Quiet System Calls in C++

Hello all

I am attempting to make quiet system calls from C++ in order to run a batch file without the user knowing. I am going to eventually make this cross platform (windows and linux) although for now i am currently looking for a windows solution.

So I guess i'm looking for two things...
1. To call a program from windows without the user knowing
2. C++ program to pause until the system call has completed

Ideas?

Hiding your intentions from the user could be bad. ;)

Such a task is O/S specific anyway, so you'll have to write it multiple ways.

>Such a task is O/S specific anyway, so you'll have to write it multiple ways.

MacGyver, I have to say, you rock at patronizing people for the sole purpose of making yourself look smarter.


If you're just running batch files, system() sounds like a good bet. AFAIK, it's "quiet".

Quote:

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Originally Posted by UMR_Student

>Such a task is O/S specific anyway, so you'll have to write it multiple ways.

MacGyver, I have to say, you rock at patronizing people for the sole purpose of making yourself look smarter.

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I really don't get how that comment is patronizing in any way.

Yeah... i dont see that either.

But yeah, call it with system()

and make sure the batch file has this at the start:

Code:

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@echo off

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I believe that will do the trick.

Well, maybe "pointless" is a more appropriate decription than "patronizing". He obviously already knows it's OS specific and will have to be written two different ways.

i tried using system() but the command prompt window appears... anyway to hide this?

I also tried ShellExecute() with the hide flag but the c++ app doesn't wait for the command to finish before continuing on. I seem to be between a rock and a hard place. But there has to be an answer out there someplace.

ShellExecuteEx can with some parameters combination return handle of the new process.
You then can wait for this handle using some of Win API waiting functions like WaitForSingleObject

how would that be? I was looking into making waitforsingleobject work for me, but ShellExecuteEx looks to return only bool values.

Ideas/explanations?

You would call it on the HANDLE variable named hProcess that is inside the struct argument you give to ShellExecuteEx().

Notes from MSDN on that parameter:

Quote:

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Handle to the newly started application. This member is set on return and is always NULL unless fMask is set to SEE_MASK_NOCLOSEPROCESS. Even if fMask is set to SEE_MASK_NOCLOSEPROCESS, hProcess will be NULL if no process was launched. For example, if a document to be launched is a URL and an instance of Microsoft Internet Explorer is already running, it will display the document. No new process is launched, and hProcess will be NULL.

Note ShellExecuteEx does not always return an hProcess, even if a process is launched as the result of the call. For example, an hProcess does not return when you use SEE_MASK_INVOKEIDLIST to invoke IContextMenu.

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Quote:

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Originally Posted by UMR_Student

Well, maybe "pointless" is a more appropriate decription than "patronizing". He obviously already knows it's OS specific and will have to be written two different ways.

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really? I've seen no evidence that he knows that.

To the op, in windows you should use CreateProcess.

If you want a portable way to do this, have a look at the proposal for Boost.Process

> really? I've seen no evidence that he knows that.

Wow.

Jesus, i know its OS specific, but don't concern yourselves with that right now.

I am currently looking into the ShellExecuteEX() right now. Any further help would be appreciated.

ChaosEngine is right, you probably want to focus on CreateProcess() instead

Code:

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#include <iostream>
#include <windows.h>

int main()
{
        bool bLoop = true;
        std::string szProg;
        SHELLEXECUTEINFO shellinfo;
       
        ZeroMemory(&shellinfo,sizeof(SHELLEXECUTEINFO));
        shellinfo.cbSize = sizeof(SHELLEXECUTEINFO);
        shellinfo.lpVerb = "open";
        shellinfo.fMask = SEE_MASK_NOCLOSEPROCESS;
        shellinfo.nShow = SW_SHOWDEFAULT;
       
        do
        {
                std::cout << "Enter a string to pass to ShellExecuteEx: ";
                std::cout.flush();
                getline(std::cin,szProg);
                if(szProg.compare("exit"))
                {
                        // process command
                        shellinfo.lpFile = szProg.c_str();
                        ShellExecuteEx(&shellinfo);
                        if(shellinfo.hProcess)
                        {
                                std::cout << "Waiting for process..." << std::endl;
                                WaitForSingleObject(shellinfo.hProcess,INFINITE);
                        }
                        else std::cout << "Error starting process." << std::endl;
                }
                else bLoop = false;
        }while(bLoop);
       
        return 0;
}

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Code:

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                string cmdline = "pscp.exe -r -batch -scp -pw \""+m_password+"\" \""+m_file+"\" \""+m_username+"\"@\""+m_host+"\":\""+m_remotedir+"\"";

                STARTUPINFO          si = { sizeof(si) };
                PROCESS_INFORMATION  pi;
                char                *szExe = (char *)cmdline.c_str();

                if(CreateProcess(0, (LPSTR)szExe, 0, 0, FALSE, 0, 0, 0, &si, &pi))
                {
                        WaitForSingleObject(pi.hProcess, INFINITE);
                        CloseHandle(pi.hProcess);
                        CloseHandle(pi.hThread);
                }

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Thanks for your guys' help.

> char *szExe = (char *)cmdline.c_str();
This is dangerous, casting away the const-ness of an object.

Especially since CreateProcess() indicates that it can be modified.