multica-ai/multica · error

write file: %w

Error message

write file: %w

What it means

Final write of the downloaded bytes with os.WriteFile to destPath = filepath.Join(outputDir, filename). Wraps OS write errors: permission denied, destination is a directory, disk full, or name too long.

Source

Thrown at server/cmd/multica/cmd_attachment.go:172

	// Download the file content.
	data, err := client.DownloadFile(ctx, downloadURL)
	if err != nil {
		return fmt.Errorf("download file: %w", err)
	}

	// Write to the output directory, creating it if needed so `-o` works
	// against a directory that does not exist yet (the help example's
	// `-o ./attachments` in a clean workdir).
	outputDir, _ := cmd.Flags().GetString("output-dir")
	if outputDir != "" {
		if err := os.MkdirAll(outputDir, 0o755); err != nil {
			return fmt.Errorf("create output directory: %w", err)
		}
	}
	destPath := filepath.Join(outputDir, filename)

	if err := os.WriteFile(destPath, data, 0o644); err != nil {
		return fmt.Errorf("write file: %w", err)
	}

	// Print the absolute path so agents can reference the file.
	abs, err := filepath.Abs(destPath)
	if err != nil {
		abs = destPath
	}
	fmt.Fprintln(os.Stderr, "Downloaded:", abs)

	// Also print as JSON for --output json compatibility.
	return cli.PrintJSON(os.Stdout, map[string]any{
		"id":       strVal(att, "id"),
		"filename": filename,
		"path":     abs,
		"size":     strVal(att, "size_bytes"),
	})
}

View on GitHub (pinned to 2c0912b6ec)

Solutions

1. Check `df -h <dir>` for space and `ls -l` the destination for a directory/filename collision; rename or remove the conflict
2. Ensure the output directory is writable by the current user
3. Download to a different output dir (-o /tmp/att) to isolate a bad destination
4. If filename looks pathological, rename after download

# check for directory/filename collision and writability before download
[ ! -d "./attachments/$expected_name" ] || { echo 'name collides with a directory' >&2; exit 1; }
[ -w ./attachments ] || { echo 'output dir not writable' >&2; exit 1; }

When it happens

Trigger: The server-supplied filename collides with an existing directory name in the output dir; output dir not writable; disk full; filename from metadata containing path separators or being extremely long (filesystem limit).

Common situations: Attachments named like `data` colliding with an existing `data/` directory; running as non-root into /mnt dirs; full disks on small VMs/containers; unusual unicode filenames from other OSes hitting filesystem limits.

Related errors

• create output directory: %w
• read file %s: %w
• get attachment: %w
• attachment has no download URL
• download file: %w

AI-assisted analysis of multica-ai/multica@2c0912b6ec (2026-08-15). Data as JSON: /api/errors/44b395873579daee. Report an issue: GitHub.