bzip2 - Unix, Linux Command
bzip2 - To compress or decompress named file(s).
bzip2 [ -cdfkqstvzVL123456789 ] [ filenames ... ]
Compared with gzip, bzip2 creates smaller archives but has a slower decompression time and higher memory use. bzip2 compresses files using the Burrows-Wheeler block sorting text compression algorithm, and Huffman coding. The command-line options provided are deliberately very similar to those of GNU gzip, but they are not identical. bzip2 expects a list of file names along with the command-line flags. Each file is replaced by a compressed version of itself, with the name original_name.bz2. Each compressed file has the same modification date, permissions, and, when possible, ownership as the corresponding original, so that these properties can be correctly restored at decompression time.
File name handling is naive in the sense that there is no mechanism for preserving original file names, permissions, ownerships or dates in filesystems which lack these concepts, or have serious file name length restrictions, such as MS-DOS. bzip2 and bunzip2 by default will not overwrite existing files. To overwrite, specify the -f flag.
|-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. Normally, bzip2 will not overwrite existing output files. Also forces bzip2 to break hard links to files, which it otherwise wouldn't do. bzip2 normally declines to decompress files which don't have the correct magic header bytes. If forced (-f), however, it will pass such files through unmodified. This is how GNU gzip behaves.|
|-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. During compression, -s selects a block size of 200k, which limits memory use to around the same figure, at the expense of your compression ratio. In short, if your machine is low on memory (8 megabytes or less), use -s for everything.|
|-q --quiet||Suppress non-essential warning messages. Messages pertaining to I/O errors and other critical events will not be suppressed.|
|-v --verbose||Verbose mode -- 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.|
|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.|
|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, bzip now has an improved algorithm which renders these flags irrelevant.|
To compress the file sample.txt and replace it with a compressed version named sample.txt.bz2
$ bzip2 sample.txt $ ls sample.txt.bz2
To compress the file sample.txt, keep the uncompressed version and create the new file.
$ bzip2 -k sample.txt $ ls sample.txt sample.txt.bz2
To combine a set of mp3 music files into one file with tar and then zip the result with bzip2.
$ tar -cf music.tar 1.mp3 2.mp3 3.mp3 $ bzip2 music.tar $ ls 1.mp3 2.mp3 3.mp3 music.tar.bz2
To combine a set of mp3 music files into one file with tar and then zip the result with bzip2 in single command.
$ tar -cjf music.tar.bz2 miles.mp3 chet.mp3 charlie.mp3 $ ls music.tar.bz2 miles.mp3 chet.mp3 charlie.mp3