Question: When retrieving data from Firebase, we typically use the code below (or some reiteration of it)

```
...observeSingleEvent(of: .value, with: { snapshot in

var tempPosts = [PostModel]()

for child in snapshot.chidren{
}

return tempPosts

})

```

but I don't exactly get what this code is doing? Can someone explain it on a high level? I've tried printing data on mulitple spots but the only data I'm getting is: Snap post or [App.PostModel]

Answer: 
all you need is:

```
awk '!/^chr(Un|M)/' file

```
Also grep can do that.

```
grep -Ev '^chr(Un|M)' file

```

GNU ed(1)

```
printf '%s\n' 'v/^chr\(Un\|M\)/p' | ed -s file

```