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IO::Compress::Bzip2(3perl) Perl Programmers Reference Guide IO::Compress::Bzip2(3perl)
NAME
IO::Compress::Bzip2 - Write bzip2 files/buffers
SYNOPSIS
use IO::Compress::Bzip2 qw(bzip2 $Bzip2Error) ;
my $status = bzip2 $input => $output [,OPTS]
or die "bzip2 failed: $Bzip2Error\n";
my $z = IO::Compress::Bzip2->new( $output [,OPTS] )
or die "bzip2 failed: $Bzip2Error\n";
$z->print($string);
$z->printf($format, $string);
$z->write($string);
$z->syswrite($string [, $length, $offset]);
$z->flush();
$z->tell();
$z->eof();
$z->seek($position, $whence);
$z->binmode();
$z->fileno();
$z->opened();
$z->autoflush();
$z->input_line_number();
$z->newStream( [OPTS] );
$z->close() ;
$Bzip2Error ;
# IO::File mode
print $z $string;
printf $z $format, $string;
tell $z
eof $z
seek $z, $position, $whence
binmode $z
fileno $z
close $z ;
DESCRIPTION
This module provides a Perl interface that allows writing bzip2 compressed data to files
or buffer.
For reading bzip2 files/buffers, see the companion module IO::Uncompress::Bunzip2.
Functional Interface
A top-level function, "bzip2", is provided to carry out "one-shot" compression between
buffers and/or files. For finer control over the compression process, see the "OO
Interface" section.
use IO::Compress::Bzip2 qw(bzip2 $Bzip2Error) ;
bzip2 $input_filename_or_reference => $output_filename_or_reference [,OPTS]
or die "bzip2 failed: $Bzip2Error\n";
The functional interface needs Perl5.005 or better.
bzip2 $input_filename_or_reference => $output_filename_or_reference [, OPTS]
"bzip2" expects at least two parameters, $input_filename_or_reference and
$output_filename_or_reference and zero or more optional parameters (see "Optional
Parameters")
The $input_filename_or_reference parameter
The parameter, $input_filename_or_reference, is used to define the source of the
uncompressed data.
It can take one of the following forms:
A filename
If the $input_filename_or_reference parameter is a simple scalar, it is assumed to be
a filename. This file will be opened for reading and the input data will be read from
it.
A filehandle
If the $input_filename_or_reference parameter is a filehandle, the input data will be
read from it. The string '-' can be used as an alias for standard input.
A scalar reference
If $input_filename_or_reference is a scalar reference, the input data will be read
from $$input_filename_or_reference.
An array reference
If $input_filename_or_reference is an array reference, each element in the array must
be a filename.
The input data will be read from each file in turn.
The complete array will be walked to ensure that it only contains valid filenames
before any data is compressed.
An Input FileGlob string
If $input_filename_or_reference is a string that is delimited by the characters "<"
and ">" "bzip2" will assume that it is an input fileglob string. The input is the
list of files that match the fileglob.
See File::GlobMapper for more details.
If the $input_filename_or_reference parameter is any other type, "undef" will be returned.
The $output_filename_or_reference parameter
The parameter $output_filename_or_reference is used to control the destination of the
compressed data. This parameter can take one of these forms.
A filename
If the $output_filename_or_reference parameter is a simple scalar, it is assumed to
be a filename. This file will be opened for writing and the compressed data will be
written to it.
A filehandle
If the $output_filename_or_reference parameter is a filehandle, the compressed data
will be written to it. The string '-' can be used as an alias for standard output.
A scalar reference
If $output_filename_or_reference is a scalar reference, the compressed data will be
stored in $$output_filename_or_reference.
An Array Reference
If $output_filename_or_reference is an array reference, the compressed data will be
pushed onto the array.
An Output FileGlob
If $output_filename_or_reference is a string that is delimited by the characters "<"
and ">" "bzip2" will assume that it is an output fileglob string. The output is the
list of files that match the fileglob.
When $output_filename_or_reference is an fileglob string,
$input_filename_or_reference must also be a fileglob string. Anything else is an
error.
See File::GlobMapper for more details.
