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Posted 29 May 2002


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Console Event Handling

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29 May 20024 min read
This article discusses how to handle console-window specific events


Everyone programs console applications one time or the other. This programming is more prevalent when people are learning to program, especially while learning the DOS based C/C++ programming. However, when one migrates to Windows programming, console application development takes a back seat. But the Win32 console development holds an important place, especially when the Win32 API contains a good amount of API dedicated to console application development. If you have noticed, even VC++, and latest development technologies like C#, also supports console project development. Console applications are good candidates for testing the core functionality of your Windows application without the unnecessary overhead of a GUI.

But there's always been a sense of helplessness in regard to how to know when certain system related events have occurred, like when user if logging off, or the system is being shutdown, or handling control+break or control+C keyboard events, etc. For a Windows based application, getting to know when such events occur is no problem since they are having a message queue assigned to them that is polled, and assuming that the concerned event is programmed for, it can be handled pretty easily. But this isn't the case with a console application that has no concept of a message queue.

This article intends to discuss how you can handle all kinds of console-based events in any console application. Once you have gone through it, you will see for yourself how trivial this seemingly helpless task is :)

Setting Console Traps

The first step in handling console application events is to setup an even trap, technically referred to as installing an event handler. For this purpose, we utilize the SetConsoleCtrlHandler Win32 API that is prototyped as shown below:

BOOL SetConsoleCtrlHandler(
    PHANDLER_ROUTINE HandlerRoutine, // handler function
    BOOL Add // add or remove handler

The HandlerRoutine parameter is a pointer to a function that has the following prototype:

BOOL WINAPI HandlerRoutine(
    DWORD dwCtrlType   //  control signal type

All the HandlerRoutine takes is a DWORD parameter that tells what console event has taken place. The parameter can take the following values:

  • CTRL_C_EVENT - occurs when the user presses CTRL+C, or when it is sent by the GenerateConsoleCtrlEvent API.
  • CTRL_BREAK_EVENT - occurs when the user presses CTRL+BREAK, or when it is sent by the GenerateConsoleCtrlEvent API.
  • CTRL_CLOSE_EVENT - occurs when attempt is made to close the console, when the system sends the close signal to all processes associated with a given console.
  • CTRL_LOGOFF_EVENT - occurs when the user is logging off. One cannot determine, however, which user is logging off.
  • CTRL_SHUTDOWN_EVENT - occurs when the system is being shutdown, and is typically sent to services.

Upon receiving the event, the HandlerRoutine can either choose to do some processing, or ignore the event. If the routine chooses not to handle the event, it should return FALSE, and the system shall then proceed to the next installed handler. But incase the routine does handle the event, it should then return TRUE, after doing all the processing it requires. The CTRL_CLOSE_EVENT, CTRL_LOGOFF_EVENT and CTRL_SHUTDOWN_EVENT are typically used to perform any cleanup that is required by the application, and then call the ExitProcess API. Thus, the system has has some timeouts associated with these three events, which is 5 seconds for CTRL_CLOSE_EVENT, and 20 seconds for the other two. If the process doesn't respond within the timeout period, Windows shall then proceed to display the End Task dialog box to the user. If the user proceeds to end the task, then the application will not have any opportunity to perform cleanup. Thus, any cleanup that is required should complete well within the timeout period. Below is an exemplification of the handler routine:

BOOL WINAPI ConsoleHandler(DWORD CEvent)
    char mesg[128];

    case CTRL_C_EVENT:
            "CTRL+C received!","CEvent",MB_OK);
            "CTRL+BREAK received!","CEvent",MB_OK);
            "Program being closed!","CEvent",MB_OK);
            "User is logging off!","CEvent",MB_OK);
            "User is logging off!","CEvent",MB_OK);

    return TRUE;

Now that we have seen how the handler routine works, lets see how to install the handler. To do so, as mentioned earlier in the article, we use the SetConsoleCtrlHandler API as shown below:

if (SetConsoleCtrlHandler(
    // unable to install handler... 
    // display message to the user
    printf("Unable to install handler!\n");
    return -1;

The first parameter is a function pointer of the type PHANDLER_ROUTINE, whose prototype has been discussed earlier. The second parameter, if set to TRUE, tries installing the handler, and if set to FALSE, attempts the un-installation. If either attempts are successful, the return value is TRUE. Otherwise FALSE is returned.

So, that's all there is to handling the console application events. After handler is installed, your application will receive the events as and by they come, and when the execution is about to be terminated, the handler maybe un-installed. Pretty easy, eh :) ?


This article has no explicit license attached to it but may contain usage terms in the article text or the download files themselves. If in doubt please contact the author via the discussion board below.

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About the Author

Kumar Gaurav Khanna
Web Developer
United States United States
I hold Early Acheiver in MCSE 2000, MCSE NT 4.0, MCP+I, and actively involved in programming using C/C++, .NET framework, C#, Win32 API, VB, ASP and MFC.

I also have various publications to my credit at MSDN Online Peer Journal, Windows Developer Journal (, Developer 2.0 (, and PC Quest (

Comments and Discussions

QuestionDelay exit timeout Pin
tallcat0815-Oct-14 22:09
Membertallcat0815-Oct-14 22:09 
GeneralDoes not work anymore with Windows 7 [modified] Pin
FredericSivignonPro10-Jun-11 4:27
MemberFredericSivignonPro10-Jun-11 4:27 
GeneralLock computer Pin
Deepak Kumar Singh7-Dec-04 2:04
MemberDeepak Kumar Singh7-Dec-04 2:04 
GeneralRe: Lock computer Pin
Deepak Kumar Singh7-Dec-04 19:13
MemberDeepak Kumar Singh7-Dec-04 19:13 
GeneralNice, but ... Pin
Anonymous9-Apr-03 15:12
MemberAnonymous9-Apr-03 15:12 
GeneralMessageBox Pin
Sarwan Aggarwal27-Aug-03 16:18
MemberSarwan Aggarwal27-Aug-03 16:18 
GeneralRe: MessageBox Pin
yjip14-Nov-03 23:26
Memberyjip14-Nov-03 23:26 
GeneralRe: MessageBox Pin
yathirajkulal11-Jan-11 18:45
Memberyathirajkulal11-Jan-11 18:45 
GeneralRe: Nice, but ... Pin
Toal Ber G. Iron1-Feb-13 20:53
MemberToal Ber G. Iron1-Feb-13 20:53 
QuestionHow can I pass control-break to console application? Pin
Slimer30-Mar-03 22:42
MemberSlimer30-Mar-03 22:42 
GeneralArgh! Pin
Anonymous18-Feb-03 19:34
MemberAnonymous18-Feb-03 19:34 
GeneralRe: Argh! Pin
Anonymous3-May-04 23:58
MemberAnonymous3-May-04 23:58 
Questionhow can i get the source code! Pin
Anonymous14-Nov-02 22:26
MemberAnonymous14-Nov-02 22:26 
AnswerSameple code Re: how can i get the source code! Pin
SMuddasu15-Nov-02 8:29
MemberSMuddasu15-Nov-02 8:29 
GeneralRe: Sameple code Re: how can i get the source code! Pin
Xkirill13-Jul-09 3:30
MemberXkirill13-Jul-09 3:30 
QuestionWhere is the Source gone? Pin
SilliconXP31-May-02 17:14
MemberSilliconXP31-May-02 17:14 

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