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 of 400 MB/s per core, linearly scalable with multi-core CPUs. It
23 features an extremely fast decoder, with speed in multiple GB/s per
24 core, typically reaching RAM speed limit on multi-core systems. The
25 native 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 preserves original files
32 · lz4 compresses a single file by default (see -m for multiple files)
34 · lz4 file1 file2 means : compress file1 into file2
36 · lz4 file.lz4 will default to decompression (use -z to force com‐
38 pression)
39 · lz4 shows real-time notification statistics during compression or
41 decompression of a single file (use -q to silence them)
42 · If no destination name is provided, result is sent to stdout except
44 if stdout is the console.
45 · If no destination name is provided, and if stdout is the console,
47 file is compressed into file.lz4.
48 · As a consequence of previous rules, note the following example :
50 lz4 file | consumer sends compressed data to consumer through std‐
51 out, hence it does not create file.lz4.
52 · Another consequence of those rules is that to run lz4 under nohup,
54 you should provide a destination file: nohup lz4 file file.lz4,
55 because nohup writes the specified command´s output to a file.
56 Default behaviors can be modified by opt-in commands, detailed below.
60 · lz4 -m makes it possible to provide multiple input filenames, which
62 will be compressed into files using suffix .lz4. Progress notifica‐
63 tions are also disabled by default (use -v to enable them). This
64 mode has a behavior which more closely mimics gzip command line,
65 with the main remaining difference being that source files are pre‐
66 served by default.
67 · Similarly, lz4 -m -d can decompress multiple *.lz4 files.
69 · It´s possible to opt-in to erase source files on successful com‐
71 pression or decompression, using --rm command.
72 · Consequently, lz4 -m --rm behaves the same as gzip.
74 Concatenation of .lz4 files
78 It is possible to concatenate .lz4 files as is. lz4 will decompress
79 such files as if they were a single .lz4 file. For example:
80 lz4 file1 > foo.lz4
84 lz4 file2 >> foo.lz4
85 Then lz4cat foo.lz4 is equivalent to cat file1 file2.
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91 Short commands concatenation
92 In some cases, some options can be expressed using short command -x or
93 long command --long-word. Short commands can be concatenated together.
94 For example, -d -c is equivalent to -dc. Long commands cannot be con‐
95 catenated. They must be clearly separated by a space.
96 Multiple commands
98 When multiple contradictory commands are issued on a same command line,
99 only the latest one will be applied.
100 Operation mode
102 -z --compress
103 Compress. This is the default operation mode when no operation
104 mode option is specified, no other operation mode is implied
105 from the command name (for example, unlz4 implies --decompress),
106 nor from the input file name (for example, a file extension .lz4
107 implies --decompress by default). -z can also be used to force
108 compression of an already compressed .lz4 file.
109 -d --decompress --uncompress
111 Decompress. --decompress is also the default operation when the
112 input filename has an .lz4 extension.
113 -t --test
115 Test the integrity of compressed .lz4 files. The decompressed
116 data is discarded. No files are created nor removed.
117 -b# Benchmark mode, using # compression level.
119 Operation modifiers
121 -# Compression level, with # being any value from 1 to 16. Higher
122 values trade compression speed for compression ratio. Values
123 above 16 are considered the same as 16. Recommended values are 1
124 for fast compression (default), and 9 for high compression.
125 Speed/compression trade-off will vary depending on data to com‐
126 press. Decompression speed remains fast at all settings.
127 -f --[no-]force
129 This option has several effects:
130 If the target file already exists, overwrite it without prompt‐
132 ing.
133 When used with --decompress and lz4 cannot recognize the type of
135 the source file, copy the source file as is to standard output.
136 This allows lz4cat --force to be used like cat (1) for files
137 that have not been compressed with lz4.
138 -c --stdout --to-stdout
140 Force write to standard output, even if it is the console.
141 -m --multiple
143 Multiple input files. Compressed file names will be appended a
144 .lz4 suffix. This mode also reduces notification level. lz4 -m
145 has a behavior equivalent to gzip -k (it preserves source files
146 by default).
147 -r operate recursively on directories. This mode also sets -m (mul‐
149 tiple input files).
150 -B# Block size [4-7](default : 7)
152 -B4= 64KB ; -B5= 256KB ; -B6= 1MB ; -B7= 4MB
153 -BD Block Dependency (improves compression ratio on small blocks)
155 --[no-]frame-crc
157 Select frame checksum (default:enabled)
158 --[no-]content-size
160 Header includes original size (default:not present)
161 Note : this option can only be activated when the original size
162 can be determined, hence for a file. It won´t work with unknown
163 source size, such as stdin or pipe.
164 --[no-]sparse
166 Sparse mode support (default:enabled on file, disabled on std‐
167 out)
168 -l Use Legacy format (typically for Linux Kernel compression)
170 Note : -l is not compatible with -m (--multiple) nor -r
171 Other options
173 -v --verbose
174 Verbose mode
175 -q --quiet
177 Suppress warnings and real-time statistics; specify twice to
178 suppress errors too
179 -h -H --help
181 Display help/long help and exit
182 -V --version
184 Display Version number and exit
185 -k --keep
187 Preserve source files (default behavior)
188 --rm Delete source files on successful compression or decompression
190 -- Treat all subsequent arguments as files
192 Benchmark mode
194 -b# Benchmark file(s), using # compression level
195 -e# Benchmark multiple compression levels, from b# to e# (included)
197 -i# Minimum evaluation in seconds [1-9] (default : 3)
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201 Report bugs at: https://github.com/lz4/lz4/issues
202
204 Yann Collet
205lz4 1.8.1 2018-01-13 LZ4(1)