Getting-Started-with-Lua-on-Ubuntu

Posted on Edited on Disqus:

最近工作上需要在 Redis 上面寫 Script，Redis 從 2.6.0 版之後包了 Lua interpreter 進去開始支援用 Lua 語言寫 Script， 所以花一些時間去熟悉久仰的 Lua 語言。

筆記一下在 Ubuntu 18.04 上手 Lua 的過程。

Install

Ubuntu 18.04 可以安裝到最新的 Lua 版本是 Lua 5.3

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~$ sudo apt install lua5.3
~$ lua5.3
Lua 5.3.3  Copyright (C) 1994-2016 Lua.org, PUC-Rio
>

不過要注意的是 Redis 中的 EVAL 版本是 5.1[1]

Building from the source

~$ sudo apt install libreadline-dev
~$ git clone https://github.com/lua/lua
~$ cd ./lua
~$ make all
~$ mv ./lua ./lua /usr/local/bin
~$ lua
Lua 5.4.0 Copyright (C) 1994-2019 Lua.org, PUC-Rio

Example: Hello, world!

Interactive Mode

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~$ lua
lua
Lua 5.4.0  Copyright (C) 1994-2019 Lua.org, PUC-Rio
> print("Hello, world!")
Hello, world!
>

helloworld.lua

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~$ vim helloworld.lua
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function helloWorld(name)
	assert(type(name) == "string", "name expects a string")
	return string.format("Hello, %s!", name)
end

print(helloWorld("world"))
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~$ lua helloworld.lua
Hello, world!

Unit Test

要在 Lua 寫 Unit Test 的話，根據 Unit Testing - lua-users wiki 的範例是使用 bluebird75/luaunit。

安裝 luaunit module 以 Lua 5.4 為例

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~$ lua -v | awk '{print $2}'
5.4.0
~$ sudo mkdir -p /usr/local/share/lua/5.4/luaunit/
~$ sudo curl -o /usr/local/share/lua/5.4/luaunit/init.lua https://raw.githubusercontent.com/bluebird75/luaunit/master/luaunit.lua

安裝 luaunit module 以 5.3 為例

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lua5.3 -v | awk '{print $2}'
5.3.3
~$ sudo mkdir -p /usr/share/lua/5.3
~$ sudo curl -o /usr/share/lua/5.3/luaunit.lua https://raw.githubusercontent.com/bluebird75/luaunit/master/luaunit.lua

Example: helloWorld module

helloworld.lua

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module = {}

function module.helloWorld(name)
	assert(type(name) == "string", "name expects a string")
	return string.format("Hello, %s!", name)
end

return module

test_helloworld.lua

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luaUnit = require("luaunit")
testModule = require("helloworld")

function testHelloWorld()
        local ret = testModule.helloWorld("world")
        luaUnit.assertEquals(type(ret), "string")
        luaUnit.assertEquals(ret, "Hello, world!")

        ret = testModule.helloWorld("ming")
        luaUnit.assertEquals(type(ret), "string")
        luaUnit.assertEquals(ret, "Hello, ming!")

        ret = testModule.helloWorld(integer)
        luaUnit.assertEquals(type(ret), "string")
        luaUnit.assertEquals(ret, "Hello, ming!")
end

os.exit(luaUnit.LuaUnit.run())

Run LuaUnit

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~$ lua test_helloworld.lua -v
Started on Mon Jul  8 15:06:09 2019
    testHelloWorld ... Ok
=========================================================
Ran 1 tests in 0.000 seconds, 1 success, 0 failures
OK

Error Handling

helloworld.lua

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module = {}

local function helloWorld(name)
	-- assert(type(name) == "string", {message="name expects a string"})
	if type(name) ~= "string" then
		error({message="name expects a string"})
	end

	return string.format("Hello, %s!", name)
end

function module.HelloWorld(name)
	-- Error Handling
	-- Reference: https://blog.golang.org/error-handling-and-go
	local success, result = pcall(helloWorld, name)
	if not success then
		return "", result.message
	end

	return result, nil
end

return module

test_helloworld.lua

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luaUnit = require("luaunit")
testModule = require("helloworld")

function testHelloWorld()
	local ret, err = testModule.HelloWorld("world")
	luaUnit.assertNil(err)
	luaUnit.assertEquals(type(ret), "string")
	luaUnit.assertEquals(ret, "Hello, world!")

	ret, err = testModule.HelloWorld("ming")
	luaUnit.assertNil(err)
	luaUnit.assertEquals(type(ret), "string")
	luaUnit.assertEquals(ret, "Hello, ming!")
end

function testHelloWorldWrongCase()
	local ret, err = testModule.HelloWorld(123)
	luaUnit.assertNotNil(err)
	luaUnit.assertEquals(ret, "")
	luaUnit.assertEquals(err, "name expects a string")
end

os.exit(luaUnit.LuaUnit.run())
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~$ lua test_helloworld.lua -v
Started on Mon Jul  8 15:42:30 2019
    testHelloWorld ... Ok
    testHelloWorldWrongCase ... Ok
=========================================================
Ran 2 tests in 0.000 seconds, 2 successes, 0 failures
OK

Remark

  1. “EVAL is a Lua 5.1 script.” - redis.io

Reference & Resource

  • Programming in Lua
  • lua-users wiki
  • Lua Tutorial - tutorialspoint
  • Learn Lua in 15 Minutes
    Lua on Ubuntu18.04 | Ming’s blog