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.
- -#
- 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
- -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
- -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