bunzip2 - Unix, Linux Command


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bunzip2- To compress or decompress named file(s) .


bunzip2 [ -fkvsVL ] [ filenames ... ] 


bunzip2 decompresses all specified files. Files which were not created by bzip2 will be detected and ignored, and a warning issued. bzip2 attempts to guess the filename for the decompressed file from that of the compressed file as follows:

filename.bz2 becomes filename

filename.bz becomes filename

filename.tbz2 becomes filename.tar

filename.tbz becomes filename.tar

anyothername becomes anyothername.out

If the file does not end in one of the recognised endings, .bz2, .bz, .tbz2 or .tbz, bzip2 complains that it cannot guess the name of the original file, and uses the original name with .out appended. As with compression, supplying no filenames causes decompression from standard input to standard output. bunzip2 will correctly decompress a file which is the concatenation of two or more compressed files. The result is the concatenation of the corresponding uncompressed files. Integrity testing (-t) of concatenated compressed files is also supported.



-c --stdout Compress or decompress to standard output.
-d --decompress Force decompression. bzip2, bunzip2 and bzcat are really the same program, and the decision about what actions to take is done on the basis of which name is used. This flag overrides that mechanism, and forces bzip2 to decompress.
-z --compress The complement to -d: forces compression, regardless of the invokation name.
-t --test Check integrity of the specified file(s), but don't decompress them. This really performs a trial decompression and throws away the result.
-f --force Force overwrite of output files. Default is not to overwrite. Also forces breaking of hard links to files.
-k --keep Keep (don't delete) input files during compression or decompression.
-s --small Reduce memory usage, for compression, decompression and testing. Files are decompressed and tested using a modified algorithm which only requires 2.5 bytes per block byte. This means any file can be decompressed in 2300k of memory, albeit at about half the normal speed.
-q --quiet Suppress non-essential warning messages. Messages pertaining to I/O errors and other critical events will not be suppressed.
-v --verbose show the compression ratio for each file processed. Further -v's increase the verbosity level, spewing out lots of information which is primarily of interest for diagnostic purposes.
-L --license -V --version Display the software version, license terms and conditions
-1 (or --fast) to -9 (or -best) Set the block size to 100 k, 200 k ... 900 k when compressing. Has no effect when decompressing. The --fast and --best aliases are primarily for GNU gzip compatibility. In particular, --fast doesn't make things significantly faster. And --best merely selects the default behaviour
-- Treats 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, for example: bzip2 -- -myfilename.
--repetitive-fast --repetitive-best These flags are redundant in versions 0.9.5 and above. They provided some coarse control over the behaviour of the sorting algorithm in earlier versions, which was sometimes useful. 0.9.5 and above have an improved algorithm which renders these flags irrelevant.



To compress a file named test.txt using command bunzip2 

$ bunzip2 -z test.txt


ls -lrt
total 7

-rw-rw-r-- 1 nubo nubo 121 Jan 7 11:47 test.txt.bz2


To Decompress a bzip2 compressed file:

$ bunzip2 file.txt.bz2


ls -lrt
total 7

-rw-rw-r-- 1 nubo nubo 121 Jan 7 11:47 test.txt


To decompress a file and keep the original .bz2 file:

$ bunzip2 -c test.txt.bz2 > test.txt OR $ bunzip2 -k test.txt.bz2

ls -lrt
total 7
-rw-rw-r-- 1 nubo nubo 121 Jan 7 11:47 test.txt.bz2
-rw-rw-r-- 1 nubo nubo 132 Jan 7 11:55 test.txt


To test compressed file integrity:

$ bunzip2 -t test.txt.bz2


To Display software version and License:

$ bunzip2 -L


bzip2, a block-sorting file compressor. Version 1.0.6, 6-Sept-2010.

Copyright (C) 1996-2010 by Julian Seward.

This program is free software; you can redistribute it and/or modify
it under the terms set out in the LICENSE file, which is included
in the bzip2-1.0.6 source distribution.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
LICENSE file for more details.


To decompress a file using less memory (at most 2500k):

$  bunzip2 -s test.txt.bz2


ls -lrt
total 7

-rw-rw-r-- 1 nubo nubo 121 Jan 7 11:47 test.txt

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