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added zstdgrep documentation 

presenting `zstdgrep` limit regarding dictionary compression
with workaround recommended by @tobwen (#1268)
dev
Yann Collet 2018-08-09 12:28:25 -07:00
parent 1bc69b9cb5
commit 51e71a5ec7
1 changed files with 22 additions and 8 deletions
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@ -185,7 +185,7 @@ version is less than `128 MiB`).
Compression Speed vs Ratio | Decompression Speed Compression Speed vs Ratio | Decompression Speed
---------------------------|--------------------- ---------------------------|---------------------
![Compression Speed vs Ratio](../doc/images/ldmCspeed.png "Compression Speed vs Ratio") | ![Decompression Speed](../doc/images/ldmDspeed.png "Decompression Speed") ![Compression Speed vs Ratio](https://raw.githubusercontent.com/facebook/zstd/v1.3.3/doc/images/ldmCspeed.png "Compression Speed vs Ratio") | ![Decompression Speed](https://raw.githubusercontent.com/facebook/zstd/v1.3.3/doc/images/ldmDspeed.png "Decompression Speed")
| Method | Compression ratio | Compression speed | Decompression speed | | Method | Compression ratio | Compression speed | Decompression speed |
|:-------|------------------:|-------------------------:|---------------------------:| |:-------|------------------:|-------------------------:|---------------------------:|
@ -208,10 +208,24 @@ The below table illustrates this on the [Silesia compression corpus].
[Silesia compression corpus]: http://sun.aei.polsl.pl/~sdeor/index.php?page=silesia [Silesia compression corpus]: http://sun.aei.polsl.pl/~sdeor/index.php?page=silesia
| Method | Compression ratio | Compression speed | Decompression speed | | Method | Compression ratio | Compression speed | Decompression speed |
|:-------|------------------:|-------------------------:|---------------------------:| |:-------|------------------:|------------------:|---------------------:|
| `zstd -1` | `2.878` | `231.7 MB/s` | `594.4 MB/s` | | `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 -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` | `3.274` | `77.1 MB/s` | `464.2 MB/s` |
| `zstd -5 --long` | `3.319` | `51.7 MB/s` | `371.9 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` | `3.523` | `16.4 MB/s` | `489.2 MB/s` |
| `zstd -10 --long`| `3.566` | `16.2 MB/s` | `415.7 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`