How can I pass a parameter to the wanted function when using Perl's File::Find?

Question

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How do I pass parameters to the File::Find subroutine that processes each file?

One can use Perl's File::Find module like this:

find( \&wanted, @directories);

How can we add a parameter to the wanted function?

For example, I want to traverse the files in /tmp extracting some information from each file and the result should be stored to a different directory. The output dir should be given as a parameter.

Answer 1

You use a closure:

use File::Copy;

my $outdir= "/home/me/saved_from_tmp";
find( sub { copy_to( $outdir, $_); }, '/tmp');

sub copy_to
  { my( $destination_dir, $file)= @_;
    copy $file, "$destination_dir/$file" 
      or die "could not copy '$file' to '$destination_dir/$file': $!";
  }

Answer 2

You can create any sort of code reference you like. You don't have to use a reference to a named subroutine. For many examples of how to do this, see my File::Find::Closures module. I created that module to answer precisely this question.

Answer 3

File::Find's contract specifies what information is passed to &wanted.

The wanted function takes no arguments but rather does its work through a collection of variables.

• $File::Find::dir is the current directory name,
• $_ is the current filename within that directory
• $File::Find::name is the complete pathname to the file.

If there is extra information you want to make available in the callback, you can create a sub reference that calls your wanted sub with the desired parameters.