% This LaTeX document was generated using the LaTeX backend of PlDoc,
% The SWI-Prolog documentation system



\section{library(www_browser): Open a URL in the users browser}

\label{sec:wwwbrowser}

This library deals with the highly platform specific task of opening a
web page. In addition, is provides a mechanism similar to
\predref{absolute_file_name}{3} that expands compound terms to concrete URLs. For
example, the SWI-Prolog home page can be opened using:

\begin{code}
?- www_open_url(swipl(.)).
\end{code}

\vspace{0.7cm}

\begin{description}
    \predicate{www_open_url}{1}{+Url}
Open URL in running version of the users' browser or start a new
browser. This predicate tries the following steps:

\begin{enumerate}
    \item If a prolog flag (see \predref{set_prolog_flag}{2}) \const{browser} is set
and this is the name of a known executable, use this. The
flag may be set to \verb$Command-Mode$, where mode is one of \const{fg}
or \const{bg}, requesting Command to run in foreground or background
mode. Default is \const{bg}.
    \item On Windows, use \verb$win_shell(open, URL)$
    \item Find a generic `open' comment. Candidates are \verb$xdg-open$,
\const{open} or \verb$gnome-open$.
    \item If a environment variable \verb$BROWSER$ is set
and this is the name of a known executable, use this.
    \item Try to find a known browser.
@tbd Figure out the right tool in step 3 as it is not
uncommon that multiple are installed.
\end{enumerate}

    \predicate[multifile]{known_browser}{2}{+FileBaseName, -Compatible}
True if browser \arg{FileBaseName} has a remote protocol compatible to
\arg{Compatible}.

    \predicate{expand_url_path}{2}{+Spec, -URL}
Expand \arg{URL} specifications similar to \predref{absolute_file_name}{3}. The
predicate \predref{url_path}{2} plays the role of \predref{file_search_path}{2}.

\begin{tags}
    \tag{Errors}
\verb$existence_error(url_path, Spec)$ if the location is not
defined.
\end{tags}
\end{description}