Provides a means of adding a Lua function as an output filter. As with input filters, output filters work as coroutines, first yielding before buffers are sent, then yielding whenever a bucket needs to be passed down the chain, and finally (optionally) yielding anything that needs to be appended to the input data. The global variable bucket holds the buckets as they are passed onto the Lua script:

LuaOutputFilter myOutputFilter "/www/filter.lua" output_filter
<Files "*.lua">
 SetOutputFilter myOutputFilter
</Files>

--[[
 Example output filter that escapes all HTML entities in the output
]]--
function output_filter(r)
 coroutine.yield("(Handled by myOutputFilter)<br/>\n") -- Prepend some data to the output,
 -- yield and wait for buckets.
 while bucket do -- For each bucket, do...
 local output = r:escape_html(bucket) -- Escape all output
 coroutine.yield(output) -- Send converted data down the chain
 end
 -- No more buckets available.
end

As with the input filter, the output filter supports denying/skipping a filter if it is deemed unwanted:

function output_filter(r)
 if not r.content_type:match("text/html") then
 return -- Simply deny filtering, passing on the original content instead
 end
 coroutine.yield() -- wait for buckets
 ... -- insert filter stuff here
end

Lua filters with mod_filter

When a Lua filter is used as the underlying provider via the FilterProvider directive, filtering will only work when the filter-name is identical to the provider-name.

See "Modifying contents with Lua filters" for more information.