When doing a `tail -f error.log`, how to insert programmatically a line break after nothing has been appened to the file for 3 seconds ?

(obviously, once one line break has been added, no other line break should be added until other line(s) of text is added to the log file)

For instance, these lines are appened to error.log :

```
foo
bar
boo [[wait 4 seconds]]
2far
2foo
2bar
2boo [[wait 40 seconds]]
2far

```

This would be the output in the console :

```
foo
bar
boo

2far
2foo
2bar
2boo

2far

```