Tribblix: manual page: bzip3.1

bzip3(1) User Commands bzip3(1)

NAME

bzip3 - an efficient statistical file compressor and spiritual
successor to bzip2

SYNOPSIS

bzip3 [ -BbcdehftV ] [ filenames ... ]

bz3cat is equivalent to bzip3 -dc

bunzip3 is equivalent to bzip3 -d

DESCRIPTION

Compress or decompress a file using run length encoding and Lempel
Ziv prediction, followed by the Burrows-Wheeler transform and
arithmetic coding. bzip3, like its ancestor bzip2, excels at
compressing text or source code.

The command-line options are deliberately very similar to those of
bzip2, but they are not identical.

bzip3 expects at most two filenames intertwined with flags. bzip3
will by default not overwrite existing files. If this behaviour is
intended, use the -f flag.

If no file names are specified, bzip3 will compress from standard
input to standard output, refusing to output binary data to a
terminal. The -e flag (encode) is implied.

bunzip3 (or, bzip3 -d equivalently) decompresses data from standard
input to the standard output, refusing to read from a terminal.

If two files are specified, the first one is used in place of
standard input, and the second one is used in place of standard
output.

If the -c flag is present, bzip3 will read from the specified file
and output data to standard output instead. Otherwise, if decoding,
bzip3 will try to guess the decompressed filename by removing the
.bz3 extension. If not present, an error will be reported. If
encoding, the output filename will be generated by appending the .bz3
extension to the input filename.

OPTIONS

-B --batch
Enable batch mode. By default, bzip3 will error if more than
two files are passed, and the two files specified are always
treated as input and output. The batch mode makes bzip3 treat
every file as input, so for example bzip3 -Bd *.bz3 will
decompress all .bz3 files in the current directory.

-b --block N
Set the block size to N mebibytes. The minimum is 1MiB, the
maximum is 511MiB.

-c --stdout
Force writing output data to the standard output if one file
is specified.

-d --decode
Force decompression.

-e/-z --encode
Force compression (default behaviour).

-f --force
Overwrite existing files.

-h --help
Display a help message and exit.

-j --jobs N
Set the amount of parallel worker threads that process one
block each.

-k --keep
Keep (don't delete) the input files. Set by default, provided
only for compatibility with other compressors.

-v --verbose
Set verbose output mode to see compression statistics.

-V --version
Display version information and exit.

-t --test
Verify the validity of compressed blocks.

-- Treat all subsequent arguments as file names, even if they
start with a dash. This is so you can handle files with names
beginning with a dash.

FILE FORMAT

Compression is performed as long as the input block is longer than 64
bytes. Otherwise, it's coded as a literal block. In all other cases,
the compressed data is written to the file. The file format has
constant overhead of 9 bytes per file and from 9 to 17 bytes per
block. Random data is coded so that expansion is generally under
0.8%.

bzip3 uses 32-bit CRC to ensure that the decompressed version of a
file is identical to the original. This guards against corruption of
the compressed data.

MEMORY MANAGEMENT

The -b flag sets the block size in mebibytes (MiB). The default is 16
MiB. Compression and decompression memory usage can be estimated as:

6 x block size

Larger block sizes usually give rapidly diminishing returns. It is
also important to appreciate that the decompression memory
requirement is set at compression time by the choice of block size.
In general, try and use the largest block size memory constraints
allow, since that maximises the compression achieved. Compression
and decompression speed are virtually unaffected by block size.

AUTHOR

Kamila Szewczyk, kspalaiologos@gmail.com.

https://github.com/kspalaiologos/bzip3

Thanks to: Ilya Grebnov, Benjamin Strachan, Caleb Maclennan, Ilya
Muravyov, package maintainers - Leah Neukirchen, Grigory Kirillov,
Maciej Barc, Robert Schutz, Petr Pisar, and others. Also everyone who
sent patches, helped with portability problems, encouraged me to work
on bzip3 and lent me machines for performance tests.