc = WAIT_OBJECT_0;
manual_triggered = 0;
}
else
{
waitRc = WaitForSingleObject(hev, 500);
}
if (waitRc == WAIT_OBJECT_0)
{
`logprint`f(LOG_DBG, "Received command to run process\n");
CreateChildOutFile();
stdOutEvt = CreateEvent(&psa, TRUE, FALSE, 0);
stdOutOvl.hEvent = stdOutEvt;
stdErrEvt = CreateEvent(&psa, TRUE, FALSE, 0);
stdErrOvl.hEvent = stdErrEvt;
gStdOutReadHand = CreateNamedPipe(STD_OUT_PIPE_NAME, PIPE_ACCESS_DUPLEX + FILE_FLAG_OVERLAPPED, PIPE_TYPE_BYTE + PIPE_READMODE_BYTE,
PIPE_UNLIMITED_INSTANCES, 4096, 4096, 0, &psa);
if (gStdOutReadHand == INVALID_HANDLE_VALUE)
{
log(LOG_DBG, "Error %d on create STDOUT pipe\n", GetLastError());
}
gStdErrReadHand = CreateNamedPipe(STD_ERR_PIPE_NAME, PIPE_ACCESS_DUPLEX + FILE_FLAG_OVERLAPPED, PIPE_TYPE_BYTE + PIPE_READMODE_BYTE,
PIPE_UNLIMITED_INSTANCES, 4096, 4096, 0, &psa);
if (gStdErrReadHand == INVALID_HANDLE_VALUE)
{
log(LOG_DBG, "Error %d on create STDERR pipe\n", GetLastError());
}
runProcess();
log(LOG_DBG, "After runProcess, new PID is %d/%x\n", piProcInfo.dwProcessId, piProcInfo.dwProcessId);
if (piProcInfo.dwProcessId == 0)
{
log(LOG_DBG, "runProcess failed, closing child STDIN/STDERR\n");
closeChildPipes();
#define FAIL_MSG "Child process failed to start\n"
writeChildOutFile(FAIL_MSG, strlen(FAIL_MSG) );
CloseHandle(hChildOut);
}
else
{
log(LOG_DBG, "Child process created, setting up for redir/restart/termination\n");
issueRead(gStdOutReadHand, &stdOutOvl, stdOutBuff, &stdOutBytesAvail);
//log(LOG_DBG, "After read set on STDOUT\n");
issueRead(gStdErrReadHand, &stdErrOvl, stdErrBuff, &stdErrBytesAvail);
//log(LOG_DBG, "After read set on STDERR\n");
HANDLE harr[4];
for(;;)
{
harr[0] = hev;
harr[1] = piProcInfo.hProcess;
harr[2] = stdOutEvt;
harr[3] = stdErrEvt;
DWORD waitRc2 = WaitForMultipleObjects(4, harr, FALSE, 500);
#if 0
if (waitRc2 == -1)
{
log(LOG_DBG, "Wait error %d\n", GetLastError());
Sleep(500);
}
log(LOG_DBG, "waitRc2 %d\n", waitRc2);
#endif
if ((waitRc2 - WAIT_OBJECT_0) == 0)
{
log(LOG_DBG, "Woke up because another trigger command was received\n");
#define NEW_CMD_MSG "Child process is being terminated because new trigger received\n"
writeChildOutFile(NEW_CMD_MSG, strlen(NEW_CMD_MSG));
terminateChild();
CloseHandle(hChildOut);
manual_triggered = 1;
break;
}
else if ((waitRc2 - WAIT_OBJECT_0) == 1)
{
//log(LOG_DBG, "Woke up because child has terminated\n");
closeChildPipes();
#define NORM_MSG "Normal child process termination\n"
writeChildOutFile(NORM_MSG, strlen(NORM_MSG));
CloseHandle(hChildOut);
break;
}
else if ((waitRc2 - WAIT_OBJECT_0) == 2)
