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diff --git a/programs/README.md b/programs/README.md index 7668d49a2073..53706de727b7 100644 --- a/programs/README.md +++ b/programs/README.md @@ -10,7 +10,7 @@ There are however other Makefile targets that create different variations of CLI - `zstd-decompress` : version of CLI which can only decompress zstd format -#### Compilation variables +### Compilation variables `zstd` scope can be altered by modifying the following `make` variables : - __HAVE_THREAD__ : multithreading is automatically enabled when `pthread` is detected. @@ -61,6 +61,24 @@ There are however other Makefile targets that create different variations of CLI 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 @@ -69,11 +87,11 @@ There are however other Makefile targets that create different variations of CLI Example : `make zstd BACKTRACE=1` -#### Aggregation of parameters +### Aggregation of parameters CLI supports aggregation of parameters i.e. `-b1`, `-e18`, and `-i1` can be joined into `-b1e18i1`. -#### Symlink shortcuts +### 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. @@ -86,7 +104,7 @@ When the name of the symlink has a specific value, it triggers an associated beh - `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 +### 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`), @@ -106,7 +124,7 @@ Usage of the dictionary builder and created dictionaries with CLI: 3. Decompress with the dictionary: `zstd --decompress FILE.zst -D dictionaryName` -#### Benchmark in Command Line Interface +### 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. @@ -118,7 +136,7 @@ One can select compression levels starting from `-b` and ending with `-e`. The `-i` parameter selects minimal time used for each of tested levels. -#### Usage of Command Line Interface +### Usage of Command Line Interface The full list of options can be obtained with `-h` or `-H` parameter: ``` Usage : @@ -142,23 +160,34 @@ Advanced arguments : -q : suppress warnings; specify twice to suppress errors too -c : force write to standard output, even if it is the console -l : print information about zstd compressed files +--exclude-compressed: only compress files that are not previously compressed --ultra : enable levels beyond 19, up to 22 (requires more memory) ---long : enable long distance matching (requires more memory) +--long[=#]: enable long distance matching with given window log (default: 27) +--fast[=#]: switch to very fast compression levels (default: 1) +--adapt : dynamically adapt compression level to I/O conditions +--stream-size=# : optimize compression parameters for streaming input of given number of bytes +--size-hint=# optimize compression parameters for streaming input of approximately this size +--target-compressed-block-size=# : make compressed block near targeted size + -T# : spawns # compression threads (default: 1, 0==# cores) + -B# : select size of each job (default: 0==automatic) +--rsyncable : compress using a rsync-friendly method (-B sets block size) --no-dictID : don't write dictID into header (dictionary compression) --[no-]check : integrity check (default: enabled) +--[no-]compress-literals : force (un)compressed literals -r : operate recursively on directories +--output-dir-flat[=directory]: all resulting files stored into `directory`. +--format=zstd : compress files to the .zst format (default) --format=gzip : compress files to the .gz format ---format=xz : compress files to the .xz format ---format=lzma : compress files to the .lzma format --test : test compressed file integrity --[no-]sparse : sparse mode (default: disabled) -M# : Set a memory usage limit for decompression +--no-progress : do not display the progress bar -- : All arguments after "--" are treated as files 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 args ---train-fastcover[=k=#,d=#,f=#,steps=#,split=#,shrink[=#],accel=#] : use the fastcover algorithm with optional args +--train-fastcover[=k=#,d=#,f=#,steps=#,split=#,accel=#,shrink[=#]] : use the fast cover algorithm with optional args --train-legacy[=s=#] : use the legacy algorithm with selectivity (default: 9) -o file : `file` is dictionary name (default: dictionary) --maxdict=# : limit dictionary to specified size (default: 112640) @@ -172,16 +201,19 @@ Benchmark arguments : --priority=rt : set process priority to real-time ``` -#### Restricted usage of Environment Variables -Using environment variables to set parameters has security implications. -Therefore, this avenue is intentionally restricted. -Only `ZSTD_CLEVEL` is supported currently, for setting compression level. -`ZSTD_CLEVEL` can be used to set the level between 1 and 19 (the "normal" range). -If the value of `ZSTD_CLEVEL` is not a valid integer, it will be ignored with a warning message. -`ZSTD_CLEVEL` just replaces the default compression level (`3`). -It can be overridden by corresponding command line arguments. +### Passing parameters through Environment Variables +`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). +This 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` only replaces the default compression level, +it can then be overridden by corresponding command line arguments. + +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`. -#### Long distance matching mode +### 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. @@ -205,12 +237,12 @@ 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 -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`| +| `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. @@ -233,7 +265,7 @@ The below table illustrates this on the [Silesia compression corpus]. | `zstd -10 --long`| `3.566` | `16.2 MB/s` | `415.7 MB/s` | -#### zstdgrep +### 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 : |