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From: bernie@metapro.DIALix.oz.au (Bernd Felsche)
Newsgroups: comp.lang.perl
Subject: Re: Perl and Cnews (was: While learning PERL... a suggestion)
Message-ID: <1991Feb5.032342.25108@metapro.DIALix.oz.au>
Date: 5 Feb 91 03:23:42 GMT
References: <1991Jan23.230154.27272@dbsm.oz.au> <1991Jan24.174047.2897@NCoast.ORG> <1991Feb2.150543.569@haapi.uci.com> <1991Feb04.033031.2714@convex.com>
Organization: MetaPro Systems, Perth, Western Australia
Lines: 47

In <1991Feb04.033031.2714@convex.com> tchrist@convex.COM (Tom Christiansen) writes:

>Look at /usr/local/lib/news/newsbin/expire/recovact for another good
>candidate.  Here's a loop in it:

>    while read group max min fourth
>    do
>        dir=`echo $group | tr . / `     # map ng name to directory name
>        new=
>        if test -d $NEWSARTS/$dir
>        then
>            new=`ls $NEWSARTS/$dir | egrep '^[0-9]+$' | sort -n | tail -1`
>        fi
>        case "$new" in
>        "")     new=$max        ;;      # no files -- preserve old value
>        *)      if test "$new" -lt "$max"       # old value more recent (!)
>            then
>                new="$max"
>            fi
>            ;;
>        esac
>        dots="`echo $max | tr 0123456789 ..........`"
>        max="`expr 0000000000$new : '.*\('$dots'\)$'`"  # preserve length
>        echo $group $max $min $fourth
>    done <active >active.new


>I'm quite certain that would run faster in perl.  

Sure it would. One fork-exec is a *lot* faster than seven (7) per
newsgroup (I'm assuming lots of built-in shell bits). There are over
700 newsgroups on our machine.

The use of "ls" to generate filenames is a trifle silly, especially as
it's only being used to find the maximum article number. A simple perl
routine could read the directory and simply look for a maximum. It
doesn't even have to sort. (btw: if people didn't screw around with
timestamps so badly, then new="`ls -tr [0-9]*|tail -1`" would have
done the same trick.)

I'm only now starting to play with Perl, but I can easily see why
it's so popular for things like this.
-- 
 _--_|\  Bernd Felsche         #include <std/disclaimer.h>
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