stop the interrupts and termination in linux using C

The tutorial is how to stop the interrupts and termination in linux using C.
The communication with the the program using the Linux kernel can be done by using the mechanism called signal

Often we use the Ctrl  +  C interrupt to stop any running C program in terminal.
But we can easily stop it.
Firstly, let's see an example of Ctrl  +  C

---

#include<stdio.h>
void main()
{
while(1)
printf("Stop me using the Ctrl + C");
}

---

Output is

Now this program is infinite loop and can be stopped by using the Ctrl  +  C interrupt.
But we can easily disable the Ctrl  +  C interrupt.
See the next C program.

---

#include<stdio.h>
#include<signal.h>   //for signal ()
void disable_Ctrlc(int signum)
{
printf("Sorry even Ctrl + C is disabled");
}
void main()
{
signal(SIGINT,disable_Ctrlc);   //it is library function
while(1)
printf("Ctrl + C also can't stop me");

}

---

As you can see from above screenshot that this program will not be stopped even after using the Ctrl + C interrupt.

1. signal() is the library function which registers a signal handler for various signals.
2. First parameter of signal specifies the ID of the signal that we wish to register.Here we are using the signal SIGINT(INT->  interrupt).
3. Second parameter is the address of the function that should be called when signal is received
4. So when we press Ctrl + C, the registered handler, which we named disable_Ctrlc, is gonna be called. As we haven't done anything with it, it'll not stop the running program.

The question is, How to stop this program?
well, we can use the ps command to see the PID of this process.
And then stop that process using kill command.
Now the twist is that we can also stop kill command to stop our program.
See the below see C code

---

#include<stdio.h>
#include<signal.h>   //for signal ()
void disable_Ctrlc(int signum)
{
printf("Sorry even Ctrl + C is disabled");
}
void disable_kill(int signum)
{
printf("Sorry even kill is disabled");
}
void main()
{
signal(SIGINT,disable_Ctrlc);   //to register signal handler fo SIGINT
signal(SIGTERM,disable_kill);   //to register signal handler fo SIGTERM
while(1)
printf("Ctrl + C and kill also can't stop me");

}

---

1. So when we press Ctrl + C, the registered handler, which we named disable_Ctrlc, is gonna be called. As we haven't done anything with it, it'll not stop the running program.
2. And when we use kill PID the registered handler, which we named disable_kill, is gonna be called. As we also haven't done anything with it, it'll also not be able stop the running program.

Now if we want to stop our unstoppable program, we have to use kill -SIGKILL PID command where PID is the PID of our program. As SIGKILL signal is uncatchable signal it will forcible terminate our program.

So guys, it's all about how to stop the interrupts and termination in linux using C.
You can ask anytime if you wanna know more. Keep learning.