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How to Tail a file that rolls over

Posted on 2002-05-31
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Last Modified: 2010-04-21
I have a file "a.log" that when it gets to 1MB, renames to "a.log.1"  The new files is created to continue loggin called "a.log".

I want to send the out put of "a.log" to a log file on a nfs mounted directory in real time.  The "tail -f" command will work up until the file reaches 1MB and renames itself.  The "tail" command stops working at this point.

How can I get it to ouput the files contents after the 1MB limit is reached?

Thanx
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Question by:RudePuppyDog
3 Comments
 
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bira earned 100 total points
ID: 7047939
Hi
   Instead of "tail -f" , use a script like this:

    while true
    do
    tail -50 a.log
    done

  So, even when the a.log reaches 1MB and is renamed,
  it will go on showing the last 50 lines of the new one.
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by:tekweni
ID: 7048452
I dont have access to a unix box right now, but something like this may be worth putting into a script..

#!/bin/sh
while (1)
do
    tail -50 a.log.1 > /tmp/junkfile
    tail -50 a.log >> /tmp/junkfile
    cat /tmp/junkfile
    sleep 2
done

It almost certainly needs debugging, but the goal is to show you the last 50 entries regardless of the rollover between files.
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LVL 51

Expert Comment

by:ahoffmann
ID: 7049818
get GNU version of tail, and use

  tail --retry -f a.log
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