
  [;1m-spec group_leader() -> pid().[0m

  Returns the process identifier of the group leader for the process
  evaluating the function.

  Every process is a member of some process group and all groups
  have a group leader. All I/O from the group is channeled to the
  group leader. When a new process is spawned, it gets the same
  group leader as the spawning process. Initially, at system
  startup, [;;4minit[0m is both its own group leader and the group leader
  of all processes.
