/usr/lib/swi-prolog/doc/Manual/url.html

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<h2 id="sec:url"><a id="sec:A.31"><span class="sec-nr">A.31</span> <span class="sec-title">library(url): 
Analysing and constructing URL</span></a></h2>

<p><a id="sec:url"></a>

<dl class="tags">
<dt class="mtag">author</dt>
<dd>
- Jan Wielemaker <br>
- Lukas Faulstich
</dd>
<dt class="tag">deprecated</dt>
<dd>
New code should use <code>library(uri)</code>, provided by the <code>clib</code> 
package.
</dd>
</dl>

<p>This library deals with the analysis and construction of a URL, 
Universal Resource Locator. URL is the basis for communicating locations 
of resources (data) on the web. A URL consists of a protocol identifier 
(e.g. HTTP, FTP, and a protocol-specific syntax further defining the 
location. URLs are standardized in RFC-1738.

<p>The implementation in this library covers only a small portion of the 
defined protocols. Though the initial implementation followed RFC-1738 
strictly, the current is more relaxed to deal with frequent violations 
of the standard encountered in practical use.

<dl class="latex">
<dt class="pubdef"><span class="pred-tag">[det]</span><a id="global_url/3"><strong>global_url</strong>(<var>+URL, 
+Base, -Global</var>)</a></dt>
<dd class="defbody">
Translate a possibly relative <var>URL</var> into an absolute one.

<dl class="tags">
<dt class="tag">Errors</dt>
<dd>
<code>syntax_error(illegal_url)</code> if <var>URL</var> is not legal.
</dd>
</dl>

</dd>
<dt class="pubdef"><a id="is_absolute_url/1"><strong>is_absolute_url</strong>(<var>+URL</var>)</a></dt>
<dd class="defbody">
True if <var>URL</var> is an absolute <var>URL</var>. That is, a <var>URL</var> 
that starts with a protocol identifier.</dd>
<dt class="pubdef"><a id="http_location/2"><strong>http_location</strong>(<var>?Parts, 
?Location</var>)</a></dt>
<dd class="defbody">
Construct or analyze an HTTP location. This is similar to
<a class="pred" href="url.html#parse_url/2">parse_url/2</a>, but only 
deals with the location part of an HTTP URL. That is, the path, search 
and fragment specifiers. In the HTTP protocol, the first line of a 
message is

<pre class="code">
&lt;Action&gt; &lt;Location&gt; HTTP/&lt;version&gt;
</pre>

<table class="arglist">
<tr><td><var>Location</var> </td><td>Atom or list of character codes. </td></tr>
</table>
</dd>
<dt class="pubdef"><span class="pred-tag">[det]</span><a id="parse_url/2"><strong>parse_url</strong>(<var>+URL, 
-Attributes</var>)</a></dt>
<dd class="defbody">
Construct or analyse a <var>URL</var>. <var>URL</var> is an atom holding 
a <var>URL</var> or a variable. <var>Attributes</var> is a list of 
components. Each component is of the format Name(Value). Defined 
components are:

<dl class="latex">
<dt><strong>protocol</strong>(<var>Protocol</var>)</dt>
<dd class="defbody">
The used protocol. This is, after the optional <code>url:</code>, an 
identifier separated from the remainder of the <var>URL</var> using :.
<a class="pred" href="url.html#parse_url/2">parse_url/2</a> assumes the <code>http</code> 
protocol if no protocol is specified and the <var>URL</var> can be 
parsed as a valid HTTP url. In addition to the RFC-1738 specified 
protocols, the <code>file</code> protocol is supported as well.
</dd>
<dt><strong>host</strong>(<var>Host</var>)</dt>
<dd class="defbody">
<var>Host</var>-name or IP-address on which the resource is located. 
Supported by all network-based protocols.
</dd>
<dt><strong>port</strong>(<var>Port</var>)</dt>
<dd class="defbody">
Integer port-number to access on the <code>\</code>arg{Host}. This only 
appears if the port is explicitly specified in the <var>URL</var>. 
Implicit default ports (e.g., 80 for HTTP) do <i>not</i> appear in the 
part-list.
</dd>
<dt><strong>path</strong>(<var>Path</var>)</dt>
<dd class="defbody">
(File-) path addressed by the <var>URL</var>. This is supported for the
<code>ftp</code>, <code>http</code> and <code>file</code> protocols. If 
no path appears, the library generates the path <code>/</code>.
</dd>
<dt><strong>search</strong>(<var>ListOfNameValue</var>)</dt>
<dd class="defbody">
Search-specification of HTTP <var>URL</var>. This is the part after the
<code>?</code>, normally used to transfer data from HTML forms that use 
the <code>GET</code> protocol. In the <var>URL</var> it consists of a 
www-form-encoded list of Name=Value pairs. This is mapped to a list of 
Prolog Name=Value terms with decoded names and values.
</dd>
<dt><strong>fragment</strong>(<var>Fragment</var>)</dt>
<dd class="defbody">
<var>Fragment</var> specification of HTTP <var>URL</var>. This is the 
part after the <code>#</code> character.
</dd>
</dl>

<p>The example below illustrates all of this for an HTTP <var>URL</var>.

