Provided by: lz4_1.8.2-1ubuntu1_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  16.  Higher  values  trade
              compression speed for compression ratio. Values above 16 are considered the same as
              16. 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.

       -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)

              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 in seconds [1-9] (default : 3)


       Report bugs at:


       Yann Collet