{
//log(LOG_DBG, "Woke up because child has stdout\n");
if (GetOverlappedResult(gStdOutReadHand, &stdOutOvl, &bytesRead, TRUE))
{
writeChildOutFile(stdOutBuff, bytesRead);
ResetEvent(stdOutEvt);
issueRead(gStdOutReadHand, &stdOutOvl, stdOutBuff, &stdOutBytesAvail);
}
}
else if ((waitRc2 - WAIT_OBJECT_0) == 3)
{
//log(LOG_DBG, "Woke up because child has stderr\n");
if (GetOverlappedResult(gStdErrReadHand, &stdErrOvl, &bytesRead, TRUE))
{
writeChildOutFile(stdErrBuff, bytesRead);
ResetEvent(stdErrEvt);
issueRead(gStdErrReadHand, &stdErrOvl, stdErrBuff, &stdErrBytesAvail);
}
}
else
{
if (gShuttingDown)
{
log(LOG_DBG, "Woke with active child and service is terminating\n");
#define SHUTDOWN_MSG "Child process is being terminated because the service is shutting down\n"
writeChildOutFile(SHUTDOWN_MSG, strlen(SHUTDOWN_MSG));
terminateChild();
CloseHandle(hChildOut);
break;
}
}
if (gShuttingDown)
{
break;
}
}
}
}
else if (gShuttingDown)
{
break;
}
CloseHandle(gStdOutReadHand);
CloseHandle(gStdErrReadHand);
}
return 0;
}
void writeChildOutFile(char *msg, int len)
{
DWORD bytesWritten;
WriteFile(hChildOut, msg, len, &bytesWritten, 0);
}
void terminateChild(void)
{
if (piProcInfo.dwProcessId != 0)
{
TerminateProcess(piProcInfo.hProcess, -1);
CloseHandle(piProcInfo.hThread);
CloseHandle(piProcInfo.hProcess);
closeChildPipes();
}
}
void closeChildPipes(void)
{
CloseHandle(g_hChildStd_OUT_Wr);
CloseHandle(g_hChildStd_ERR_Wr);
}
void runProcess(void)
{
SECURITY_ATTRIBUTES saAttr;
// Set the bInheritHandle flag so pipe handles are inherited.
saAttr.nLength = sizeof(SECURITY_ATTRIBUTES);
saAttr.bInheritHandle = TRUE;
saAttr.lpSecurityDescriptor = NULL;
// Create a pipe for the child process's STDOUT.
TCHAR szCmdline[]=TEXT("cmd.exe /C C:\\temp\\RunnerService.bat");
STARTUPINFO siStartInfo;
BOOL bSuccess = FALSE;
// Set up members of the PROCESS_INFORMATION structure.
ZeroMemory( &piProcInfo, sizeof(PROCESS_INFORMATION) );
g_hChildStd_OUT_Wr = CreateFile (STD_OUT_PIPE_NAME,
FILE_WRITE_DATA,
0,
&saAttr,
OPEN_EXISTING,
0,
NULL);
if (g_hChildStd_OUT_Wr == INVALID_HANDLE_VALUE)
{
log(LOG_DBG, "Error creating child proc stdout file %d\n", GetLastError());
}
g_hChildStd_ERR_Wr = CreateFile (STD_ERR_PIPE_NAME,
FILE_WRITE_DATA,
0,
&saAttr,
OPEN_EXISTING,
0,
NULL);
if (g_hChildStd_ERR_Wr == INVALID_HANDLE_VALUE)
{
log(LOG_DBG, "Error creating child proc stderr file %d\n", GetLastError());
}
// Set up members of the STARTUPINFO structure.
// This structure specifies the STDIN and STDOUT handles for redirection.
