Fork로 자식 프로세스 생성 실습

(추후 수정)

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <unistd.h>
#include <sys/wait.h>
 
int main(int argc, char *argv[], char *env[]) {
    pid_t my_pid, parent_pid, child_pid;
    int status;
 
    // get and print my pid and my parent's pid.
    my_pid = getpid();
    parent_pid = getppid();
    printf("\nParent : My PID is %d.\n\n", my_pid);
    printf("Parent : My parent's PID is %d.\n\n", parent_pid);
 
    // print error message if fork() fails
    if((child_pid = fork()) < 0)
    {
        perror("fork failure");
        exit(1);
    }
 
    // fork() == 0 for child process
    if(child_pid == 0)
    {
        printf("\nChild : I am a new-born process!\n\n");
        my_pid = getpid();
        parent_pid = getppid();
        printf("Child : My PID is %d.\n\n", my_pid);
        printf("Child : My parent's PID is %d.\n\n", parent_pid);
        printf("Child : I will sleep 3 seconds and then execute - date - command.\n\n");
 
        sleep(3);
        printf("Child : Now, I woke up and I'm executing date command.\n\n");
        execl("/bin/date", "date", 0, 0);
        perror("execl() failure!\n\n");
 
        printf("This print is after execl() and should not have been executed if execl were successful!\n\n");
        sleep(5);
        _exit(1);
    }
    // parent process
    else
    {
        printf("\nParent : I created a child process.\n\n");
        printf("Parent : My child's PID is %d.\n\n", child_pid);
        system("ps -acefl | grep ercal");
        printf("\n\n");
        wait(&status);  // can use wait(NULL) since exit status frum child is not used.
        printf("\nParent : My child is dead. I am going to leave.\n\n");
    }
    return 0;
}