ruvnet/RuView · error

cannot write {output}: {e}

Error message

cannot write {output}: {e}

What it means

std::fs::write failed while persisting the serialized BaselineCalibration (to_bytes output) to the --output path in finalise_and_save. The underlying io::Error is OS-level: missing parent directory, permission denied, disk full, or the path naming an existing directory. The calibration itself succeeded; only persistence failed, and finalize() consumed the recorder, so the frames are lost unless re-captured.

Source

Thrown at v2/crates/wifi-densepose-cli/src/calibrate.rs:218

        frames, target, score.amplitude_z_median, score.amplitude_z_max, motion_str
    );
}

// ---------------------------------------------------------------------------
// Finalise + persist
// ---------------------------------------------------------------------------

fn finalise_and_save(recorder: CalibrationRecorder, output: &str) -> Result<()> {
    let frames = recorder.frames_recorded();
    eprintln!("[calibrate] finalising baseline from {frames} frames…");

    let baseline: BaselineCalibration = recorder
        .finalize()
        .map_err(|e| anyhow::anyhow!("calibration failed: {e}"))?;

    let bytes = baseline.to_bytes();
    std::fs::write(output, &bytes)
        .map_err(|e| anyhow::anyhow!("cannot write {output}: {e}"))?;

    eprintln!(
        "[calibrate] baseline saved to {output} ({} bytes)",
        bytes.len()
    );
    eprintln!(
        "[calibrate] summary: frames={} tier={:?} subcarriers={}",
        baseline.frame_count,
        baseline.tier,
        baseline.subcarriers.len(),
    );
    Ok(())
}

// ---------------------------------------------------------------------------
// Tier helper
// ---------------------------------------------------------------------------

View on GitHub (pinned to 4685618388)

Solutions

1. Create the parent directory of --output (mkdir -p) and re-run the calibration — the recorder was consumed, so frames must be re-captured
2. Check ownership and permissions on the target directory (ls -ld, chown/chmod as needed)
3. Point --output to a filesystem with free space
4. Ensure --output is a file path, not an existing directory

Example fix

// before
let bytes = baseline.to_bytes();
std::fs::write(output, &bytes)
    .map_err(|e| anyhow::anyhow!("cannot write {output}: {e}"))?;

// after
if let Some(parent) = std::path::Path::new(output).parent() {
    std::fs::create_dir_all(parent)
        .map_err(|e| anyhow::anyhow!("cannot create {}: {e}", parent.display()))?;
}
let bytes = baseline.to_bytes();
std::fs::write(output, &bytes)
    .map_err(|e| anyhow::anyhow!("cannot write {output}: {e}"))?;

fn output_writable(path: &str) -> bool {
    let p = std::path::Path::new(path);
    p.parent().map(|d| d.is_dir()).unwrap_or(true)
        && std::fs::OpenOptions::new().write(true).create(true).truncate(false).open(p).is_ok()
}

match std::fs::write(output, &bytes) {
    Ok(()) => {}
    Err(e) if e.kind() == std::io::ErrorKind::NotFound => {
        eprintln!("parent directory missing for {output} — mkdir -p it");
    }
    Err(e) => return Err(anyhow::anyhow!("cannot write {output}: {e}")),
}

When it happens

Trigger: --output points into a directory that does not exist; the target directory is read-only or owned by another user; disk fills after a long capture; --output names an existing directory.

Common situations: Writing to an artifacts/ path never created in a fresh checkout; running the CLI as a different user than the directory owner; small tmpfs in containers; typos in the output path.

Related errors

• cannot create output dir {}: {e}
• cannot read baseline {path}: {e} — run `calibrate` first
• cannot write {}: {e}
• cannot read {path}: {e}
• data_dir not accessible {}: {e}

AI-assisted analysis of ruvnet/RuView@4685618388 (2026-08-16). Data as JSON: /api/errors/942d38d3668cc8bf. Report an issue: GitHub.