o/COPY

o/COPY copies a directory tree to one or more destinations at once.

• Hashing. Each file gets an xxh64 checksum during the copy (the value recorded in MHL output). Verification is on by default: o/COPY re-reads the source and destinations and confirms all xxh64 values match. Disable that with --dont-verify or verify=False.

• ASC MHL (default on). Each destination gets an ASC Media Hash List (ASC MHL) history: the ascmhl folder, chain file, and XML generation manifests that document checksums together with file metadata, following the layout defined in the spec and read/written by the mhllib / ascmhl reference implementation. o/COPY supplies the xxh64 from the copy step so sealing does not hash file contents again. For flat *.mhl files in the original Media Hash List format instead, use --legacy-mhl or legacy_mhl=True. --no-mhl / mhl=False skips writing MHL output.

• Skip-existing (default on). A destination file is fast-skipped only when its size and modification time match the source (within a small tolerance) and o/COPY already trusts an xxh64 for that path. Trusted digests are resolved in this order: .ocopy-checkpoint, an ASC MHL history in an ascmhl folder, then a legacy flat *.mhl. If metadata matches but no trusted hash exists while integrity is required, o/COPY re-reads and verifies so ASC MHL records are never written empty. A destination that exists but disagrees raises unless --overwrite / overwrite=True.

• Integrity off. If both --no-mhl and --dont-verify are set (or mhl=False and verify=False in code), only size/mtime are used for skip-existing; hashes are not checked.

• Resume. While a run is in progress, each destination tree keeps a .ocopy-checkpoint sidecar. When the run finishes without error, those files are removed (including when MHL output is disabled). If you interrupt the CLI, it exits with code 3, leaves checkpoints in place, and does not append a new ASC MHL generation or other MHL output. Run ocopy again to continue and finish.

Installation / Update

Recommended: uv

uv is an extremely fast Python package and project manager, written in Rust. If you do not have it yet: with Homebrew, run brew install uv; for the official standalone installer and everything else, see Installing uv.

uv tool install ocopy

Update an existing install:

uv tool upgrade ocopy

With pipx

If you prefer the pip ecosystem, pipx does the same job as uv tool install: it puts each CLI app in its own environment and exposes the ocopy command on your PATH.

pipx install ocopy

pipx upgrade ocopy

Usage

CLI

After install the command is ocopy. Pass a source directory and one or more destination directories (each path must already exist and be a writable folder):

ocopy /path/to/source /path/to/dest1 /path/to/dest2

Run ocopy --help for the full flag list. The introduction above describes skip-existing, verification, ASC MHL histories vs. legacy flat MHL, and checkpoints.

During a long run the CLI tries to keep the system from going to idle sleep; that is best-effort and may not work in headless setups, and o/COPY will warn and continue copying.

Python

import tempfile
from pathlib import Path
from time import sleep

from ocopy.verified_copy import CopyJob


def simple_example():
    # For the sake of this example we will create temporary directory.
    # You will not be doing this in your code.
    with tempfile.TemporaryDirectory() as tmp:
        tmp = Path(tmp)

        # Define source and destination directories
        source = tmp / "source"
        destinations = [tmp / "destination_1", tmp / "destination_2", tmp / "destination_3"]

        # Create some test content
        source.mkdir(parents=True, exist_ok=True)
        (source / "testfile").write_text("Some test content")

        # ``CopyJob`` starts work as soon as it is constructed.
        job = CopyJob(source, destinations, overwrite=True, verify=True)
        while job.finished is not True:
            sleep(0.1)

        # Print errors
        for error in job.errors:
            print(f"Failed to copy {error.source.name}:\n{error.error_message}")

        # Show the start of the latest ASC MHL generation (XML hash list)
        gen = next((destinations[0] / source.name / "ascmhl").glob("*.mhl"))
        print(gen.read_text()[:800])


if __name__ == "__main__":
    simple_example()

Development

This project uses uv for dependency management, Ruff for linting and formatting, and ty for type checking.

# Create the virtual environment and install runtime + dev dependencies
uv sync

# Run tests
uv run pytest

# Lint, format, and type check
uv run ruff check .
uv run ruff format .
uv run ty check