add `zcat` symlink support, suggested by @wtarreau
added some test
also updated relevant doc
+ fixed a mistake in `lz4` symlink support :
lz4 utility doesn't remove source files by default (like zstd, but unlike gzip).
The symlink must behave the same.
diff --git a/programs/README.md b/programs/README.md
index 2da9a6d..1331a68 100644
--- a/programs/README.md
+++ b/programs/README.md
@@ -11,44 +11,14 @@
#### Compilation variables
-`zstd` scope can be altered by modifying the following 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 compilation with multithread support, using HAVE_THREAD=1.
- In which case, linking stage will fail if `pthread` library cannot be found.
- This might be useful to prevent silent feature disabling.
-
-- __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 might be 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 might be 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 might be useful to prevent silent feature disabling.
+ 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.
@@ -61,11 +31,54 @@
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.
+
#### 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
@@ -155,7 +168,7 @@
#### 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.
+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
@@ -168,7 +181,7 @@
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`).
+version is less than `128 MiB`).
Compression Speed vs Ratio | Decompression Speed
---------------------------|---------------------
@@ -202,8 +215,3 @@
| `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` |
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