main.c

#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <string.h>

int main(int argc, char* argv[])
{
    int SomeValue = 100;
    int pid = fork();
    int fd = open("test_file", O_WRONLY|O_CREAT|O_TRUNC, 0666);

    const char *parentMessage = "1111111";
    const char *childMessage =  "22222222222222\n";

    if(pid > 0)
    {
        printf("hello from the parent process, chid pid = %d\n", pid);
        sleep(2);
        printf("parent's SomeValue = %d\n", SomeValue);
        write(fd, parentMessage, strlen(parentMessage) * sizeof(char));
    }
    else if(pid == 0)
    {
        printf("hello from the child process\n");
        SomeValue = 200;
        printf("child's SomeValue = %d\n", SomeValue);
        write(fd, childMessage, strlen(childMessage) * sizeof(char));
    }
    else
    {
        printf("fork() failed!!\n");
    }

    close(fd);

    return 0;
}