Maybe just leave this running 

tail -F file-B | grep --line-buffered -A 3 -B 3 xxx >>file-A

[download]

and just look at file-A every 20 minutes...

In reply to Re: extract the tail from a string (with new lines) containing a substring by tybalt89
in thread extract the tail from a string (with new lines) containing a substring by jjmoka

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