PIGZ(1) BSD General Commands Manual PIGZ(1)
pigz, unpigz -- compress or expand files
pigz [-0..9cdfhiKkLlNnqRrTtz] [-b blocksize] [-p threads] [-S suffix] [file ...]
unpigz [-cfhiKkLlNnqRrTtz] [-b blocksize] [-p threads] [-S suffix] [file ...]
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(3)), 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.
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 decompres-
sion, 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).
Compressed files can be restored to their original form using pigz -d or unpigz.
-#, --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 com-
pression). Level 0 is no compression.
-b, --blocksize mmm Set compression block size to mmm K (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, --zip Compress to PKWare zip (.zip) single entry format.
-k, --keep Do not delete original file after processing.
-L, --license Display the pigz license and quit.
-l, --list List the contents of the compressed input.
-N, --name Store/restore file name and mod time in/from header.
-n, --no-name Do not store or restore file name in/from header.
-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.
-S, --suffix .sss Use suffix .sss instead of .gz (for compression).
-T, --no-time Do not store or restore mod time in/from header.
-t, --test Test the integrity of the compressed input.
-V, --version Show the version of pigz.
-v, --verbose Provide more verbose output.
-z, --zlib Compress to zlib (.zz) instead of gzip format.
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, 2008, 2009, 2010 Mark Adler <email@example.com>
BSD June 19, 2010 BSD