xar (archiver)

xar, short for eXtensible ARchiver, is an open-source file archiving and compression utility. It is designed to be a successor to the traditional tar archiving format, offering features such as XML metadata for enhanced archive descriptions and error detection. xar is primarily used in macOS for package installation and software distribution, though it can be used on other Unix-like operating systems as well.

Key features of xar include:

• XML Metadata: xar archives contain an XML header describing the archive's contents, including file names, sizes, permissions, and checksums. This XML header makes xar archives self-describing and allows for easier manipulation and inspection of the archive's contents.

• Data Compression: xar supports various compression algorithms, including zlib and bzip2, to reduce the size of the archived files. This allows for more efficient storage and transmission of data.

• Checksums: xar incorporates checksums to ensure data integrity. This feature helps to detect corruption of the archived files during storage or transmission.

• Digital Signatures: xar supports digital signatures, allowing for verification of the archive's authenticity and preventing tampering. This is particularly useful for software distribution, ensuring that the software has not been modified since it was created by the original author.

• Extensibility: The xar format is designed to be extensible, allowing for the addition of new features and metadata without breaking compatibility with older versions.

xar is often used in macOS installation packages (.pkg files). It is a command-line utility, and tools are available for graphical user interface-based creation and extraction of xar archives. Although xar provides improvements over traditional archiving tools like tar, it is not as widely adopted outside of the Apple ecosystem.