Aim:

Write a C/C++ program that creates a zombie and then calls system to execute the ps command to verify that the process is zombie.

Theory:

In unix terminology, a process that has terminated, but whose parent has not yet waited for it, is called a zombie.

fork()

Syntax:

 #include<unistd.h>
 pid_t fork(void);

fork() creates a new process by duplicating the calling process. The new process, referred to as the child, is an exact duplicate of the calling process, referred to as the parent.

Sleep() : Delay for a specified amount of time.

System()

Syntax:

 #include <stdlib.h>
 int system(const char *command);

system() executes a command specified in command by calling /bin/sh -c command, and returns after the command has been completed.

Code:

 #include<stdio.h> 
 #include<unistd.h>
 #include<stdlib.h>
   int main()
     {
        int pid;
        if((pid=fork())<0)
                printf("fork error\n");
        else if(pid==0)
                _exit(0);
        sleep(2);
        system( "ps -o pid,ppid,state,tty,command");
        _exit(0);
     }

Output:

• Open a terminal
• Change directory to the file location in the terminal
• Complile the program by using the command cc usp-lab-07.c -o usp07.out
• Run usp07.out

Screenshots: