Re: [PATCH] Use perl instead of tac

From: Jörg Sommer <joerg@alea.gnuu.de>
Date: Apr 28, 2008, 15:15 UTC
Message-ID: <slrng1bqhb.25r.joerg@alea.gnuu.de>
In-Reply-To: <86k5iib0g9.fsf@blue.stonehenge.com>

Hallo Randal,

Randal L. Schwartz <merlyn@stonehenge.com> wrote:

Show 7 quoted lines

>>>>>> "Jörg" == Jörg Sommer <joerg@alea.gnuu.de> writes:
>
> Jörg> What about using a shell function and a *big* variable or an intermediate
> Jörg> file?
>
> What makes you think that's any more faster or efficient than calling Perl
> at this point?

Nothing. My intention was not the speed, but the dependency on Perl. But your are right. Except from the point that my suggestion is broken, it's *much* slower:

% time dash -c 'while IFS= read -r line; do rev="$line $rev"; done; printf "%s" "$rev"' < gitk-git/gitk-wish DN dash -c < gitk-git/gitk-wish > /dev/null 2> /dev/null 17,89s user 2,68s system 96% cpu 21,352 total

% time tac < gitk-git/gitk-wish DN tac < gitk-git/gitk-wish > /dev/null 2> /dev/null 0,01s user 0,01s system 91% cpu 0,017 total

% time perl -e 'print reverse <>' < gitk-git/gitk-wish DN perl -e 'print reverse <>' < gitk-git/gitk-wish > /dev/null 2> /dev/null 0,07s user 0,01s system 59% cpu 0,141 total

But I doubt this hurts, because we don't have such a big input.

% wc -l git.c 390 git.c

% time dash -c 'while IFS= read -r line; do rev="$line $rev"; done; printf "%s" "$rev"' < git.c DN dash -c < git.c > /dev/null 2> /dev/null 0,04s user 0,04s system 62% cpu 0,115 total

And what about something like this: 'tac || rev || perl …'

Bye, Jörg.

-- 
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was er frisst, er würde umgehend Bauer werden.
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