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Editorial Team
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Asked: 2026-06-05T01:14:48+00:00

I have a simple program (in C) that create two child process, wait on

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I have a simple program (in C) that create two child process, wait on an inherited pipe each, and put the output in a file.

Everything works well, except that after some write/read cycle on the two pipe, when the child ends, the call to ReadFile block, waiting for data on the pipe. I use the following pattern:

...
//create pipe1
CreatePipe(&hReadDup,&hWrite,&saAttr,0);
DuplicateHandle(GetCurrentProcess(),hReadDup,GetCurrentProcess(),&hRead,0,FALSE,DUPLICATE_SAME_ACCESS);
CloseHandle(hReadDup);


si.cb = sizeof(si);
si.dwFlags = STARTF_USESTDHANDLES;
si.hStdOutput = hWrite;   

CreateProcess(  NULL,
        const_cast<LPWSTR>(cmd2.c_str()), //the command to execute
        NULL,
        NULL,
        TRUE,
        0,
        NULL,
        NULL,
        &si, //si.
        &pi
    );

...
CloseHandle(hWrite); // EDIT: this was the operation not properly done!

while(cont){
    ...
    cont = ReadFile(hRead,buf,50, &actual,NULL);
    ...
}
...

The last call (after child process exit) block.
Idea of why (and, if not, how to debug this)?

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1 Answer

  1. Editorial Team

    I found out the solution myself (wich actually was a coding error).
    I wasn’t closing the parent’s write handle of the pipe properly (hWrite), so, the synchronous ReadFile wasn’t able to report me back the child process termination.

    If somebody has the same problem, make sure you close the inheritable handle of the pipe before starting the I/O operation on that pipe (as MSDN reports, cannot find again were).

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