pbzip2

Compress a file

$ pbzip2 [path/to/file]

$ pbzip2 -p[4] [path/to/file]

$ tar -cf [path/to/compressed_file].tar.bz2 [[-I|--use-compress-program]] "pbzip2 [-option1 -option2 ...]" [path/to/file]

$ pbzip2 [[-d|--decompress]] [path/to/compressed_file.bz2]

$ pbzip2 [[-h|--help]]

pbzip2 [options] [files...]
pbzip2 -d [options] [files...]
pbzip2 -c [options] [files...]
(If no files are specified, pbzip2 processes standard input/output)

-d, --decompress
    Force pbzip2 to operate in decompression mode, extracting content from .bz2 files.

-k, --keep
    Retain (do not delete) input files after successful compression or decompression. By default, input files are removed upon successful processing.

-p, --processors <N>
    Specify the number of processors (CPU cores or threads) to utilize for compression or decompression. This is the primary control for parallelism. If omitted, pbzip2 typically attempts to use all available CPU cores.

-f, --force
    Force overwrite of any existing output files without prompting for confirmation. Use with caution to prevent unintentional data loss.

-v, --verbose
    Enable verbose output, displaying more detailed information about the processing progress, such as file names and compression/decompression rates.

-b, --blocksize <N>
    Set the compression block size in 100-kilobyte units (ranging from 1 to 9, with 9 being the default). Larger block sizes can sometimes yield slightly better compression ratios but may consume more memory and potentially limit parallelism for very small files.

-m, --megabytes <N>
    Define the maximum amount of memory (in megabytes) that each processing thread can use. This option helps manage overall memory consumption, particularly when using a large number of threads.

pbzip2 is a parallel implementation of bzip2, specifically designed to take advantage of multi-core and multi-processor systems.
It utilizes PThreads to split the compression or decompression task across multiple CPU cores, thereby significantly speeding up operations on large files compared to the single-threaded bzip2 utility.
The output produced by pbzip2 is fully compatible with standard bzip2, meaning files compressed with pbzip2 can be seamlessly decompressed by bzip2 (and vice-versa).
This tool is particularly useful in environments where the high compression ratios of bzip2 are desired, but single-threaded performance would be a bottleneck, such as in large-scale data archiving, backups, and high-performance computing scenarios.

While pbzip2 significantly speeds up bzip2 operations on multi-core systems, it has some limitations:
For very small files, the overhead of managing parallel threads might negate performance benefits or even lead to slower processing compared to single-threaded bzip2.
Memory consumption can become substantial when using a high number of threads in conjunction with large block sizes (e.g., the default 900KB per block).
The degree of parallelism is inherently limited by the input file size and the inherent compressibility characteristics of the data within; highly compressible data or tiny files may not fully utilize all cores.

pbzip2 is designed to work seamlessly with standard input (stdin) and standard output (stdout). This capability makes it extremely versatile for piping with other Linux commands. For example, you can compress a tar archive directly: `tar cf - . | pbzip2 > archive.tar.bz2`, or decompress one: `pbzip2 -d < archive.tar.bz2 | tar xf -`.

Upon successful completion of its operation, pbzip2 returns an exit status of 0. Any non-zero exit status indicates that an error occurred or the process terminated abnormally. This behavior is crucial for scripting, allowing for robust error handling and conditional execution within automated workflows.

The original bzip2 compression algorithm was developed by Julian Seward in the late 1990s, known for its strong compression ratios. However, it was designed as a single-threaded application.
As multi-core processors became ubiquitous, the single-threaded nature of bzip2 became a significant bottleneck for large datasets. To address this, pbzip2 was initiated by Jeff Gilchrist, aiming to bring parallel processing capabilities to the existing bzip2 algorithm.
Its development focused on leveraging the increasing core counts in modern CPUs, making bzip2's excellent compression performance more practical and efficient for large-scale data processing without requiring a redesign of the fundamental compression algorithm.

bzip2(1), gzip(1), pigz(1), tar(1), xz(1), pixz(1)