<pre class="code">
?- parse_url('http://www.xyz.org/hello?msg=Hello+World%21#x',
       P).

P = [ protocol(http),
      host('www.xyz.org'),
      fragment(x),
      search([ msg = 'Hello World!'
             ]),
      path('/hello')
    ]
</pre>

<p>By instantiating the parts-list this predicate can be used to create 
a <var>URL</var>.</dd>
<dt class="pubdef"><span class="pred-tag">[det]</span><a id="parse_url/3"><strong>parse_url</strong>(<var>+URL, 
+BaseURL, -Attributes</var>)</a></dt>
<dd class="defbody">
Similar to <a class="pred" href="url.html#parse_url/2">parse_url/2</a> 
for relative URLs. If <var>URL</var> is relative, it is resolved using 
the absolute <var>URL</var> <var>BaseURL</var>.</dd>
<dt class="pubdef"><span class="pred-tag">[det]</span><a id="www_form_encode/2"><strong>www_form_encode</strong>(<var>+Value, 
-XWWWFormEncoded</var>)</a></dt>
<dt class="pubdef"><span class="pred-tag">[det]</span><a id="www_form_encode/2"><strong>www_form_encode</strong>(<var>-Value, 
+XWWWFormEncoded</var>)</a></dt>
<dd class="defbody">
En/decode to/from application/x-www-form-encoded. Encoding encodes all 
characters except RFC 3986 <i>unreserved</i> (ASCII
<code>alnum</code> (see <a class="pred" href="chartype.html#code_type/2">code_type/2</a>)), 
and one of "-._&nbsp;" using percent encoding. Newline is mapped to <code>%OD%OA</code>. 
When decoding, newlines appear as a single newline (10) character.

<p>Note that a space is encoded as <code>%20</code> instead of <code>+</code>. 
Decoding decodes both to a space.

<dl class="tags">
<dt class="tag">deprecated</dt>
<dd>
Use <span class="pred-ext">uri_encoded/3</span> for new code.
</dd>
</dl>

</dd>
<dt class="pubdef"><span class="pred-tag">[semidet]</span><a id="set_url_encoding/2"><strong>set_url_encoding</strong>(<var>?Old, 
+New</var>)</a></dt>
<dd class="defbody">
Query and set the encoding for URLs. The default is <code>utf8</code>. 
The only other defined value is <code>iso_latin_1</code>.

<dl class="tags">
<dt class="tag">To be done</dt>
<dd>
Having a global flag is highly inconvenient, but a work-around for old 
sites using ISO Latin 1 encoding.
</dd>
</dl>

</dd>
<dt class="pubdef"><span class="pred-tag">[det]</span><a id="url_iri/2"><strong>url_iri</strong>(<var>+Encoded, 
-Decoded</var>)</a></dt>
<dt class="pubdef"><span class="pred-tag">[det]</span><a id="url_iri/2"><strong>url_iri</strong>(<var>-Encoded, 
+Decoded</var>)</a></dt>
<dd class="defbody">
Convert between a URL, encoding in US-ASCII and an IRI. An IRI is a 
fully expanded Unicode string. Unicode strings are first encoded into 
UTF-8, after which %-encoding takes place.</dd>
<dt class="pubdef"><span class="pred-tag">[det]</span><a id="parse_url_search/2"><strong>parse_url_search</strong>(<var>?Spec, 
?Fields:list(Name=Value)</var>)</a></dt>
<dd class="defbody">
Construct or analyze an HTTP search specification. This deals with form 
data using the MIME-type
<code>application/x-www-form-urlencoded</code> as used in HTTP GET 
requests.</dd>
<dt class="pubdef"><span class="pred-tag">[det]</span><a id="file_name_to_url/2"><strong>file_name_to_url</strong>(<var>+File, 
-URL</var>)</a></dt>
<dt class="pubdef"><span class="pred-tag">[semidet]</span><a id="file_name_to_url/2"><strong>file_name_to_url</strong>(<var>-File, 
+URL</var>)</a></dt>
<dd class="defbody">
Translate between a filename and a file:<code>//</code> <var>URL</var>.

<dl class="tags">
<dt class="tag">To be done</dt>
<dd>
Current implementation does not deal with paths that need special 
encoding.
</dd>
</dl>

</dd>
</dl>

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swi-prolog-nox 6.6.4-2ubuntu1 / usr / lib / swi-prolog / doc / Manual / url.html
