Operating_System/main.c

#include <stdio.h>
#include <stdlib.h>
#include "fun.h"

void eval(char *cmdline);
void sigint_handler();
pid_t getpid(void);
pid_t main_proc_pid;

int main()
{
    char cmdline[MAXLINE];
    main_proc_pid = getpid();
    signal(SIGINT, sigint_handler);

    while(1)
    {
        printf("COMMAND->");
        fflush(stdin);
        fgets(cmdline, MAXLINE, stdin);    
        eval(cmdline);
        history(cmdline);
    }
    return 0;
}

void sigint_handler() 
{
    pid_t pid = getpid();
    if(pid != main_proc_pid)
    {
        exit(0);
    }
}