The three IO streams that can be redirected
Test whether the child process is still running
Send the process a signal
Redirect stderr to stdout
Redirect a standard IO for the child to an FD
Redirect a standard IO for the child to a pipe
Run the child with the given arguments.
Suspend fiber until the child process finishes
Returns the pid of the child.
Parent side end of standard streams
Subprocess handler
Do not create direct instances of this struct. Use ProcessManager.alloc instead.