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BitLogger/docs/api/runtime-sink-file-flush.md
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2026-06-13 23:11:39 +08:00

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---
name: runtime-sink-file-flush
group: api
category: runtime
update-time: 20260613
description: Flush the file sink behind a RuntimeSink when one is present.
key-word:
- runtime
- sink
- file
- public
---
## Runtime-sink-file-flush
Flush the file sink behind a `RuntimeSink`. This helper is the direct file-specific runtime flush surface for code that owns a sink value instead of a `ConfiguredLogger`.
### Interface
```moonbit
pub fn RuntimeSink::file_flush(self : RuntimeSink) -> Bool {
```
#### input
- `self : RuntimeSink` - Runtime sink whose file sink should be flushed.
#### output
- `Bool` - Whether the underlying file flush succeeded.
### Explanation
Detailed rules explaining key parameters and behaviors
- Plain `File` runtime variants forward directly to `FileSink::flush()`.
- `QueuedFile` runtime variants first attempt `sink.flush()` on the queue wrapper, then call `sink.sink.flush()` on the wrapped file sink.
- For `QueuedFile`, the queue flush result is ignored and the returned `Bool` comes from the inner file flush.
- Non-file runtime variants return `false`.
### How to Use
Here are some specific examples provided.
#### When Need Explicit Direct File Durability Steps
When code holds a file-backed `RuntimeSink` directly and should flush it explicitly:
```moonbit
ignore(sink.file_flush())
```
In this example, the runtime sink attempts to flush its file-backed output directly.
#### When Need A File-specific Success Flag
When code should branch on the outcome of a direct file flush:
```moonbit
let ok = sink.file_flush()
```
In this example, callers can distinguish file flush success from a non-file sink shape.
### Error Case
e.g.:
- If the runtime sink is not file-backed, the method returns `false`.
- If callers want generic queue or sink advancement instead of file-specific behavior, `flush()` is the broader API.
### Notes
1. Prefer this helper when direct runtime code specifically cares about file flush behavior.
2. Queued file sinks may perform both queue flush work and file flush work here.