Spawn.PgidProcess group IDs
Representation of the second parameter to setpgid. If a value of this type is provided to spawn, the child will immediately set its pgid accordingly.
val new_process_group : tSets the child's pgid to the same as its process id. Equivalent to calling setpgid(0, 0).
val of_pid : int -> tRaises Invalid_arg if the value is not strictly positive.