Your browser sucks, JavaScript disabled! Gunnar's console needs JavaScript and WebAssembly. Git over SSH on port 2222 does not.

nordisk/znippy-zoomies

zstd-sys-rs/zstd/programs/README.md

Command Line Interface for Zstandard library

Command Line Interface (CLI) can be created using the make command without any additional parameters. There are however other Makefile targets that create different variations of CLI:

Compilation variables

zstd scope can be altered by modifying the following make variables :

Aggregation of parameters

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

Symlink shortcuts

It's possible to invoke zstd through a symlink. When the name of the symlink has a specific value, it triggers an associated behavior.

Dictionary builder in Command Line Interface

Zstd offers a training mode, which can be used to tune the algorithm for a selected type of data, by providing it with a few samples. The result of the training is stored in a file selected with the -o option (default name is dictionary), which can be loaded before compression and decompression.

Using a dictionary, the compression ratio achievable on small data improves dramatically. These compression gains are achieved while simultaneously providing faster compression and decompression speeds. Dictionary work if there is some correlation in a family of small data (there is no universal dictionary). Hence, deploying one dictionary per type of data will provide the greater benefits. Dictionary gains are mostly effective in the first few KB. Then, the compression algorithm will rely more and more on previously decoded content to compress the rest of the file.

Usage of the dictionary builder and created dictionaries with CLI:

  1. Create the dictionary : zstd --train PathToTrainingSet/* -o dictionaryName
  2. Compress with the dictionary: zstd FILE -D dictionaryName
  3. Decompress with the dictionary: zstd --decompress FILE.zst -D dictionaryName

Benchmark in Command Line Interface

CLI includes in-memory compression benchmark module for zstd. The benchmark is conducted using given filenames. The files are read into memory and joined together. It makes benchmark more precise as it eliminates I/O overhead. Multiple filenames can be supplied, as multiple parameters, with wildcards, or directory names can be used with -r option. If no file is provided, the benchmark will use a procedurally generated "lorem ipsum" content.

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 minimal time used for each of tested levels.

The benchmark can also be used to test specific parameters, such as number of threads (-T#), or advanced parameters (--zstd=#), or dictionary compression (-D DICTIONARY), and many others available on command for regular compression and decompression.

Usage of Command Line Interface

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

*** Zstandard CLI (64-bit) v1.5.6, by Yann Collet ***

Compress or decompress the INPUT file(s); reads from STDIN if INPUT is `-` or not provided.

Usage: zstd [OPTIONS...] [INPUT... | -] [-o OUTPUT]

Options:
  -o OUTPUT                     Write output to a single file, OUTPUT.
  -k, --keep                    Preserve INPUT file(s). [Default]
  --rm                          Remove INPUT file(s) after successful (de)compression.

  -#                            Desired compression level, where `#` is a number between 1 and 19;
                                lower numbers provide faster compression, higher numbers yield
                                better compression ratios. [Default: 3]

  -d, --decompress              Perform decompression.
  -D DICT                       Use DICT as the dictionary for compression or decompression.

  -f, --force                   Disable input and output checks. Allows overwriting existing files,
                                receiving input from the console, printing output to STDOUT, and
                                operating on links, block devices, etc. Unrecognized formats will be
                                passed-through through as-is.

  -h                            Display short usage and exit.
  -H, --help                    Display full help and exit.
  -V, --version                 Display the program version and exit.

Advanced options:
  -c, --stdout                  Write to STDOUT (even if it is a console) and keep the INPUT file(s).

  -v, --verbose                 Enable verbose output; pass multiple times to increase verbosity.
  -q, --quiet                   Suppress warnings; pass twice to suppress errors.
  --trace LOG                   Log tracing information to LOG.

  --[no-]progress               Forcibly show/hide the progress counter. NOTE: Any (de)compressed
                                output to terminal will mix with progress counter text.

  -r                            Operate recursively on directories.
  --filelist LIST               Read a list of files to operate on from LIST.
  --output-dir-flat DIR         Store processed files in DIR.
  --output-dir-mirror DIR       Store processed files in DIR, respecting original directory structure.
  --[no-]asyncio                Use asynchronous IO. [Default: Enabled]

  --[no-]check                  Add XXH64 integrity checksums during compression. [Default: Add, Validate]
                                If `-d` is present, ignore/validate checksums during decompression.

  --                            Treat remaining arguments after `--` as files.

Advanced compression options:
  --ultra                       Enable levels beyond 19, up to 22; requires more memory.
  --fast[=#]                    Use to very fast compression levels. [Default: 1]
  --adapt                       Dynamically adapt compression level to I/O conditions.
  --long[=#]                    Enable long distance matching with window log #. [Default: 27]
  --patch-from=REF              Use REF as the reference point for Zstandard's diff engine.

  -T#                           Spawn # compression threads. [Default: 1; pass 0 for core count.]
  --single-thread               Share a single thread for I/O and compression (slightly different than `-T1`).
  --auto-threads={physical|logical}
                                Use physical/logical cores when using `-T0`. [Default: Physical]

  -B#                           Set job size to #. [Default: 0 (automatic)]
  --rsyncable                   Compress using a rsync-friendly method (`-B` sets block size).

  --exclude-compressed          Only compress files that are not already compressed.

  --stream-size=#               Specify size of streaming input from STDIN.
  --size-hint=#                 Optimize compression parameters for streaming input of approximately size #.
  --target-compressed-block-size=#
                                Generate compressed blocks of approximately # size.

  --no-dictID                   Don't write `dictID` into the header (dictionary compression only).
  --[no-]compress-literals      Force (un)compressed literals.
  --[no-]row-match-finder       Explicitly enable/disable the fast, row-based matchfinder for
                                the 'greedy', 'lazy', and 'lazy2' strategies.