ZeroMemory( &siStartInfo, sizeof(STARTUPINFO) );
siStartInfo.cb = sizeof(STARTUPINFO);
siStartInfo.hStdOutput = g_hChildStd_OUT_Wr;
siStartInfo.hStdError = g_hChildStd_ERR_Wr;
siStartInfo.dwFlags |= STARTF_USESTDHANDLES;
// Create the child process.
bSuccess = CreateProcess(NULL,
szCmdline, // command line
NULL, // process security attributes
NULL, // primary thread security attributes
TRUE, // handles are inherited
0, // creation flags
NULL, // use parent's environment
NULL, // use parent's current directory
&siStartInfo, // STARTUPINFO pointer
&piProcInfo); // receives PROCESS_INFORMATION
}
void CreateChildOutFile(void)
{
SYSTEMTIME st;
SECURITY_ATTRIBUTES sa;
char fName[_MAX_PATH];
InitSAPtr(&sa);
GetLocalTime(&st);
sprintf(fName, "C:\\TEMP\\runsvcchild_%02d_%02d_%02d_%04d.out", st.wHour, st.wMinute, st.wSecond, st.wMilliseconds);
hChildOut = CreateFile(fName, GENERIC_WRITE, FILE_SHARE_READ, &sa, CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL, 0);
}
void issueRead(HANDLE hFile, OVERLAPPED *overLapped, char *buf, DWORD *dwRead)
{
//log(LOG_DBG, "Start of issueRead, hfile %08x, ovl is %08x\n", hFile, overLapped);
BOOL brc = ReadFile(hFile, buf, 4096, dwRead, overLapped);
if (!brc)
{
DWORD dwle = GetLastError();
if (dwle != ERROR_IO_PENDING)
{
log(LOG_DBG, "Error %d on ReadFile\n", dwle);
}
}
else
{
// log(LOG_DBG, "Read issued\n");
}
}
I think you did everything right. But cmd.exe prints nothing or very little amount of data after start and your ReadFile blocks. If you move your cycle
while (true) {
bStatus = ReadFile(g_hChildStd_OUT_Rd, aBuf, sizeof(aBuf), &dwRead, NULL);
if (!bStatus || dwRead == 0) {
break;
}
aBuf[dwRead] = '\0';
printf("%s\n", aBuf);
}
into background thread and run other cycle which will read your input and send it to cmd.exe, I think you can see any effect.
Either you can make read buffer smaller (16 bytes e.g.).
I tried Stephen Quan's answer out and got a segfault. Perhaps someone with more experience might know why that is. At any rate, this should be a more correct example of what he was trying to do:
#include <windows.h>
#include <cstddef>
#include <string>
#include <vector>
#include <cwchar>
using std::string;
using std::wstring;
using std::vector;
using std::size_t;
static inline wstring widen(string str) {
size_t wchar_count = str.size() + 1;
vector<wchar_t> buf(wchar_count);
return wstring{ buf.data(), (size_t)MultiByteToWideChar(CP_UTF8, 0, str.c_str(), -1, buf.data(), (int)wchar_count) };
}
static inline string narrow(wstring wstr) {
int nbytes = WideCharToMultiByte(CP_UTF8, 0, wstr.c_str(), (int)wstr.length(), NULL, 0, NULL, NULL);
vector<char> buf(nbytes);
return string{ buf.data(), (size_t)WideCharToMultiByte(CP_UTF8, 0, wstr.c_str(), (int)wstr.length(), buf.data(), nbytes, NULL, NULL) };
}
string evaluate_shell(string command) {
string output;
wstring wstr_command = widen(command);
wchar_t cwstr_command[32768];
wcsncpy(cwstr_command, wstr_command.c_str(), 32768);
BOOL ok = TRUE;
HANDLE hStdInPipeRead = NULL;
HANDLE hStdInPipeWrite = NULL;
HANDLE hStdOutPipeRead = NULL;
HANDLE hStdOutPipeWrite = NULL;
