# $filename = "./ipc/ipc1.htm";
# $file_dir = &dir($filename);
$file_dir = "/usr1/www/pages/mhs/psychotherapy/ipc";
$href     = "../progs/acroread.exe";
$dir = &expand_dir($file_dir,$href);


print "file_dir = $file_dir, href = $href\n";
print "  now dir = $dir\n";


sub dir {
   # returns the directory part of a filename
   # makes no attempt to check the filename othewise for legality
   local ($filename) = @_;
   local ($dir,$slash);
   $slash = rindex($filename,"/");
   if ($slash > 0) {
      $dir = substr($filename,0,$slash);
   } else {
      $dir = ".";
   }
   $dir;
}



sub expand_dir {
   # expands a relative address supplied as $href
   # given the directory (".") in $file_dir
   # will not (at present) deal with a silly reference like "./../filename"
   # nor will it detect illegal forms like ".../filename" or ".././filename"
   local ($file_dir,$href) = @_;
   local ($filename,$dir,$slash);

   #### first return to calling routine if href is absolute
   if ($href =~ /^\//) {
      return ($www_offset.$href);
   }


   #### make sure $file_dir doesn't have a trailing slash
   if ($file_dir =~ m#/$#) {
      chop($file_dir);
   }

   if ($href =~ /\.\./) {
      @href = split(/\//,$href);
      @dir  = reverse(split(/\//,$file_dir));
      $filename = pop(@href); # shift the filename off the end of the href
      while (@href && ($href[0] eq "..")) {
         shift(@href);
         shift(@dir);
      }
      @dir = reverse(@dir);
      $dir = join('/',@dir);
      $href = join('/',@href);
      $href = $dir."/".$href."/".$filename;
   } elsif ($href =~ m#^(\.)/#) {
      #### is an explicit reference to current directory so replace "." with $file_dir
      $href =~ s#^.#$file_dir#;
   } else {
      #### must be just an implicit reference to current directory so just splice
      $href = $file_dir."/".$href;
   }
   $href;
}