zstd-1.5.0.tar.gz

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: - `zstd` : default CLI supporting gzip-like arguments; includes dictionary builder, benchmark, and supports decompression of legacy zstd formats - `zstd_nolegacy` : Same as `zstd` but without support for legacy zstd formats - `zstd-small` : CLI optimized for minimal size; no dictionary builder, no benchmark, and no support for legacy zstd formats - `zstd-compress` : version of CLI which can only compress into zstd format - `zstd-decompress` : version of CLI which can only decompress zstd format ### Compilation variables `zstd` scope can be altered by modifying the following `make` variables : - __HAVE_THREAD__ : multithreading is automatically enabled when `pthread` is detected. It's possible to disable multithread support, by setting `HAVE_THREAD=0`. Example : `make zstd HAVE_THREAD=0` It's also possible to force multithread support, using `HAVE_THREAD=1`. In which case, linking stage will fail if neither `pthread` nor `windows.h` library can be found. This is useful to ensure this feature is not silently disabled. - __ZSTD_LEGACY_SUPPORT__ : `zstd` can decompress files compressed by older versions of `zstd`. Starting v0.8.0, all versions of `zstd` produce frames compliant with the [specification](../doc/zstd_compression_format.md), and are therefore compatible. But older versions (< v0.8.0) produced different, incompatible, frames. By default, `zstd` supports decoding legacy formats >= v0.4.0 (`ZSTD_LEGACY_SUPPORT=4`). This can be altered by modifying this compilation variable. `ZSTD_LEGACY_SUPPORT=1` means "support all formats >= v0.1.0". `ZSTD_LEGACY_SUPPORT=2` means "support all formats >= v0.2.0", and so on. `ZSTD_LEGACY_SUPPORT=0` means _DO NOT_ support any legacy format. if `ZSTD_LEGACY_SUPPORT >= 8`, it's the same as `0`, since there is no legacy format after `7`. Note : `zstd` only supports decoding older formats, and cannot generate any legacy format. - __HAVE_ZLIB__ : `zstd` can compress and decompress files in `.gz` format. This is ordered through command `--format=gzip`. Alternatively, symlinks named `gzip` or `gunzip` will mimic intended behavior. `.gz` support is automatically enabled when `zlib` library is detected at build time. It's possible to disable `.gz` support, by setting `HAVE_ZLIB=0`. Example : `make zstd HAVE_ZLIB=0` It's also possible to force compilation with zlib support, using `HAVE_ZLIB=1`. In which case, linking stage will fail if `zlib` library cannot be found. This is useful to prevent silent feature disabling. - __HAVE_LZMA__ : `zstd` can compress and decompress files in `.xz` and `.lzma` formats. This is ordered through commands `--format=xz` and `--format=lzma` respectively. Alternatively, symlinks named `xz`, `unxz`, `lzma`, or `unlzma` will mimic intended behavior. `.xz` and `.lzma` support is automatically enabled when `lzma` library is detected at build time. It's possible to disable `.xz` and `.lzma` support, by setting `HAVE_LZMA=0`. Example : `make zstd HAVE_LZMA=0` It's also possible to force compilation with lzma support, using `HAVE_LZMA=1`. In which case, linking stage will fail if `lzma` library cannot be found. This is useful to prevent silent feature disabling. - __HAVE_LZ4__ : `zstd` can compress and decompress files in `.lz4` formats. This is ordered through commands `--format=lz4`. Alternatively, symlinks named `lz4`, or `unlz4` will mimic intended behavior. `.lz4` support is automatically enabled when `lz4` library is detected at build time. It's possible to disable `.lz4` support, by setting `HAVE_LZ4=0` . Example : `make zstd HAVE_LZ4=0` It's also possible to force compilation with lz4 support, using `HAVE_LZ4=1`. In which case, linking stage will fail if `lz4` library cannot be found. This is useful to prevent silent feature disabling. - __ZSTD_NOBENCH__ : `zstd` cli will be compiled without its integrated benchmark module. This can be useful to produce smaller binaries. In this case, the corresponding unit can also be excluded from compilation target. - __ZSTD_NODICT__ : `zstd` cli will be compiled without support for the integrated dictionary builder. This can be useful to produce smaller binaries. In this case, the corresponding unit can also be excluded from compilation target. - __ZSTD_NOCOMPRESS__ : `zstd` cli will be compiled without support for compression. The resulting binary will only be able to decompress files. This can be useful to produce smaller binaries. A corresponding `Makefile` target using this ability is `zstd-decompress`. - __ZSTD_NODECOMPRESS__ : `zstd` cli will be compiled without support for decompression. The resulting binary will only be able to compress files. This can be useful to produce smaller binaries. A corresponding `Makefile` target using this ability is `zstd-compress`. - __BACKTRACE__ : `zstd` can display a stack backtrace when execution generates a runtime exception. By default, this feature may be degraded/disabled on some platforms unless additional compiler directives are applied. When triaging a runtime issue, enabling this feature can provide more context to determine the location of the fault. Example : `make zstd BACKTRACE=1` ### 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. - `zstdmt` : compress using all cores available on local system. - `zcat` : will decompress and output target file using any of the supported formats. `gzcat` and `zstdcat` are also equivalent. - `gzip` : if zlib support is enabled, will mimic `gzip` by compressing file using `.gz` format, removing source file by default (use `--keep` to preserve). If zlib is not supported, triggers an error. - `xz` : if lzma support is enabled, will mimic `xz` by compressing file using `.xz` format, removing source file by default (use `--keep` to preserve). If xz is not supported, triggers an error. - `lzma` : if lzma support is enabled, will mimic `lzma` by compressing file using `.lzma` format, removing source file by default (use `--keep` to preserve). If lzma is not supported, triggers an error. - `lz4` : if lz4 support is enabled, will mimic `lz4` by compressing file using `.lz4` format. If lz4 is not supported, triggers an error. - `unzstd` and `unlz4` will decompress any of the supported format. - `ungz`, `unxz` and `unlzma` will do the same, and will also remove source file by default (use `--keep` to preserve). ### 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 dict