PIGZ(1) General Commands Manual PIGZ(1)
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 suf-
fix ] [ 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 calcu-
lated in parallel. The compressed data is written in order to the out-
put, 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. Speci-
fying -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 com-
pression 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 decom-
pression can be turned off by specifying one process ( -dp 1 or -tp 1
).
All options on the command line are processed before any names are pro-
cessed. 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 com-
pression method (best compression). -0 is no compression. -11
gives a few percent better compression at a severe cost in exe-
cution 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
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 cur-
rent 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 proces-
sors)
-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 "-")
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 war-
ranty. 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 AT alumni.edu>
December 26, 2017 PIGZ(1)
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