Acquire / archive · All operations

List the files in an archive

A variant of Unpack an archive

Read an archive as an index, one row per member with its name, size and date, without extracting it.

Status

In arcform

Not built yet

arcform does not do this yet. Its place on the roadmap

What other tools call it

Meridian's classification; an independent blind rating agreed on 95.7% of 324 rows (variant, version 3).

VisiData (2)
  • tar (loader)read 2026-09-23

    Load tar archive as an index of its files; also filetype tbz2, tgz, txz

  • zip (loader)read 2026-09-23

    Load zip archive as an index of its files; also filetype whl

Background

A ZIP file's central directory lets a reader list the files in the archive relatively quickly, without reading the entire archive.[1] A tar archive keeps each file's metadata, such as name, size and timestamps, in a header before the file, so the archive must be read in sequence to list it.[2] DuckDB's zipfs extension adds an archive_contents table function that returns a table of the files in an archive.[3]

When to use it

Listing a tar archive with tar tf displays the names of all its files without extracting any, so problematic files can be found and left out before extraction.[2] Python's ZipFile.extractall takes an optional members argument, which must be a subset of the list ZipFile.namelist returns.[4] List an archive before unpacking it, and extract only the members a later step needs. (Meridian's view)

In Python's zipfile module, each member's ZipInfo records compress_size, the size of the compressed data, and file_size, the size of the uncompressed file.[4]

Because ZIP files may be appended to, only the files named in the central directory at the end of a ZIP file are valid.[1] The order of the file entries in a ZIP file's central directory need not match the order of the entries in the archive.[1] Python's ZipInfo.date_time returns the timestamp from the ZIP central directory, a format that cannot represent dates before 1980 and is read as local time rather than Coordinated Universal Time (UTC).[4] Treat the dates in a ZIP listing as the creator's local clock, and sort by name rather than trust the listing's order. (Meridian's view)

The method

A ZIP file is identified by an end of central directory record at the end of the archive, and each central directory entry gives a file's name, other metadata and an offset to its data.[1] The archive_contents function of DuckDB's zipfs extension can return columns such as file_name, file_size, is_directory and is_encrypted.[3]

The tar format was designed without a centralised index or table of contents, because it was meant for streaming to tape backup devices.[2] With a well-formed tar file on a seekable medium, the tar program can find a file relatively quickly by skipping file data according to the size field in each header.[2] When a tar file is compressed whole, the compression format is usually not seekable, which prevents tar from skipping through it that way.[2] Python's TarFile.getmembers returns the members of a tar archive as TarInfo objects, in the same order as the members in the archive.[5]

Sources

  1. [1]ZIP (file format) - Wikipediasecondary source
  2. [2]tar (computing) - Wikipediasecondary source
  3. [3]zipfs – DuckDB Community Extensionsdocumentation
  4. [4]zipfile — Work with ZIP archives — Python 3.15.2 documentationdocumentation
  5. [5]tarfile — Read and write tar archive files — Python 3.15.2 documentationdocumentation