MAN page from Fedora 21 lz4-r131-1.fc21.x86_64.rpm
Section: User Commands (1)
NAMElz4, unlz4, lz4cat
- Compress or decompress .lz4 files
- 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.
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.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
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.
When multiple contradictory commands are issued on a same command line,only the latest one will be applied.
- -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.
fast compression (default)
- -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
block size [4-7](default : 7)
B4= 64KB ; B5= 256KB ; B6= 1MB ; B7= 4MB
block dependency (improve compression ratio)
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)
use Legacy format (useful for Linux Kernel compression)
- -v, --verbose
- -q, --quiet
suppress warnings; specify twice to suppress errors too
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.
iteration loops [1-9](default : 3), benchmark mode only
Report bugs at: https://github.com/Cyan4973/lz4
- Concatenation of .lz4 files
- Short commands concatenation
- Multiple commands
- Operation mode
- Operation modifiers
- Other options
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