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POCreateProcess and CreatePipe to execute a process and return output as a string in VC++
 

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    <p>I am trying to use <code>CreateProcess</code> and <code>CreatePipe</code> to execute a process from within a Windows Forms C++/CLR application in Visual Studio 2010.</p> <p>From within my Windows forms app I want to execute a child process (console app) and return the output as a <code>std::string</code>, <code>std::wstring</code>, or <code>System::String^</code> within my Windows forms app. Additionally, I do not want the newly created child process to spawn a window.</p> <p>The console application is of my own creation, so I have control of it's source too.</p> <p>I have seen the following examples, but I do not understand how to modify the code to accomplish what I am trying to do:</p> <ul> <li><a href="http://msdn.microsoft.com/en-us/library/ms682499(VS.85).aspx" rel="nofollow noreferrer">MSDN</a></li> <li><a href="http://code.google.com/p/kgui/source/browse/trunk/kguithread.cpp" rel="nofollow noreferrer">kgui</a></li> <li><a href="http://www.codeproject.com/KB/cpp/9505Yamaha_1.aspx" rel="nofollow noreferrer">A simpler MFC based function</a></li> </ul> <p>The MSDN code appears to be written as two console apps, one calling the other. The code is confusing to me. I've only been working in C++ for about 4 months, so I still don't understand everything. It appears to reference a text file, which I don't need to do.</p> <p>Is there a simpler way to do this than MSDN's 200+ lines of code or kgui's 300+ lines of code?</p> <p>The answer <a href="https://stackoverflow.com/questions/1184433/execute-a-process-and-return-its-standard-output-in-vc">here</a> was helpful, but over simplistic. I was hoping to see a basic source example (one that doesn't involve hundreds of lines of complex code would be preferable). I would have used the MFC code, but I had difficulty adapting it to my purposes (I'm not using MFC).</p> <p>Following is my adaptation of the code from Code Project:</p> <pre><code>string ExecuteExternalFile(string csExeName, string csArguments) { string csExecute; csExecute=csExeName + " " + csArguments; SECURITY_ATTRIBUTES secattr; ZeroMemory(&amp;secattr,sizeof(secattr)); secattr.nLength = sizeof(secattr); secattr.bInheritHandle = TRUE; HANDLE rPipe, wPipe; //Create pipes to write and read data CreatePipe(&amp;rPipe,&amp;wPipe,&amp;secattr,0); // STARTUPINFO sInfo; ZeroMemory(&amp;sInfo,sizeof(sInfo)); PROCESS_INFORMATION pInfo; ZeroMemory(&amp;pInfo,sizeof(pInfo)); sInfo.cb=sizeof(sInfo); sInfo.dwFlags=STARTF_USESTDHANDLES; sInfo.hStdInput=NULL; sInfo.hStdOutput=wPipe; sInfo.hStdError=wPipe; //Create the process here. CreateProcess(0,(LPWSTR)csExecute.c_str(),0,0,TRUE,NORMAL_PRIORITY_CLASS|CREATE_NO_WINDOW,0,0,&amp;sInfo,&amp;pInfo); CloseHandle(wPipe); //now read the output pipe here. char buf[100]; DWORD reDword; string m_csOutput,csTemp; BOOL res; do { res=::ReadFile(rPipe,buf,100,&amp;reDword,0); csTemp=buf; m_csOutput+=csTemp; }while(res); return m_csOutput; } </code></pre> <p>I have tried using this from within my Windows Forms app, and while it compiles ok and doesn't cause any errors, it doesn't seem to work either. I have no idea why.</p> <p>This is how I executed the above code:</p> <pre><code>std::string ping = ExecuteExternalFile("ping.exe", "127.0.0.1"); </code></pre> <p>It did not appear to do anything, except that on the first execution it give a very strange 3 characters as an output, then on subsequent executions, nothing.</p>
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    1. COYou're doing it the hard way, not sure why. Use the ProcessStartInfo::RedirectStandardOutput property instead.
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    2. CO"Use the ProcessStartInfo::RedirectStandardOutput property instead." Can you please explain what you mean in more detail? Maybe provide a link to an example?
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    3. COCopy/pasta that into a google query. Take the first hit, it's a good one.
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