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C/C++ API Documentation | 2026.1

# Signaler::Intr()

Coordinate execution of all functions registered by `Signaler::OnIntr()`.

Virtual? | No |
Class | `Signaler` |
Arguments | None |
Returns | `void` |

## Notes

`Intr()` is the `Signaler` class’s main handler for interrupt signals.

Most P4 Server client applications do not need to call `Intr()` directly, because it is called directly from the internal handler function that catches the interrupt signals.

This internal handler function also causes the process to exit, returning an exit status of -1 to the operating system. (For instance, `signaler.Intr()``; exit( -1 )`)

If you require more flexible or complex interrupt handling, replace the default interrupt handler function with your own by using the ANSI C `signal(2)` function, and call `Intr()` to execute the registered functions.

## Caveat

`Intr()` does not deregister functions after they have been called. When calling a registered function twice might cause a failure, immediately deregister it using `DeleteOnIntr()` after the function has been called.

## See also

`Signaler::OnIntr()`

## Example

    #include <unistd.h>    // for sleep()
    #include <signal.h>
    #include <stdhdrs.h>
    #include <strbuf.h>
    #include <signaler.h>

    class MyClass
    {
        public:
        void         Set( StrPtr *d ) { data = *d; }
        const StrPtr *Get()           { return &data; }
        void         Identify()       { printf( "I'm %s\n", data.Text() ); }

        private:
        StrBuf       data;
    };

    static int intrCount = 0;
    static const int maxIntr = 3;

    // Replacement handler for SIGINT signals. Overrides Signaler class's
    // default handler to avoid immediate exit.

    static void trap_interrupt( int sig )
    {
        intrCount++;
        printf( "Received SIGINT. Calling registered functions...\n" );
        signaler.Intr();
        printf( "All functions done\n\n" );
        if ( intrCount >= maxIntr )
        {
            printf( "Interrupt limit hit. Exiting...\n" );
            exit( 0 );
        }
    }

    static void InterruptHandler( void *p )
    {
        MyClass      *m = ( MyClass * )p;
        m->Identify();

        // Don't identify this object again
        signaler.DeleteOnIntr( p );
    }

    int main( int argc, char **argv )
    {
        signal( SIGINT, trap_interrupt );
        signaler.Catch();

        int objCount = 5;
        int nextId = 1;
        for ( ; ; )
        {
            int i;
            for ( i = nextId; i < nextId + objCount; i++ )
            {
                StrBuf data;

                data.Set( "Object" );
                data << i;

                MyClass *p = new MyClass;
                p->Set( &data );

                printf( "Registering %s\n", data.Text() );
                signaler.OnIntr( InterruptHandler, ( void * )p );
            }

            nextId = i;
            printf( "\n" );
            printf( "Hit ^C to fire the interrupt handler [%d to go]\n",
                    maxIntr - intrCount );
            sleep( 10 );
        }

        exit( 0 );
    }

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