Nginx + LUA, how to output file? - nginx

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.

Answer 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)
';

Answer 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.