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Diffstat (limited to 'programs/lz4.1.md')
| -rw-r--r-- | programs/lz4.1.md | 48 |
1 files changed, 32 insertions, 16 deletions
diff --git a/programs/lz4.1.md b/programs/lz4.1.md index 12b8e29..56c0053 100644 --- a/programs/lz4.1.md +++ b/programs/lz4.1.md @@ -31,29 +31,29 @@ The native file format is the `.lz4` format. `lz4` supports a command line syntax similar _but not identical_ to `gzip(1)`. Differences are : - * `lz4` preserves original files * `lz4` compresses a single file by default (see `-m` for multiple files) * `lz4 file1 file2` means : compress file1 _into_ file2 * `lz4 file.lz4` will default to decompression (use `-z` to force compression) + * `lz4` preserves original files * `lz4` shows real-time notification statistics during compression or decompression of a single file (use `-q` to silence them) - * If no destination name is provided, result is sent to `stdout` - _except if stdout is the console_. - * If no destination name is provided, __and__ if `stdout` is the console, - `file` is compressed into `file.lz4`. - * As a consequence of previous rules, note the following example : - `lz4 file | consumer` sends compressed data to `consumer` through `stdout`, - hence it does _not_ create `file.lz4`. - * Another consequence of those rules is that to run `lz4` under `nohup`, - you should provide a destination file: `nohup lz4 file file.lz4`, - because `nohup` writes the specified command's output to a file. + * When no destination is specified, result is sent on implicit output, + which depends on `stdout` status. + When `stdout` _is Not the console_, it becomes the implicit output. + Otherwise, if `stdout` is the console, the implicit output is `filename.lz4`. + * It is considered bad practice to rely on implicit output in scripts. + because the script's environment may change. + Always use explicit output in scripts. + `-c` ensures that output will be `stdout`. + Conversely, providing a destination name, or using `-m` + ensures that the output will be either the specified name, or `filename.lz4` respectively. Default behaviors can be modified by opt-in commands, detailed below. * `lz4 -m` makes it possible to provide multiple input filenames, which will be compressed into files using suffix `.lz4`. - Progress notifications are also disabled by default (use `-v` to enable them). + Progress notifications become disabled by default (use `-v` to enable them). This mode has a behavior which more closely mimics `gzip` command line, with the main remaining difference being that source files are preserved by default. * Similarly, `lz4 -m -d` can decompress multiple `*.lz4` files. @@ -81,8 +81,7 @@ In some cases, some options can be expressed using short command `-x` or long command `--long-word`. Short commands can be concatenated together. For example, `-d -c` is equivalent to `-dc`. -Long commands cannot be concatenated. -They must be clearly separated by a space. +Long commands cannot be concatenated. They must be clearly separated by a space. ### Multiple commands @@ -114,6 +113,10 @@ only the latest one will be applied. * `-b#`: Benchmark mode, using `#` compression level. +* `--list`: + List information about .lz4 files. + note : current implementation is limited to single-frame .lz4 files. + ### Operation modifiers * `-#`: @@ -126,12 +129,21 @@ only the latest one will be applied. Decompression speed remains fast at all settings. * `--fast[=#]`: - switch to ultra-fast compression levels. + Switch to ultra-fast compression levels. The higher the value, the faster the compression speed, at the cost of some compression ratio. If `=#` is not present, it defaults to `1`. This setting overrides compression level if one was set previously. Similarly, if a compression level is set after `--fast`, it overrides it. +* `--best`: + Set highest compression level. Same as -12. + +* `--favor-decSpeed`: + Generate compressed data optimized for decompression speed. + Compressed data will be larger as a consequence (typically by ~0.5%), + while decompression speed will be improved by 5-20%, depending on use cases. + This option only works in combination with very high compression levels (>=10). + * `-D dictionaryName`: Compress, decompress or benchmark using dictionary _dictionaryName_. Compression and decompression must use the same dictionary to be compatible. @@ -155,6 +167,7 @@ only the latest one will be applied. Multiple input files. Compressed file names will be appended a `.lz4` suffix. This mode also reduces notification level. + Can also be used to list multiple files. `lz4 -m` has a behavior equivalent to `gzip -k` (it preserves source files by default). @@ -166,8 +179,11 @@ only the latest one will be applied. Block size \[4-7\](default : 7)<br/> `-B4`= 64KB ; `-B5`= 256KB ; `-B6`= 1MB ; `-B7`= 4MB +* `-BI`: + Produce independent blocks (default) + * `-BD`: - Block Dependency (improves compression ratio on small blocks) + Blocks depend on predecessors (improves compression ratio, more noticeable on small blocks) * `--[no-]frame-crc`: Select frame checksum (default:enabled) |