Program: hrefsub

hrefsub makes substitutions in HTML files, so that the changes only apply to the text in HREF fields of <A href="..."> tags. For instance, if you had the scooby.html file from the previous example, and you've moved shergold.html to be cards.html, you need simply say: 

% hrefsub shergold.html cards.html scooby.html <HTML><HEAD><TITLE>Hi!</TITLE></HEAD><BODY> <H1>Welcome to Scooby World!</H1> I have <A href="pictures.html">pictures</A> of the crazy dog himself. Here's one!<P> <IMG src="scooby.jpg" ALT="Good doggy!"><P> <BLINK>He's my hero!</BLINK> I would like to meet him some day, and get my picture taken with him.<P> P.S. I am deathly ill. <a href="cards.html">Please send cards</A>. </BODY></HTML>

The HTML::Filter manual page has a BUGS section that says:

Comments in declarations are removed from the declarations and then inserted as separate comments after the declaration. If you turn on strict_comment(), then comments with embedded "-\|-" are split into multiple comments.

This version of hrefsub will always lowercase the <a> and the attribute names within this tag when substitution occurs. If $foo is a multiword string, then the text given to MyFilter->text may be broken such that these words do not come together; i.e., the substitution does not work. There should probably be a new option to HTML::Parser to make it not return text until the whole segment has been seen. Also, some people may not be happy with having their 8-bit Latin-1 characters replaced by ugly entities, so htmlsub does that, too.

Example 20.12: hrefsub

#!/usr/bin/perl -w # hrefsub - make substitutions in <A href="..."> fields of HTML files # from Gisle Aas <gisle@aas.no> sub usage {
 die "Usage: $0 <from>
<to>
<file>...\n"
}
my $from = shift or usage; my $to = shift or usage; usage unless @ARGV; # The HTML::Filter subclass to do the substitution. package MyFilter; require HTML::Filter; @ISA=qw(HTML::Filter); use HTML::Entities qw(encode_entities); sub start {
 my($self, $tag, $attr, $attrseq, $orig) = @_; if ($tag eq 'a' && exists $attr->{href}) {
 if ($attr->{href} =~ s/\Q$from/$to/g) {
 # must reconstruct the start tag based on $tag and $attr. # wish we instead were told the extent of the 'href' value # in $orig. my $tmp = "<$tag";
for (@$attrseq) {
 my $encoded = encode_entities($attr->{$_}); $tmp .= qq( $_="$encoded ");
}
$tmp .= ">"; $self->output($tmp);
return;
}
} $self->output($orig);
}
# Now use the class. package main; foreach (@ARGV) {
 MyFilter->new->parse_file($_);
}