How to call the lfs module in ngx_lua?

Question

I want to use lfs module in my ngx_lua programe, I download the source package from github and compile it with luajit2.0.3. The static file is in /usr/local/lib. My nginx.conf's content are as follow:

http {
    lua_shared_dict  my_cache 10m;
    lua_package_cpath '/usr/local/lib/lfs.so';

    init_worker_by_lua_file  'conf/cop/check1.lua';
    ...
}

The check1.lua's content are as follow:

local time_at = ngx.timer.at
local shared = ngx.shared
local log = ngx.log
local delay = 5
local ngx_err = ngx.ERR
local handler, updateip, checkfile
local my_cache = shared["my_cache"]
local filename = '/home/nginx/conf/cop/ip.txt'

local lfs = require "lfs"
local attribute = lfs.attribute

if not my_cache then
    log(ngx_err, "disappear the shared dict")
    return
end

checkfile = function (filename)
    local attr = attributes(filename)
    if attr then
        return attr.modification
    else
        return nil
    end
end

updateip = function (filename)
    my_cache:flush_all()
    local fp = io.open(filename, "r")
    if not fp then
        log(ngx_err, "failed to open file")
        return
    end
    for line in fp:lines() do
        my_cache:set(line, line)
    end
end

handler = function (premature, filename)
    -- do some routine job in Lua just like a cron job
    if premature then
        return
    end
    local mod
    local md5result, flags = my_cache:get("md5")
    if not md5result then
        mod = checkfile(filename)
        updateip(filename)
        my_cache:set("md5", mod)
    else
        mod = checkfile(filename)
        if mod ~= md5result then
            updateip(filename)
            my_cache:set("md5", mod)
        end
    end
    local ok, err = time_at(delay, handler, filename)
    if not ok then
        log(ngx_err, "failed to create the timer: ", err)
        return
    end
end

local ok, err = time_at(delay, handler, filename)
if not ok then
    log(ngx_err, "failed to create the timer: ", err)
    return
end

When I start my nginx, there are some wrongs happened. The content are as follow:

2014/04/28 16:36:54 [error] 9437#0: lua entry thread aborted: runtime error: 

/home/nginx/conf/cop/check1.lua:22: attempt to call upvalue    'attributes' (a nil value) stack traceback: coroutine 0:
/home/nginx/conf/cop/check1.lua: in function 'checkfile'
/home/nginx/conf/cop/check1.lua:50: in function </home/nginx/conf/cop/check1.lua:42>, context: ngx.timer

How can I do for it? But I use the luajit command line, it is ok:

LuaJIT 2.0.3 -- Copyright (C) 2005-2014 Mike Pall. http://luajit.org/
JIT: ON CMOV SSE2 SSE3 SSE4.1 fold cse dce fwd dse narrow loop abc sink fuse
> lfs = require "lfs"
> attr = lfs.attributes('check1.lua')
> print(attr.modification)
1398678137
> 

Answer 1

Notice the following lines:

local attribute = lfs.attribute
.
.
.
checkfile = function (filename)
    local attr = attributes(filename)

You are creating the variable attribute from lfs.attribute instead of lfs.attributes . Also, you are later trying to call attributes instead of attribute .

Change the following

local attribute = lfs.attribute

to

local attributes = lfs.attributes