This library deals with the highly platform specific task of opening 
a web page. In addition, is provides a mechanism similar to
absolute_file_name/3 
that expands compound terms to concrete URLs. For example, the 
SWI-Prolog home page can be opened using:
?- www_open_url(swipl(.)).
- www_open_url(+Url)
- 
Open URL in running version of the users’browser or start a new 
browser. This predicate tries the following steps:
 
- If a prolog flag (see set_prolog_flag/2) browseris set and this is the name of a known executable, use this. The flag 
may be set toCommand-Mode, where mode is one offgorbg, requesting Command to run in foreground or 
background mode. Default isbg.
- On Windows, use win_shell(open, URL)
- Find a generic‘open’comment. Candidates are xdg-open,openorgnome-open.
- If a environment variable BROWSERis set and this is 
the name of a known executable, use this.
- Try to find a known browser. @tbd Figure out the right tool in step 
3 as it is not uncommon that multiple are installed.
 
- [multifile]known_browser(+FileBaseName, 
-Compatible)
- 
True if browser FileBaseName has a remote protocol compatible 
to
Compatible.
- expand_url_path(+Spec, 
-URL)
- 
Expand URL specifications similar to absolute_file_name/3. 
The predicate url_path/2 plays the role of file_search_path/2.
- Errors
- 
existence_error(url_path, Spec)if the location is not 
defined.