Need a fast "tail -f" like command 1

[schu]

I need a command which acts like tail -f.
Instead it should not go into an endless loop but instead show differences between the current and previous run.

I used awk, and wc methods to store line pointer but method is too slow and uses up quite a lot of IO resources because the file is quite big.

Perl seems to work but still seem to take up alot of CPU resources.



Thanks in advance

 

[Annihilannic]

Write a C programme and lseek() to the correct position in the file?

Annihilannic.

 

[Annihilannic]

Another idea... why not save the previous file size in a variable somewhere, and then calculate the difference between the previous file size and current file size, and use tail -1234c filename where 1234 is difference.

Annihilannic.

 

[WhiteVolg]

Nice solution Annihilannic.. That's got style...
something like

#use a reasonable starting value
DELAY=10
LAST_SIZE=$((`ls -l $1|awk '{print $5}'`-1024 ))

while true
  do
    TAIL_OFFSET=$(( `ls -l $1|awk '{print $5}'` -${LAST_SIZE} ))
    tail -${TAIL_OFFSET}c $1
    LAST_SIZE=`ls -l $1|awk '{print $5}'`
    sleep $DELAY
   done

or one could redirect the ls ouput to a file and read it in from there as well..