lz4 man page

." ." lz4.1: This is a manual page for 'lz4' program. This file is part of the ." lz4 <http://www.lz4.org/> project. ." Author: Yann Collet ." ." No hyphenation

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 -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 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 preserves original files
lz4 compresses a single file by default (use -m for multiple files)
lz4 file1 file2 means : compress file1 into file2
When no destination name is provided, compressed file name receives a .lz4 suffix
When no destination name is provided, if stdout is not the console, it becomes the output (like a silent -c)
Therefore lz4 file > /dev/null will not create file.lz4
lz4 file shows real-time statistics during compression (use -q to silent them)

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 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 file names.
By default, the second filename is used as the destination filename for the compressed file.
With -m , it is possible to 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 (typically used for Linux Kernel compression)
note : -l is not compatible with -m (--multiple)

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

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)
-r
operate recursively on directories

Bugs

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

Author

Yann Collet

Info

2015-03-21 lz4 User Commands