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I am trying to count the number of SQL queries per second from a log file and I want to do it in real time by pipeing stdout from grep into some command. ( I am doing some performance testing )

I could write it myself, but thought for sure this would exist.

I looked at wc but didn't see an option to allow this.

I could also use it to count requests per second by piping a tail from the access log.

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I am looking for something more generally useful that what that question refers to. –  digidigo Jan 31 '13 at 17:05

3 Answers 3

up vote 8 down vote accepted

Maybe you should try logtop ?

tail -f foobar.log |logtop
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Is this the log top you are referring to? github.com/JulienPalard/logtop –  digidigo Jan 31 '13 at 17:03
Yes, if you are using debian there is a package in repository packages.debian.org/wheezy/logtop –  klocek Jan 31 '13 at 21:45
dang I think this is what I need but I couldn't get it to compile on CentOs –  digidigo Feb 2 '13 at 4:07

pv is your command! For example:

tail -f /var/log/nginx/access.log | pv --line-mode --rate > /dev/null

pv pipes stdin directly over to stdout, which I'm piping into /dev/null because I only care about the counts. This command has pv print to stderr the current rate of lines / second. There are also options like:

  • -b (total number of lines),
  • --average-rate (average rate since starting), and
  • --timer (tracks how long the pipe has been going).

If you don't say --line-mode, it'll count bytes, which is probably not what you want for server logs, but could be handy elsewhere.

Final note: ... | pv -lb > file.txt is a lot like ... | tee file.txt | awk '{printf "\r%lu", NR}', which is also handy for counting lines, but the pv call is way shorter, though the output is not quite as exciting.

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watch -n 5 "mysqladmin status | awk -F'  ' '{ print \$NF }'"
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I couldn't get this to work. You sure about the syntax? –  digidigo Jan 31 '13 at 17:04
Which error do you get? Have you configured ~/.my.cnf to run mysqladmin without prompting for password? –  quanta Feb 1 '13 at 0:57

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