Running the example above yields the following: You can easily use them to store messages in a log-like manner and return the resulting array once your code finishes running. Lua’s tables are associative arrays and are the only “container” data structures of the language. Don’t despair, however, because there’s more than one way to skin a cat (meeeeeow!?!). when you don’t have access to the Redis host or when the log is too noisy to work with comfortably). by tailing the log file).Ĭons: There are cases in which this approach isn’t a viable option (e.g. In addition, you can view the logged message in near real-time (i.e. Pros: Using the log file is often the easiest way to trace your workflow. For more information, see EVAL‘s documentation. The redis.log function accepts two arguments: the first one is the message’s log level (choose being between LOG_DEBUG, LOG_VERBOSE, LOG_NOTICE and LOG_WARNING), and the second argument is the to-be-logged value. This function, conveniently named redis.log, is dead simple to use – just call it from your script like so: Redis’ embedded Lua engine provides a function that prints to its log file (configured with the loglevel and logfile directives in your nf). To make this somewhat easier (and perhaps save your wall from a few bangs), here are five ways you can gain Superman-like X-Ray vision into your Lua script. That’s because your code runs within the server itself, making it much harder to gain visibility into the code’s innards. When developing Lua scripts for Redis (a feature that’s available from version 2.6 onwards) this can become even trickier. It requires patience, effort and in many cases a touch of inspiration to correctly identify the root cause of a failure. Tracking down these issues isn’t an easy task. Even if you are a good programmer who writes good code (or a great programmer who steals it), use proven methodologies and design patterns, employ only best-of-breed tools, and submit to peers’ code reviews… despite your best efforts, you’re likely to find yourself time and time again banging your head against the wall because of an elusive gremlin. Software defects are a fact of life because software is made by fleshware, and humans err. “In this world nothing is certain, except death, taxes … and BUGS.” If you’ve ever written even a single line of code, you know that Benjamin Franklin’s famous quote should be amended to: Update 1: I’ve followed up on the topic with a vastly superior debugging method so check out part 2 – redis-lua-debugger and its accompanying post <- mini-update: rld is no longer maintained as it isn’t compatible with v3+. Mother of all Updates: Redis v3.2 features its very own Lua debugger. I don't have zlib or a base64 C library handy, so for example's sake lets say we wanted to let our Lua script use the MessageBox function from the user32.dll library in Windows.Or: To Err is Human, To Fix Debug. Writing a Lua module is actually super easy, and you can tailor the interface to be more idiomatic for Lua. If you had a Lua interpreter with a built-in FFI, or you found a FFI Lua module you could load, you could probably get this to work, but it's really more trouble than it's worth. Your zlib and/or base64 libraries know nothing about Lua. ![]() Lua can load the library and call that function, and it's up to that function to actually expose functionality to Lua using the Lua API. How do I actually create or call an existing c library in Lua?Īn arbitrary library, not written for use by Lua? You generally can't.Ī Lua consumable "module" must be linked against the Lua API - the same version as the host interpreter, such as Lua5.1.dll in the root of the Wireshark directory - and expose a C-callable function matching the lua_CFunction signature. ".\\?.dll " LUA_CDIR"?.dll " LUA_CDIR"loadall.dll" ** path of the directory of the executable file of the current process. ** In Windows, any exclamation mark ('!') in the path is replaced by the The module would be searched in places defined in Your Lua interpreter's luaconf.h file. NOTE: Lua module package managers like LuaRocks orĪlso, simply loading a Lua module usually consists of one line: local zlib = require("zlib") Only difference, there are already plain-Lua libraries for that. The same applies to base64 encoding/decoding. Writing Your own Lua zlib library wrapper, following those standards.There are two ways You could solve Your problem: *.so/*.dll must follow some specific standard, which is bluntly mentioned in programming in Lua#26.2 and lua-users wiki, code sample. You can't load any existing C library, which was not created for Lua, with plain Lua.
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