zstd(1) User Commands zstd(1)
NAME
zstd, unzstd, zstdcat - Compress or decompress .zst files
SYNOPSIS
zstd [OPTIONS] [-|INPUT-FILE] [-o <OUTPUT-FILE>]
unzstd is equivalent to zstd -d
zstdcat is equivalent to zstd -dc
DESCRIPTION
zstd is a fast lossless compression algorithm. It is based on the LZ77
family, with further FSE & huff0 entropy stages. zstd offers
configurable compression speed, with fast modes at > 200 MB/s per core.
It also features a very fast decoder, with speed > 500 MB/s per core.
zstd command line is generally similar to gzip, but features the
following differences :
- Source files are preserved by default
It's possible to remove them automatically by using --rm command
- By default, when compressing a single file, zstd displays progress
notifications and result summary.
Use -q to turn them off
OPTIONS
-# # compression level [1-22] (default:3)
-d, --decompress
decompression
-D file
use `file` as Dictionary to compress or decompress FILE(s)
-o file
save result into `file` (only possible with a single INPUT-
FILE)
-f, --force
overwrite output without prompting
-c, --stdout
force write to standard output, even if it is the console
--rm remove source file(s) after successful compression or
decompression
-k, --keep
keep source file(s) after successful compression or
decompression.
This is the default behavior.
-r operate recursively on directories
-h/-H, --help
display help/long help and exit
-V, --version
display Version number and exit
-v, --verbose
verbose mode
-q, --quiet
suppress warnings, interactivity and notifications.
specify twice to suppress errors too.
-C, --check
add integrity check computed from uncompressed data
-t, --test
Test the integrity of compressed files. This option is
equivalent to --decompress --stdout > /dev/null.
No files are created or removed.
-- All arguments after -- are treated as files
DICTIONARY
zstd offers dictionary compression, useful for very small files and
messages. It's possible to train zstd with some samples, the result of
which is saved into a file called `dictionary`. Then during
compression and decompression, make reference to the same dictionary.
It will improve compression ratio of small files. Typical gains range
from ~10% (at 64KB) to x5 better (at <1KB).
--train FILEs
use FILEs as training set to create a dictionary.
The training set should contain a lot of small files (> 100).
and weight typically 100x the target dictionary size
(for example, 10 MB for a 100 KB dictionary)
-o file
dictionary saved into `file` (default: dictionary)
--maxdict #
limit dictionary to specified size (default : 112640)
--dictID #
A dictionary ID is a locally unique ID that a decoder can use
to verify it is using the right dictionary.
By default, zstd will create a 4-bytes random number ID.
It's possible to give a precise number instead.
Short numbers have an advantage : an ID < 256 will only need 1
byte in the compressed frame header,
and an ID < 65536 will only need 2 bytes. This compares
favorably to 4 bytes default.
However, it's up to the dictionary manager to not assign twice
the same ID to 2 different dictionaries.
-s# dictionary selectivity level (default: 9)
the smaller the value, the denser the dictionary, improving its
efficiency but reducing its possible maximum size.
BENCHMARK
-b# benchmark file(s) using compression level #
-i# minimum evaluation time, in seconds (default : 3s), benchmark
mode only
-B# cut file into independent blocks of size # (default: no block)
BUGS
Report bugs at:- https://github.com/facebook/zstd/issues
AUTHOR
Yann Collet
zstd 2015-08-22 zstd(1)
zstd 1.1.0 - Generated Mon Oct 3 20:32:02 CDT 2016