Objective: Process & Pipes. We want to develop a program that fill a global rand

Question

Objective: Process & Pipes.

We want to develop a program that fill a global random array of integers and ask to the user for a number (between 0 and 9) to search.

Then, the main program (parent) will:

> create 4 children process

>send to each child, using a pipe, the element to look for and the range (from/to) where it has to look for the element (each child will look in a 25% of the array).

> Wait for every child sends its result using other pipe and ends.

Every child process will:

>receive from father, using a pipe, the element to look for and the range (from/to) where it has to look for the element.

> look for the element in its part of the arary

> send its result to father using other pipe and ends

You can use these functions:

}

return -1; }

Execution Example:

$ lab10

Number to search in Vector :5

Child 0 responds with 3

Child 1 responds with 28

Child 2 responds with 60

Child 3 responds with 75

$ lab10

Number to search in Vector :5

Child 0 responds with 2

Child 1 responds with -1

Child 2 responds with 58

Child 3 responds with 79

Explanation / Answer

#include<iostream>
#include<sys/types.h>
#include<unistd.h>
#include<sys/wait.h>
using namespace std;

const int NO_OF_CHILDREN = 6;

const int PARENT_CONTROL = (2 - NO_OF_CHILDREN);

const int SIZE_OF_INT = sizeof(int);

const int INITIAL_NUMBER_OF_SEATS = 100;

void travel_agent (int* child_to_parent, int* parent_to_child, int id);

int main(){
int child_to_parent[2];
int parent_to_child[2];
pipe(child_to_parent);
pipe(parent_to_child);

pid_t shut_down[NO_OF_CHILDREN];

  
int seats_left = INITIAL_NUMBER_OF_SEATS;


int pid;

  
for (int i = 0; i < NO_OF_CHILDREN; i++){

pid = fork();

//error catching. a pid < 0 is returned when there is a failure
if (pid < 0){
cout << "OH SNAP! Child " << i << " failed";
return -1;
}

  
if (pid == 0 ) {

  
cout << "CHILD: " << i << " CREATED " << getpid() << endl;

  
travel_agent(child_to_parent, parent_to_child, i);
break;
}
else{
  
shut_down[i] = pid;
}
}


if (pid>0){ //parent and control function
bool loop = true;

//in a loop
while (loop){

write(parent_to_child[1], &seats_left, SIZE_OF_INT);
read(child_to_parent[0], &seats_left, SIZE_OF_INT);

if (seats_left > 0)
cout << "the main just read seats_left: " << seats_left << endl;

if (seats_left < PARENT_CONTROL){
loop = false;
cout << "Parent exit loop. PID: " << getpid() << endl;
}
}

  
for (int i = 0; i < NO_OF_CHILDREN; i++){
cout << "Waiting for PID: " << shut_down[i] << " to finish" << endl;
waitpid(shut_down[i], NULL, 0);
cout << "PID: " << shut_down[i] << " has shut down" << endl;
}
}   

cout << "Did we all Join? There will be 7 of us if we did. PID: " << getpid() << endl;
if (pid>0)
cout << "There are no ZOMBIES!" << endl;

return 0;
}

void travel_agent (int* child_to_parent, int* parent_to_child, int id){
bool loop = true;

while (loop){

int seats_left = 0;

read(parent_to_child[0], &seats_left, SIZE_OF_INT);

if (seats_left > 0){
cout << "I am Child: " << id << " There are: " << seats_left << " seats, booking one!";
cout << " My PID is : " << getpid() << endl;
seats_left--;

if (seats_left == 0)
loop=false;

write(child_to_parent[1], &seats_left, SIZE_OF_INT);
usleep(100);
}


else{
loop = false;
seats_left--;
write(child_to_parent[1], &seats_left, SIZE_OF_INT);
}
}
}

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