[CentOS] sendmail and rbl blocking - generating statistics

Ryan Simpkins centos at ryansimpkins.com
Wed Mar 14 20:35:09 UTC 2007

On Wed, March 14, 2007 14:08, Will McDonald wrote (trimmed):
> On 14/03/07, Ryan Simpkins <centos at ryansimpkins.com> wrote:
>> Try doing a simple 'cat /var/log/maillog | grep -c check_relay'
> You can avoid the unnecessary 'cat' by just passing the filename to grep directly:
> # grep -c 'checK_relay.*spamhaus' /var/log/maillog
> # grep -c 'checK_relay.*spamcop' /var/log/maillog
> # grep -c 'checK_relay.*njabl' /var/log/maillog
> Would probably be more efficient and faster, you can test with 'time' to verify
this. You're spawning one process 'grep', instead of three seperate processes,
'cat, 'grep' and 'grep' again.

Am I using time right to measure it?

# time cat /var/log/maillog | grep check_relay | grep -c njabl

real    0m0.299s
user    0m0.289s
sys     0m0.009s

# time grep -c 'check_relay.*njabl' /var/log/maillog

real    0m0.404s
user    0m0.402s
sys     0m0.000s

Is the first 'time' measuring the whole one-liner, or just the time it takes to 'cat'?

I also tried this:
time echo `cat /var/log/maillog | grep check_relay | grep -c njabl` 8

real    0m0.325s
user    0m0.312s
sys     0m0.012s

time echo `grep -c 'check_relay.*njabl' /var/log/maillog`

real    0m0.411s
user    0m0.408s
sys     0m0.002s

I ran these several times mixed back and forth to try and see if they were flukes,
these numbers appear to be representitive of the average. What do you get on your
system? Maybe passing the file name to grep gets faster as the file size increases?

wc /var/log/maillog
  12323  142894 1588860 /var/log/maillog

I wonder if the issue here is actually the 'stuff*morestuff' as that might be a more
expensive match:

time echo `grep -c 'check_relay' /var/log/maillog | grep njabl`

real    0m0.269s
user    0m0.263s
sys     0m0.006s


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