Question

Write a C program that has a local and a global variable. The program uses a fork to create a child process. The parent process modifies both variables to be 10 and 20 and prints out the values. Then the child process modifies both variables to be 100 and 200 and prints out the values? Explain the program output?

Answer 1

#include <stdio.h> 
#include <sys/types.h> 
#include <unistd.h>  
#include <sys/wait.h>

int globalVar = 1;

int main() {
        int localVar = 2;

        if(fork() == 0) {
                // child process
                globalVar = 100;
                localVar = 200;
                printf("Child process: Global: %d, Local: %d\n", globalVar, localVar);
        } else {
                // parent process
                globalVar = 10;
                localVar = 20;
                printf("Parent process: Global: %d, Local: %d\n", globalVar, localVar);
        }
        waitpid(-1, NULL, 0);

        return 0; 
}

$saved gcc version 4.6.3 main.c #include <stdio.h> #include <sys/types.h> #include <unistd.h> #include Parent process: Global: 10, Local: 20 Child process: Global: 100, Local: 200 3 <sys/wait.h> 6 int globalVar 1; 7 8 int main) 9 int localVar-2; 10 if(fork()-=0) { 12 13 14 15 // child process globalVar 100; localVar200; printf(child process: Global: globalVar, localVar); %d, Local: %d\n, } else { 16 17 18 19 20 // parent process globalVar - 10; localVar -20; printf(Parent process: globalVar, localvar); Global : %d, Local: %d\n, 21 waitpid(-1, NULL, 0); 23 24 25 return e;$

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