Bangs (Searching Another Site)

A bang sends a search to another site instead of searching Fess. It works like the bangs of DuckDuckGo: put ! and a short trigger word in the query, and Fess sends the rest of the query to the site the trigger stands for.

Query Goes to
airplane !g Google, searching for airplane
!w Ohm's law Wikipedia, searching for Ohm's law
!g The home page of Google
airplane !unknown Fess, as a normal search (! means NOT, see NOT Search (Excluding Words))

Bangs are provided by the fess-webapp-bangs plugin, which requires Fess 15.9 or later. Install it from [System > Plugin] in the admin console or with bin/fess-setup install plugin fess-webapp-bangs (see Plugin), and restart Fess.

How a Bang Is Recognized

  • A bang is ! followed by a trigger, written as a separate word. The trigger is case-insensitive.

  • The bang is removed from the query, and the rest of the query is sent to the URL of the bang.

  • When a query holds more than one defined bang, only the first one counts.

  • A trigger that is not defined is not a bang. !unknown is searched as usual, and excludes the word unknown.

  • -g and NOT g still exclude the word g. Only !g is a bang.

The search page and /api/v2/search follow the redirect: the API returns redirect_url (see Search API), and the bootstrap theme bundled with Fess navigates to it. Other themes need the same handling.

Callers that cannot redirect, such as chat, MCP, the v1 and classic JSON APIs, and the admin search, do not send the search elsewhere. They drop the bang and search the rest of the query.

Defining Bangs

Bangs are defined by the system property bangs.definitions. Set it in app/WEB-INF/conf/system.properties, or pass it as -Dfess.system.bangs.definitions=.... A change in system.properties is picked up without restarting Fess.

The value is a whitespace-separated list of trigger=url entries. In the URL, {query} is replaced with the URL-encoded rest of the query:

bangs.definitions=g=https://www.google.com/search?q={query} w=https://en.wikipedia.org/wiki/Special:Search?search={query}

  • A trigger cannot contain whitespace, (, ), !, ", = or :.

  • Only absolute http or https URLs are accepted.

  • An entry that does not follow these rules is not used. A warning is written to the Fess log, and the other entries stay in effect.

  • If the same trigger is defined twice, the first definition is used.

  • An empty value turns every bang off.

When bangs.definitions is not set, the following five bangs are available:

Trigger Site
g Google
b Bing
ddg DuckDuckGo
w Wikipedia (English)
gh GitHub

Setting bangs.definitions replaces this list. To keep the defaults and add one more, write all of the entries you need.