How to Gracefully Handle Ctrl-C Interrupts in C with the Sigaction Function?

Intercepting Ctrl-C Events in C

Intercepting Ctrl-C Events is a necessary task in programming, especially when you want Gracefully respond to unexpected interruptions.

Use Sigaction

In C, it is more reliable to use the sigaction function to handle signals. The syntax is as follows:

int sigaction(int signum, const struct sigaction *act, struct sigaction *oldact);

Where:

• signum: The number of the signal to be processed, for Ctrl-C, it is SIGINT.
• act: Specifies the action of the new signal handler.
• oldact: Stores previous behavior.

In the example given by Thomas, the sigaction structure is as follows:

struct sigaction sigIntHandler;

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

Where:

• sa_handler: points to the handler function.
• sa_mask: The signal mask to prevent during processing of this signal.
• sa_flags: additional flags, usually 0.

Use this sigaction structure with the SIGINT signal:

sigaction(SIGINT, &sigIntHandler, NULL);

Handler function

Finally, you need a handler function to respond to the signal. In the example, my_handler just prints a message and exits the program:

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

Full code

Here is the complete code using sigaction to capture Ctrl-C events :

#include 
#include 
#include 
#include 

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;    
}

By using sigaction you can reliably catch Ctrl-C incident and take appropriate action.

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