If the $output_filename_or_reference parameter is any other type, "undef" will be
returned.
Notes
When $input_filename_or_reference maps to multiple files/buffers and
$output_filename_or_reference is a single file/buffer the input files/buffers will be
stored in $output_filename_or_reference as a concatenated series of compressed data
streams.
Optional Parameters
The optional parameters for the one-shot function "bzip2" are (for the most part)
identical to those used with the OO interface defined in the "Constructor Options"
section. The exceptions are listed below
"AutoClose => 0|1"
This option applies to any input or output data streams to "bzip2" that are
filehandles.
If "AutoClose" is specified, and the value is true, it will result in all input
and/or output filehandles being closed once "bzip2" has completed.
This parameter defaults to 0.
"BinModeIn => 0|1"
This option is now a no-op. All files will be read in binmode.
"Append => 0|1"
The behaviour of this option is dependent on the type of output data stream.
o A Buffer
If "Append" is enabled, all compressed data will be append to the end of the
output buffer. Otherwise the output buffer will be cleared before any compressed
data is written to it.
o A Filename
If "Append" is enabled, the file will be opened in append mode. Otherwise the
contents of the file, if any, will be truncated before any compressed data is
written to it.
o A Filehandle
If "Append" is enabled, the filehandle will be positioned to the end of the file
via a call to "seek" before any compressed data is written to it. Otherwise the
file pointer will not be moved.
When "Append" is specified, and set to true, it will append all compressed data to
the output data stream.
So when the output is a filehandle it will carry out a seek to the eof before writing
any compressed data. If the output is a filename, it will be opened for appending. If
the output is a buffer, all compressed data will be appended to the existing buffer.
Conversely when "Append" is not specified, or it is present and is set to false, it
will operate as follows.
When the output is a filename, it will truncate the contents of the file before
writing any compressed data. If the output is a filehandle its position will not be
changed. If the output is a buffer, it will be wiped before any compressed data is
output.
Defaults to 0.
Examples
Here are a few example that show the capabilities of the module.
Streaming
This very simple command line example demonstrates the streaming capabilities of the
module. The code reads data from STDIN, compresses it, and writes the compressed data to
STDOUT.
$ echo hello world | perl -MIO::Compress::Bzip2=bzip2 -e 'bzip2 \*STDIN => \*STDOUT' >output.bz2
The special filename "-" can be used as a standin for both "\*STDIN" and "\*STDOUT", so
the above can be rewritten as
$ echo hello world | perl -MIO::Compress::Bzip2=bzip2 -e 'bzip2 "-" => "-"' >output.bz2
Compressing a file from the filesystem
To read the contents of the file "file1.txt" and write the compressed data to the file
"file1.txt.bz2".
use strict ;
use warnings ;
use IO::Compress::Bzip2 qw(bzip2 $Bzip2Error) ;
my $input = "file1.txt";
bzip2 $input => "$input.bz2"
or die "bzip2 failed: $Bzip2Error\n";
Reading from a Filehandle and writing to an in-memory buffer
To read from an existing Perl filehandle, $input, and write the compressed data to a
buffer, $buffer.
use strict ;
use warnings ;
use IO::Compress::Bzip2 qw(bzip2 $Bzip2Error) ;
use IO::File ;
my $input = IO::File->new( "<file1.txt" )
or die "Cannot open 'file1.txt': $!\n" ;
my $buffer ;
bzip2 $input => \$buffer
or die "bzip2 failed: $Bzip2Error\n";
Compressing multiple files
To compress all files in the directory "/my/home" that match "*.txt" and store the
compressed data in the same directory
use strict ;
use warnings ;
use IO::Compress::Bzip2 qw(bzip2 $Bzip2Error) ;
bzip2 '</my/home/*.txt>' => '<*.bz2>'
or die "bzip2 failed: $Bzip2Error\n";
and if you want to compress each file one at a time, this will do the trick
use strict ;
use warnings ;
use IO::Compress::Bzip2 qw(bzip2 $Bzip2Error) ;
for my $input ( glob "/my/home/*.txt" )
{
my $output = "$input.bz2" ;
bzip2 $input => $output
or die "Error compressing '$input': $Bzip2Error\n";
}
OO Interface
Constructor
The format of the constructor for "IO::Compress::Bzip2" is shown below
my $z = IO::Compress::Bzip2->new( $output [,OPTS] )
or die "IO::Compress::Bzip2 failed: $Bzip2Error\n";
It returns an "IO::Compress::Bzip2" object on success and undef on failure. The variable
$Bzip2Error will contain an error message on failure.
