| options | | 32 bit |
| |
| bit | hex | octal | decimal | c++ name | Description |
| 0 | 1 | 1 | 1 | WNOHANG | which means to return immediately if no child has exited. |
| 1 | 2 | 2 | 2 | WUNTRACED | which means to also return for children which are stopped (but not traced), and whose status has not been reported. Status for traced children which are stopped is provided also without this option. |
| 29 | 20000000 | 4000000000 | 536870912 | __WNOTHREAD | Don't wait on children of other threads in this group. |
| 30 | 40000000 | 10000000000 | 1073741824 | __WALL | Wait on all children, regardless of type. |
| 31 | 80000000 | 20000000000 | 2147483648 | __WCLONE | Wait only on non-SIGCHLD children. |
