Provided by: liblz4-tool_0.0~r131-2ubuntu3_amd64
lz4, unlz4, lz4cat - Compress or decompress .lz4 files
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.
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 example: lz4 file1 > foo.lz4 lz4 file2 >> foo.lz4 then lz4cat 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. 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 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 -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
Report bugs at: https://github.com/Cyan4973/lz4