Using clone

• The Linux specific function call, clone, is an alternative to fork that provides more control over which process resources are shared between the parent and child processes.

  #include <sched.h>
  int __clone(int (*fn) (void *arg), void *child_stack, int flags, 
              void *arg)
  

• This function exists to facilitate the implementation of pthreads. It is generally recommended that you use the portable pthreads_create() to create a thread instead, although clone provides more flexibility.
  1. The first argument is a pointer to the function to be executed.
  2. The second argument is a pointer to a stack that you have allocated for the child process.
  3. The third argument, flags, is CLONE_* flags (shown in Table 4.1).
  4. The fourth argument, arg, is passed to the child function; its function is entirely up to the user.
• The call returns the process ID of the child process created. In the event of an error, the value -1 will be returned and errno will be set.