This code will shutdown your system??????

ankitkhasa543

#include<stdio.h>
#include<stdlib.h>
#include<signal.h>
#include<unistd.h>
void handler(int);
int main()
{
        int ret;
        ret = fork();
        switch(ret)
        {
                case -1:
                        perror("!fork() fail!");
                        exit(EXIT_FAILURE);
                case 0:
                        signal(SIGINT,handler);
                        while(1)
                        {
                                printf("**********child*********\n");
                                sleep(1);
                                kill(getppid(),SIGINT);
                        }
                        break;
                default:
                        signal(SIGINT,handler);
                        while(1)
                        {
                                printf("**********parent*********\n");
                                sleep(1);
                                pause();
                        }
                        break;
        }
        return 0;
}
void handler(int sig)
{
        printf("===========================signal==========================\n signal no.: %d\n",sig);
        signal(SIGINT,SIG_DFL);
}

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In this we duplicate the process using fork() system call
Using pause() call we put parent in pause state
When I try to resume the parent process using "ctrl+c" my system is shutting down
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adeshagarwal02

Why you put kill(getppid(),SIGINT); in while(1) the kill sending SIGINT to parent again and again,
and you wrote pause in while(1) in parent process.
so please correct this 2 things

sankalpnegi2310

This code is basically trying to kill the parent process, so when it hits real parent of the child the parent will run the signal handler, setting a default signal handler for the next signals of SIGINT type.So any next SIGINT will kill the real parent of the child .
The child will then be an orphan, and will be adopted by some system process.
So the next time the kill(getppid(), SIGINT) is executed it will send SIGINT to the new parent of the orphaned child, which has variable consequences :

If the adopting parent is the standard init process, the system will be rebooted
If the adopting process is some daemon process (eg systemd in fedora) the user will be logged off and will return to the login screen, with some issues indicated like abnormal logoff etc. (My system Fedora 4.11.5-200.fc25.x86_64
does so !!)

The nature of adopting parent depends on the kernel versions, for newer kernels (say 4.4x) the init process no longer serves as universal parent for orphaned proceses, instead they are adopted by some daemon processes like systemd(fedora), upstart (ubuntu) and etc. depending upon the OS distro.

Moreover, the SIGINT may hit the parent before pause() (depending on scheduler placement so a default handler is set) and then when you send Ctrl + c from keyboard, the parent will be killed, and the signal from child will kill the process adopting it, as explained above, which in your case am guessing is init(), hence the restart.

This code will shutdown your system??????

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