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. 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.
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.
- -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 destination 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 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 (useful for Linux Kernel compression)
- -v, --verbose
-
verbose mode
- -q, --quiet
-
suppress warnings and real-time statistics; 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), 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/Cyan4973/lz4/issues