SECURITY_ATTRIBUTES sa = { sizeof(SECURITY_ATTRIBUTES), NULL, TRUE };
ok = CreatePipe(&hStdInPipeRead, &hStdInPipeWrite, &sa, 0);
if (ok == FALSE) return "";
ok = CreatePipe(&hStdOutPipeRead, &hStdOutPipeWrite, &sa, 0);
if (ok == FALSE) return "";
STARTUPINFOW si = { };
si.cb = sizeof(STARTUPINFOW);
si.dwFlags = STARTF_USESTDHANDLES;
si.hStdError = hStdOutPipeWrite;
si.hStdOutput = hStdOutPipeWrite;
si.hStdInput = hStdInPipeRead;
PROCESS_INFORMATION pi = { };
if (CreateProcessW(NULL, cwstr_command, NULL, NULL, TRUE, CREATE_NO_WINDOW, NULL, NULL, &si, &pi)) {
while (WaitForSingleObject(pi.hProcess, 5) == WAIT_TIMEOUT) {
MSG msg;
if (PeekMessage(&msg, NULL, 0, 0, PM_REMOVE)) {
TranslateMessage(&msg);
DispatchMessage(&msg);
}
}
CloseHandle(hStdOutPipeWrite);
CloseHandle(hStdInPipeRead);
char buffer[4096] = { };
DWORD dwRead = 0;
ok = ReadFile(hStdOutPipeRead, buffer, 4095, &dwRead, NULL);
while (ok == TRUE) {
buffer[dwRead] = 0;
ok = ReadFile(hStdOutPipeRead, buffer, 4095, &dwRead, NULL);
}
CloseHandle(hStdOutPipeRead);
CloseHandle(hStdInPipeWrite);
CloseHandle(pi.hProcess);
CloseHandle(pi.hThread);
output = narrow(widen(buffer));
while (output.back() == '\r' || output.back() == '\n')
output.pop_back();
}
return output;
}

How do I call ::CreateProcess in c++ to launch a Windows executable?

Looking for an example that:
Launches an EXE
Waits for the EXE to finish.
Properly closes all the handles when the executable finishes.
Something like this:
STARTUPINFO info={sizeof(info)};
PROCESS_INFORMATION processInfo;
if (CreateProcess(path, cmd, NULL, NULL, TRUE, 0, NULL, NULL, &info, &processInfo))
{
WaitForSingleObject(processInfo.hProcess, INFINITE);
CloseHandle(processInfo.hProcess);
CloseHandle(processInfo.hThread);
}
There is an example at http://msdn.microsoft.com/en-us/library/ms682512(VS.85).aspx
Just replace the argv[1] with your constant or variable containing the program.
#include <windows.h>
#include <stdio.h>
#include <tchar.h>
void _tmain( int argc, TCHAR *argv[] )
{
STARTUPINFO si;
PROCESS_INFORMATION pi;
ZeroMemory( &si, sizeof(si) );
si.cb = sizeof(si);
ZeroMemory( &pi, sizeof(pi) );
if( argc != 2 )
{
printf("Usage: %s [cmdline]\n", argv[0]);
return;
}
// Start the child process.
if( !CreateProcess( NULL, // No module name (use command line)
argv[1], // Command line
NULL, // Process handle not inheritable
NULL, // Thread handle not inheritable
FALSE, // Set handle inheritance to FALSE
0, // No creation flags
NULL, // Use parent's environment block
NULL, // Use parent's starting directory
&si, // Pointer to STARTUPINFO structure
&pi ) // Pointer to PROCESS_INFORMATION structure
)
{
printf( "CreateProcess failed (%d).\n", GetLastError() );
return;
}
// Wait until child process exits.
WaitForSingleObject( pi.hProcess, INFINITE );
// Close process and thread handles.
CloseHandle( pi.hProcess );
CloseHandle( pi.hThread );
}
If you application is a Windows GUI application then using the code below to do the waiting is not ideal as messages for your application will not be getting processing. To the user it will look like your application has hung.
