lz4, unlz4, lz4cat - Compress or decompress .lz4 files
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.
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. lz4 supports a command line syntax similar to gzip(1). The native file format is the .lz4 format.
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
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, 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.
fast compression (default)
- -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 output 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 the compressed file will be filename.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