PIGZ(1) PIGZ(1)
December 26, 2017
NAME
pigz, unpigz - compress or expand files
SYNOPSIS
pigz [ -cdfhikKlLmMnNqrRtz0..9,11 ] [ -b blocksize ] [ -p threads ] [ -S suffix
] [ name ... ]
unpigz [ -cfhikKlLmMnNqrRtz ] [ -b blocksize ] [ -p threads ] [ -S
suffix ] [ name ... ]
DESCRIPTION
Pigz compresses using threads to make use of multiple processors and
cores. The input is broken up into 128 KB chunks with each compressed
in parallel. The individual check value for each chunk is also
calculated in parallel. The compressed data is written in order to
the output, and a combined check value is calculated from the
individual check values.
The compressed data format generated is in the gzip, zlib, or single-
entry zip format using the deflate compression method. The
compression produces partial raw deflate streams which are
concatenated by a single write thread and wrapped with the appropriate
header and trailer, where the trailer contains the combined check
value.
Each partial raw deflate stream is terminated by an empty stored block
(using the Z_SYNC_FLUSH option of zlib), in order to end that partial
bit stream at a byte boundary. That allows the partial streams to be
concatenated simply as sequences of bytes. This adds a very small
four to five byte overhead to the output for each input chunk.
The default input block size is 128K, but can be changed with the -b
option. The number of compress threads is set by default to the
number of online processors, which can be changed using the -p option.
Specifying -p 1 avoids the use of threads entirely.
The input blocks, while compressed independently, have the last 32K of
the previous block loaded as a preset dictionary to preserve the
compression effectiveness of deflating in a single thread. This can
be turned off using the -i or --independent option, so that the blocks
can be decompressed independently for partial error recovery or for
random access. This also inserts an extra empty block to flag
independent blocks by prefacing each with the nine-byte sequence (in
hex): 00 00 FF FF 00 00 00 FF FF.
Decompression can't be parallelized, at least not without specially
prepared deflate streams for that purpose. As a result, pigz uses a
single thread (the main thread) for decompression, but will create
three other threads for reading, writing, and check calculation, which
can speed up decompression under some circumstances. Parallel
decompression can be turned off by specifying one process ( -dp 1 or
-tp 1 ).
- 1 - Formatted: April 20, 2024
PIGZ(1) PIGZ(1)
December 26, 2017
All options on the command line are processed before any names are
processed. If no names are provided on the command line, or if "-" is
given as a name (but not after "--"), then the input is taken from
stdin.
Compressed files can be restored to their original form using pigz -d
or unpigz.
OPTIONS
-# --fast --best
Regulate the speed of compression using the specified digit #,
where -1 or --fast indicates the fastest compression method (less
compression) and -9 or --best indicates the slowest compression
method (best compression). -0 is no compression. -11 gives a
few percent better compression at a severe cost in execution
time, using the zopfli algorithm by Jyrki Alakuijala. The
default is -6.
-b --blocksize mmm
Set compression block size to mmmK (default 128KiB).
-c --stdout --to-stdout
Write all processed output to stdout (won't delete).
-d --decompress --uncompress
Decompress the compressed input.
-f --force
Force overwrite, compress .gz, links, and to terminal.
-h --help
Display a help screen and quit.
-i --independent
Compress blocks independently for damage recovery.
-k --keep
Do not delete original file after processing.
-K --zip
Compress to PKWare zip (.zip) single entry format.
-l --list
List the contents of the compressed input.
-L --license
Display the pigz license and quit.
-m --no-time
Do not store or restore the modification time. -Nm will store or
- 2 - Formatted: April 20, 2024
PIGZ(1) PIGZ(1)
December 26, 2017
restore the name, but not the modification time. Note that the
order of the options is important.
-M --time
Store or restore the modification time. -nM will store or restore
the modification time, but not the name. Note that the order of
the options is important.
-n --no-name
Do not store or restore the file name or the modification time.
This is the default when decompressing. When the file name is not
restored from the header, the name of the compressed file with
the suffix stripped is the name of the decompressed file. When
the modification time is not restored from the header, the
modification time of the compressed file is used (not the current
time).
-N --name
Store or restore both the file name and the modification time.
This is the default when compressing.
-p --processes n
Allow up to n processes (default is the number of online
processors)
-q --quiet --silent
Print no messages, even on error.
-r --recursive
Process the contents of all subdirectories.
-R --rsyncable
Input-determined block locations for rsync.
-S --suffix .sss
Use suffix .sss instead of .gz (for compression).
-t --test
Test the integrity of the compressed input.
-v --verbose
Provide more verbose output.
-V --version
Show the version of pigz. -vV also shows the zlib version.
-z --zlib
Compress to zlib (.zz) instead of gzip format.
-- All arguments after "--" are treated as file names (for names
that start with "-")
- 3 - Formatted: April 20, 2024
PIGZ(1) PIGZ(1)
December 26, 2017
These options are unique to the -11 compression level:
-F --first
Do iterations first, before block split (default is last).
-I, --iterations n
Number of iterations for optimization (default 15).
-J, --maxsplits n
Maximum number of split blocks (default 15).
-O --oneblock
Do not split into smaller blocks (default is block splitting).
COPYRIGHT NOTICE
This software is provided 'as-is', without any express or implied
warranty. In no event will the author be held liable for any damages
arising from the use of this software.
Copyright (C) 2007-2017 Mark Adler <madler@alumni.caltech.edu>
- 4 - Formatted: April 20, 2024
