How can I intercept Ctrl C signals in C ?

Intercepting Control-C Signals in C

In the realm of programming, it's often necessary to capture keyboard events, such as the ubiquitous Ctrl C, which typically triggers program termination. This article addresses this specific need: how to intercept Ctrl C signals in C .

Capturing Ctrl C Events

In C , there are two primary methods for capturing Ctrl C events: signal and sigaction.

Using sigaction

The sigaction function provides a more reliable approach compared to signal, as it offers greater control and portability across different implementations. To use sigaction, follow these steps:

1. Include necessary headers:

   #include <signal.h>
   #include <stdlib.h>
   #include <stdio.h>
   #include <unistd.h>

2. Define a signal handler function:

   void my_handler(int s){
       printf("Caught signal %d\n",s);
       exit(1); 
   }

   In this handler, you can specify the actions to be performed when Ctrl C is pressed.

3. Configure the sigaction:

   struct sigaction sigIntHandler;
   
   sigIntHandler.sa_handler = my_handler;
   sigemptyset(&sigIntHandler.sa_mask);
   sigIntHandler.sa_flags = 0;
   
   sigaction(SIGINT, &sigIntHandler, NULL);

   Here, you attach your signal handler to the Ctrl C signal (SIGINT) and specify signal-related settings.

4. Pause the program:

   pause();

   This function causes the program to wait for signals, including Ctrl C.

Example:

The following example demonstrates how to use sigaction to capture Ctrl C events:

#include <signal.h>
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>

void my_handler(int s){
       printf("Caught signal %d\n",s);
       exit(1); 
}

int main(int argc,char** argv)
{
   struct sigaction sigIntHandler;

   sigIntHandler.sa_handler = my_handler;
   sigemptyset(&sigIntHandler.sa_mask);
   sigIntHandler.sa_flags = 0;

   sigaction(SIGINT, &sigIntHandler, NULL);

   pause();

   return 0;    
}

When you run this program and press Ctrl C, it will print "Caught signal 2" and exit gracefully.

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