ptardiff

tar [OPTIONS] --diff [ARCHIVE_OR_FILES...]
tar [OPTIONS] -d [ARCHIVE_OR_FILES...]

Note: When comparing an archive to the filesystem, the archive path is usually specified with -f.

--diff, -d
    Compare archive members to corresponding files on disk.

-f ARCHIVE, --file=ARCHIVE
    Specify the archive file to operate on. Essential when comparing an archive.

-v, --verbose
    List files processed. When used with --diff, it shows details of differences found.

-N DATE, --newer=DATE, --after-date=DATE
    Only consider files newer than DATE for comparison.

--exclude=PATTERN
    Exclude files or directories matching PATTERN from the comparison.

--ignore-failed-read
    Do not exit with a non-zero status if a file cannot be read during the comparison.

--no-recursion
    Do not recurse into directories when comparing. By default, --diff is recursive for directories.

The command ptardiff is not a standard or widely recognized utility in common Linux distributions. It is highly probable that this refers to the `tar --diff` (or `-d`) functionality, which compares the contents of a `tar` archive with files on the filesystem. This analysis proceeds assuming the user intended to inquire about `tar`'s archive comparison capabilities.

`tar --diff` is a powerful feature of the `tar` utility used to compare the contents of a `tar` archive with files on the filesystem, or implicitly to compare two archives by comparing extracted contents. It reports discrepancies in file size, modification times, permissions, and file content. This function is essential for verifying archive integrity, checking for unauthorized modifications, or confirming successful backups. It can show which files are missing from the archive, which have changed, and which are new.

As ptardiff is not a standard command, this analysis focuses on `tar --diff`.

`tar --diff` primarily compares an archive against the live filesystem. Directly comparing two separate `tar` archives requires extracting one or both, and then using external tools like `diff -r` on the extracted directories.

It reports differences based on metadata (permissions, ownership, timestamps) and content. Minor timestamp differences might be reported even if content is identical.

The exact behavior and available options can vary slightly between different `tar` implementations (e.g., GNU `tar` vs. BSD `tar`).

`tar --diff` exits with status 0 if no differences are found, 1 if differences are found, and a value greater than 1 if a fatal error occurs during the operation.

When comparing an archive that contains directories, `tar --diff` automatically performs a recursive comparison of the directory contents by default, unless `--no-recursion` is specified.

The `tar` (tape archive) utility originated in Unix in the early 1970s, designed for backing up files to tape drives. Over time, it evolved to support various storage media and functionalities. The `diff` (compare) functionality was introduced as a standard part of the `tar` utility to provide integrity checks and facilitate backup verification, making it a fundamental feature for managing archived data.

tar(1), diff(1), cmp(1), md5sum(1), sha256sum(1)