WaitForSingleObject(&processInfo.hProcess, INFINITE)
Something like the untested code below might be better as it will keep processing the windows message queue and your application will remain responsive:
//-- wait for the process to finish
while (true)
{
//-- see if the task has terminated
DWORD dwExitCode = WaitForSingleObject(ProcessInfo.hProcess, 0);
if ( (dwExitCode == WAIT_FAILED )
|| (dwExitCode == WAIT_OBJECT_0 )
|| (dwExitCode == WAIT_ABANDONED) )
{
DWORD dwExitCode;
//-- get the process exit code
GetExitCodeProcess(ProcessInfo.hProcess, &dwExitCode);
//-- the task has ended so close the handle
CloseHandle(ProcessInfo.hThread);
CloseHandle(ProcessInfo.hProcess);
//-- save the exit code
lExitCode = dwExitCode;
return;
}
else
{
//-- see if there are any message that need to be processed
while (PeekMessage(&message.msg, 0, 0, 0, PM_NOREMOVE))
{
if (message.msg.message == WM_QUIT)
{
return;
}
//-- process the message queue
if (GetMessage(&message.msg, 0, 0, 0))
{
//-- process the message
TranslateMessage(&pMessage->msg);
DispatchMessage(&pMessage->msg);
}
}
}
}
if your exe happens to be a console app, you might be interested in reading the stdout and stderr -- for that, I'll humbly refer you to this example:
http://support.microsoft.com/default.aspx?scid=kb;EN-US;q190351
It's a bit of a mouthful of code, but I've used variations of this code to spawn and read.
On a semi-related note, if you want to start a process that has more privileges than your current process (say, launching an admin app, which requires Administrator rights, from the main app running as a normal user), you can't do so using CreateProcess() on Vista since it won't trigger the UAC dialog (assuming it is enabled). The UAC dialog is triggered when using ShellExecute(), though.
Here is a new example that works on windows 10. When using the windows10 sdk you have to use CreateProcessW instead. This example is commented and hopefully self explanatory.
#ifdef _WIN32
#include <Windows.h>
#include <iostream>
#include <stdio.h>
#include <tchar.h>
#include <cstdlib>
#include <string>
#include <algorithm>
class process
{
public:
static PROCESS_INFORMATION launchProcess(std::string app, std::string arg)
{
// Prepare handles.
STARTUPINFO si;
PROCESS_INFORMATION pi; // The function returns this
ZeroMemory( &si, sizeof(si) );
si.cb = sizeof(si);
ZeroMemory( &pi, sizeof(pi) );
//Prepare CreateProcess args
std::wstring app_w(app.length(), L' '); // Make room for characters
std::copy(app.begin(), app.end(), app_w.begin()); // Copy string to wstring.
std::wstring arg_w(arg.length(), L' '); // Make room for characters
std::copy(arg.begin(), arg.end(), arg_w.begin()); // Copy string to wstring.
std::wstring input = app_w + L" " + arg_w;
wchar_t* arg_concat = const_cast<wchar_t*>( input.c_str() );
const wchar_t* app_const = app_w.c_str();
// Start the child process.
