lz4(1) User Commands lz4(1) NAME lz4, unlz4, lz4cat - Compress or decompress .lz4 files SYNOPSIS lz4 [OPTIONS] [-|INPUT-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 lz4 2015-03-21 lz4(1)