On Monday 03 December 2007 10:34, [EMAIL PROTECTED] wrote:
>
> John W.Krahn <[EMAIL PROTECTED]> writes:
> >
> > If you want to incorporate the grep into the perl program then this
> > may work (UNTESTED):
>
> It works with 1 change and one caveat, The cavaet is that the file
> names in $ARGV must be absolute format or the program fails.
The following program does not use the $ARGV variable, nor does Perl
use it.
> That
> has something to do with File::Finds builtin of cd ing to the source
> directory I think.
???
> Johns program; with a few questions and annotations:
> (stripping the normal reply (>) indicators:
>
> #!/usr/bin/perl
> use warnings;
> use strict;
>
> use File::Find;
>
> ( my $myscript = $0 ) =~ s!\A.*/!!;
>
> @ARGV == 3 or die "usage: $myscript 'REGEX' SOMEDIRECTORY
> TARGETDIRECTORY\n";
>
> my $regex = qr/$ARGV[0]/;
>
> my ( $SrcDir, $TrgDir ) = @ARGV[ 1, 2 ];
>
> ## [HP I would have thought it would cause perl to still treat ARGV
> as ## file names since its value is not zeroed out by the above ##
> operations, but apparently that is not a problem
> ## ]
@ARGV is just an array, you can process its contents in whatever way
you like. The contents are assumed to be file names when you use the
special <> readline operator.
> my ( $OldCnt, $Num );
>
> ## [HP $Num needs to be set to zero because this section
> ## will eventually throw this error:
> ## Use of uninitialized value in numeric lt (<) at ./Krahn.pl line 20
> ## if it isn't
OK, change that line to:
my ( $Num, $OldCnt ) = 0;
> $Num = 0;
>
> ## ]
>
> { opendir my $dh, $TrgDir or die "Cannot open '$TrgDir' $!";
> while ( my $file = readdir $dh ) {
> next unless -f "$TrgDir/$file" and $file =~ /\A\d+\z/;
> $Num = $file if $Num < $file;
> $OldCnt++;
> }
> }
>
> ## [ I don't really understand the format of having the `open' and
> ## processing enclosed in {}. Don't think I've noticed that before..
> ## But the clause is nice and tidy.. thanks
> ## ]
It is used to limit the scope of the lexical variables, particulary the
directory handle $dh which will be closed automatically when it goes
out of scope.
> my $CopyCnt;
> find sub {
> return unless -f and /\A\d+\z/;
> open my $fh, '<:raw', $_
> or die "Cannot open '$_' $!";
> my $size = -s $fh;
> $size == read $fh, my $data, $size
> or die "Cannot read '$_' $!";
> return unless $data =~ $regex;
>
> ## [HP I don't really understand how `return' operates here. Is it
> ## doing the same job as `next'?
> ## ]
'next' works inside loops. Because this is inside a subroutine you
have to use 'return'.
> $Num++;
> open my $out, '>:raw', "$TrgDir/$Num"
> or die "Cannot open '$TrgDir/$Num' $!";
> print $out $data
> or die "Cannot print to '$TrgDir/$Num' $!";
> $CopyCnt++;
> }, $SrcDir;
>
> ## [ I don't really understand why some of the processing is done. I
> ## hadn't seen `:raw' used before but apparently the :raw part is
> ## there to handle the possiblitiy of different line endings in the
> ## files. Then size is checked; apparently to ensure the size
> reported ## in -s is the same when `read'
Correct.
> ## And then the data is `printed' to its new home instead of just
> ## being copied there.... why is that being done?
It is being copied, since all the data from the old file is in the
$data variable it is copied to the new file.
> ## ]
HTH
John
--
use Perl;
program
fulfillment
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