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146 lines
4.3 KiB
Groff
146 lines
4.3 KiB
Groff
.PU
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.TH bzip2 1
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.SH NAME
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bzme \- recompress gziped, ziped, ... files into bzip2
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.SH SYNOPSIS
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.ll +8
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.B bzmz
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.RB [ " \-fh " ]
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[
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.I "filenames \&..."
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]
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.SH DESCRIPTION
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.I bzme
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recompresses files using the Burrows-Wheeler block sorting text compression
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algorithm, and Huffman coding. Compression is generally considerably better
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than that achieved by more conventional LZ77/LZ78-based compressors,
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and approaches the performance of the PPM family of statistical compressors.
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.I bzme
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expects a list of file names to accompany the command-line flags.
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Each file is replaced by a recompressed version of itself, with the name
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as described in
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.B "NEW NAMES"
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section.
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.I bzme
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won't overwrite by default existing files. If you want this to happen, specify
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the \-f flag.
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.SH "NEW NAMES"
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.I bzip2
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attempts to guess the filename for the decompressed file
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from that of the compressed file as follows:
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filename.tgz becomes filename.tar.bz2
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filename.tar.gz becomes filename.tar.bz2
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filename.zip becomes filename.tar.bz2
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filename.z becomes filename.bz2
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filename.Z becomes filename.bz2
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filename.gz becomes filename.bz2
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If the file does not end in one of the recognised endings, \fI.tgz\fP,
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or \fI.zip\fP,
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.I bzme
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complains that it cannot guess if the name of the recompressed file (ie it
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doesn't detect the original name to be a file compressed in a known format)
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.SH OPTIONS
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.TP
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.B \-f
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Force overwrite of output files, even if
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.I -k
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is used. Normally,
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.I bzip2
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will not overwrite existing output files.
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.TP
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.B \-k
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Keep (don't delete) input files during compression
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or decompression.
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.".TP
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.".B \-q --quiet
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."Suppress non-essential warning messages. Messages pertaining to
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."I/O errors and other critical events will not be suppressed.
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.".TP
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.".B \-v --verbose
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."Verbose mode -- dysplay space gain (default)
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.".TP
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.".B \-L --license -V --version
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."Display the software version, license terms and conditions.
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.SH SECURITY
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.I bzme
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will keep source file if there's an error while decompressing source file
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or recompressing new file (or
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.I -k
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option is used of course).
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.I bzme
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won't overwite the target file, even if
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.I -k
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option is used, if the source file doesn't exists.
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As a self-check for your protection,
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.I bzip2
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uses 32-bit CRCs to make sure that the decompressed version of a file is
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identical to the original.
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.BR
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This offers a better protection against corruption
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of the compressed data than offered by gzip.
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.SH SPACE GAIN
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Compression is only performed if the compressed file is smaller than the
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original: the original file is only removed if the newly compressed file
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is smaller, else the new recompressed file is deleted.
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Text (aka non binary) files're quite nearly always better compressed
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by bzip2 rather than gzip.
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.SH MEMORY VS SPACE TRADEOFF
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There're two things :
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.TP
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.B Consumed CPU time
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The needed cpu time is reduced by decompressing only one time.
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Files to recompress were compressed through compress or gzip, used to be
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decompressed by gunzip -t in order to check that the original file was ok.
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This resulted in passing two times the data in the decompression process
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(one to check integrity, one to recompress).
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temporary space usage will be zero since bzme will use a pipe
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rather than a temporary file as it does in the early ages.
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Source error're detected through bash PIPESTATUS feature.
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.TP
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.B Occupied space
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While recompressing files, if they were compressed through compress or gzip,
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temporary space usage will be zero since bzme will use a pipe
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rather than a temporary file as it did in the early ages.
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Source error're detected through bash PIPESTATUS feature.
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Zip files're still fully decompressed on disk.
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As for the recompressed file and original file, only the smallest file
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is kept.
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.SH RETURN VALUES
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0 for a normal exit.
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1 will be returned if an unknown option is passed.
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.SH BUGS
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Bash getopt (which is used to analyse options) isn't gnu style aware, ie cmd
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opt1 file1 file2 opt2 will result in ignoring opt2 option.
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Solaris/SunOs du doesn't supports gnu option, and thus, bzme won't
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work on those OSes unless GNU fileutils got installed.
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.BR
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I had once a day patched bzme to use right options for solaris but i had
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lost my changes.
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.LP
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So solaris remains unsupported.
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.SH "SEE ALSO"
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bzip2(1), bunzip2(1)
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.SH AUTHOR
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Thierry Vignaud <tvignaud@mandrakesoft.com>, 1999-2002
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