Recipe 20.20 Program: htmlsub
This program makes substitutions in HTML files so changes happen only in normal text. If you had the file scooby.html that contained:
<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="shergold.html">Please send cards</A>. </BODY></HTML>
you could use htmlsub to change every occurrence of the word "picture" in the document text to read "photo". It prints the new document on STDOUT:
% htmlsub picture photo scooby.html <HTML><HEAD><TITLE>Hi!</TITLE></HEAD> <BODY><H1>Welcome to Scooby World!</H1> I have <A HREF="pictures.html">photos</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 photo taken with him.<P> P.S. I am deathly ill. <A HREF="shergold.html">Please send cards</A>. </BODY></HTML
The program is shown in Example 20-12.
Example 20-12. htmlsub
#!/usr/bin/perl -w
# htmlsub - make substitutions in normal text 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;
# Build the HTML::Filter subclass to do the substituting.
package MyFilter;
use HTML::Filter;
@ISA=qw(HTML::Filter);
use HTML::Entities qw(decode_entities encode_entities);
sub text
{
my $self = shift;
my $text = decode_entities($_[0]);
$text =~ s/\Q$from/$to/go; # most important line
$self->SUPER::text(encode_entities($text));
}
# Now use the class.
package main;
foreach (@ARGV) {
MyFilter->new->parse_file($_);
}
