Handling SIGINT (Ctrl+c From Keyboard) in C

If you have developed a shell for your own command line program in python; you are likely to have used something like following code.

try:
    # your stuff..
except KeyboardInterrupt:
    pass

The above code is used to ignore the KeyboardInterrupt ie. when you press Ctrl+c from the keyboard. python makes it really easy for you.

If you want to do the same thing in c you need to handle what in nix world called as singnals. Here is a good description of what signals are, it is taken from yolinux

Signals are software interrupts delivered to a process by the operating system.
Signals can also be issued by the operating system based on system or error
conditions. 

What happens when you press Ctrl+c from the keyboard is the os delivers a Interrupt signal to the process that is running in your bash or whatever shell you are currently running. While developing a shell you need to ignore this interrupt. If you happen to be developing this shell in c, you will have to do the following things in order to handle SIGINT.

• include signal.h
• Write a function to handle signal.
• Register that function as a callback function for signal.

Following is the demo for that.

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

// The callback function.
void
exit_func(int signal_number)
{
    if (signal_number == 2)
    {
        printf("Ctrl+c Pressed, exitting...\n");
    }
}

int main()
{
    // register the callback function for signal from os.
    signal(SIGINT, exit_func);

    // do your stuff here
    // ...
    while (1)
    {
        sleep(1);
    }

    return EXIT_SUCCESS;
}