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BitLogger/docs/api/configured-logger-file-policy.md
2026-05-12 14:58:22 +08:00

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---
name: configured-logger-file-policy
group: api
category: runtime
update-time: 20260512
description: Read the current runtime file policy from a configured file-backed logger.
key-word:
- logger
- runtime
- file
- public
---
## Configured-logger-file-policy
Read the current runtime file policy from a `ConfiguredLogger`. This helper exposes the active append, auto-flush, and rotation settings as one policy object.
### Interface
```moonbit
pub fn ConfiguredLogger::file_policy(self : ConfiguredLogger) -> FileSinkPolicy {}
```
#### input
- `self : ConfiguredLogger` - Config-driven runtime logger whose current file policy should be inspected.
#### output
- `FileSinkPolicy` - Current runtime file policy.
### Explanation
Detailed rules explaining key parameters and behaviors
- File-backed sinks return their current runtime file policy.
- Queued file sinks forward the policy from the wrapped file sink.
- Non-file sinks return a neutral fallback policy value.
- This helper is broader than `file_append_mode()` or `file_auto_flush()` because it returns the whole policy object.
### How to Use
Here are some specific examples provided.
#### When Need Full Runtime Policy Visibility
When diagnostics should inspect the active file policy as one object:
```moonbit
let policy = logger.file_policy()
```
In this example, append, flush, and rotation settings are read together.
#### When Compare Current And Default Policy
When runtime drift from defaults should be inspected explicitly:
```moonbit
let current = logger.file_policy()
let defaults = logger.file_default_policy()
```
In this example, callers can compare current runtime settings with the initial policy snapshot.
### Error Case
e.g.:
- If the configured sink is not file-backed, the return value is a neutral fallback policy rather than a real active file policy.
- If callers only need one field from the policy, a narrower helper may be simpler.
### Notes
1. Use this helper when file policy should be handled as one object.
2. Pair it with `file_set_policy(...)` for roundtrip-style policy management.