detach

/*
 *  call-seq:
 *     Process.detach(pid)   => thread
 *
 *  Some operating systems retain the status of terminated child
 *  processes until the parent collects that status (normally using
 *  some variant of <code>wait()</code>. If the parent never collects
 *  this status, the child stays around as a <em>zombie</em> process.
 *  <code>Process::detach</code> prevents this by setting up a
 *  separate Ruby thread whose sole job is to reap the status of the
 *  process _pid_ when it terminates. Use <code>detach</code>
 *  only when you do not intent to explicitly wait for the child to
 *  terminate.  <code>detach</code> only checks the status
 *  periodically (currently once each second).
 *
 *  The waiting thread returns the exit status of the detached process
 *  when it terminates, so you can use <code>Thread#join</code> to
 *  know the result.  If specified _pid_ is not a valid child process
 *  ID, the thread returns +nil+ immediately.
 *
 *  In this first example, we don't reap the first child process, so
 *  it appears as a zombie in the process status display.
 *
 *     p1 = fork { sleep 0.1 }
 *     p2 = fork { sleep 0.2 }
 *     Process.waitpid(p2)
 *     sleep 2
 *     system("ps -ho pid,state -p #{p1}")
 *
 *  <em>produces:</em>
 *
 *     27389 Z
 *
 *  In the next example, <code>Process::detach</code> is used to reap
 *  the child automatically.
 *
 *     p1 = fork { sleep 0.1 }
 *     p2 = fork { sleep 0.2 }
 *     Process.detach(p1)
 *     Process.waitpid(p2)
 *     sleep 2
 *     system("ps -ho pid,state -p #{p1}")
 *
 *  <em>(produces no output)</em>
 */

static VALUE
proc_detach(VALUE obj, VALUE pid)
{
    rb_secure(2);
    return rb_detach_process(NUM2INT(pid));
}