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 LZMA(1)                         LZMA utils                          LZMA(1)
                                 23 Dec 2005



 NAME
      lzma, unlzma, lzcat - LZMA compression and decompression tool


 SYNOPSIS
      lzma [-123456789cdefhkLqtvV] [-S suffix] [filenames ...]
      unlzma [-cfhkLqtvV] [-S suffix] [filenames ...]
      lzcat [-fhLqV] [filenames ...]


 DESCRIPTION
      LZMA (Lempel-Ziv-Markov chain-Algorithm) is an improved version of
      famous LZ77 compression algorithm. It was improved in way of maximum
      increasing of compression ratio, keeping high decompression speed and
      low memory requirements for decompressing.

      lzma command line tool has a similar interface to gzip(1) and bzip2(1)
      and is intended to make use of LZMA compression easy for the users who
      are already familiar with gzip and bzip2.

      In this manual lzma is compared mostly to bzip2 because that is
      currently one of the most widely used free software to compress tar
      files made for distribution.  Comparing lzma to gzip is not practical
      because neither lzma nor bzip2 can compete with gzip in compression
      speed. On the other hand the compression ratio of gzip is worse than
      of lzma and bzip2.

      lzma provides notably better compression ratio than bzip2 especially
      with files having other than plain text content. The other advantage
      of lzma is fast decompression which is many times quicker than bzip2.
      The major disadvantage is that achieving the highest compression
      ratios requires extensive amount of system resources, both CPU time
      and RAM. Also software to handle LZMA compressed files is not
      installed by default on most distributions.

      When compressing or decompressing with lzma, the new file will have
      the same ownership information, permissions and timestamps as the
      original file. However the this information is not stored into the
      compressed file like gzip does.


 STREAMED VS. NON-STREAMED
      LZMA files can be either streamed or non-streamed. Non-streamed files
      are created only when the size of the file being compressed is known.
      In practice this means that the source file must be a regular file. In
      other words, if compressing from the standard input or from a named
      pipe (fifo) the compressed file will always be streamed.

      Both streamed and non-streamed files are compressed identically; the
      only differences are found from the beginnings and ends of LZMA
      compressed files: Non-streamed files contain the uncompressed size of



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 LZMA(1)                         LZMA utils                          LZMA(1)
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      the file in the LZMA file header; streamed files have uncompressed
      size marked as unknown. To know where to stop decoding, streamed files
      have a special End Of Stream marker at the end of the LZMA file. The
      EOS marker makes streamed files five or six bytes bigger than non-
      streamed.

      So in practice creating non-streamed files has two advantages: 1) the
      compressed file is a few bytes smaller and 2) the uncompressed size of
      the file can be checked without decompressing the file. To view the
      data stored in the LZMA header use lzmainfo(1).


 OPTIONS
      Short options can be grouped like -cd.

      -c --stdout --to-stdout
           The output is written to the standard output. The original files
           are kept unchanged. When compressing to the standard output there
           can be only one input file. This option is implied when input is
           read from the standard input or the script is invoked as lzcat.

      -d --decompress --uncompress
           Force decompression regardless of the invocation name. This the
           default when called as unlzma or lzcat.

      -f --force
           Force compression or decompression even if source file is a
           symlink, target exists, or target is a terminal. In contrast to
           gzip and bzip2, if input data is not in LZMA format, --force does
           not make lzma behave like cat.  lzma never prompts if target file
           should be overwritten; existing files are skipped or, in case of
           --force, overwritten.

      -h --help
           Show a summary of supported options and quit.

      -k --keep
           Do not delete the input files after compression or decompression.

      -L --license
           Show licensing information of lzma.

      -q --quiet
           Suppress all warnings. You can still check the exit status to
           detect if a warning had been shown.

      -S --suffix .suf
           Use .suf instead of the default .lzma.  A null suffix forces
           unlzma to decompress all the given files regardless of the
           filename suffix.




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 LZMA(1)                         LZMA utils                          LZMA(1)
                                 23 Dec 2005



      -t --test
           Check the integrity of the compressed file(s). Without --verbose
           no output is produced if no errors are found.

      -v --verbose
           Show the filename and percentage reduction of each processes
           file.

      -V --version
           Show the version number of lzma.

      -z --compress
           Force compression regardless of the invocation name.

      -1 .. -9
           Set the compression ratio. See the next chapter for detailed
           information. These options have no effect when decompressing.

      --fast
           Alias to -1.

      --best
           Alias to -9.


 COMPRESSION OPTIONS AND MEMORY USAGE
      The compression options of lzma are divided to two groups. The first
      two (-1 and -2) are designed for fast compression speed.  -3 .. -9
      provide good to excellent compression ratio but require more CPU time
      and system memory.

      For relatively fast compression with medium compression ratio -1 is
      the recommended setting. It's faster than 'bzip2 --fast' and usually
      creates smaller files than 'bzip2 --best'.  -2 makes somewhat smaller
      files but doubles the compression time close to what 'bzip2 --best'
      takes.

      Generally for excellent compression ratio, acceptable compression time
      and memory requirements (about 83 MB for compression, 9 MB for
      decompression) you should use -7 which is also the default.  -8 and -9
      will give some gain especially with bigger files (>=tens of megabytes)
      but also increase the CPU and memory requirements dramatically. See
      the table below for memory requirements of different compression
      settings.

          Flag   Compress usage    Decompress usage
           -1          2 MB               1 MB
           -2         12 MB               2 MB
           -3         12 MB               1 MB
           -4         16 MB               2 MB
           -5         26 MB               3 MB



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 LZMA(1)                         LZMA utils                          LZMA(1)
                                 23 Dec 2005



           -6         45 MB               5 MB
           -7         83 MB               9 MB
           -8        159 MB              17 MB
           -9        311 MB              33 MB


 DIAGNOSTICS
      Exit status:
      0 - Everything OK.
      1 - An error occurred.
      2 - Something worth a warning happened but no errors.


 AUTHORS
      The LZMA algorithm and the implementation used in LZMA utils was
      developed by Igor Pavlov. The original code is available in LZMA SDK
      which can be found from http://7-zip.org/sdk.html .

      lzma command line tool was written by Ville Koskinen.
      http://tukaani.org/lzma/

      This manual page is inspired by manual pages of gzip and bzip2.


 SEE ALSO
      lzmadec(1), lzmainfo(1), gzip(1), bzip2(1)




























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