Consider the following commands: 

```
bash$ seq 1 3 | awk '{print $0 | "cat"; print "0"}'
0
0
0
1
2
3
bash$ seq 1 3 | awk '{print $0 | "cat"; fflush("cat"); print "0"}'
0
0
0
1
2
3
bash$ seq 1 3 | awk '{print $0 | "cat"; close("cat"); print "0"}'
1
0
2
0
3
0

```

Why does not the `fflush` command work here, whereas `close` works. That is: produces the expected output.