Re: How to profile the grep engine despite the "/dev/null optimization" ?

[alexandre . ferrieux]

On 5/29/23 23:18, Zev Weiss wrote:
> On Sat, May 27, 2023 at 02:20:02PM PDT, alexandre.ferrieux@orange.com wrote:
>
> > [...] nowadays, grep *detects* /dev/null and behaves differently in that case:
> > it sets the done_on_match flag, and accordingly exits very quickly, on the 
> > first matching line of your hundreds-of-gigabytes test file....
> Note that while it's far less commonly used in this way, /dev/zero provides the 
> same property of discarding all written data -- and from a quick inspection of 
> src/grep.c, grep does not appear to detect it for optimization purposes, so I 
> suspect it would suit your purposes well.

Wow, thanks a lot Zev ! I was completely unaware of the input semantics of 
/dev/zero :)

Indeed it solves the problem for me. However, I'm still perplexed by the 
(7-yr-old) decision to let grep "behave as grep -q" without warning (nor 
documentation).
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