1LZ4(1) User Commands LZ4(1)
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6 lz4 - lz4, unlz4, lz4cat - Compress or decompress .lz4 files
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9 lz4 [OPTIONS] [-|INPUT-FILE] OUTPUT-FILE
10 unlz4 is equivalent to lz4 -d
12 lz4cat is equivalent to lz4 -dcfm
14 When writing scripts that need to decompress files, it is recommended
16 to always use the name lz4 with appropriate arguments (lz4 -d or lz4
17 -dc) instead of the names unlz4 and lz4cat.
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20 lz4 is an extremely fast lossless compression algorithm, based on
21 byte-aligned LZ77 family of compression scheme. lz4 offers compression
22 speeds > 500 MB/s per core, linearly scalable with multi-core CPUs. It
23 features an extremely fast decoder, offering speed in multiple GB/s per
24 core, typically reaching RAM speed limit on multi-core systems. The na‐
25 tive file format is the .lz4 format.
26 Difference between lz4 and gzip
28 lz4 supports a command line syntax similar but not identical to
29 gzip(1). Differences are :
30 • lz4 compresses a single file by default (see -m for multiple files)
32 • lz4 file1 file2 means : compress file1 into file2
34 • lz4 file.lz4 will default to decompression (use -z to force com‐
36 pression)
37 • lz4 preserves original files (see --rm to erase source file on com‐
39 pletion)
40 • lz4 shows real-time notification statistics during compression or
42 decompression of a single file (use -q to silence them)
43 • When no destination is specified, result is sent on implicit out‐
45 put, which depends on stdout status. When stdout is Not the con‐
46 sole, it becomes the implicit output. Otherwise, if stdout is the
47 console, the implicit output is filename.lz4.
48 • It is considered bad practice to rely on implicit output in
50 scripts. because the script´s environment may change. Always use
51 explicit output in scripts. -c ensures that output will be stdout.
52 Conversely, providing a destination name, or using -m ensures that
53 the output will be either the specified name, or filename.lz4 re‐
54 spectively.
55 Default behaviors can be modified by opt-in commands, detailed below.
59 • lz4 -m makes it possible to provide multiple input filenames, which
61 will be compressed into files using suffix .lz4. Progress notifica‐
62 tions become disabled by default (use -v to enable them). This mode
63 has a behavior which more closely mimics gzip command line, with
64 the main remaining difference being that source files are preserved
65 by default.
66 • Similarly, lz4 -m -d can decompress multiple *.lz4 files.
68 • It´s possible to opt-in to erase source files on successful com‐
70 pression or decompression, using --rm command.
71 • Consequently, lz4 -m --rm behaves the same as gzip.
73 Concatenation of .lz4 files
77 It is possible to concatenate .lz4 files as is. lz4 will decompress
78 such files as if they were a single .lz4 file. For example:
79 lz4 file1 > foo.lz4
83 lz4 file2 >> foo.lz4
84 Then lz4cat foo.lz4 is equivalent to cat file1 file2.
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90 Short commands concatenation
91 In some cases, some options can be expressed using short command -x or
92 long command --long-word. Short commands can be concatenated together.
93 For example, -d -c is equivalent to -dc. Long commands cannot be con‐
94 catenated. They must be clearly separated by a space.
95 Multiple commands
97 When multiple contradictory commands are issued on a same command line,
98 only the latest one will be applied.
99 Operation mode
101 -z --compress
102 Compress. This is the default operation mode when no operation
103 mode option is specified, no other operation mode is implied
104 from the command name (for example, unlz4 implies --decompress),
105 nor from the input file name (for example, a file extension .lz4
106 implies --decompress by default). -z can also be used to force
107 compression of an already compressed .lz4 file.
108 -d --decompress --uncompress
110 Decompress. --decompress is also the default operation when the
111 input filename has an .lz4 extension.
112 -t --test
114 Test the integrity of compressed .lz4 files. The decompressed
115 data is discarded. No files are created nor removed.
