. . lz4 - 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 -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\. .

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 (see -m for multiple files) . lz4 file1 file2 means : compress file1 into file2 . lz4 shows real-time notification statistics during compression or decompression of a single file (use -q to silent them) . If no destination name is provided, result is sent to stdout except if stdout is the console\. . If no destination name is provided, and if stdout is the console, file is compressed into file\.lz4\. . As a consequence of previous rules, note the following example : lz4 file | consumer sends compressed data to consumer through stdout, hence it does not create any file\.lz4\. . .

Default behaviors can be modified by opt-in commands, detailed below\. .

lz4 -m makes it possible to provide multiple input filenames, which will be compressed into files using suffix \.lz4\. Progress notifications are also disabled by default\. This mode has a behavior which more closely mimics gzip command line, with the main difference being that source files are preserved by default\. . It\'s possible to opt-in to erase source files on successful compression or decompression, using --rm command\. . Consequently, lz4 -m --rm behaves the same as gzip\. . . 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 .

. 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 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\. .

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-# 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 input files\. Compressed file names will be appended a \.lz4 suffix\. This mode also reduces notification level\. lz4 -m has a behavior equivalent to gzip -k (it preserves source files by default)\. .

-r operate recursively on directories\. This mode also sets -m (multiple input files)\. .

-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 for Linux Kernel compression) .

Note : -l is not compatible with -m (--multiple) nor -r .

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-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 Preserve source files (default behavior) .

--rm Delete source files on successful compression or decompression .

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-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 .

Report bugs at: https://github\.com/lz4/lz4/issues . Yann Collet