AR File Handling for Python

Common errors

• ModuleNotFoundError: No module named 'unix_ar'

  cause The package is installed via `pip install unix-ar`, but the top-level module to import is `unix_ar`, not `ar`.
  fix Ensure you are importing `unix_ar`. Correct: `import unix_ar` or `from unix_ar import Archive`.

• unix_ar.ARFormatError: Unknown AR format

  cause The AR archive file you are trying to read is not in the supported BSD variant format. This library has limited support for different AR formats.
  fix Confirm the format of your AR file. If it's not BSD-compatible, this library may not be able to process it. You might need to use a different tool or library, or convert the archive to a supported format.

• FileNotFoundError: [Errno 2] No such file or directory: 'some_file.ar'

  cause The specified archive file path for `unix_ar.open()` in read mode ('r') does not exist, or the path for a file being added in write mode ('w') is incorrect.
  fix Double-check the file paths. Ensure the archive exists for reading, or that the source files exist when creating/adding to an archive.

Warnings

• deprecated The library has not been updated since June 2019 and is marked as 'Development Status :: 4 - Beta' on PyPI. There may be a lack of active maintenance and support for newer Python versions or bug fixes.
  Fix: Evaluate if the current feature set meets your needs. For critical projects, consider alternatives or be prepared to maintain a fork.
• gotcha The library primarily supports the BSD variant of the AR archive format. Other variants (e.g., AIX, GNU ar, System V) may not be compatible, leading to errors or corrupted archives when reading/writing.
  Fix: Verify the AR archive format you are working with. If you need to handle non-BSD variants, this library may not be suitable. The `ar` command line tool itself has several variants for specific platforms.
• gotcha When interacting with AR files created by the `ar` command-line tool, especially with the GNU `ar`'s default 'deterministic mode' (`-D`), metadata like UIDs, GIDs, and modification times might be set to zero. This library may preserve or re-create full metadata, which could lead to inconsistencies if you expect 'deterministic' output.
  Fix: Be aware of the `ar -D` flag's implications if you're mixing Python `unix-ar` operations with external `ar` command usage. If precise metadata is crucial, explicitly check and handle it.

Install

• pip install unix-ar Install latest version

Imports

• Archive
  wrong:

  import ar

  correct:

  from unix_ar import Archive

  The PyPI package name is 'unix-ar', but the primary module is 'unix_ar'.
• open

  import unix_ar; unix_ar.open(...)

  The `open` function is a convenient entry point, similar to `zipfile.open` or `tarfile.open`.

Quickstart

This quickstart demonstrates how to create a new AR archive, add files to it, and then read its contents and extract specific members using `unix_ar.open()` and `Archive` methods.

import unix_ar
import os

# Create some dummy files
with open("file1.txt", "w") as f:
    f.write("This is file 1.")
with open("file2.txt", "w") as f:
    f.write("This is file 2.")

# Create an AR archive
with unix_ar.open("my_archive.ar", "w") as ar_file:
    ar_file.add("file1.txt")
    ar_file.add("file2.txt", arcname="renamed_file2.txt")

print("Archive 'my_archive.ar' created with file1.txt and renamed_file2.txt.")

# Read from the archive
with unix_ar.open("my_archive.ar", "r") as ar_file:
    print("\nMembers in the archive:")
    for member in ar_file.getmembers():
        print(f"  - Member name: {member.name}, size: {member.size} bytes")
        if member.name == "renamed_file2.txt":
            extracted_data = ar_file.extractfile(member).read().decode('utf-8')
            print(f"    Content of {member.name}: '{extracted_data}'")

# Clean up dummy files and archive
os.remove("file1.txt")
os.remove("file2.txt")
os.remove("my_archive.ar")
print("\nCleaned up dummy files and archive.")