fork() demo

#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>

int main()
{
pid_t self, parent, child;

self   = getpid();
parent = getppid();

int i=0, n=0;

printf("PID: %d, PPID: %d (before fork) \n", self, parent);

child =fork();

if(child==0) { // child process
  printf("child=fork() == 0 (child process)\n");
  printf("PID: %d, PPID= %d\n", getpid(), getppid());

  // i, n in child process
  // to demostrate child and process have their own data.
  for(i=0; i<5; i++) {
     printf("[Child ] i=%d, n=%3d\n", i, n+=10);
     sleep(1);
  }

} else {      // parent process
  printf("child=fork() != 0 (parent process)\n");
  printf("PID: %d, PPID= %d\n", getpid(), getppid());

  // i, n in parent process
  // to demostrate child and process have their own data.
  for(i=0; i<5; i++) {
     printf("[Parent] i=%d, n=%3d\n", i, n+=100);
     sleep(1);
  }

}

return 0;
}

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