UHTML–Example

Delivering identical data

The content of the <head> section usually remains widely unaltered across all HTML files of a website. The vantage of keeping the constant part in a single separate file is obvious. To realize this with UHTML we need to create an <include> tag that inserts the content of one file called head-data into a html file. We assume that we have an include directory in our document root where we keep our overlapping chunks of HTML code in single files. Assuming UHTML is installed on our system, the UHTML file could then look like this:

index.uhtml
  <html>
    <head>
      <include file="/include/head-data">
      ...
    </head>
  ...
  </html>

The functionality of the <include> tag is an asset in many projects. Following the mentioned naming convention proposal the perl code is placed in a file named include.pm located in the subdirectory UHTML of the script (CGI) directory. The file include.pm could then look like that:

include.pm
  use uHTML ;
  sub Include($) {
  my $Node = shift;
  $Node->map(join('',<FH>),'')
    if $Node->Attr('file') and
      open FH,$ENV{'DOCUMENT_ROOT'}.$Node->Attr('file');
  }
  uHTML->registerTag('include',\&Include);

Linking with FCGI, Plack and nginx

Nginx serves only static files and expects an external server to handle dynamic content. UHTML works well with Plack over the FCGI interface. For this purpose UHTML must be installed system wide.

To link the small library above with our website a FCGI hook is needed. We place the necessary code in a file called uHTML.psgi in the script directory:

uHTML.psgi
use uHTML;
use Encode;
sub
{
my $env  = shift ;
my( $FILE,$DATA,$HTML,@HEAD,$LEN ) ;
if( open $FILE,$env->{'PATH_TRANSLATED'} and
$LEN = -s $FILE and
read( $FILE,$DATA,$LEN ) == $LEN )
{
$HTML = uHTML::recoded_list( $DATA,$env ) ;
$LEN = 0 ;
$LEN += length Encode::encode( 'UTF-8',$_ )
foreach @{$HTML} ;
push @HEAD,'Content-Type','text/html; charset=UTF-8' ;
push @HEAD,'Content-Length',$LEN ;
push @HEAD,'x-powered-by','uHTML' ;
return [ 200,\@HEAD, $HTML ] ;
}
return [ 404,
[ 'Content-Type' => 'text/plain' ],
[ 'File Not Found' ]
] ;
}

Now we can start the FCGI server with plack using:

plackup -s FCGI -S /tmp/uHTML -a /srv/cgi-bin/uHTML.psgi

In the nginx configuration we add the section redirecting UHTML requests to our plackup server:

nginx configuration
location ~ \.uhtml$
{
  try_files $uri /index.uhtml =404 ;
  fastcgi_keep_conn on ;
  fastcgi_split_path_info ^()(.*uhtml)$;
  fastcgi_pass unix:/tmp/uHTML ;
  fastcgi_index index.uhtml;
  fastcgi_param URI $uri;
  fastcgi_param SCRIPT_FILENAME
      $document_root$fastcgi_script_name;
  fastcgi_param SCRIPT_NAME $fastcgi_script_name;
  fastcgi_param PATH_TRANSLATED
      $document_root$fastcgi_path_info;
  fastcgi_param QUERY_STRING $query_string;
  fastcgi_param REQUEST_METHOD $request_method;
  fastcgi_param CONTENT_TYPE $content_type;
  fastcgi_param CONTENT_LENGTH $content_length;
  fastcgi_param REQUEST_URI $request_uri;
  fastcgi_param REQUEST $request;
  fastcgi_param REQUEST_SCHEME $scheme ;
  fastcgi_param REQUEST_FILE $request_filename;
  fastcgi_param DOCUMENT_URI $document_uri;
  fastcgi_param DOCUMENT_ROOT $document_root;
  fastcgi_param SERVER_PROTOCOL $server_protocol;
  fastcgi_param GATEWAY_INTERFACE CGI/1.1;
  fastcgi_param SERVER_SOFTWARE nginx/$nginx_version;
  fastcgi_param REMOTE_ADDR $remote_addr;
  fastcgi_param REMOTE_PORT $remote_port;
  fastcgi_param SERVER_ADDR $server_addr;
  fastcgi_param SERVER_PORT $server_port;
  fastcgi_param SERVER_NAME $server_name;
  fastcgi_param HOST_NAME $hostname;
  fastcgi_param HTTPS $https;
  fastcgi_param HTTP_COOKIE $http_cookie;
  fastcgi_param HTTP_ACCEPT_LANGUAGE $http_accept_language;
  fastcgi_param REDIRECT_STATUS 200;
  fastcgi_param SCRIPT_ROOT /srv/cgi-bin ;
  fastcgi_param DATA_ROOT /srv/cgi-bin ;
}
location /
{
}

Linking with CGI and Apache

On systems with Apache and CGI UHTML can be installed in two ways, system-wide or website local. System-wide installation is preferred, it makes UHTML available for all websites hosted on the system, but needs root privileges. Website local installation is possible without root privileges. It provides UHTML just for the particular site.

To link the small library above with our website a CGI hook is needed. We place the necessary code in a file called uhtml.pl in the script directory:

uhtml.pl
 #!/usr/bin/perl
 use uHTML;
 open $FILE,"$ENV{'DOCUMENT_ROOT'}$ENV{'PATH_INFO'}"
  or die "File: $ENV{'PATH_INFO'} not found";
 print "Content-type: text/html\n\n";
 print uHTML::recode(join('',<$FILE>));

To get the functionality “magically” into all *.uhtml files, we add some lines into the .htaccess file in our DOCUMENT_ROOT :

.htaccess
 DirectoryIndex index.uhtml
 RewriteEngine on
 RewriteRule ^(/?)(.*\.uhtml) $1cgi-bin/uhtml.pl/$2 [L,QSA]

This full working example shows just the basic principle how to add an user-tag into a website using UHTML . It do not show the use of attribute functions or request initialisation, but including any of this two is trivial.

Example with all files and directories as needed by apache:

uHTML Example (1.35kB, from 23.02.2021, 16:00:23)

UHTML–Example

Delivering identical data

Linking with FCGI, Plack and nginx

Linking with CGI and Apache

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