LBZIP2

Section: lbzip2-0.12 (1)
Updated: lbzip2.1,v 1.30 2009-01-25 17:42:17 lacos Exp
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NAME

lbzip2 - parallel bzip2 filter  

SYNOPSIS

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 malloc_trace.pl Perl script (part of the source distribution).
-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 README in the source distribution 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, they are both fixed at the maximum bzip2 block size of 899,981 bytes.  

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; 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/


 

Index

NAME
SYNOPSIS
DESCRIPTION
OPTIONS
ENVIRONMENT
EXIT STATUS
BUGS
AUTHOR
COPYRIGHT
THANKS
SEE ALSO

This document was created by man2html, using the manual pages.
Time: 00:08:44 GMT, January 10, 2012