bz3cat(1)

1bzip3(1)                    General Commands Manual                   bzip3(1)
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NAME

6       bzip3  - an efficient statistical file compressor and spiritual succes‐
7       sor to bzip2
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SYNOPSIS

11       bzip3 [ -BbcdehftV ] [ filenames ...  ]
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13       bz3cat is equivalent to bzip3 -dc
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15       bunzip3 is equivalent to bzip3 -d
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DESCRIPTION

18       Compress or decompress a file using run length encoding and Lempel  Ziv
19       prediction,  followed  by  the Burrows-Wheeler transform and arithmetic
20       coding.  bzip3, like its ancestor bzip2, excels at compressing text  or
21       source code.
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23       The  command-line  options  are  deliberately  very similar to those of
24       bzip2, but they are not identical.
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26       bzip3 expects at most two filenames intertwined with flags.  bzip3 will
27       by  default  not  overwrite  existing  files.  If this behaviour is in‐
28       tended, use the -f flag.
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30       If no file names are specified, bzip3 will compress from standard input
31       to  standard  output, refusing to output binary data to a terminal. The
32       -e flag (encode) is implied.
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34       bunzip3 (or, bzip3 -d equivalently) decompresses data from standard in‐
35       put to the standard output, refusing to read from a terminal.
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37       If  two files are specified, the first one is used in place of standard
38       input, and the second one is used in place of standard output.
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40       If the -c flag is present, bzip3 will read from the specified file  and
41       output  data  to standard output instead. Otherwise, if decoding, bzip3
42       will try to guess the decompressed filename by removing the .bz3 exten‐
43       sion.  If not present, an error will be reported. If encoding, the out‐
44       put filename will be generated by appending the .bz3 extension  to  the
45       input filename.
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OPTIONS

49       -B --batch
50              Enable batch mode. By default, bzip3 will error if more than two
51              files are passed, and the two files specified are always treated
52              as input and output. The batch mode makes bzip3 treat every file
53              as input, so for example bzip3 -Bd  *.bz3  will  decompress  all
54              .bz3 files in the current directory.
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56       -b --block N
57              Set the block size to N mebibytes. The minimum is 1MiB, the max‐
58              imum is 511MiB.
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60       -c --stdout
61              Force writing output data to the standard output if one file  is
62              specified.
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64       -d --decode
65              Force decompression.
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67       -e/-z --encode
68              Force compression (default behaviour).
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70       -f --force
71              Overwrite existing files.
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73       -h --help
74              Display a help message and exit.
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76       -j --jobs N
77              Set the amount of parallel worker threads that process one block
78              each.
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80       -k --keep
81              Keep (don't delete) the input files. Set  by  default,  provided
82              only for compatibility with other compressors.
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84       -v --verbose
85              Set verbose output mode to see compression statistics.
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87       -V --version
88              Display version information and exit.
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90       -t --test
91              Verify the validity of compressed blocks.
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93       --     Treat all subsequent arguments as file names, even if they start
94              with a dash. This is so you can handle files with  names  begin‐
95              ning with a dash.
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FILE FORMAT

98       Compression  is  performed as long as the input block is longer than 64
99       bytes. Otherwise, it's coded as a literal block. In  all  other  cases,
100       the  compressed  data  is written to the file. The file format has con‐
101       stant overhead of 9 bytes per file and from 9 to 17  bytes  per  block.
102       Random data is coded so that expansion is generally under 0.8%.
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104       bzip3 uses 32-bit CRC to ensure that the decompressed version of a file
105       is identical to the original. This guards  against  corruption  of  the
106       compressed data.
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MEMORY MANAGEMENT

110       The  -b  flag sets the block size in mebibytes (MiB). The default is 16
111       MiB. Compression and decompression memory usage can be estimated as:
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113              6 x block size
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115       Larger block sizes usually give rapidly  diminishing  returns.   It  is
116       also  important to appreciate that the decompression memory requirement
117       is set at compression time by the choice of block  size.   In  general,
118       try and use the largest block size memory constraints allow, since that
119       maximises the  compression  achieved.   Compression  and  decompression
120       speed are virtually unaffected by block size.
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AUTHOR

124       Kamila Szewczyk, kspalaiologos@gmail.com.
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126       https://github.com/kspalaiologos/bzip3
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128       Thanks  to:  Ilya Grebnov, Benjamin Strachan, Caleb Maclennan, Ilya Mu‐
129       ravyov, package maintainers - Leah Neukirchen, Grigory Kirillov, Maciej
130       Barc,  Robert  Schutz,  Petr  Pisar, and others. Also everyone who sent
131       patches, helped with portability problems, encouraged  me  to  work  on
132       bzip3 and lent me machines for performance tests.
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