Lua脚本报错：尝试索引nil全局变量'nmap'问题求助

报错lua: discovery_n.lua:12: attempt to index a nil value (global 'nmap')的核心原因是：你直接用Lua解释器运行脚本，但nmap.registry是Nmap脚本引擎（NSE）专属API，只有当脚本被Nmap调用执行时才会加载这些全局变量，直接跑Lua脚本自然找不到nmap对象。

1. 替换JSON解析依赖 #

用标准Lua的JSON库（比如dkjson）替代NSE的nmap.registry.fromJSON：

• 先通过LuaRocks安装dkjson：执行luarocks install dkjson

2. 简化Nmap输出处理 #

你的需求是把Nmap扫描结果保存为XML文件，无需用NSE API解析后再转XML——直接将Nmap命令输出的原始XML内容写入文件即可，省去中间转换步骤。

修复后的完整代码 #

#!/usr/bin/env lua

local io = require('io')
local dkjson = require('dkjson')

-- Read JSON file
local file, err = io.open("discovery.json", "r")
if not file then
    error("Error: " .. err .. "\nJSON file not found, please make sure the file exists and the path is correct")
end
local json_data = file:read("*all")
file:close()

-- Parse JSON data with dkjson
local data, parse_err = dkjson.decode(json_data)
if not data then
    error("Error parsing JSON: " .. parse_err)
end

-- Extract IP addresses
local host_list = data.Detail.host_list
if type(host_list) ~= "table" then
    error("host_list is not a table")
end

-- Iterate over host_list
for _, host in ipairs(host_list) do
    local ip_v4_address = host.host.ip_v4_address
    if not ip_v4_address then
        print("Skipping host: no IPv4 address found")
        goto continue
    end

    -- Run nmap command and capture XML output
    local nmap_command = "nmap -oX - " .. ip_v4_address
    local nmap_handle = io.popen(nmap_command, "r")
    if not nmap_handle then
        print("Failed to run nmap command for " .. ip_v4_address)
        goto continue
    end
    local nmap_output = nmap_handle:read("*all")
    local exit_code = nmap_handle:close()

    if exit_code ~= 0 then
        print("Nmap scan for " .. ip_v4_address .. " failed with exit code: " .. exit_code)
        goto continue
    end

    -- Write XML output to file
    local output_file, file_err = io.open(ip_v4_address .. ".xml", "w")
    if output_file then
        output_file:write(nmap_output)
        output_file:close()
        print("Nmap scan for " .. ip_v4_address .. " completed, result saved to " .. ip_v4_address .. ".xml")
    else
        print("Error writing file for " .. ip_v4_address .. ": " .. file_err)
    end

    ::continue::
end

额外说明 #

• 如果确实需要在Lua中解析Nmap的XML输出，可以使用Lua的XML库（比如luaexpat），但对于你的需求来说直接保存原始XML更高效。
• 确保运行脚本的用户有执行Nmap的权限，以及读写目标文件的权限。

内容的提问来源于stack exchange，提问作者Kris Armstrong