How do I trap ctrl-c SIGINT in a C console app

Question

I would like to be able to trap CTRL C in a C  console application so that I can carry out some cleanups before exiting  What is the best way of doing this

User · Answer

In my case  I passed an async lambda to Console CancelKeyPress  which won t work

User · Answer

The Console CancelKeyPress event is used for this  This is how it s used   public static void Main string   args        Console CancelKeyPress    delegate              call methods to clean up             while  true         When the user presses Ctrl   C the code in the delegate is run and the program exits  This allows you to perform cleanup by calling necessairy methods  Note that no code after the delegate is executed   There are other situations where this won t cut it  For example  if the program is currently performing important calculations that can t be immediately stopped  In that case  the correct strategy might be to tell the program to exit after the calculation is complete  The following code gives an example of how this can be implemented   class MainClass       private static bool keepRunning   true       public static void Main string   args                Console CancelKeyPress    delegate object sender  ConsoleCancelEventArgs e                e Cancel   true              MainClass keepRunning   false                      while  MainClass keepRunning                   Do your work in here  in small chunks                 If you literally just want to wait until ctrl-c                 not doing anything  see the answer using set-reset events                    Console WriteLine  exited gracefully              The difference between this code and the first example is that e Cancel is set to true  which means the execution continues after the delegate  If run  the program waits for the user to press Ctrl   C  When that happens the keepRunning variable changes value which causes the while loop to exit  This is a way to make the program exit gracefully

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I can carry out some cleanups before exiting  What is the best way of doing this   Thats is the real goal  trap exit  to make your own stuff  And neigther answers above not makeing it right  Because  Ctrl C is just one of many ways to exiting app    What in dotnet c  is needed for it - so called cancellation token passed to Host RunAsync ct  and then  in exit signals traps  for Windows it would be      private static readonly CancellationTokenSource cts   new CancellationTokenSource        public static int Main string   args                   For gracefull shutdown  trap unload event         AppDomain CurrentDomain ProcessExit     sender  e    gt                        cts Cancel                exitEvent Wait                        Console CancelKeyPress     sender  e    gt                        cts Cancel                exitEvent Wait                        host RunAsync cts           Console WriteLine  Shutting down            exitEvent Set            return 0

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I d like to add to Jonas  answer  Spinning on a bool will cause 100  CPU utilization  and waste a bunch of energy doing a lot of nothing while waiting for CTRL C   The better solution is to use a ManualResetEvent to actually  wait  for the CTRL C   static void Main string   args        var exitEvent   new ManualResetEvent false        Console CancelKeyPress     sender  eventArgs    gt                                      eventArgs Cancel   true                                    exitEvent Set                                          var server   new MyServer           example     server Run         exitEvent WaitOne        server Stop

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I d like to add to Jonas  answer  Spinning on a bool will cause 100  CPU utilization  and waste a bunch of energy doing a lot of nothing while waiting for CTRL C   The better solution is to use a ManualResetEvent to actually  wait  for the CTRL C   static void Main string   args        var exitEvent   new ManualResetEvent false        Console CancelKeyPress     sender  eventArgs    gt                                      eventArgs Cancel   true                                    exitEvent Set                                          var server   new MyServer           example     server Run         exitEvent WaitOne        server Stop

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Here is a complete working example  paste into empty C  console project   using System  using System Collections Generic  using System Linq  using System Runtime InteropServices  using System Text  using System Threading   namespace TestTrapCtrlC       public class Program           static bool exitSystem   false            region Trap application termination          DllImport  Kernel32            private static extern bool SetConsoleCtrlHandler EventHandler handler  bool add            private delegate bool EventHandler CtrlType sig           static EventHandler  handler           enum CtrlType               CTRL C EVENT   0              CTRL BREAK EVENT   1              CTRL CLOSE EVENT   2              CTRL LOGOFF EVENT   5              CTRL SHUTDOWN EVENT   6                    private static bool Handler CtrlType sig                Console WriteLine  Exiting system due to external CTRL-C  or process kill  or shutdown                   do your cleanup here             Thread Sleep 5000     simulate some cleanup delay              Console WriteLine  Cleanup complete                   allow main to run off             exitSystem   true                 shutdown right away so there are no lingering threads             Environment Exit -1                return true                     endregion          static void Main string   args                   Some biolerplate to react to close window event  CTRL-C  kill  etc              handler    new EventHandler Handler               SetConsoleCtrlHandler  handler  true                  start your multi threaded program here             Program p   new Program                p Start                   hold the console so it doesn   t run off the end             while   exitSystem                    Thread Sleep 500                                    public void Start                    start a thread and start doing some processing             Console WriteLine  Thread started  processing

