[padding](https://stackoverflow.com/questions/6916805/why-does-a-base64-encoded-string-have-an-sign-at-the-end)
```sh
$ echo YXNkcQo= | base64 -d
asdq
$ echo YXNkcQo | base64 -d
asdq
base64: invalid input
```
 
```sh
$echo YXNkcQo= | awk '{if (length % 4 == 0){print}}' | base64 -d 
asdq
$ echo YXNkcQo | awk '{if (length % 4 == 0){print}}' | base64 -d 
$
```