user3341592 user3341592 - 5 months ago 10
Bash Question

Auto-insert blank lines in `tail -f`

Having a log file such as:

[DEBUG][2016-06-24 11:10:10,064][DataSourceImpl] - [line A...]
[DEBUG][2016-06-24 11:10:10,069][DataSourceImpl] - [line B...]
[DEBUG][2016-06-24 11:10:12,112][DataSourceImpl] - [line C...]


which is under
tail -f
real-time monitoring, is it possible to auto-insert (via a command we would pipe to the
tail
) "blank lines" after, let's say, 2 seconds of inactivity?

Expected result:

[DEBUG][2016-06-24 11:10:10,064][DataSourceImpl] - [line A...]
[DEBUG][2016-06-24 11:10:10,069][DataSourceImpl] - [line B...]
---
[DEBUG][2016-06-24 11:10:12,112][DataSourceImpl] - [line C...]


(because there is a gap of more than 2 seconds between 2 successive lines).

Answer
awk -F'[][\\- ,:]+' '1'

The above will split fields on ], [, -, ,, and :, so that each field is as described below:

[DEBUG][2016-06-24 11:10:10,064][DataSourceImpl] - [line A...]
 22222  3333 44 55 66 77 88 999  ...

You can then concatenate some of the fields and use that to measure time difference:

tail -f input.log | awk -F'[][\\- ,:]+' '{ curr=$3$4$5$6$7$8$9 }
                      prev + 2000 < curr { print "" } # Print empty line if two seconds 
                                                      # have passed since last record.
                                         { prev=curr } 1'