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This question is very similar to    Capture console exit C   Here is how I solved this problem  and dealt with the user hitting the X as well as Ctrl-C  Notice the use of ManualResetEvents  These will cause the main thread to sleep which frees the CPU to process other threads while waiting for either exit  or cleanup  NOTE  It is necessary to set the TerminationCompletedEvent at the end of main  Failure to do so causes unnecessary latency in termination due to the OS timing out while killing the application   namespace CancelSample       using System      using System Threading      using System Runtime InteropServices       internal class Program                    lt summary gt              Adds or removes an application-defined HandlerRoutine function from the list of handler functions for the calling process              lt  summary gt               lt param name  handler  gt A pointer to the application-defined HandlerRoutine function to be added or removed  This parameter can be NULL  lt  param gt               lt param name  add  gt If this parameter is TRUE  the handler is added  if it is FALSE  the handler is removed  lt  param gt               lt returns gt If the function succeeds  the return value is true  lt  returns gt           DllImport  Kernel32            private static extern bool SetConsoleCtrlHandler ConsoleCloseHandler handler  bool add                 lt summary gt              The console close handler delegate               lt  summary gt               lt param name  closeReason  gt              The close reason               lt  param gt               lt returns gt              True if cleanup is complete  false to run other registered close handlers               lt  returns gt          private delegate bool ConsoleCloseHandler int closeReason                 lt summary gt               Event set when the process is terminated               lt  summary gt          private static readonly ManualResetEvent TerminationRequestedEvent                lt summary gt              Event set when the process terminates               lt  summary gt          private static readonly ManualResetEvent TerminationCompletedEvent                lt summary gt              Static constructor              lt  summary gt          static Program                            Do this initialization here to avoid polluting Main   with it                also this is a great place to initialize multiple static                variables              TerminationRequestedEvent   new ManualResetEvent false               TerminationCompletedEvent   new ManualResetEvent false               SetConsoleCtrlHandler OnConsoleCloseEvent  true                           lt summary gt              The main console entry point               lt  summary gt               lt param name  args  gt The commandline arguments  lt  param gt          private static void Main string   args                           Wait for the termination event             while   TerminationRequestedEvent WaitOne 0                                    Something to do while waiting                 Console WriteLine  Work                                  Sleep until termination             TerminationRequestedEvent WaitOne                    Print a message which represents the operation             Console WriteLine  Cleanup                    Set this to terminate immediately  if not set  the OS will                eventually kill the process              TerminationCompletedEvent Set                            lt summary gt              Method called when the user presses Ctrl-C              lt  summary gt               lt param name  reason  gt The close reason lt  param gt          private static bool OnConsoleCloseEvent int reason                           Signal termination             TerminationRequestedEvent Set                    Wait for cleanup             TerminationCompletedEvent WaitOne                    Don t run other handlers  just exit              return true

User · Answer

In my case  I passed an async lambda to Console CancelKeyPress  which won t work

User · Answer

Here is a complete working example  paste into empty C  console project   using System  using System Collections Generic  using System Linq  using System Runtime InteropServices  using System Text  using System Threading   namespace TestTrapCtrlC       public class Program           static bool exitSystem   false            region Trap application termination          DllImport  Kernel32            private static extern bool SetConsoleCtrlHandler EventHandler handler  bool add            private delegate bool EventHandler CtrlType sig           static EventHandler  handler           enum CtrlType               CTRL C EVENT   0              CTRL BREAK EVENT   1              CTRL CLOSE EVENT   2              CTRL LOGOFF EVENT   5              CTRL SHUTDOWN EVENT   6                    private static bool Handler CtrlType sig                Console WriteLine  Exiting system due to external CTRL-C  or process kill  or shutdown                   do your cleanup here             Thread Sleep 5000     simulate some cleanup delay              Console WriteLine  Cleanup complete                   allow main to run off             exitSystem   true                 shutdown right away so there are no lingering threads             Environment Exit -1                return true                     endregion          static void Main string   args                   Some biolerplate to react to close window event  CTRL-C  kill  etc              handler    new EventHandler Handler               SetConsoleCtrlHandler  handler  true                  start your multi threaded program here             Program p   new Program                p Start                   hold the console so it doesn   t run off the end             while   exitSystem                    Thread Sleep 500                                    public void Start                    start a thread and start doing some processing             Console WriteLine  Thread started  processing

User · Answer

Console TreatControlCAsInput   true  has worked for me

User · Answer

See MSDN   Console CancelKeyPress Event  Article with code samples   Ctrl-C and the  NET console application

