This is my problem:
- Create processes
- Make a shared variable of char buffer
- Each process will write a char value (for lets say 50 times) i.e. 'A','B', 'C' etc. into the shared memory and will print out the buffer size after it ends
- I need to add sleep statement so that the order of adding char values to shared value is like this
Child -> Grand child 1 -> Grand child 2 -> Great Grand child 1 -> Great Grand child 2 - At the end print the final buffer
So first of all I want to create process like this, parent process will have a child process. Child process will have grand child process each and each one of the grand child will have great grand child as show here.
I am using IF-ELSE structure to achieve this but I need to create all process first and then start working, don't know how to achieve this. I don't know what is wrong with the code processes are not adding anything into the buffer or the shared value. The reason I am saying this because when process print the buffer size after its execution, it is same for each process.
Code
#include <iostream>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include<stdio.h>
#include <sys/wait.h>
#include<sys/ipc.h>
#include<sys/shm.h>
using namespace std;
// Driver Code
int main()
{
// number of chars values the process will write
int child_chrs = 1000;
int grand_child1_chrs = 700;
int grand_child2_chrs = 300;
int great_grand_child1_chrs = 700;
int great_grand_child2_chrs = 300;
int fd[2];
pipe(fd);
int shared_index = 0, n =0;
write(fd[1], &n, sizeof(n));
key_t key = ftok("shmfile",65); // generate unique key
int shmid = shmget(key,1024,0666|IPC_CREAT); // get identifier in shmid
char *stringValue = (char*) shmat(shmid,(void*)0,0); // attach to shared memory
cout << "Parent process has been created." << endl;
cout << "Shared memory creation was successful." << endl;
if (fork() == 0) // Child
{
if(fork() == 0) // Grand Child 1
{
if(fork() == 0) // Great Grand Child 1
{
while(great_grand_child1_chrs!=0)
{
shared_index = read(fd[0], &shared_index, sizeof(int));
*(stringValue+shared_index) = 'Y';
great_grand_child1_chrs--;
shared_index++;
write(fd[1], &shared_index, sizeof(int));
}
cout << "From Great-grandchild1 process - I just finished and the buffer size = " << shared_index << endl;
cout << "From Great-grandchild1 process terminated normally\n";
}
else // Great Grand Child 2
{
while(grand_child1_chrs!=0)
{
shared_index = read(fd[0], &shared_index, sizeof(int));
*(stringValue+shared_index) = 'B';
grand_child1_chrs--;
shared_index++;
write(fd[1], &shared_index, sizeof(int));
}
cout << "From Great-grandchild2 process - I just finished and the buffer size = " << shared_index << endl;
cout << "From Great-grandchild2 process terminated normally\n";
}
}
else // Grand Child 2
{
if(fork() == 0) // Grand Child 1
{
if(fork() == 0) // Grand Child 2
{
while(great_grand_child2_chrs!=0)
{
shared_index = read(fd[0], &shared_index, sizeof(int));
*(stringValue+shared_index) = 'Z';
great_grand_child2_chrs--;
shared_index++;
write(fd[1], &shared_index, sizeof(int));
//cout<<"\nshared index: "<<shared_index;
}
cout << "From Grandchild1 process - I just finished and the buffer size = " << shared_index << endl;
cout << "The Grandchild1 process terminated normally.\n";
}
else // Grand Child 2
{
while(grand_child2_chrs!=0)
{
shared_index = read(fd[0], &shared_index, sizeof(int));
*(stringValue+shared_index) = 'C';
grand_child2_chrs--;
shared_index++;
write(fd[1], &shared_index, sizeof(int));
}
cout << "From Grandchild2 process - I just finished and the buffer size = " << shared_index << endl;
cout << "The Grandchild2 process terminated normally.\n";
}
}
else // Child
{
while(child_chrs!=0)
{
shared_index = read(fd[0], &shared_index, sizeof(int));
*(stringValue+shared_index) = 'A';
child_chrs--;
shared_index++;
write(fd[1], &shared_index, sizeof(int));
}
cout << "From Child process - I just finished and the buffer size = " << shared_index << endl;
cout << "The Child process terminated normally.\n";
}
}
}
else // Parent
{
wait(NULL);
cout<<"\n\nResultant Buffer is:\n\n";
cout << "From Parent process - I am exiting and final buffer size = " << shared_index << endl;
shmdt(stringValue);
cout << "Shared memory has been released.\n";
}
}
Output
From Child process - I just finished and the buffer size = 5
The Child process terminated normally.
Resultant Buffer is:
From Parent process - I am exiting and final buffer size = 0
Shared memory has been released.
From Grandchild2 process - I just finished and the buffer size = 5
The Grandchild2 process terminated normally.
Note: I know the code is in C++ and it needs to be in C the example that I found was in C++ when I started coding this, but I don't the changes that will make it a C code. I might be doing silly mistakes as I am not a great C programmer I am experienced in Java, Python, Ruby and C# but C is not something I have experience in.