If you are running Perl 5.005 or better the object, $z, returned from IO::Compress::Bzip2
can be used exactly like an IO::File filehandle. This means that all normal output file
operations can be carried out with $z. For example, to write to a compressed file/buffer
you can use either of these forms
$z->print("hello world\n");
print $z "hello world\n";
The mandatory parameter $output is used to control the destination of the compressed data.
This parameter can take one of these forms.
A filename
If the $output parameter is a simple scalar, it is assumed to be a filename. This
file will be opened for writing and the compressed data will be written to it.
A filehandle
If the $output parameter is a filehandle, the compressed data will be written to it.
The string '-' can be used as an alias for standard output.
A scalar reference
If $output is a scalar reference, the compressed data will be stored in $$output.
If the $output parameter is any other type, "IO::Compress::Bzip2"::new will return undef.
Constructor Options
"OPTS" is any combination of zero or more the following options:
"AutoClose => 0|1"
This option is only valid when the $output parameter is a filehandle. If specified,
and the value is true, it will result in the $output being closed once either the
"close" method is called or the "IO::Compress::Bzip2" object is destroyed.
This parameter defaults to 0.
"Append => 0|1"
Opens $output in append mode.
The behaviour of this option is dependent on the type of $output.
o A Buffer
If $output is a buffer and "Append" is enabled, all compressed data will be
append to the end of $output. Otherwise $output will be cleared before any data
is written to it.
o A Filename
If $output is a filename and "Append" is enabled, the file will be opened in
append mode. Otherwise the contents of the file, if any, will be truncated
before any compressed data is written to it.
o A Filehandle
If $output is a filehandle, the file pointer will be positioned to the end of
the file via a call to "seek" before any compressed data is written to it.
Otherwise the file pointer will not be moved.
This parameter defaults to 0.
"BlockSize100K => number"
Specify the number of 100K blocks bzip2 uses during compression.
Valid values are from 1 to 9, where 9 is best compression.
The default is 1.
"WorkFactor => number"
Specifies how much effort bzip2 should take before resorting to a slower fallback
compression algorithm.
Valid values range from 0 to 250, where 0 means use the default value 30.
The default is 0.
"Strict => 0|1"
This is a placeholder option.
Examples
TODO
Methods
print
Usage is
$z->print($data)
print $z $data
Compresses and outputs the contents of the $data parameter. This has the same behaviour as
the "print" built-in.
Returns true if successful.
printf
Usage is
$z->printf($format, $data)
printf $z $format, $data
Compresses and outputs the contents of the $data parameter.
Returns true if successful.
syswrite
Usage is
$z->syswrite $data
$z->syswrite $data, $length
$z->syswrite $data, $length, $offset
Compresses and outputs the contents of the $data parameter.
Returns the number of uncompressed bytes written, or "undef" if unsuccessful.
write
Usage is
$z->write $data
$z->write $data, $length
$z->write $data, $length, $offset
Compresses and outputs the contents of the $data parameter.
Returns the number of uncompressed bytes written, or "undef" if unsuccessful.
flush
Usage is
$z->flush;
Flushes any pending compressed data to the output file/buffer.
TODO
Returns true on success.
tell
Usage is
$z->tell()
tell $z
Returns the uncompressed file offset.
eof
Usage is
$z->eof();
eof($z);
Returns true if the "close" method has been called.
seek
$z->seek($position, $whence);
seek($z, $position, $whence);
Provides a sub-set of the "seek" functionality, with the restriction that it is only legal
to seek forward in the output file/buffer. It is a fatal error to attempt to seek
backward.
Empty parts of the file/buffer will have NULL (0x00) bytes written to them.
