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Now *THAT* is helpful! Descriptive yet succinct w/ references. Methodical.
Awesome.
--Ken Wolcott
On Thu, May 1, 2008 at 6:13 PM, Chas. Owens <chas.owens@[EMAIL PROTECTED]
> wrote:
> On Thu, May 1, 2008 at 8:45 PM, Richard Lee <rich.japh@[EMAIL PROTECTED]
> wrote:
> snip
> > ls -ltr | tail -100 | cut -d' ' -f13
> snip
>
> Let's pick this apart, shall we?
>
> ls -tr gets all of the (non-hidden) files in the current directory
> reverse sorted by time (the l is unnecessary and is why you need the
> cut later) and the tail takes the last one hundred (or fewer) of them.
>
> Well, Perl can get all of the (non-hidden) files in the current
> directory very easily with glob*:
>
> my @[EMAIL PROTECTED]
= <*>;
>
> The next step is to sort them on mtime (largest mtime values last)
> using stat** to get the mtime and sort*** to sort the list:
>
> my @[EMAIL PROTECTED]
= sort { (stat $a)[9] <=> (stat $b)[9] } <*>;
>
> All of those calls to stat to get the mtime during the sort can be
> expensive, so we might want to do a Schwartzian Transform**** to speed
> it up:
>
> my @[EMAIL PROTECTED]
=
> map { $_->[1] }
> sort { $a->[0] <=> $b->[0] }
> map { [(stat)[9], $_] } <*>;
>
> To get the last hundred files we can use a list slice***** using the
> range operator******:
>
> my @[EMAIL PROTECTED]
= (
> map { $_->[1] }
> sort { $a->[0] <=> $b->[0] }
> map { [(stat)[9], $_] } <*>
> )[-100 .. -1];
>
> But this leaves use with undefs if we have fewer than one hundred
> files in the current directory, so we need a grep******* to weed them
> out:
>
> my @[EMAIL PROTECTED]
= grep defined, (
> map { $_->[1] }
> sort { $a->[0] <=> $b->[0] }
> map { [( stat)[9], $_ ] } <*>
> )[-100 .. -1];
>
> * http://perldoc.perl.org/functions/glob.html
> ** http://perldoc.perl.org/functions/stat.html
> *** http://perldoc.perl.org/functions/sort.html
> **** http://en.wikipedia.org/wiki/Schwartzian_transform
> ***** http://perldoc.perl.org/perldata.html#Slices
> ****** http://perldoc.perl.org/perlop.html#Range-Operators
> ******* http://perldoc.perl.org/functions/grep.html
>
> --
> Chas. Owens
> wonkden.net
> The most im****tant skill a programmer can have is the ability to read.
>
> --
> To unsubscribe, e-mail: beginners-unsubscribe@[EMAIL PROTECTED]
> For additional commands, e-mail: beginners-help@[EMAIL PROTECTED]
> http://learn.perl.org/
>
>
>
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