lz4(1)                           User Commands                          lz4(1)



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


SYNOPSIS
       lz4 [OPTIONS] [-|INPUT-FILE] <OUTPUT-FILE>

       unlz4 is equivalent to lz4 -d
       lz4cat is equivalent to lz4 -dc

       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 lz4cat.



DESCRIPTION
       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.

       lz4 supports a command line syntax similar but not identical to
       gzip(1).  Differences are : lz4 preserve original files ; lz4 file1
       file2 means : compress file1 into file2 ; lz4 file shows real-time
       statistics during compression .

       Default behaviors can be modified by opt-in commands, described below.
       lz4 --quiet --multiple more closely mimics gzip behavior.


   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


OPTIONS
   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 extensionq

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

   Operation modifiers
       -1
               fast compression (default)

       -9
               high compression


       -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 file names.
               By default, the second filename is used as the destination
              filename for the compressed file.
               With -m , you can specify any number of input filenames. Each
              of them will be compressed independently, and the resulting name
              of each compressed file will be filename.lz4


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

       -BD
               block dependency (improves compression ratio on small blocks)

       --[no-]frame-crc
               select frame checksum (default:enabled)

       --[no-]content-size
               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.

       --[no-]sparse
               sparse mode support (default:enabled on file, disabled on
              stdout)

       -l
               use Legacy format (useful for Linux Kernel compression)

   Other options
       -v, --verbose
               verbose mode

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

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

       -V, --version
               display Version number and exit

       -k, --keep
               Don't delete source file.  This is default behavior anyway, so
              this option is just for compatibility with gzip/xz.

       -b
               benchmark file(s)

       -i#
               iteration loops [1-9](default : 3), benchmark mode only


BUGS
       Report bugs at: https://github.com/Cyan4973/lz4/issues


AUTHOR
       Yann Collet



lz4                               2015-03-21                            lz4(1)