Mini Project(PIC)!

Contributers-

Shivam L1-2
Vipul Jain L1-18
Mudit Kumar Tyagi L1-22
Vaibhav Upreti L1-30

Zombie Process

About

A zombie or a "defunct process" in Linux(or UNIX based kernel) is a process that has been completed, but its entry still remains in the process table due to lack of correspondence between the parent and child processes. Usually, a parent process keeps a check on the status of its child processes through the wait() function. When the child process has finished, the wait function signals the parent to completely exit the process from the memory. However, if the parent fails to call the wait function for any of its children, the child process remains alive in the system as a dead or zombie process. These zombie processes might accumulate, in large numbers, on your system and affect its performance.

Flowchart

A chart to illustrate Zombie process working

graph LR
A[Parent Process] -- wait --> B[Parent Process]
A -- fork--> C[Child Process]
C -- exec--> F[Child Process]

F -- exit-->E[Zombie Process]
E --> B

Code & Guide to run

Save this file as zombie.c in your folder

```c
#include <stdlib.h>
#include <sys/types.h>
#include <unistd.h>

int main ()
{
  pid_t child_pid;

  child_pid = fork ();
  if (child_pid > 0) {
    sleep (60);
  }
  else {
    exit (0);
  }
  return 0;
}

The following process will run in your terminal for 60s even after closing this. You can check this by running the following commands-

Run the code in your terminal by entering these two commands or use coderunner VSC extension

gcc zombie.c

Now run the zombie program:

./a.out

The ps command will now also show this defunct process, open a new terminal and use the below command to check the defunct process:

ps -ef | grep a.out
  501  9366  6755   0  5:40pm ttys000    0:00.00 ./a.out
  501  9367  9366   0  5:40pm ttys000    0:00.00 (a.out)
  501  9397  8546   0  5:40pm ttys002    0:00.00 grep --color=auto --exclude-dir=.bzr --exclude-dir=CVS --exclude-dir=.git --exclude-dir=.hg --exclude-dir=.svn --exclude-dir=.idea --exclude-dir=.tox a.out

Output Screenshot

Running the Zombie process:

Logs & Output:

Create a project to find sum of digits of a number until a single digit is occurred (without using recursion or iterative (loop) statements).

About

goto statements are used in such cases

Flowchart

A chart to illustrate the algorithm-

Code & Guide to run

Save this file as zombie.c in your folder

```c
#include<stdio.h>
int  main(){
int  sum=0;
int  num;
printf("-------------------------------------------------------------- \n");
printf("Enter number: ");
scanf("%d",  &num);
jumpto:
sum+=num%10;
num/=10;
if  (num==0){
printf("Sum of the digits of the number= %d",  sum);
return  0;
}
else
goto  jumpto;
}

Output Screenshot

Output Screenshot -