Simple C program for process excution using Fork( ) System call

Fork ( ) system call for execution of parent and child process

#include<stdio.h>
#include<sys/types.h>
#include<unistd.h>
int main() 
{
// make two process which run same
// program after this instruction
     fork();
     printf("Hello world!\n");
     return 0;
}

OUTPUT

 

Here we can see same program & code for both parent and child processes . in this program fork ( ) is the parent process that create a new child process . After new process is created both parent and child follow the next instruction exactly following the fork ( ) statement which is here " printf("Hello world!\n"); ".  

This is the reason we got same output twice each for a process .

Now let's try another program for more clear understanding of the concept of Fork ( ) system call and child process creations.

 

Count no of times hello is printed

#include<stdio.h>
#include<sys/types.h>
#include<unistd.h>
int  main()
{
      fork();
      fork();
      fork();
      printf("hello \n");
      return 0;
}

OUTPUT

 

fork ( ) system call (Same program & different code for parent and child)

#include<stdio.h>

#include <sys/types.h>

#include<unistd.h>

void forkexample( ) 

{

    // child process because return value zero

   if (fork()==0)

        printf("Hello from Child!\n");

   // parent process because return value non-zero.

   else    

        printf("Hello from Parent!\n"); 

}

int main()

{ 

    forkexample();

    return 0; 

}

OUTPUT :