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Controlling console applications

, 4 Feb 2002
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Run console applications and controll/use their input/output streams
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Console windows and application output

During a "simple" project I discovered the tedious task of capturing the output of a console window into a control of the application. The additional difficulty was to hide the console window, thus hiding the application.

As it was to be expected, things were not as easy as redirecting output into a file and reading that file back in.

So I started creating a wrapper class for this task and it proved harder than it seemed at first. The provided sample in the MSDN did not mention the most important things and leaves more questions then it solves.

Searching around on various code sites shed some more light on the topic. Finally I could assemble a working solution. (Although there are some minor wishes left)

The CSpawn Class

This class has a pretty simple interface. A constructor, an execute function, an output function and finally a test to see if it is still active. The execute function and the output function are available in various flavours.

For the feedback you must derive a class from CSpawnConsumer and overload the Consume() function.

Usually it looks like this:

class CSpawnConsumer1 : public CSpawnConsumer
{
public:
    explicit CSpawnConsumer1(CMyEdit* pEdit)
                                   : m_pEdit(pEdit){}
    void Consume(TCHAR* p, DWORD dw)
    {
        m_pEdit->DoWhateverWithTheInput(p);
    }

private:
    CMyEdit* m_pEdit;
};

This class is called from the thread reading the output of the console window.

You can use the CSpawn class in two ways:

  1. Using the constructor method CSpawn::CSpawn(CString& exe, CSpawnConsumer* sc)
  2. Or creating a CSpawn variable and calling Execute(CString& exe, CSpawnConsumer* sc)

The default implementation will spawn the executable by resolving the ComSpec environment variable (normally CMD.EXE or COMMAND.EXE) and passing parameters to the given application.

You can provide user input to a running application by calling SendInput().

The Sample

The included sample project shows a simple edit control where any text entered is passed to the standard command interpreter and returns the results into the same edit control.

It shows how to interface with the CSpawn class in the most common way.

Compatibility

CSpawn was tested under Windows 2000 and Windows XP in Unicode and MBCS (both included in demo project) using Visual C++ 6.0 SP5 and MFC 6. Its not tested with .NET and MFC 7.

Revision History

19 Jun 2002 - Initial Revision

License

This article, along with any associated source code and files, is licensed under The Microsoft Public License (Ms-PL)

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Comments and Discussions

 
GeneralCaptureConsole.DLL - A universal Console Output Redirector for all Compilers PinmemberElmue3-Feb-09 6:10 
GeneralLinewise reading data Pinmembersmzhaq26-Sep-07 22:24 
QuestionHow to terminate early Pinmemberacjohnson557-Jul-06 9:25 
Does anyone know how to add support to this class for early thread termination?? I could do some guess and check, but I don't have much Windows API experience
QuestionError storing m_hSaveStdout ? PinmemberJohn P. Curtis25-Feb-06 18:56 
AnswerRe: Error storing m_hSaveStdout ? PinmemberSaurweinAndreas26-Feb-06 4:20 
GeneralI fixed a bug PinmemberJunho Ryu27-Sep-05 2:17 
GeneralRe: I fixed a bug Pinmemberacjohnson557-Jul-06 9:22 
GeneralRe: I fixed a bug Pinmemberjoeasnake21-Nov-07 15:32 
QuestionRe: I fixed a bug Pinmemberrl7477-May-08 5:46 
GeneralInvalid Handle exception when creating several CSpawn classes Pinmemberjohnpsquared1-Aug-04 13:26 
Questionmultiline output? Pinmembermikemurphy28-Feb-04 10:39 
AnswerRe: multiline output? Pinmemberjohnpsquared1-Aug-04 13:33 
Questionhow to get all stdout during batch command mode PinsussAnonymous18-Dec-03 10:24 
GeneralVC++ Newbie Help Pinmembermessy17-Oct-03 12:05 
GeneralSmall bug fix Pinmembermschoneman23-Sep-03 14:13 
GeneralInvoking &quot;.cmd&quot; files Pinmemberdshah13-Jun-03 3:41 
GeneralbRet = GetExitCodeProcess always true Pinmemberdonaldw25-Apr-03 12:36 
GeneralGetting stdout immediately PinmemberMilhouse1006-Mar-03 0:49 
GeneralRe: Getting stdout immediately PinmemberAndreas Saurwein6-Mar-03 1:19 
GeneralRe: Getting stdout immediately PinsussAnonymous17-Mar-03 10:35 
GeneralSendInput Question Pinsuss6R15U28-Sep-02 23:47 
GeneralRe: SendInput Question PinmemberAndreas Saurwein4-Oct-02 0:24 
GeneralHelp! with CSpawn class... Pinmemberjohnpsquared1-Aug-04 13:29 
GeneralQuestion when using with processes that spawn other processes PinmemberJim Crafton18-Sep-02 9:40 
GeneralRe: Question when using with processes that spawn other processes PinmemberAndreas Saurwein23-Sep-02 1:06 
Generalnon-starter for win9x/ME Pinsussumeca7416-Sep-02 10:46 
GeneralRe: non-starter for win9x/ME PinmemberAndreas Saurwein23-Sep-02 1:08 
GeneralRedirecting existing process IO PinmemberAnonymous22-Aug-02 4:15 
GeneralRe: Redirecting existing process IO PinsussAndreas Saurwein26-Aug-02 1:02 
GeneralWrong function! PinmemberNguyen Binh5-Aug-02 23:44 
GeneralRe: Wrong function! PinmemberAndreas Saurwein6-Aug-02 2:22 
GeneralRe: Wrong function! PinmemberJim Crafton22-Aug-02 8:25 
General4k limitation PinmemberBed / Placid18-Jun-02 5:23 
GeneralRe: 4k limitation PinmemberAndreas Saurwein18-Jun-02 5:55 
Generalillegal memory access in Release config (Non-Unicode). PinmemberBlade[DMS]4-Mar-02 6:54 
GeneralRe: illegal memory access in Release config (Non-Unicode). PinmemberAndreas Saurwein4-Mar-02 12:01 
GeneralRe: illegal memory access in Release config (Non-Unicode). PinmemberBlade[DMS]4-Mar-02 23:08 
GeneralVerry cool PinmemberJim Crafton8-Feb-02 8:44 
Generaldirecting cout/stdout to window PinmemberN Singh6-Feb-02 12:00 
GeneralRe: directing cout/stdout to window PinmemberAndreas Saurwein6-Feb-02 12:10 

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