Le jeu. 24 août 2023 à 08:58, Daniel Green <ddgr...@gmail.com> a écrit :
> Re Perl's read speed, it's faster when not doing the line number check for > every line. So `perl -ne 'print if (/pattern/)'` is only ~2.60s, compared > to ~3.28s for `perl -ne 'print if ($. == 1 || /pattern/)'`. Doing nothing > in Perl, i.e., `perl -ne ''` is only ~1.38s. > > Dan > > On Wed, Aug 23, 2023 at 6:22 PM Paul Jackson <p...@usa.net> wrote: > > > Ah - those times show another reason why one might > > be motivated to keep requesting more options be added > > to grep. > > > > From those timings, and from looking at the source, it's clear > > that the FSF rewrote grep from scratch, sometime back in the > > late 1980's or early 1990's, to have fast reads, whereas sed is > > still using stdio fread in a classical manner, which is a painfully > > slower double copy solution. > > > > If sed were still a widely used command in performance sensitive > > applications, it should have some serious TLC applied to its > > performance. > > > > However, since the pool of Jurassic Park Dinosaurs who can (and > > perhaps do) compose sed commands in their sleep is a nearly > > extinct breed, I see no sufficient interest in accepting such a rewrite > > of sed, even if it showed up as a proposed checkin. > > > > That grep can even seriously beat perl for such raw read performance > > is impressive. Perl used to be the King of such challenges. > > > > -- > > Paul Jackson > > p...@usa.net > > > > > > > with a function, something like this : headgrep() { head -1 "$2" grep "$1" "$2" }