1LZ4(1)                           User Commands                          LZ4(1)
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NAME

6       lz4 - lz4, unlz4, lz4cat - Compress or decompress .lz4 files
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SYNOPSIS

9       lz4 [OPTIONS] [-|INPUT-FILE] OUTPUT-FILE
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11       unlz4 is equivalent to lz4 -d
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13       lz4cat is equivalent to lz4 -dcfm
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15       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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DESCRIPTION

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.
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27   Difference between lz4 and gzip
28       lz4 supports a  command  line  syntax  similar  but  not  identical  to
29       gzip(1). Differences are :
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31       ·   lz4 preserves original files
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33       ·   lz4 compresses a single file by default (see -m for multiple files)
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35       ·   lz4 file1 file2 means : compress file1 into file2
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37       ·   lz4  shows  real-time notification statistics during compression or
38           decompression of a single file (use -q to silent them)
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40       ·   If no destination name is provided, result is sent to stdout except
41           if stdout is the console.
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43       ·   If  no  destination name is provided, and if stdout is the console,
44           file is compressed into file.lz4.
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46       ·   As a consequence of previous rules, note the  following  example  :
47           lz4  file | consumer sends compressed data to consumer through std‐
48           out, hence it does not create any file.lz4.
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52       Default behaviors can be modified by opt-in commands, detailed below.
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54       ·   lz4 -m makes it possible to provide multiple input filenames, which
55           will be compressed into files using suffix .lz4. Progress notifica‐
56           tions are also disabled by default. This mode has a behavior  which
57           more  closely  mimics  gzip  command line, with the main difference
58           being that source files are preserved by default.
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60       ·   It´s possible to opt-in to erase source files  on  successful  com‐
61           pression or decompression, using --rm command.
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63       ·   Consequently, lz4 -m --rm behaves the same as gzip.
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67   Concatenation of .lz4 files
68       It  is  possible  to  concatenate .lz4 files as is. lz4 will decompress
69       such files as if they were a single .lz4 file. For example: lz4 file1 >
70       foo.lz4 lz4 file2 >> foo.lz4
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72       then lz4cat foo.lz4
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74       is equivalent to : cat file1 file2
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OPTIONS

77   Short commands concatenation
78       In  some cases, some options can be expressed using short command -x or
79       long command --long-word. Short commands can be concatenated  together.
80       For  example,  -d -c is equivalent to -dc. Long commands cannot be con‐
81       catenated. They must be clearly separated by a space.
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83   Multiple commands
84       When multiple contradictory commands are issued on a same command line,
85       only the latest one will be applied.
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87   Operation mode
88       -z --compress
89              Compress.  This  is the default operation mode when no operation
90              mode option is specified, no other  operation  mode  is  implied
91              from the command name (for example, unlz4 implies --decompress),
92              nor from the input file name (for example, a file extension .lz4
93              implies  --decompress  by default). -z can also be used to force
94              compression of an already compressed .lz4 file.
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96       -d --decompress --uncompress
97              Decompress. --decompress is also the default operation when  the
98              input filename has an .lz4 extension.
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100       -t --test
101              Test  the  integrity  of compressed .lz4 files. The decompressed
102              data is discarded. No files are created nor removed.
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104       -b#    Benchmark mode, using # compression level.
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106   Operation modifiers
107       -#     Compression level, with # being any value from 1 to  16.  Higher
108              values  trade  compression  speed  for compression ratio. Values
109              above 16 are considered the same as 16. Recommended values are 1
110              for  fast  compression  (default),  and  9 for high compression.
111              Speed/compression trade-off will vary depending on data to  com‐
112              press. Decompression speed remains fast at all settings.
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114       -f --[no-]force
115              This option has several effects:
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117              If  the target file already exists, overwrite it without prompt‐
118              ing.
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120              When used with --decompress and lz4 cannot recognize the type of
121              the  source file, copy the source file as is to standard output.
122              This allows lz4cat --force to be used like  cat  (1)  for  files
123              that have not been compressed with lz4.
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125       -c --stdout --to-stdout
126              Force write to standard output, even if it is the console.
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128       -m --multiple
129              Multiple  input  files. Compressed file names will be appended a
130              .lz4 suffix. This mode also reduces notification level.  lz4  -m
131              has  a behavior equivalent to gzip -k (it preserves source files
132              by default).
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134       -r     operate recursively on directories. This mode also sets -m (mul‐
135              tiple input files).
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137       -B#    Block size [4-7](default : 7)
138              -B4= 64KB ; -B5= 256KB ; -B6= 1MB ; -B7= 4MB
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140       -BD    Block Dependency (improves compression ratio on small blocks)
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142       --[no-]frame-crc
143              Select frame checksum (default:enabled)
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145       --[no-]content-size
146              Header includes original size (default:not present)
147              Note  : this option can only be activated when the original size
148              can be determined, hence for a file. It won´t work with  unknown
149              source size, such as stdin or pipe.
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151       --[no-]sparse
152              Sparse  mode  support (default:enabled on file, disabled on std‐
153              out)
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155       -l     Use Legacy format (typically for Linux Kernel compression)
156              Note : -l is not compatible with -m (--multiple) nor -r
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158   Other options
159       -v --verbose
160              Verbose mode
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162       -q --quiet
163              Suppress warnings and real-time  statistics;  specify  twice  to
164              suppress errors too
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166       -h -H --help
167              Display help/long help and exit
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169       -V --version
170              Display Version number and exit
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172       -k --keep
173              Preserve source files (default behavior)
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175       --rm   Delete source files on successful compression or decompression
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177   Benchmark mode
178       -b#    Benchmark file(s), using # compression level
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180       -e#    Benchmark multiple compression levels, from b# to e# (included)
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182       -i#    Minimum evaluation in seconds [1-9] (default : 3)
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184       -r     Operate recursively on directories
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BUGS

187       Report bugs at: https://github.com/lz4/lz4/issues
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AUTHOR

190       Yann Collet
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194lz4 1.7.4                        November 2016                          LZ4(1)
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