/*
Step1: Using the fork() function to create a new process.

Step2: Using command line to kill the process.
	kill -kill 1899

Step3: Repeat step1 and use system calls to kill process.
	
*/
#include<stdio.h>
#include<unistd.h>

int main()
{
    pid_t newpid = fork();
    if(newpid==0)
    {
        for(;;)
            pause();
    }
    printf("pid = %d\n",newpid);
    wait(NULL);
    printf("Child process is finished.\n");
}

 

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

int main()
{
    pid_t newpid;
    printf("Input the pid of the process you want to kill -> ");
    scanf("%d",&newpid);
    kill(newpid,SIGKILL);
}

 

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

struct sigaction newact;

/* here is the signal handler */ 
void catch_alarm_2(int sig_num)   /* the argument is signal number  */
{   
    /* re-set the signal handler again to catch_int, for next time */
    sigaction(SIGINT, &newact, NULL);
}
void catch_int_1(int sig_num)   /* the argument is signal number  */
{   
    /* re-set the signal handler again to catch_int, for next time */
    signal(SIGINT, catch_int_1);
    printf("How are you?\n",sig_num);
}
void catch_int_2(int sig_num)   /* the argument is signal number  */
{   
    /* re-set the signal handler again to catch_int, for next time */
    signal(SIGINT, catch_int_2);
    printf("I am fine!\n",sig_num);
}
void catch_alarm_1(int sig_num)   /* the argument is signal number  */
{   
    /* re-set the signal handler again to catch_int, for next time */
    signal(SIGINT, catch_int_2);
    signal(SIGALRM, catch_alarm_2);
    alarm(3);
}

int main(int argc, char* argv[])
{
    sigaction(SIGINT, NULL, &newact);
    
    /* set the INT (Ctrl-C) signal handler to 'catch_int' */
    signal(SIGINT, catch_int_1);
    signal(SIGALRM, catch_alarm_1);
    alarm(3);

    /* now, lets get into an infinite loop of doing nothing. */
    for ( ;; )
        pause();
} 
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