unlzma

LZMA(1)                     General Commands Manual                    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 version of fa-
       mous LZ77 compression algorithm. It was improved in way of maximum  in-
       creasing 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  cur-
       rently  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 re-
       quires  extensive  amount  of  system resources, both CPU time and RAM.
       Also software to handle LZMA compressed files is not installed  by  de-
       fault 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 com-
       pressed 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 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.

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 sym-
              link, 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  tar-
              get  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  decompres-
              sion.

       -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 un-
              lzma  to  decompress all the given files regardless of the file-
              name 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 de-
              compressing.

       --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 com-
       pression.

AUTHORS
       The LZMA algorithm and the implementation used in LZMA utils was devel-
       oped  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)