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BitLogger/docs/api/configured-logger-file-path.md
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Nanaloveyuki 3bac025acf πŸ“ Fix policy test and doc
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---
name: configured-logger-file-path
group: api
category: runtime
update-time: 20260707
description: Read the effective file path used by the configured runtime logger, with a compatibility fallback for non-file sinks.
key-word:
- logger
- runtime
- file
- public
---
## Configured-logger-file-path
Read the effective file path used by a `ConfiguredLogger`. This helper is useful for diagnostics, support output, and confirming which file-backed runtime sink is active.
`file_path()` is the compatibility form. For truthful file-semantics detection, prefer `file_path_or_none()`.
### Interface
```moonbit
pub fn ConfiguredLogger::file_path(self : ConfiguredLogger) -> String {}
```
#### input
- `self : ConfiguredLogger` - Config-driven runtime logger whose file path should be inspected.
#### output
- `String` - Effective runtime file path, or an empty string for non-file sinks.
### Explanation
Detailed rules explaining key parameters and behaviors
- File-backed sinks return their current file path through the wrapped `RuntimeSink`.
- Queued file sinks forward the wrapped inner file sink path.
- Non-file sinks return an empty string.
- This fallback keeps older callers source-compatible, but it does not truthfully express whether file semantics exist.
- New diagnostic code should prefer `file_path_or_none()`.
- This helper is observation-only and does not modify file state.
### How to Use
Here are some specific examples provided.
#### When Need Runtime Path Diagnostics
When diagnostics should show which file is active:
```moonbit
println(logger.file_path())
```
In this example, operators can verify the effective destination path directly.
#### When Build Support Output
When application state dumps should include file destination info:
```moonbit
let path = logger.file_path()
```
In this example, the path can be surfaced without reading broader runtime state.
### Error Case
e.g.:
- If the configured sink is not file-backed, the method returns an empty string.
- If callers need a truthful file-semantics check, use `file_path_or_none()`.
- If callers need richer file status than just the path, `file_state_or_none()` or `file_runtime_state()` is the better API.
### Notes
1. Use this helper for direct runtime path visibility.
2. Empty string is a compatibility fallback; `file_path_or_none()` is the recommended truthful API.