SWI-Prolog -- http_reply_from

Documentation
- Reference manual
- Packages
  - SWI-Prolog HTTP support
    - The HTTP server libraries
      - library(http/http_files): Serve plain files from a hierarchy
        
        http_reply_from_files/3

Availability::- use_module(library(http/http_files)).

http_reply_from_files(+Dir, +Options, +Request)

HTTP handler that serves files from the directory Dir. This handler uses http_reply_file/3 to reply plain files. If the request resolves to a directory, it uses the option indexes to locate an index file (see below) or uses http_reply_dirindex/3 to create a listing of the directory.

Options:

indexes(+List): List of files tried to find an index for a directory. The default is ['index.html'].
not_found(+Action): Action defines what happens if the target file was not found. Options: fail makes the handler fail silently. 404 make the handler call http_404/2. Default is fail.

Note that this handler must be tagged as a prefix handler (see http_handler/3 and module introduction). This also implies that it is possible to override more specific locations in the hierarchy using http_handler/3 with a longer path-specifier.

When using http_handler/3 to bind this predicate to an HTTP location, make sure it is bound to a location that ends in a /. When using http:location/3 to define symbolic names to HTTP locations this is written as

:- http_handler(aliasname(.), http_reply_from_files(srcdir, []), [prefix]).

Dir

is either a directory or an path-specification as used by absolute_file_name/3. This option provides great flexibility in (re-)locating the physical files and allows merging the files of multiple physical locations into one web-hierarchy by using multiple user:file_search_path/2 clauses that define the same alias.

See also: The hookable predicate file_mime_type/2 is used to determine the Content-type from the file name.

Examples

Serve static files from an HTTP server

The SWI-Prolog HTTP server doesn't not server static files by default. You explicitly have to add a handler telling it to do so. The declarations below tell the server to serve files from the current directory under / on the server.

:- use_module(library(http/http_server)).
:- use_module(library(http/http_files)).

:- http_handler(root(.), http_reply_from_files('.', []), [prefix]).

Now, start the server and visit http://localhost:8080/.

?- http_server([port(localhost:8080)]).
% Started server at http://localhost:8080/
true.

Remarks

Note that the localhost: only binds the loopback network, avoiding to expose your website to the outside world.
The first argument of http_reply_from_files/3 is subject to search using absolute_file_name/3. This allows to abstract the physical location of the directory as well as virtually merge the contents of multiple physical directories.