#!/usr/bin/perl -w
use strict;
use Digest::SHA1 qw(sha1_hex);
sub _print_usage {
  print STDERR 'Usage: sha1sum <foaf_file_name>', "\n";
  exit 1;
}
my $file = shift @ARGV or _print_usage;
-e $file or _print_usage;
open( FILE, "< $file" ) or _print_usage;
foreach my $line ( <FILE> ) {
    if ( $line =~ /<foaf:mbox rdf:resource="(.+)"/ ) {
	my $sha1sum = sha1_hex($1);
	$line =~ s!<.+$!<foaf:mbox_sha1sum>$sha1sum</foaf:mbox_sha1sum>!;
    }
    print $line;
}
close( FILE );
__END__

=head1 NAME

sha1sum.pl

=head1 DESCRIPTION

This simple program is designed replace all instances of <foaf:mbox> in a FOAF file with <foaf:mbox_sha1sum>s instead.  This might be useful if you are concerned with the privacy aspects of publishing lists of names and associated email addresses in human-readable form on the web or are worried about spammers scanning your FOAF file.

Simply pass the name of your FOAF file as an argument.  Output goes to STDOUT.

=head1 SEE ALSO

Sam Ruby has code snippets from several languages for generating SHA1 digests avavilable from his website <http://www.intertwingly.net/blog/1545.html>.

There is more information about FOAF available on the web at <http://www.foaf-project.org/>.

=head1 AUTHOR

Sam Pearson <http://sgp.me.uk/>

=head1 LICENSE

Public Domain.  Do whatever you want with it.

THIS SOFTWARE IS PROVIDED AS IS AND WITHOUT ANY WARRANTY OF ANY KIND.  USE AT YOUR OWN RISK!