# warn() [Logging](https://rustic-game-engine.pages.dev/markdown/api/logging.md) ## Compatibility **Supported languages:** Lua 5.4, Luau, JavaScript and HTML/inline JavaScript; other languages use rustic.print/rustic.warn. Use a compatible native engine build and the language tools required by your binding. This does not establish browser/mobile export or release qualification for every OS. The signature below is the shared reference notation; language examples show the actual binding syntax. Question marks mark optional arguments and explicit defaults are shown where recorded. Do not copy reference notation as a typed declaration. See [Feature status and compatibility](https://rustic-game-engine.pages.dev/markdown/reference/compatibility.md) for API 1.0/1.1 and per-method restrictions. Engine release tags and Docs v0.1 are independent versions. ## Signature `warn(...)` ## Setup and usage Log lifecycle transitions and recoverable errors. Avoid per-frame logging outside short debugging sessions because bounded queues can drop excessive output. ## Parameters | Variable | Type | Required | Description | | --- | --- | --- | --- | | `level` | string | Yes | debug, info, warn, or error. | | `message` | string | Yes | Human-readable diagnostic text. | ## Return and timing No value. The message is queued for the bounded console sink. ## Execution behavior Core write timing differs between immediate Lua host calls, deferred JavaScript/Web commands and external SDK query flushes. Scheduled actions advance with the scene clock; synchronous queries evaluate at the call. Follow [execution rules](https://rustic-game-engine.pages.dev/markdown/guides/scripting.md#when-mutations-take-effect) and the return/timing notes for this category. ## Language examples Use these snippets inside Start/on_start after generating the Programming Workspace and attaching the script. Python imports rustic, Game and instance from rustic; C++ includes rustic.hpp; C includes rustic.h; C# uses using static Rustic; Java runs inside a Rustic subclass; PHP declares global $rustic, $Game, $instance in its callback. HTML uses an inline script in a ui/ asset. See [Lifecycle callbacks](https://rustic-game-engine.pages.dev/markdown/callbacks.md) for complete registration examples. Public-property examples require a declared integer health property. Scene examples require the named objects to exist before Play. ### Lua 5.4 ```lua rustic.log('info', 'player spawned') print("spawned") warn("low health") ``` ### JavaScript ```javascript rustic.log('info', 'player spawned'); print("spawned"); warn("low health"); ``` ### Python ```python rustic.log('info', 'player spawned') rustic.print("spawned") rustic.warn("low health") ``` ### C++ ```cpp rustic.log("info", "player spawned"); rustic.print("spawned"); rustic.warn("low health"); ``` ### C# ```csharp rustic.log("info", "player spawned"); rustic.print("spawned"); rustic.warn("low health"); ``` ### Luau ```lua rustic.log('info', 'player spawned') print("spawned") warn("low health") ``` ### C ```c rustic.log("info", "player spawned"); rustic.print("spawned"); rustic.warn("low health"); ``` ### Java ```java rustic.log("info", "player spawned"); rustic.print("spawned"); rustic.warn("low health"); ``` ### PHP ```php $rustic->log('info', 'player spawned'); $rustic->print("spawned"); $rustic->warn("low health"); ``` ### HTML / inline JS ```javascript rustic.log('info', 'player spawned'); print("spawned"); warn("low health"); ``` ## Shared Logging constraints - In Lua and JavaScript, print(...) writes an info entry and warn(...) writes a warning entry to the Rustic Console. Lua separates multiple arguments with tabs; JavaScript separates them with spaces. Use rustic.log for an explicit level. External programs must not print diagnostics to stdout; stdout is reserved for protocol responses. - Every gameplay language calls the engine-owned API. Rustic supplies SDKs and dispatches callbacks; scripts do not parse requests or serialize responses. See the language guide for complete setup and callback registration. ## Errors and debugging Read the constraints above and the Console diagnostic. Invalid types, non-finite values, stale targets or unavailable native services can fail validation. A failed callback disables the behavior; a failed source reload keeps the last good instance. Exact error messages depend on the language adapter. See [Troubleshooting](https://rustic-game-engine.pages.dev/markdown/troubleshooting.md). ## Related APIs - [rustic.log()](https://rustic-game-engine.pages.dev/markdown/api/logging/log.md) - [print()](https://rustic-game-engine.pages.dev/markdown/api/logging/print.md) [All logging APIs](https://rustic-game-engine.pages.dev/markdown/api/logging.md)