title: semaphores in C
body: <p>I'm working with semaphores in C , especifically to control the access to a shared memory zone in linux. but there is one thing that I can't understand.</p>
  
  <p>I am using a mutex to control the access to a specific zone because i have 2 processes that must read/write from that zone. the thing is, when we use the fork() to create a new child process, the whole program is "copied" to another program as if they were two seperate programs right ? so, when i do V(mutex) in one process, how does the other one know he can't access  ?</p>
  
  <p>I know its a noob question but nobody could explain this to me until now.</p>