I am trying to extract a particular line from a.log which keeps appending every sec and output that into a newfile b.log which should append itself with filtered data received from a.log

I tried

tail -f a.log |grep fail| tee -a b.log

nothing in b.log

tail -f a.log |grep fail >>b.log

nothin shows up in b.log

what am i missing?

Is there an option similar to tail -f with awk?

"tail -f" command shows just last 10 lines and it keeps on refreshing...

Can you show us output of "tail -f a.log | grep fail" ?


It would be helpout to give a suggesion...

tail -f just displays the realtime appended output of the file...not just the 10lines

anyways i figured out a way using awk..but would gr8 if we can do it using grep

while true
do
  egrep 'fail' a.log > b.log
  sleep 1
done

if u r using linux, u could try:
watch -n 1 'egrep fail a.log > b.log'