File re-direction operator ">" doesn't work with CreateProcess() API

Question

I've a SupportApp.EXE which if I launch manually from windows CMD prommpt like this ::

SupportApp.EXE -t 100 > AFile.csv

works perfcetly fine & it generates a CSV file for me.

Now I want to automate same thing inside a VC++ code. So, I use CreateProcess() API for this. Code snippet below ::

TCHAR launcher[512];
    _tgetcwd(launcher, _MAX_PATH);
    TCHAR workDir[512];
    _tgetcwd(workDir, _MAX_PATH);
    _tcscat(launcher, "\\App\\SupportApp.exe");
    TCHAR cmdlineoption[512];
    _tcscpy(cmdlineoption, " -t 120 > AFile.csv");
LPTSTR appPath = (LPTSTR)cmdlineoption;


    STARTUPINFO sInfo;
    memset(&sInfo, 0, sizeof(sInfo));
    sInfo.cb = sizeof(sInfo);
    sInfo.dwFlags = STARTF_USESHOWWINDOW;
    sInfo.wShowWindow = SW_SHOWMAXIMIZED;

    PROCESS_INFORMATION pInfo;
    memset(&pInfo, 0, sizeof(pInfo));

    if (!CreateProcess(launcher, appPath, NULL, NULL, FALSE, CREATE_NEW_CONSOLE, NULL, workDir, &sInfo, &pInfo))
{
... // log error
}
// success

I see that CreateProcess() API succeeds and also i see that the -t 120 option I'm giving is also taken by this "SupportApp.exe" BUT the file redirection operator ">" is not working with CreateProcess() API.

Instead the output is directed to CMD itself. But I want output to be sent to a CSV file.

Can anyone please help me in how do I redirect the output of my "SupportApp.exe" to a file using CreateProcess() API from within my VC++ code ?

UPDATE 2:

The inputs given by reviewers are incorporated in this & the modified code snippet is below which takes the file hnadle in STARTUPINFO structure as follows::

The file is getting created but the file is empty & it doesn't have any contents from createProcess()?

TCHAR launcher[512];
        _tgetcwd(launcher, _MAX_PATH);
        TCHAR workDir[512];
        _tgetcwd(workDir, _MAX_PATH);
        _tcscat(launcher, "\\App\\SupportApp.exe");
        TCHAR cmdlineoption[512];
        _tcscpy(cmdlineoption, " -t 120 > AFile.csv");
    LPTSTR appPath = (LPTSTR)cmdlineoption;


        STARTUPINFO sInfo;
        memset(&sInfo, 0, sizeof(sInfo));
        sInfo.cb = sizeof(sInfo);
        sInfo.dwFlags |= STARTF_USESTDHANDLES; //newly added
        sInfo.wShowWindow = SW_SHOWMAXIMIZED;

        PROCESS_INFORMATION pInfo;
        memset(&pInfo, 0, sizeof(pInfo));

        sInfo.hStdInput = GetStdHandle(STD_INPUT_HANDLE);
        sInfo.hStdError = GetStdHandle(STD_ERROR_HANDLE);        

       SECURITY_ATTRIBUTES sa;
     ZeroMemory(&sa, sizeof(sa));
      sa.nLength = sizeof(sa);
    sa.bInheritHandle = TRUE;

HANDLE hn;

if(INVALID_HANDLE_VALUE != (hn = CreateFile(L"DoneDone.csv", GENERIC_READ | GENERIC_WRITE, FILE_SHARE_WRITE, &sa, CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL, 0))) { sInfo.hStdOutput = =hn; } if (!CreateProcess(launcher, appPath, NULL, NULL, FALSE, 0, NULL, workDir, &sInfo, &pInfo)) { ... // log error } // success

unwind unwind · Accepted Answer · 2014-12-09T09:55:05

Output redirection is a shell feature, i.e. the shell sets that up before starting the child.

You're not using a shell, instead going directly to the kernel asking it to start a process, so you don't get that service.

You need to set up the required redirection yourself. This is done in the STARTUPINFO's hStdOutput member. See the documentation, of course.

File re-direction operator ">" doesn't work with CreateProcess() API

2 Answers