  --format=zstd                 Compress files to the `.zst` format. [Default]
  --[no-]mmap-dict              Memory-map dictionary file rather than mallocing and loading all at once
  --format=gzip                 Compress files to the `.gz` format.
  --format=xz                   Compress files to the `.xz` format.
  --format=lzma                 Compress files to the `.lzma` format.
  --format=lz4                 Compress files to the `.lz4` format.

Advanced decompression options:
  -l                            Print information about Zstandard-compressed files.
  --test                        Test compressed file integrity.
  -M#                           Set the memory usage limit to # megabytes.
  --[no-]sparse                 Enable sparse mode. [Default: Enabled for files, disabled for STDOUT.]
  --[no-]pass-through           Pass through uncompressed files as-is. [Default: Disabled]

Dictionary builder:
  --train                       Create a dictionary from a training set of files.

  --train-cover[=k=#,d=#,steps=#,split=#,shrink[=#]]
                                Use the cover algorithm (with optional arguments).
  --train-fastcover[=k=#,d=#,f=#,steps=#,split=#,accel=#,shrink[=#]]
                                Use the fast cover algorithm (with optional arguments).

  --train-legacy[=s=#]          Use the legacy algorithm with selectivity #. [Default: 9]
  -o NAME                       Use NAME as dictionary name. [Default: dictionary]
  --maxdict=#                   Limit dictionary to specified size #. [Default: 112640]
  --dictID=#                    Force dictionary ID to #. [Default: Random]

Benchmark options:
  -b#                           Perform benchmarking with compression level #. [Default: 3]
  -e#                           Test all compression levels up to #; starting level is `-b#`. [Default: 1]
  -i#                           Set the minimum evaluation to time # seconds. [Default: 3]
  -B#                           Cut file into independent chunks of size #. [Default: No chunking]
  -S                            Output one benchmark result per input file. [Default: Consolidated result]
  -D dictionary                 Benchmark using dictionary
  --priority=rt                 Set process priority to real-time.

Passing parameters through Environment Variables

There is no "generic" way to pass "any kind of parameter" to zstd in a pass-through manner. Using environment variables for this purpose has security implications. Therefore, this avenue is intentionally restricted and only supports ZSTD_CLEVEL and ZSTD_NBTHREADS.

ZSTD_CLEVEL can be used to modify the default compression level of zstd (usually set to 3) to another value between 1 and 19 (the "normal" range).

ZSTD_NBTHREADS can be used to specify a number of threads that zstd will use for compression, which by default is 1. This functionality only exists when zstd is compiled with multithread support. 0 means "use as many threads as detected cpu cores on local system". The max # of threads is capped at ZSTDMT_NBWORKERS_MAX, which is either 64 in 32-bit mode, or 256 for 64-bit environments.

This functionality can be useful when zstd CLI is invoked in a way that doesn't allow passing arguments. One such scenario is tar --zstd. As ZSTD_CLEVEL and ZSTD_NBTHREADS only replace the default compression level and number of threads respectively, they can both be overridden by corresponding command line arguments: -# for compression level and -T# for number of threads.

Long distance matching mode

The long distance matching mode, enabled with --long, is designed to improve the compression ratio for files with long matches at a large distance (up to the maximum window size, 128 MiB) while still maintaining compression speed.

Enabling this mode sets the window size to 128 MiB and thus increases the memory usage for both the compressor and decompressor. Performance in terms of speed is dependent on long matches being found. Compression speed may degrade if few long matches are found. Decompression speed usually improves when there are many long distance matches.

Below are graphs comparing the compression speed, compression ratio, and decompression speed with and without long distance matching on an ideal use case: a tar of four versions of clang (versions 3.4.1, 3.4.2, 3.5.0, 3.5.1) with a total size of 244889600 B. This is an ideal use case as there are many long distance matches within the maximum window size of 128 MiB (each version is less than 128 MiB).

Compression Speed vs Ratio Decompression Speed
Compression Speed vs Ratio Decompression Speed
Method Compression ratio Compression speed Decompression speed
zstd -1 5.065 284.8 MB/s 759.3 MB/s
zstd -5 5.826 124.9 MB/s 674.0 MB/s
zstd -10 6.504 29.5 MB/s 771.3 MB/s
zstd -1 --long 17.426 220.6 MB/s 1638.4 MB/s
zstd -5 --long 19.661 165.5 MB/s 1530.6 MB/s
zstd -10 --long 21.949 75.6 MB/s 1632.6 MB/s

On this file, the compression ratio improves significantly with minimal impact on compression speed, and the decompression speed doubles.

On the other extreme, compressing a file with few long distance matches (such as the Silesia compression corpus) will likely lead to a deterioration in compression speed (for lower levels) with minimal change in compression ratio.

The below table illustrates this on the Silesia compression corpus.

Method Compression ratio Compression speed Decompression speed
zstd -1 2.878 231.7 MB/s 594.4 MB/s
zstd -1 --long 2.929 106.5 MB/s 517.9 MB/s
zstd -5 3.274 77.1 MB/s 464.2 MB/s
zstd -5 --long 3.319 51.7 MB/s 371.9 MB/s
zstd -10 3.523 16.4 MB/s 489.2 MB/s
zstd -10 --long 3.566 16.2 MB/s 415.7 MB/s

zstdgrep

zstdgrep is a utility which makes it possible to grep directly a .zst compressed file. It's used the same way as normal grep, for example : zstdgrep pattern file.zst

zstdgrep is not compatible with dictionary compression.

To search into a file compressed with a dictionary, it's necessary to decompress it using zstd or zstdcat, and then pipe the result to grep. For example : zstdcat -D dictionary -qc -- file.zst | grep pattern