Why does getpid() return pid_t instead of int?

Question

What\'s the logic behind calls like getpid() returning a value of type pid_t instead of an unsigned int? Or int? How does

Answer 1

Each process in the program has a specific process ID. By calling pid, we know the assigned ID of the current process.Knowing the pid is exceptionally important when we use fork(), because it returns 0 and !=0 values for child and parent copies receptively.These two videos have clear explanations: video#1 Video#2

An example: Suppose we have the following c program:

#include 
#include 
#include 
#include 


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

  printf("I am %d\n", (int) getpid());
  pid_t pid = fork();
  printf("fork returned: %d\n", (int) pid);
  if(pid<0){
    perror("fork failed");
  }
  if (pid==0){
    printf("This is a child with pid %d\n",(int) getpid());
  }else if(pid >0){
    printf("This is a parent with pid %d\n",(int)getpid());
  }

  return 0;
}

If you run it, you will get 0 for child and non zero/greater than zero for the parent.