Fork mystries....

[Aziz Kezzou]

Thank you guys,
I got it fork is creating a different process.
Currently, I am working a lot that I forget even the basic principales ;-) 
I need a break ...
-aziz


On 6/3/05, ray at redshift.com <ray at redshift.com> wrote:
> Aziz,
> 
>   Fork is for process creation.  Look up pthread_create() and/or POSIX
> thread
> creation, etc.  You should be able to find a lot of info on google with a
> quick
> search:  
> 
> http://math.arizona.edu/~swig/documentation/pthreads/
> 
>   From the OS standpoint a process is like a different program when you fork
> it.
>  A thread is more like a single program with a bunch of subsections all
> running
> at the same time, then the OS and CPU jump back and forth giving a little
> run-time to each subsection.  Threads share a common space; processes [as
> far as
> I recal] do not (which is where inter process communication comes into
> play).
> 
>   Anyway, have fun! :)
> 
> Ray
> 
> 
> At 07:55 PM 6/3/2005 -0400, Aziz Kezzou wrote:
> | Hi all,
> | It's probably not the right mailing list to ask but I am really
> | surprised about global variable sharing in a multithreaded C
> | application. If I remember well my multithreading course global
> | variables are shared between threads, right ?
> |  
> | Example :
> | ----------------------------
> | int counter = 0;
> | int main() {
> |   if( fork()==0) {
> |     while(1) {
> |       sleep(1);
> |       counter++;
> |       printf("Son : counter = %d\n", counter);      
> |     }    
> |   } else {
> |     while(1) {
> |       sleep(1);
> |       printf("Parent : counter = %d\n", counter);      
> |     }
> |  }	 
> |   return 0;
> | }
> | ----------------------------
> | 
> | All I get is :
> | Parent : counter = 0
> | Son : counter = 1
> | Son : counter = 2
> | Parent : counter = 0
> | Son : counter = 3
> | Parent : counter = 0
> | Son : counter = 4
> | Parent : counter = 0
> | 
> | why counter isn't shared between the two threads ??!
> | thanks,
> | -aziz
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