if( !CreateProcessW(
app_const, // app path
arg_concat, // Command line (needs to include app path as first argument. args seperated by whitepace)
NULL, // Process handle not inheritable
NULL, // Thread handle not inheritable
FALSE, // Set handle inheritance to FALSE
0, // No creation flags
NULL, // Use parent's environment block
NULL, // Use parent's starting directory
&si, // Pointer to STARTUPINFO structure
&pi ) // Pointer to PROCESS_INFORMATION structure
)
{
printf( "CreateProcess failed (%d).\n", GetLastError() );
throw std::exception("Could not create child process");
}
else
{
std::cout << "[ ] Successfully launched child process" << std::endl;
}
// Return process handle
return pi;
}
static bool checkIfProcessIsActive(PROCESS_INFORMATION pi)
{
// Check if handle is closed
if ( pi.hProcess == NULL )
{
printf( "Process handle is closed or invalid (%d).\n", GetLastError());
return FALSE;
}
// If handle open, check if process is active
DWORD lpExitCode = 0;
if( GetExitCodeProcess(pi.hProcess, &lpExitCode) == 0)
{
printf( "Cannot return exit code (%d).\n", GetLastError() );
throw std::exception("Cannot return exit code");
}
else
{
if (lpExitCode == STILL_ACTIVE)
{
return TRUE;
}
else
{
return FALSE;
}
}
}
static bool stopProcess( PROCESS_INFORMATION &pi)
{
// Check if handle is invalid or has allready been closed
if ( pi.hProcess == NULL )
{
printf( "Process handle invalid. Possibly allready been closed (%d).\n");
return 0;
}
// Terminate Process
if( !TerminateProcess(pi.hProcess,1))
{
printf( "ExitProcess failed (%d).\n", GetLastError() );
return 0;
}
// Wait until child process exits.
if( WaitForSingleObject( pi.hProcess, INFINITE ) == WAIT_FAILED)
{
printf( "Wait for exit process failed(%d).\n", GetLastError() );
return 0;
}
// Close process and thread handles.
if( !CloseHandle( pi.hProcess ))
{
printf( "Cannot close process handle(%d).\n", GetLastError() );
return 0;
}
else
{
pi.hProcess = NULL;
}
if( !CloseHandle( pi.hThread ))
{
printf( "Cannot close thread handle (%d).\n", GetLastError() );
return 0;
}
else
{
pi.hProcess = NULL;
}
return 1;
}
};//class process
#endif //win32
Perhaps this is the most complete?
http://goffconcepts.com/techarticles/createprocess.html
Bear in mind that using WaitForSingleObject can get you into trouble in this scenario. The following is snipped from a tip on my website:
The problem arises because your application has a window but isn't pumping messages. If the spawned application invokes SendMessage with one of the broadcast targets (HWND_BROADCAST or HWND_TOPMOST), then the SendMessage won't return to the new application until all applications have handled the message - but your app can't handle the message because it isn't pumping messages.... so the new app locks up, so your wait never succeeds.... DEADLOCK.
If you have absolute control over the spawned application, then there are measures you can take, such as using SendMessageTimeout rather than SendMessage (e.g. for DDE initiations, if anybody is still using that). But there are situations which cause implicit SendMessage broadcasts over which you have no control, such as using the SetSysColors API for instance.
The only safe ways round this are:
split off the Wait into a separate thread, or
use a timeout on the Wait and use PeekMessage in your Wait loop to ensure that you pump messages, or
use the MsgWaitForMultipleObjects API.
Here is a solution for CreateProcessA
STARTUPINFOW initInfo = { 0 };
initInfo.cb = sizeof(initInfo);
PROCESS_INFORMATION procInfo = { 0 };
CreateProcessA(PATH_FOR_EXE, NULL, NULL, NULL, FALSE, 0, NULL, NULL, (LPSTARTUPINFOA)&initInfo, &procInfo);
#include <Windows.h>
void my_cmd()
{
STARTUPINFO si;
PROCESS_INFORMATION pi;
ZeroMemory(&si, sizeof(si));
si.cb = sizeof(si);
ZeroMemory(&pi, sizeof(pi));
// CMD command here
char arg[] = "cmd.exe /c E:/Softwares/program.exe";
// Convert char string to required LPWSTR string
wchar_t text[500];
mbstowcs(text, arg, strlen(arg) + 1);
LPWSTR command = text;
// Run process
CreateProcess (NULL, command, NULL, NULL, 0,
CREATE_NO_WINDOW, NULL, NULL, &si, &pi);
}
This works fine for me. No popup windows and cmd command runs as expected. Just needed to convert the CHAR pointer into WCHAR pointer and add extra "cmd.exe /c" before every command.