116 -b# Benchmark mode, using # compression level.
118 --list List information about .lz4 files. note : current implementation
120 is limited to single-frame .lz4 files.
121 Operation modifiers
123 -# Compression level, with # being any value from 1 to 12. Higher
124 values trade compression speed for compression ratio. Values
125 above 12 are considered the same as 12. Recommended values are 1
126 for fast compression (default), and 9 for high compression.
127 Speed/compression trade-off will vary depending on data to com‐
128 press. Decompression speed remains fast at all settings.
129 --fast[=#]
131 Switch to ultra-fast compression levels. The higher the value,
132 the faster the compression speed, at the cost of some compres‐
133 sion ratio. If =# is not present, it defaults to 1. This setting
134 overrides compression level if one was set previously. Simi‐
135 larly, if a compression level is set after --fast, it overrides
136 it.
137 --best Set highest compression level. Same as -12.
139 --favor-decSpeed
141 Generate compressed data optimized for decompression speed. Com‐
142 pressed data will be larger as a consequence (typically by
143 ~0.5%), while decompression speed will be improved by 5-20%, de‐
144 pending on use cases. This option only works in combination with
145 very high compression levels (>=10).
146 -D dictionaryName
148 Compress, decompress or benchmark using dictionary dictionary‐
149 Name. Compression and decompression must use the same dictionary
150 to be compatible. Using a different dictionary during decompres‐
151 sion will either abort due to decompression error, or generate a
152 checksum error.
153 -f --[no-]force
155 This option has several effects:
156 If the target file already exists, overwrite it without prompt‐
158 ing.
159 When used with --decompress and lz4 cannot recognize the type of
161 the source file, copy the source file as is to standard output.
162 This allows lz4cat --force to be used like cat (1) for files
163 that have not been compressed with lz4.
164 -c --stdout --to-stdout
166 Force write to standard output, even if it is the console.
167 -m --multiple
169 Multiple input files. Compressed file names will be appended a
170 .lz4 suffix. This mode also reduces notification level. Can also
171 be used to list multiple files. lz4 -m has a behavior equivalent
172 to gzip -k (it preserves source files by default).
173 -r operate recursively on directories. This mode also sets -m (mul‐
175 tiple input files).
176 -B# Block size [4-7](default : 7)
178 -B4= 64KB ; -B5= 256KB ; -B6= 1MB ; -B7= 4MB
179 -BI Produce independent blocks (default)
181 -BD Blocks depend on predecessors (improves compression ratio, more
183 noticeable on small blocks)
184 -BX Generate block checksums (default:disabled)
186 --[no-]frame-crc
188 Select frame checksum (default:enabled)
189 --no-crc
191 Disable both frame and block checksums
192 --[no-]content-size
194 Header includes original size (default:not present)
195 Note : this option can only be activated when the original size
196 can be determined, hence for a file. It won´t work with unknown
197 source size, such as stdin or pipe.
198 --[no-]sparse
200 Sparse mode support (default:enabled on file, disabled on std‐
201 out)
202 -l Use Legacy format (typically for Linux Kernel compression)
204 Note : -l is not compatible with -m (--multiple) nor -r
205 Other options
207 -v --verbose
208 Verbose mode
209 -q --quiet
211 Suppress warnings and real-time statistics; specify twice to
212 suppress errors too
213 -h -H --help
215 Display help/long help and exit
216 -V --version
218 Display Version number and exit
219 -k --keep
221 Preserve source files (default behavior)
222 --rm Delete source files on successful compression or decompression
224 -- Treat all subsequent arguments as files
226 Benchmark mode
228 -b# Benchmark file(s), using # compression level
229 -e# Benchmark multiple compression levels, from b# to e# (included)
231 -i# Minimum evaluation time in seconds [1-9] (default : 3)
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235 Report bugs at: https://github.com/lz4/lz4/issues
236
238 Yann Collet
239lz4 v1.9.4 August 2022 LZ4(1)