Yann Collet 21ff1a839a updated doc to underline difference between block and frame

as this is a very frequent source of confusion for new users.

2019-04-12 11:27:44 -07:00

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Command Line Interface for LZ4 library

Build

The Command Line Interface (CLI) can be generated using the make command without any additional parameters.

The Makefile script supports all standard conventions, including standard targets (all, install, clean, etc.) and standard variables (CC, CFLAGS, CPPFLAGS, etc.).

For advanced use cases, there are targets to different variations of the CLI:

lz4 : default CLI, with a command line syntax close to gzip
lz4c : Same as lz4 with additional support legacy lz4 commands (incompatible with gzip)
lz4c32 : Same as lz4c, but forced to compile in 32-bits mode

The CLI generates and decodes LZ4-compressed frames.

Aggregation of parameters

CLI supports aggregation of parameters i.e. -b1, -e18, and -i1 can be joined into -b1e18i1.

Benchmark in Command Line Interface

CLI includes in-memory compression benchmark module for lz4. The benchmark is conducted using a given filename. The file is read into memory. It makes benchmark more precise as it eliminates I/O overhead.

The benchmark measures ratio, compressed size, compression and decompression speed. One can select compression levels starting from -b and ending with -e. The -i parameter selects a number of seconds used for each of tested levels.

Usage of Command Line Interface

The full list of commands can be obtained with -h or -H parameter:

Usage :
      lz4 [arg] [input] [output]

input   : a filename
          with no FILE, or when FILE is - or stdin, read standard input
Arguments :
 -1     : Fast compression (default)
 -9     : High compression
 -d     : decompression (default for .lz4 extension)
 -z     : force compression
 -D FILE: use FILE as dictionary
 -f     : overwrite output without prompting
 -k     : preserve source files(s)  (default)
--rm    : remove source file(s) after successful de/compression
 -h/-H  : display help/long help and exit

Advanced arguments :
 -V     : display Version number and exit
 -v     : verbose mode
 -q     : suppress warnings; specify twice to suppress errors too
 -c     : force write to standard output, even if it is the console
 -t     : test compressed file integrity
 -m     : multiple input files (implies automatic output filenames)
 -r     : operate recursively on directories (sets also -m)
 -l     : compress using Legacy format (Linux kernel compression)
 -B#    : cut file into blocks of size # bytes [32+]
                     or predefined block size [4-7] (default: 7)
 -BD    : Block dependency (improve compression ratio)
 -BX    : enable block checksum (default:disabled)
--no-frame-crc : disable stream checksum (default:enabled)
--content-size : compressed frame includes original size (default:not present)
--[no-]sparse  : sparse mode (default:enabled on file, disabled on stdout)
--favor-decSpeed: compressed files decompress faster, but are less compressed
--fast[=#]: switch to ultra fast compression level (default: 1)

Benchmark arguments :
 -b#    : benchmark file(s), using # compression level (default : 1)
 -e#    : test all compression levels from -bX to # (default : 1)
 -i#    : minimum evaluation time in seconds (default : 3s)```

License

All files in this directory are licensed under GPL-v2. See COPYING for details. The text of the license is also included at the top of each source file.

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