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How do i use tail & grep in real time here??

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# 1  
Old 04-24-2013
How do i use tail & grep in real time here??
Hi

I have a file which is updated very frequently.
Where in i wanted to use tail -f command in the script and wanted to grep for a particular word.

But the issue is when i use tail -f filename|grep "word" ...
it will show me blank until the word is found in the real time. if it shows blank it will execute the next line which i don want i want it to wait until the word is found and then perform the task
# 2  
Old 04-24-2013
What if you forget about the tail and just periodically look for the word?
Code:
while sleep 60; do
  grep -q word_to_find logfile
  if [ $? -eq 0 ]; then
    echo found word_to_find
    # take action
    # maybe break from while loop
  fi
done

# 3  
Old 04-24-2013
Why should it "show blank"? If run as you posted, it will wait forever, and every now and then print a line containing the "word" to stdout.
# 4  
Old 04-24-2013
Searching for the pattern in the whole file is not a good idea specially when there is not need for that ( this is what I understood from the requirement ).

May be you can replace grep command ( in hanson44's post) with
Code:
tail logfile | grep -q word_to_find

to search in last 10 lines only after some interval ( you can set the interval based on how frequent your file is being updated)
# 5  
Old 04-24-2013
Yes, it will run forever. Here is another possibility if you want to stick with the tail command (if your grep supports -m option).
Code:
$ tail -f logfile | grep -m 1 word_to_find
# nothing happens
# in another window, run following:
$ echo word_to_find >> logfile
# grep finds and prints word_to_find
# in another window, run following:
$ echo something_else >> logfile
# grep exits, and tail command ends
# shell is ready to execute next command

# 6  
Old 04-24-2013
If you want to check only the portions of the file added since your last visit, you might be inspired by this post.
# 7  
Old 04-24-2013
Something wrong with the link, I think...
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