User · Answer

The Console CancelKeyPress event is used for this  This is how it s used   public static void Main string   args        Console CancelKeyPress    delegate              call methods to clean up             while  true         When the user presses Ctrl   C the code in the delegate is run and the program exits  This allows you to perform cleanup by calling necessairy methods  Note that no code after the delegate is executed   There are other situations where this won t cut it  For example  if the program is currently performing important calculations that can t be immediately stopped  In that case  the correct strategy might be to tell the program to exit after the calculation is complete  The following code gives an example of how this can be implemented   class MainClass       private static bool keepRunning   true       public static void Main string   args                Console CancelKeyPress    delegate object sender  ConsoleCancelEventArgs e                e Cancel   true              MainClass keepRunning   false                      while  MainClass keepRunning                   Do your work in here  in small chunks                 If you literally just want to wait until ctrl-c                 not doing anything  see the answer using set-reset events                    Console WriteLine  exited gracefully              The difference between this code and the first example is that e Cancel is set to true  which means the execution continues after the delegate  If run  the program waits for the user to press Ctrl   C  When that happens the keepRunning variable changes value which causes the while loop to exit  This is a way to make the program exit gracefully

User · Answer

This question is very similar to    Capture console exit C   Here is how I solved this problem  and dealt with the user hitting the X as well as Ctrl-C  Notice the use of ManualResetEvents  These will cause the main thread to sleep which frees the CPU to process other threads while waiting for either exit  or cleanup  NOTE  It is necessary to set the TerminationCompletedEvent at the end of main  Failure to do so causes unnecessary latency in termination due to the OS timing out while killing the application   namespace CancelSample       using System      using System Threading      using System Runtime InteropServices       internal class Program                    lt summary gt              Adds or removes an application-defined HandlerRoutine function from the list of handler functions for the calling process              lt  summary gt               lt param name  handler  gt A pointer to the application-defined HandlerRoutine function to be added or removed  This parameter can be NULL  lt  param gt               lt param name  add  gt If this parameter is TRUE  the handler is added  if it is FALSE  the handler is removed  lt  param gt               lt returns gt If the function succeeds  the return value is true  lt  returns gt           DllImport  Kernel32            private static extern bool SetConsoleCtrlHandler ConsoleCloseHandler handler  bool add                 lt summary gt              The console close handler delegate               lt  summary gt               lt param name  closeReason  gt              The close reason               lt  param gt               lt returns gt              True if cleanup is complete  false to run other registered close handlers               lt  returns gt          private delegate bool ConsoleCloseHandler int closeReason                 lt summary gt               Event set when the process is terminated               lt  summary gt          private static readonly ManualResetEvent TerminationRequestedEvent                lt summary gt              Event set when the process terminates               lt  summary gt          private static readonly ManualResetEvent TerminationCompletedEvent                lt summary gt              Static constructor              lt  summary gt          static Program                            Do this initialization here to avoid polluting Main   with it                also this is a great place to initialize multiple static                variables              TerminationRequestedEvent   new ManualResetEvent false               TerminationCompletedEvent   new ManualResetEvent false               SetConsoleCtrlHandler OnConsoleCloseEvent  true                           lt summary gt              The main console entry point               lt  summary gt               lt param name  args  gt The commandline arguments  lt  param gt          private static void Main string   args                           Wait for the termination event             while   TerminationRequestedEvent WaitOne 0                                    Something to do while waiting                 Console WriteLine  Work                                  Sleep until termination             TerminationRequestedEvent WaitOne                    Print a message which represents the operation             Console WriteLine  Cleanup                    Set this to terminate immediately  if not set  the OS will                eventually kill the process              TerminationCompletedEvent Set                            lt summary gt              Method called when the user presses Ctrl-C              lt  summary gt               lt param name  reason  gt The close reason lt  param gt          private static bool OnConsoleCloseEvent int reason                           Signal termination             TerminationRequestedEvent Set                    Wait for cleanup             TerminationCompletedEvent WaitOne                    Don t run other handlers  just exit              return true

User · Answer

See MSDN   Console CancelKeyPress Event  Article with code samples   Ctrl-C and the  NET console application

User · Answer

See MSDN   Console CancelKeyPress Event  Article with code samples   Ctrl-C and the  NET console application

User · Answer

I can carry out some cleanups before exiting  What is the best way of doing this   Thats is the real goal  trap exit  to make your own stuff  And neigther answers above not makeing it right  Because  Ctrl C is just one of many ways to exiting app    What in dotnet c  is needed for it - so called cancellation token passed to Host RunAsync ct  and then  in exit signals traps  for Windows it would be      private static readonly CancellationTokenSource cts   new CancellationTokenSource        public static int Main string   args                   For gracefull shutdown  trap unload event         AppDomain CurrentDomain ProcessExit     sender  e    gt                        cts Cancel                exitEvent Wait                        Console CancelKeyPress     sender  e    gt                        cts Cancel                exitEvent Wait                        host RunAsync cts           Console WriteLine  Shutting down            exitEvent Set            return 0

User · Answer

Console TreatControlCAsInput   true  has worked for me

User · Answer

See MSDN   Console CancelKeyPress Event  Article with code samples   Ctrl-C and the  NET console application

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