url:parse

Documentation
- Reference manual
  - The SWI-Prolog library
    - library(url): Analysing and constructing URL
- Packages

Availability::- use_module(library(url)).(can be autoloaded)

[det]parse_url(?URL, ?Attributes)

Construct or analyse a URL. URL is an atom holding a URL or a variable. Attributes is a list of components. Each component is of the format Name(Value). Defined components are:

protocol(Protocol): The used protocol. This is, after the optional url:, an identifier separated from the remainder of the URL using :. parse_url/2 assumes the http protocol if no protocol is specified and the URL can be parsed as a valid HTTP url. In addition to the RFC-1738 specified protocols, the file protocol is supported as well.
host(Host): Host-name or IP-address on which the resource is located. Supported by all network-based protocols.
port(Port): Integer port-number to access on the \arg{Host}. This only appears if the port is explicitly specified in the URL. Implicit default ports (e.g., 80 for HTTP) do not appear in the part-list.
path(Path): (File-) path addressed by the URL. This is supported for the ftp, http and file protocols. If no path appears, the library generates the path /.
search(ListOfNameValue): Search-specification of HTTP URL. This is the part after the ?, normally used to transfer data from HTML forms that use the GET protocol. In the URL 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.
fragment(Fragment): Fragment specification of HTTP URL. This is the part after the # character.

The example below illustrates all of this for an HTTP URL.

?- 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')
    ]

By instantiating the parts-list this predicate can be used to create a URL.