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MAN page from CentOS 7 lz4-r131-2.el7.x86_64.rpm

lz4

Section: User Commands (1)
Updated: 2015-03-21
Index 

NAME

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

 

SYNOPSIS

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

unlz4is equivalent tolz4 -d
lz4catis equivalent tolz4 -dc

When writing scripts that need to decompress files,it is recommended to always use the namelz4with appropriate arguments(lz4 -dorlz4 -dc)instead of the namesunlz4andlz4cat.

 

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. lz4supports a command line syntax similar togzip(1).The native file format is the.lz4format.

 

Concatenation of .lz4 files

It is possible to concatenate.lz4files as is.lz4will decompress such files as if they were a single.lz4file. 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-xor long command--long-word .Short commands can be concatenated together. For example,-d -cis 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,unlz4implies--decompress ),nor from the input file name(for example, a file extension.lz4implies--decompressby default).-zcan also be used to force compression of an already compressed.lz4file.
-d, --decompress, --uncompress
Decompress.--decompressis also the default operation when the input filename has an.lz4extensionq
-t, --test
Test the integrity of compressed.lz4files.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--decompressandlz4cannot recognize the type of the source file,copy the source file as is to standard output.This allowslz4cat--forceto be used likecat(1)for files that have not been compressed withlz4.

-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 output filename for the compressed file.
 With-m, you can specify any number of input filenames. Each of them will be compressedindependently, and the resulting name of the compressed file will befilename.lz4

-B#

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

 block dependency (improve compression ratio)
--[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; 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

 

AUTHOR

Yann Collet


 

Index

NAME
SYNOPSIS
DESCRIPTION
Concatenation of .lz4 files
OPTIONS
Short commands concatenation
Multiple commands
Operation mode
Operation modifiers
Other options
BUGS
AUTHOR

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