CODEWITHSUNDEEP
c++clinuxubuntuprocess
DeiAndrei
DeiAndrei

Reputation: 947

How to access the same variable by multiple processes C/C++

I have recently started learning how to program in C under Linux and have written the following code to create some processes:

void generate()
{    
  int pid;

  for(int i=1;i<=10;i++)
  {
    pid = fork();  
  }

  if (pid<0)
  {
    printf("Error Fork");
    exit(1);
  }

  if(pid == 0)
  {
    printf("Fiu pid: %d --- Parinte pid: %d\n", getpid(), getppid());
    //count ++;
  }

  if(pid > 0 )
  {
    printf("Parinte pid: %d\n", getpid());
    //count++;
    wait();

  }
}

The question is: how should i declare/increment the count variable in order to print the total number of processes the function has created?

Upvotes: 0

Views: 1367

Answers (2)

lostcitizen
lostcitizen

Reputation: 528

Probably there are better approaches but.. You can append a new line/character to a temp file every time a child is created. Then you just have to count the lines/characters of the file.

Upvotes: 0

Duck
Duck

Reputation: 27572

It's simple. Fork produces a child for each parent. The answer is therefore 2^10 or 1024.

Put a printf after the fork and comment out the other extraneous output. Run as

./a.out | sort | uniq | wc

The output is is 1024.

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/wait.h>

void generate()
{
  int pid;

  for(int i=1;i<=10;i++)
  {
    pid = fork();
    printf("%d\n", getpid());
  }

  if (pid<0)
  {
    //printf("Error Fork");
    exit(1);
  }

  if(pid == 0)
  {
    //printf("Fiu pid: %d --- Parinte pid: %d\n", getpid(), getppid());
    //count ++;
  }

  if(pid > 0 )
  {
    //printf("Parinte pid: %d\n", getpid());
    //count++;
    wait(NULL);
  }
}

int main(int argc, char *argv[])
{
    generate();

    return(0);
}

Upvotes: 2

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