Provided by: lz4_1.8.3-1ubuntu1_amd64 bug


       lz4 - lz4, unlz4, lz4cat - Compress or decompress .lz4 files



       unlz4 is equivalent to lz4 -d

       lz4cat is equivalent to lz4 -dcfm

       When  writing  scripts  that need to decompress files, it is recommended to always use the
       name lz4 with appropriate arguments (lz4 -d or lz4 -dc) instead of  the  names  unlz4  and


       lz4 is an extremely fast lossless compression algorithm, based on byte-aligned LZ77 family
       of compression scheme. lz4 offers compression  speeds  of  400  MB/s  per  core,  linearly
       scalable  with  multi-core  CPUs.  It  features  an  extremely fast decoder, with speed in
       multiple GB/s per core, typically reaching RAM speed  limit  on  multi-core  systems.  The
       native file format is the .lz4 format.

   Difference between lz4 and gzip
       lz4 supports a command line syntax similar but not identical to gzip(1). Differences are :

       ·   lz4 preserves original files

       ·   lz4 compresses a single file by default (see -m for multiple files)

       ·   lz4 file1 file2 means : compress file1 into file2

       ·   lz4 file.lz4 will default to decompression (use -z to force compression)

       ·   lz4  shows  real-time notification statistics during compression or decompression of a
           single file (use -q to silence them)

       ·   If no destination name is provided, result is sent to stdout except if stdout  is  the

       ·   If  no  destination name is provided, and if stdout is the console, file is compressed
           into file.lz4.

       ·   As a consequence of previous rules, note the following example : lz4 file  |  consumer
           sends compressed data to consumer through stdout, hence it does not create file.lz4.

       ·   Another  consequence of those rules is that to run lz4 under nohup, you should provide
           a destination file: nohup lz4  file  file.lz4,  because  nohup  writes  the  specified
           command´s output to a file.

       Default behaviors can be modified by opt-in commands, detailed below.

       ·   lz4 -m makes it possible to provide multiple input filenames, which will be compressed
           into files using suffix .lz4. Progress notifications are also disabled by default (use
           -v  to  enable  them). This mode has a behavior which more closely mimics gzip command
           line, with the main remaining difference being that  source  files  are  preserved  by

       ·   Similarly, lz4 -m -d can decompress multiple *.lz4 files.

       ·   It´s   possible  to  opt-in  to  erase  source  files  on  successful  compression  or
           decompression, using --rm command.

       ·   Consequently, lz4 -m --rm behaves the same as gzip.

   Concatenation of .lz4 files
       It is possible to concatenate .lz4 files as is. lz4 will decompress such files as if  they
       were a single .lz4 file. For example:

           lz4 file1  > foo.lz4
           lz4 file2 >> foo.lz4

       Then lz4cat foo.lz4 is equivalent to cat file1 file2.


   Short commands concatenation
       In  some  cases,  some  options  can  be  expressed using short command -x or long command
       --long-word. Short commands can be concatenated together. For example, -d -c is equivalent
       to -dc. Long commands cannot be concatenated. They must be clearly separated by a space.

   Multiple commands
       When  multiple  contradictory  commands are issued on a same command line, only the latest
       one will be applied.

   Operation mode
       -z --compress
              Compress. This is the default operation mode  when  no  operation  mode  option  is
              specified,  no  other operation mode is implied from the command name (for example,
              unlz4 implies --decompress), nor from the input file  name  (for  example,  a  file
              extension  .lz4  implies  --decompress  by  default).  -z can also be used to force
              compression of an already compressed .lz4 file.

       -d --decompress --uncompress
              Decompress. --decompress is also the default operation when the input filename  has
              an .lz4 extension.

       -t --test
              Test the integrity of compressed .lz4 files. The decompressed data is discarded. No
              files are created nor removed.

       -b#    Benchmark mode, using # compression level.

   Operation modifiers
       -#     Compression level, with # being any  value  from  1  to  12.  Higher  values  trade
              compression speed for compression ratio. Values above 12 are considered the same as
              12. Recommended values are 1  for  fast  compression  (default),  and  9  for  high
              compression.  Speed/compression  trade-off will vary depending on data to compress.
              Decompression speed remains fast at all settings.

       -D dictionaryName
              Compress, decompress or benchmark using dictionary dictionaryName. Compression  and
              decompression  must  use  the  same  dictionary to be compatible. Using a different
              dictionary during decompression will either abort due to  decompression  error,  or
              generate a checksum error.

       -f --[no-]force
              This option has several effects:

              If the target file already exists, overwrite it without prompting.

              When  used  with --decompress and lz4 cannot recognize the type of the source file,
              copy the source file as is to standard output. This allows  lz4cat  --force  to  be
              used like cat (1) for files that have not been compressed with lz4.

       -c --stdout --to-stdout
              Force write to standard output, even if it is the console.

       -m --multiple
              Multiple  input  files.  Compressed file names will be appended a .lz4 suffix. This
              mode also reduces notification level. lz4 -m has a behavior equivalent to  gzip  -k
              (it preserves source files by default).

       -r     operate recursively on directories. This mode also sets -m (multiple input files).

       -B#    Block size [4-7](default : 7)
              -B4= 64KB ; -B5= 256KB ; -B6= 1MB ; -B7= 4MB

       -BD    Block Dependency (improves compression ratio on small blocks)

              switch  to  ultra-fast  compression levels. If =# is not present, it defaults to 1.
              The higher the value, the faster  the  compression  speed,  at  the  cost  of  some
              compression  ratio.  This  setting  overwrites  compression  level  if  one was set
              previously. Similarly, if a compression level is set after --fast, it overrides it.

              Select frame checksum (default:enabled)

              Header includes original size (default:not present)
              Note : this option can only be activated when the original size can be  determined,
              hence for a file. It won´t work with unknown source size, such as stdin or pipe.

              Sparse mode support (default:enabled on file, disabled on stdout)

       -l     Use Legacy format (typically for Linux Kernel compression)
              Note : -l is not compatible with -m (--multiple) nor -r

   Other options
       -v --verbose
              Verbose mode

       -q --quiet
              Suppress warnings and real-time statistics; specify twice to suppress errors too

       -h -H --help
              Display help/long help and exit

       -V --version
              Display Version number and exit

       -k --keep
              Preserve source files (default behavior)

       --rm   Delete source files on successful compression or decompression

       --     Treat all subsequent arguments as files

   Benchmark mode
       -b#    Benchmark file(s), using # compression level

       -e#    Benchmark multiple compression levels, from b# to e# (included)

       -i#    Minimum evaluation time in seconds [1-9] (default : 3)


       Report bugs at:


       Yann Collet