Getting return value of another process

I have a file where I scan each line for a certain word and return any line that contains it. Instead of scanning through the entire file, I am trying to just use 'findstr' from the command line. I know you can call commandline functions using system() or CreateProcess, however I'm not sure how I would get the output from findstr back into my program.

Try popen()
Or _popen() as microsoft calls it.

Code:

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DWORD dwExitCode;
WaitForSingleObject(hProcess, INFINITE);
GetExitCodeProcess(hProcess,&dwExitCode);

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Thanks salem