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lbzip2
Langue: en
Version: 262839 (debian - 07/07/09)
Section: 1 (Commandes utilisateur)
NAME
lbzip2 - parallel bzip2 filterSYNOPSIS
lbzip2 [-d] [-n WORKER-THREADS] [-v] [-t]lbzip2 -h
DESCRIPTION
Compress or decompress standard input to standard output, by calling Julian Seward's libbz2 from multiple threads. Lbzip2 utilizes multiple threads and an input-bound splitter even when decompressing bz2 files created by standard bzip2 (but see BUGS below).OPTIONS
- -d
- Decompress. Default mode is compression.
- -n WORKER-THREADS
- Set the number of (de)compressor threads to WORKER-THREADS. If this option is not specified, the environment variable LBZIP2_WORKER_THREADS is consulted. If also LBZIP2_WORKER_THREADS is unset or empty, then lbzip2 either queries the system for the number of online processors (if both the compilation environment and the execution environment support that) or exits with an error.
- -v
- Print condition variable statistics to standard error in the end. If this option is not specified, the environment variable LBZIP2_PRINT_STATS is consulted: statistics will be printed if and only if LBZIP2_PRINT_STATS is set to a non-empty value.
- -t
- Write memory allocation trace to standard error. If this option is not specified, the environment variable LBZIP2_TRACE_ALLOC is consulted: allocation trace will be printed if and only if LBZIP2_TRACE_ALLOC is set to a non-empty value. The trace can be checked with the /usr/share/lbzip2/malloc_trace.pl Perl script.
- -h
- Print command line help to standard error and exit.
ENVIRONMENT
- LBZIP2_WORKER_THREADS
- See -n.
- LBZIP2_PRINT_STATS
- See -v.
- LBZIP2_TRACE_ALLOC
- See -t.
EXIT STATUS
- 0
- if lbzip2 finishes successfully. This presumes that whenever it tries, lbzip2 never fails to write to standard error.
- EXIT_FAILURE
- if lbzip2 encounters any fatal error. (EXIT_FAILURE corresponds to a platform-dependent integer constant in [1..255], usually 1.)
- SIGABRT
- (via assert()) if a runtime assertion fails (ie. lbzip2 detects a bug in itself). Hopefully whoever compiled your binary wasn't bold enough to #define NDEBUG.
BUGS
The compressed output is a sequence of single-block bzip2 streams, instead of being a single multi-block bzip2 stream. Thus no output-global combined CRC can be written, and the resulting bz2 file will return multiple BZ_STREAM_ENDs when decompressed with libbz2.The multiple-workers decompressor (lbzip2 -d -n WORKER-THREADS, where WORKER-THREADS is greater than 1, either by default or by manual selection) doesn't check stream-level (combined) CRCs, only block-level CRCs. It can also fail to decompress some rare valid bz2 files. (See the Bugs section of the /usr/share/doc/lbzip2/README file for more on this.) Since the author cannot rule out that such a failure may get reported as corrupt input instead of the dedicated error message, lbzip2 doesn't reserve a separate exit status for corrupt input -- it could be misleading.
The bit-string search algorithm used in the multiple-workers decompressor is naive and slow.
Neither the input block size nor the bzip2 block size can be specified for compression. Lbzip2 configures the latter like bzip2 -9 does, and fixes the former at 899,981 bytes, in order to maximize the BWT input block size without spilling over into a second BWT input block, barring first stage RLE pathologies.
AUTHOR
Written by Laszlo Ersek <lacos@elte.hu>, http://phptest11.atw.hu/.COPYRIGHT
Copyright (C) 2008, 2009 Laszlo Ersek.This is free software. You may redistribute copies of it under the terms of the GNU General Public License, version 2:
http://www.gnu.org/licenses/gpl-2.0.html
or -- at your opinion -- any later version, eg.
http://www.gnu.org/licenses/gpl.html
THANKS
Adam Maulis at ELTE IIG; Julian Seward; Paul Sladen; Michael Thomas from Caltech HEP; Bryan Stillwell; Zsolt Bartos-Elekes; Imre Csatlos; Gabor Kovesdan; Department of Electrical and Information Engineering at the University of Oulu.SEE ALSO
- bzip2(1)
- http://www.bzip.org/
- pbzip2(1)
- http://compression.ca/pbzip2/
- bzip2smp(1)
- http://bzip2smp.sourceforge.net/
- smpbzip2(1)
- http://home.student.utwente.nl/n.werensteijn/smpbzip2/
- dbzip2(1)
- http://www.mediawiki.org/wiki/Dbzip2
- p7zip(1)
- http://p7zip.sourceforge.net/
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