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Tail -f, awk and redirection

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# 1  
Old 07-13-2006
Tail -f, awk and redirection
I want to run tail -f to continuously monitor a log file, outputing a specific field to a second log file. I can get the first portion to work with the following command:

tail -f log | awk '{if ($1 == "Rough") print $5}'

also:

awk '{if ($1 == "Rough") print $5}' <(tail -f log)

The problem is I can not redirect the stdout from these commands to a second log file. Any ideas? Thanks!


-Mikolai Fajer-
# 2  
Old 07-13-2006
Code:
tail -f log | awk '{if ($1 == "Rough") print $5}'  | tee mySecondFile.txt

# 3  
Old 07-13-2006
Quote:
Originally Posted by vgersh99
Code:
tail -f log | awk '{if ($1 == "Rough") print $5}'  | tee mySecondFile.txt

Interestingly enough the above command does not output to the file or the STDOUT (at least for me!). The following command does work:

tail -f log | tee mySecondFile.txt

As does:

awk '{if ($1 == "Rough") print $5}' | tee mySecondFile.txt

I then tried:

tail -f log | awk '{if ($1 == "Rough") print $5}' | tee mySecondFile.txt &

Curiously enough, this does work! I waited about a minute, then a long sequence of output (about 20+ lines) appeared on STDOUT and only the last five or so appeared in mySecondFile.txt. This repeats every few minutes, with again only the last few lines being placed into mySecondFile.txt. The ouput placed into mySecondFile.txt is overwritten each time. What did work is:

tail -f log | awk '{if ($1 == "Rough") print $5 | "tee mySecondFile.txt"}'

This works perfectly! Thank you for bringing the tee program to my attention.


-Mikolai Fajer-
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