The $whence parameter takes one the usual values, namely SEEK_SET, SEEK_CUR or SEEK_END.
Returns 1 on success, 0 on failure.
binmode
Usage is
$z->binmode
binmode $z ;
This is a noop provided for completeness.
opened
$z->opened()
Returns true if the object currently refers to a opened file/buffer.
autoflush
my $prev = $z->autoflush()
my $prev = $z->autoflush(EXPR)
If the $z object is associated with a file or a filehandle, this method returns the
current autoflush setting for the underlying filehandle. If "EXPR" is present, and is non-
zero, it will enable flushing after every write/print operation.
If $z is associated with a buffer, this method has no effect and always returns "undef".
Note that the special variable $| cannot be used to set or retrieve the autoflush setting.
input_line_number
$z->input_line_number()
$z->input_line_number(EXPR)
This method always returns "undef" when compressing.
fileno
$z->fileno()
fileno($z)
If the $z object is associated with a file or a filehandle, "fileno" will return the
underlying file descriptor. Once the "close" method is called "fileno" will return
"undef".
If the $z object is associated with a buffer, this method will return "undef".
close
$z->close() ;
close $z ;
Flushes any pending compressed data and then closes the output file/buffer.
For most versions of Perl this method will be automatically invoked if the
IO::Compress::Bzip2 object is destroyed (either explicitly or by the variable with the
reference to the object going out of scope). The exceptions are Perl versions 5.005
through 5.00504 and 5.8.0. In these cases, the "close" method will be called
automatically, but not until global destruction of all live objects when the program is
terminating.
Therefore, if you want your scripts to be able to run on all versions of Perl, you should
call "close" explicitly and not rely on automatic closing.
Returns true on success, otherwise 0.
If the "AutoClose" option has been enabled when the IO::Compress::Bzip2 object was
created, and the object is associated with a file, the underlying file will also be
closed.
newStream([OPTS])
Usage is
$z->newStream( [OPTS] )
Closes the current compressed data stream and starts a new one.
OPTS consists of any of the options that are available when creating the $z object.
See the "Constructor Options" section for more details.
Importing
No symbolic constants are required by IO::Compress::Bzip2 at present.
:all Imports "bzip2" and $Bzip2Error. Same as doing this
use IO::Compress::Bzip2 qw(bzip2 $Bzip2Error) ;
EXAMPLES
Apache::GZip Revisited
See IO::Compress::FAQ
Working with Net::FTP
See IO::Compress::FAQ
SUPPORT
General feedback/questions/bug reports should be sent to
<https://github.com/pmqs/IO-Compress/issues> (preferred) or
<https://rt.cpan.org/Public/Dist/Display.html?Name=IO-Compress>.
SEE ALSO
Compress::Zlib, IO::Compress::Gzip, IO::Uncompress::Gunzip, IO::Compress::Deflate,
IO::Uncompress::Inflate, IO::Compress::RawDeflate, IO::Uncompress::RawInflate,
IO::Uncompress::Bunzip2, IO::Compress::Lzma, IO::Uncompress::UnLzma, IO::Compress::Xz,
IO::Uncompress::UnXz, IO::Compress::Lzip, IO::Uncompress::UnLzip, IO::Compress::Lzop,
IO::Uncompress::UnLzop, IO::Compress::Lzf, IO::Uncompress::UnLzf, IO::Compress::Zstd,
IO::Uncompress::UnZstd, IO::Uncompress::AnyInflate, IO::Uncompress::AnyUncompress
IO::Compress::FAQ
File::GlobMapper, Archive::Zip, Archive::Tar, IO::Zlib
The primary site for the bzip2 program is <https://sourceware.org/bzip2/>.
See the module Compress::Bzip2
AUTHOR
This module was written by Paul Marquess, "pmqs AT cpan.org".
MODIFICATION HISTORY
See the Changes file.
COPYRIGHT AND LICENSE
Copyright (c) 2005-2021 Paul Marquess. All rights reserved.
This program is free software; you can redistribute it and/or modify it under the same
terms as Perl itself.
perl v5.34.0 2023-11-23 IO::Compress::Bzip2(3perl)
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On Apache
Under GNU General Public License
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