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lzma - Compression and decompression in the LZMA format - command line utility…  more info»

lzmp.1.gz

LZMA(1)                                                      LZMA(1)



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 ver‐
       sion 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  decom‐
       pressing.

       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 com‐
       pete  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 soft‐
       ware 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 com‐
       pressing 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 identi‐
       cally; the only differences are found from the beginnings and
       ends of LZMA compressed files: Non-streamed files contain the
       uncompressed size of  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 advan‐
       tages: 1) the compressed file is a few bytes smaller  and  2)
       the  uncompressed  size  of  the  file can be checked without
       decompressing the file.


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.

       -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.  These  options  have  no
              effect when decompressing.

       --fast Alias to -1.

       --best Alias to -9.


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

       It  can  be  especially useful with tar(1) patched to support
       LZMA compression.


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
       gzip(1), bzip2(1)



LZMA utils                   23 Dec 2005                     LZMA(1)
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