How to Spawn a Console App and Redirect Standard Handles

• Microsoft Win32 Application Programming Interface (API) included with:

      - Microsoft Windows NT versions 3.5 and 3.51
      - Microsoft Windows 95 version 4.0
  

This article discusses spawning a console application with CreateProcess() and redirecting its output. The standard handles are controlled with the STARTUPINFO fields hStdInput, hStdOutput, and hStdError.

In Windows NT version 3.1, if a windowed application spawned a console application, you could:

• Redirect none of its standard handles (don't use STARTF_USESTDHANDLES).

  -or-

• Redirect all of its standard handles (use STARTF_USESTDHANDLES).

In Windows NT version 3.5 and later and in Windows 95, if you set any of these fields to INVALID_HANDLE_VALUE, Windows NT will assign the default value to that handle in the console application, rather than leaving it an invalid value. Therefore, if you set STARTF_USESTDHANDLES, but fail to set one of the handle fields, this will not cause a problem for the console application. You can now redirect standard input, but not standard output, and so forth.