sed query

[Florent Peterschmitt]

Le 02/06/2013 14:16, Chris Rees a écrit :
> On 2 June 2013 11:41, Eduardo Morras <emorrasg at yahoo.es> wrote:
>> On Fri, 31 May 2013 15:01:59 +0100
>> Chris Rees <utisoft at gmail.com> wrote:
>>
>>> Hi all,
>>>
>>> I think I've discovered a strange behaviour of sed perhaps triggered
>>> by the length of a regex passed to it.  I noticed that a certain
>>> expression I passed took a very long time, and suspected the usual
>>> backtracking loop, so I started trimming it... and discovered this:
>>>
>>> [crees at pegasus]~% time sed -ne "s,^BitchX-[0-9][^|]*[\|]/usr/por,,"
>>> /var/db/pkg/INDEX-9
>>> 4.699u 0.007s 0:04.70 99.7% 40+2733k 0+0io 0pf+0w
>>> [crees at pegasus]~% time sed -ne "s,^BitchX-[0-9][^|]*[\|]/usr/po,,"
>>> /var/db/pkg/INDEX-9
>>> 0.042u 0.000s 0:00.04 100.0% 48+3216k 0+0io 0pf+0w
>>>
>>> I've looked at the code, and can't from a brief glance figure out why
>>> a slightly longer regex makes such a difference-- does it start to
>>> split it?
>>
>> Perhaps second one uses memory cache data? Run both twice and show us the second times.
>>
> 
> Nope, same.
> 
> [crees at pegasus]~% time sed -ne "s,^BitchX-[0-9][^|]*[\|]/usr/por,,"
> /var/db/pkg/INDEX-9
> 4.703u 0.007s 0:04.85 96.9% 40+2732k 210+0io 0pf+0w
> [crees at pegasus]~% time sed -ne "s,^BitchX-[0-9][^|]*[\|]/usr/por,,"
> /var/db/pkg/INDEX-9
> 4.748u 0.007s 0:04.75 99.7% 40+2732k 0+0io 0pf+0w
> 
> I also get the same on head;
> 
> [crees at medusa]~% time sed -ne "s,^BitchX-[0-9][^|]*[\|]/usr/por,,"
> /var/db/pkg/INDEX-10
> 7.813u 0.015s 0:07.96 98.2% 40+183k 0+0io 0pf+0w
> [crees at medusa]~% time sed -ne "s,^BitchX-[0-9][^|]*[\|]/usr/po,,"
> /var/db/pkg/INDEX-10
> 0.070u 0.000s 0:00.07 100.0% 45+205k 0+0io 0pf+0w
> [crees at medusa]~% uname -a
> FreeBSD medusa 10.0-CURRENT FreeBSD 10.0-CURRENT #0 r250009: Thu May
> 30 10:11:16 BST 2013     root at medusa:/usr/obj/usr/src/sys/MEDUSA
> amd64
> 
> Chris

Yes I tried too on -current. And I tried also on GNU/Linux and there
isn't this problem. Is it gnu or bsd sed ?


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