getpgid(p1)
Returns the process group ID for the given process id. Not available on all platforms.
Process.getpgid(Process.ppid()) #=> 25527
static VALUE proc_getpgid(VALUE obj, VALUE pid) { rb_pid_t i; i = getpgid(NUM2PIDT(pid)); if (i < 0) rb_sys_fail(0); return PIDT2NUM(i); }