Nginx + LUA, how to output file?

Question

Having trouble with file output in Nginx + Lua. I chosen LUA, because nginx logic is pretty complicated, based on referrer or subdomains, etc.

Having request like /img/am1/s/1.jpg I need to check if file exists in /somepath/am1/1.jpg. If it exists, then output it, otherwise proxy request to backend.

Solution 1

Ok, found it

content_by_lua '
    local file = "/path..."
    local f = io.open(file, "rb")
    local content = f:read("*all")
    f:close()
    ngx.print(content)
';

Solution 2

If someone need to know how to output last n lines from file:

location /service-man/log {
            default_type 'text/plain';
            content_by_lua '

                    local log_path = "/path/to/log.log"
                    -- Opens a file in read
                    file = io.open(log_path, "r")
                    if file==nil
                    then
                        ngx.say(log_path .. " can\'t read or does not exists")
                        return
                    end

                    -- sets the default input file
                    io.input(file)

                    local lines = {}
                    -- read the lines in table lines
                    for line in io.lines() do
                        table.insert(lines, line)
                    end
                    io.close(file)

                    log_limit = 10
                    if #lines < log_limit then
                        log_start = 0
                    else
                        log_len = #lines
                        log_start = log_len - log_limit
                    end

                    local one_line = ""

                    for i, line in ipairs(lines) do

                        if i > log_start then
                            one_line = one_line .. line .. "\\n"
                        end

                    end

                    ngx.say(one_line)
            ';

}

Should be compatible with nginx/1.6.2 and Lua 5.3.

Please share if you know how to make it in more optimal way.