SWI-Prolog for SHaring: a SWI-Prolog web IDE
Prolog JavaScript HTML CSS Other
Latest commit 7021949 Feb 21, 2017 @JanWielemaker JanWielemaker Updated profile


SWISH: A web based SWI-Prolog environment

Online version

SWISH can be used to access SWI-Prolog at the address below. We try to keep this server continuously online. You can use this server for playing, courses or sharing and discussing ideas. We have not yet dealt with scalable hosting nor with really reliable and scalable storage for saved programs. We hope to keep all your programs online for at least multiple years.


Get JavaScript requirements

Using bower

Install bower for your platform. On Ubuntu, this implies getting node and npm by installing two packages and next use npm to install bower:

sudo apt-get install npm nodejs-legacy
sudo npm install -g bower

Once you have bower, run the following from the toplevel of swish to get the dependencies:

bower install
make src

Download as zip

As installing node and bower is not a pleasure on all operating systems, you can also download the dependencies as a single zip file from http://www.swi-prolog.org/download/swish/swish-bower-components.zip. Unpack the zip file, maintaining the directory structure, from the swish root directory to create the directory web/bower_components.

Last updated: Apr 1, 2016: Added sparklines

Get the latest SWI-Prolog

Install the latest SWI-Prolog development version. As SWISH is very much in flux and depends on the recent SWI-Prolog pengines and sandboxing libraries, it is quite common that you need the nightly build (Windows) or build the system from the current git development repository swipl-devel.git.

Feb 3, 2017: SWI-Prolog 7.4.0-rc1 and 7.5.0 support SWISH completely.

Running SWISH

With a sufficiently recent Prolog installed, start the system by opening run.pl either by running swipl run.pl (Unix) or opening run.pl from the Windows explorer.

Now direct your browser to http://localhost:3050/

If you want to know what the latest version looks like, go to http://swish.swi-prolog.org/

Configuring SWISH

There is a lot that can be configured in SWISH. Roughly:

  • Make additional libraries available, e.g., RDF support, database connections, link to R, etc.

  • Configure authentication and authorization. The default is not to demand and run commands sandboxed. At the other extreme you can configure the system to demand login for all access and provide full access to Prolog.

Configuration is done by reading *.pl files from the directory config-enabled. The directory config-available contains templates that can be copied and optionally edited to create a configuration.

Running SWISH without sandbox limitations

By default, SWISH does not require the user to login but lets you run only safe commands. If you want to use SWISH for unrestricted development, enable the config file auth_http_always.pl:

mkdir -p config-enabled
(cd config-enabled && ln -s ../config-available/auth_http_always.pl)

Next, for first usage, you need to create a user. The authentication module defines swish_add_user/0, which asks for details about the user to be created and updates or creates a file called passwd. At the moment Group and E-Mail are stored, but not used.

?- swish_add_user.
% Password file: /home/jan/src/prolog/swish/passwd (update)
User name: bob
Real name: Bob Hacker
Group:     user
E-Mail:    bob@hacker.org

If you now try to run a command in SWISH, it will prompt for a user and password. After authentication you can run any Prolog predicate.

NOTE Authentication uses HTTP digest authentication by default. This authentication method uses a challenge-response method to verify the password and ensures the credentials change with every request such that old credentials cannot be re-used by an attacker. Unfortunately, the server stores the password as the SHA1 hash created from the user, password and realm. This is relatively vulnerable to brute-force attacks for anyone who gains access to the password file due to the low computational overhead of SHA1 and the lack of a user-specific salt. Also note that the exchanged commands and replies are not encrypted. Secure servers should use HTTPS.

Optional login

Instead of using auth_http_always.pl you can use auth_http.pl, which allows for unauthenticated -sandboxed- usage as well as logging in to the server and get unrestricted access. In addition, several social login modules are provided to login using Google, etc. Currently these provide no additional rights. A more fine grained authorization scheme is planned.

Running as a service

The script daemon.pl is provided to run SWISH as a service or daemon on Unix systems. Run this to get an overview of the options.

./daemon.pl --help

This script can be used to start SWISH as a daemon from the command line, start SWISH from service managers such as upstart or systemd and simplifies running as an HTTPS server. See https://github.com/triska/letswicrypt.


Most of the application is realised using client-side JavaScript, which can be found in the directory web/js. The JavaScript files use RequireJS for dependency tracking and jQuery for structuring the JavaScript as jQuery plugins. The accompanying CSS is in web/css. More details about the organization of the JavaScript is in web/js/README.md

There are two overal pages. web/swish.html provides a static page and lib/page.pl provides a Prolog frontend to generate the overal page or parts thereof dynamically. The latter facilitates smoothless embedding in SWI-Prolog web applications.

Development and debugging

No building is needed to run the system from sources. For public installations you probably want to create the minified JavaScript and CSS files to reduce network traffic and startup time. You need some more tools for that:

% [sudo] npm install -g jsdoc
% [sudo] npm install -g requirejs
% [sudo] npm install -g clean-css

You also need GNU make installed as make and SWI-Prolog as swipl. With all that in place, the following command creates the minified versions:

% make

The default main page (/) is generated from lib/page.pl. It uses minified JavaScript and CSS from web/js/swish-min.js web/css/swish-min.css when available. If the minified files are not present, the server automatically includes the full source. The generated files may be removed using

make clean

Alternatively, use of the minified files can be disable from Prolog using this command and reloading the page:

?- debug(nominified).


The JavaScript is documented using JsDoc. The generated documentation is available in web/js/doc/index.html.