Lua:
Writing to standard error

How to:

In Lua, writing to stderr can be achieved using the io.stderr:write() function. Here’s how you can write a simple error message to standard error:

io.stderr:write("Error: Invalid input.\n")

Should you need to output a variable or combine multiple pieces of data, concatenate them within the write function:

local errorMessage = "Invalid input."
io.stderr:write("Error: " .. errorMessage .. "\n")

Sample Output on stderr:

Error: Invalid input.

For more complex scenarios, or when working with larger applications, you might consider third-party logging libraries such as LuaLogging. With LuaLogging, you can direct logs to different destinations, including stderr. Here’s a brief example:

First, ensure LuaLogging is installed using LuaRocks:

luarocks install lualogging

Then, to write an error message to stderr using LuaLogging:

local logging = require("logging")
local logger = logging.stderr()
logger:error("Error: Invalid input.")

This approach offers the advantage of standardized logging across your application, with the added flexibility of setting log levels (e.g., ERROR, WARN, INFO) through a simple API.