On Wed, March 14, 2007 14:08, Will McDonald wrote (trimmed):
> On 14/03/07, Ryan Simpkins <centos@xxxxxxxxxxxxxxxx> 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
8
real 0m0.299s
user 0m0.289s
sys 0m0.009s
# time grep -c 'check_relay.*njabl' /var/log/maillog
8
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`
8
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
-Ryan
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