SilverB1rd has asked for the wisdom of the Perl Monks concerning the following question:

I'm trying to make a vary simple but flexible script to read the number a files in a directory and output the current, previous, and next items with the previous and next items check to make sure they stay within the total number of files. It would be used to make a web page where you can browse pictures but since most of the coding is done in the template I assume it could be used to view just about any sequentially numbered set of files. Any pointers on making it better/faster/more virsatile?
#!/usr/bin/perl -w ## Modules and setup use CGI; use HTML::Template; ## check perldoc HTML::Template for more informati +on use strict; $CGI::POST_MAX=1024 * 1; # max 1k post $CGI::DISABLE_UPLOADS = 1; # No uploads ## Setup vars my $ThisScript = 'pictureview.cgi'; my ($q) = new CGI; my $DisplayPicture; my $DirPath; ## Check for picture peram if ($q->param('Picture')) { $DisplayPicture = ($q->param('Picture'))*1; } else { $DisplayPicture = 1; } ## Count number of files. my @LFiles = (); opendir (DIR, "./"); @LFiles = grep {not /^(\.\.?|template\.html|pictureview\.cgi)$/} readdir(DIR); closedir (DIR); my $TotalFiles = $#LFiles + 1; ## Correct to first file = 1 my $PreviousPicture; my $NextPicture; ## ## Make sure numbers are good (Bounds checking) ## if ($DisplayPicture == 0) { $DisplayPicture = 1;} if ($DisplayPicture > $TotalFiles) { $DisplayPicture = 1;} if ($DisplayPicture == 1) { $PreviousPicture = $TotalFiles; } else { $PreviousPicture = $DisplayPicture - 1; } if ($DisplayPicture == $TotalFiles) { $NextPicture = 1;} else { $NextPicture = $DisplayPicture + 1; } ## Load template my $Template = HTML::Template->new(filename => "./template.html"); ## Insert vars into template $Template->param('PreviousPicture' => "$PreviousPicture"); $Template->param('PictureToView' => "$DisplayPicture"); $Template->param('NextPicture' => "$NextPicture"); ## Print Header and Template print $q->header, $Template->output(); ## Bye exit;
P.S. I'm positive this has been done before but what the heck I can make one as too.

PT - Perl Tanks %100 Perl programming game

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Re: How can it be done better?
by perlguy (Deacon) on Jul 02, 2003 at 23:19 UTC

    Here is my go at it. I think a bunch of your logic at the bottom is difficult to read at first glance, so I tried to simplify it based upon the first numbered picture being 1 (and thus not 0).

    The logic for previous, next, and this picture all works, unless there are no files (and thus my die statement when reading the number of pictures, if it is 0). It might be even better to break that math out into some subroutines, especially if you will be doing it in more than one place.

    This is untested, as I didn't take the time to write the accessory templates, but this should be a good starting place. (comments added where I deemed necessary)

    ## Modules and setup use CGI; use HTML::Template; use strict; $CGI::POST_MAX=1024 * 1; # max 1k post $CGI::DISABLE_UPLOADS = 1; # No uploads # Your script name is already a property, # so this isn't generally necessary - # just call $ENV{SCRIPT_NAME} # instead of $ThisScript; my $ThisScript = $ENV{SCRIPT_NAME}; # better to create new CGI object this way with ->new() my $q = CGI->new(); my $template = HTML::Template->new( filename => "./template.html" ); # instead of making variables that we'll later use # only once, let's just do the math when defining # the template params: $template->param( PreviousPicture => $q->param('Picture') - 1 || NumberOfPictures(), PictureToView => $q->param('Picture') || 1, NextPicture => $q->param('Picture') % NumberOfPictures() + 1, ); print $q->header, $template->output(); { # we'll go ahead and cache the number for # future calls without re-reading the directory # we don't need a global variable for this, so # we'll limit the scope of this cached variable to # this block. my $cached_number_of_pics; sub NumberOfPictures { return $cached_number_of_pics if defined $cached_number_of_pics; opendir(DIR, "./") || die "Couldn't open directory: $@\n"; my @LFiles = grep { not /^(\.\.?|template\.html|pictureview\.cgi)$/ } readdir(DIR); closedir(DIR); # We don't really have a reason to continue # if there are no files, so die. die "No files -- I have no idea what to do\n" unless @LFiles; $cached_number_of_pics = @LFiles; # probably not necessary to force scalar # context, but... return scalar @LFiles; } }