text editing from tail -f

[jgercken]

New to this and having problems:

I'm trying to monitor a file with tail -f and pipe it's output to a script that filters based on a file, makes some substitutions, and then dumps to another file.

How would you go about doing this?
-Jeff





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[olded]

Jeff:

You're asking a hard question. The best I've been able to come up with is using the tee command to send the output to another file:

tail -f data.file|tee -a new.file

Since tail -f is actually an endless loop until you interrupt, I don't know what else you can do.

Maybe somebody else smarter than I can help you further.

Regards,

Ed

 

[jgercken]

Well tail -f data.file >> new.file seems to work alright as I don't need to see the output. I'm wondering if there is a way to edit strings in a stream. IE cat infile|edit|edit >> output

The goal is to make it psudo realtime and use it to monitor syslog messages.

Also I can't get this to work.
if [ string `fgrep -iv file -f file2`]

It always evaluates as true. Thoughts on this?
-Jeff ----------------------------------------
Wasabi Pop Tarts! Write Kellogs today!

 

[toolkit]

It is entirely possible. For example:

tail -f foo | sed -e 's/foo/bar/' >> bar

However, output is buffered, so you may not see the second file grow immediately. For example. Try the following:

while true ; do echo foo >> foo ; /bin/ls -l bar; done

Use CTRL-C to get out of this loop. A way of getting a more immediate response is:

tail -f foo | perl -n -e 'if(/foo/){s/foo/bar/;$|=1;print}' >> bar

I'm sure there are better ways to specify the output file buffering. Anyone??

 

[AHinMaine]

here's how you can do it in a shell script:

#!/bin/sh
tail -f /var/log/filename | 
   while read field1 field2 field3 field4 etc
      do
         if [ "$field1" = "something" ] ; then
            echo "do this "
         fi
      done

--
Andy

http://www.nachoz.com