[CentOS] sendmail and rbl blocking - generating statistics

John Summerfield debian at herakles.homelinux.org
Wed Mar 14 22:56:36 UTC 2007

Will McDonald wrote:
> On 14/03/07, John Summerfield <debian at herakles.homelinux.org> wrote:
>> Ryan Simpkins wrote:
>> >
>> > Am I using time right to measure it?
>> No, you're timing the cat only.
> I don't think that's the case, you know. If I run the following:

[summer at bilby ~]$ time sleep 10s;sleep 10s

real    0m10.011s
user    0m0.000s
sys     0m0.003s
[summer at bilby ~]$ time sleep 10s|sleep 10s

real    0m10.002s
user    0m0.001s
sys     0m0.003s
[summer at bilby ~]$ time sleep 10s | time sleep 10s
0.00user 0.00system 0:09.99elapsed 0%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (0major+150minor)pagefaults 0swaps

real    0m10.011s
user    0m0.000s
sys     0m0.006s
[summer at bilby ~]$

> [wmcdonald at stella ~]$ ls -lh /tmp/messages.1
> -rw-r--r--  1 root root 4.3M Mar 14 20:03 /tmp/messages.1
> [wmcdonald at stella ~]$ time cat /tmp/messages.1 1> /dev/null
> real    0m0.018s
> user    0m0.001s
> sys     0m0.017s
> [wmcdonald at stella ~]$ time cat /tmp/messages.1 | grep  '*.foo' 1> /dev/null
> real    0m0.047s
> user    0m0.021s
> sys     0m0.026s
> Running both commands repeatedly shows similar time differences, I
> think 'time''s timing the execution time of the whole command.

I think that writing to a pipe is more expensive than writing to 
/dev/null. Needs buffering etc.


time cat /tmp/messages.1 | grep \ | grep  '*.foo' 1> /dev/null



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