# perldoc > Image::ExifTool::BuildTagLookup

## NAME
    [Image::ExifTool::BuildTagLookup](https://www.chedong.com/phpMan.php/perldoc/Image%3A%3AExifTool%3A%3ABuildTagLookup/markdown) - Build ExifTool tag lookup tables

## DESCRIPTION
    This module is used to generate the tag lookup tables in [Image::ExifTool::TagLookup](https://www.chedong.com/phpMan.php/perldoc/Image%3A%3AExifTool%3A%3ATagLookup/markdown).pm and tag
    name documentation in [Image::ExifTool::TagNames](https://www.chedong.com/phpMan.php/perldoc/Image%3A%3AExifTool%3A%3ATagNames/markdown).pod, as well as HTML tag name documentation. It
    is used before each new ExifTool release to update the lookup tables and documentation, but it
    is not used otherwise. It also performs some validation and consistency checks on the tag
    tables.

## SYNOPSIS
      use [Image::ExifTool::BuildTagLookup](https://www.chedong.com/phpMan.php/perldoc/Image%3A%3AExifTool%3A%3ABuildTagLookup/markdown);

      $builder = new [Image::ExifTool::BuildTagLookup](https://www.chedong.com/phpMan.php/perldoc/Image%3A%3AExifTool%3A%3ABuildTagLookup/markdown);

      # update [Image::ExifTool::TagLookup](https://www.chedong.com/phpMan.php/perldoc/Image%3A%3AExifTool%3A%3ATagLookup/markdown)
      $ok = $builder->WriteTagLookup('lib/Image/ExifTool/TagLookup.pm');

      # update the tag name documentation
      $ok = $builder->WriteTagNames('lib/Image/ExifTool/TagNames.pod','html');

      # print some statistics
      my $count = $$builder{COUNT};
      foreach (sort keys %$count) {
          printf "%5d %s\n", $$count{$_}, $_;
      }

## MEMBER VARIABLES
    PRESERVE_DATE
        Flag to preserve "Last revised" date in HTML files. Set before calling WriteTagNames().

    COUNT
        Reference to hash containing counting statistics. Keys are the descriptions, and values are
        the numerical counts. Valid after BuildTagLookup object is created, but additional
        statistics are added by WriteTagNames().

    WRITE_PSEUDO
        Returned list of writable pseudo tags.

## AUTHOR
    Copyright 2003-2022, Phil Harvey (philharvey66 at gmail.com)

    This library is free software; you can redistribute it and/or modify it under the same terms as
    Perl itself.

## SEE ALSO
    Image::[ExifTool(3pm)](https://www.chedong.com/phpMan.php/man/ExifTool/3pm/markdown), [Image::ExifTool](https://www.chedong.com/phpMan.php/perldoc/Image%3A%3AExifTool/markdown)::[TagLookup(3pm)](https://www.chedong.com/phpMan.php/man/TagLookup/3pm/markdown), [Image::ExifTool](https://www.chedong.com/phpMan.php/perldoc/Image%3A%3AExifTool/markdown)::[TagNames(3pm)](https://www.chedong.com/phpMan.php/man/TagNames/3pm/markdown)