fish-shell/doc_src/emit.txt

\section emit emit - Emit a generic event

\subsection block-synopsis Synopsis
 <tt>emit EVENT_NAME</tt>

\subsection emit-description Description

The emit builtin fires a generic fish event. Such events can be caught by special functions called event handlers. 

\subsection emit-example Example

The following code first defines an event handler for the generic
event named 'test_event', and then emits an event of that type.

<pre>function event_test --on-event test_event
    echo event test!!!
end

emit test_event</pre>