Maths with tail

Entropy1024 · 01-14-2018, 11:59 AM

I'm attempting to manage the size of a log file using tail.
I have a string called maxlog which is set to 30 ie

Code:

maxlog=30

Then later in the code after checking if the log file length is over 30 lines I used the following bit of code to remove two of the oldest entries:

Code:

tail -n ${maxlog} - 2 /home/tim/Documents/$HOSTNAME/$HOSTNAME"_"ip.log > /tmp/templog.log && mv /tmp/templog.log /home/tim/Documents/$HOSTNAME/$HOSTNAME"_"ip.log

However it does not work. What is the correct syntax?

Many thanks for any help.
Tim

pan64 · 01-14-2018, 12:05 PM

Code:

${maxlog} - 2

simply incorrect, this is not the right way to do arithmetics. You need to use:

Code:

$((maxlog - 2))

Entropy1024 · 01-14-2018, 12:12 PM

Quote:

Originally Posted by pan64

Code:

${maxlog} - 2

simply incorrect, this is not the right way to do arithmetics. You need to use:

Code:

$((maxlog - 2))

That's great thank you for the correct syntax.