IO::Com...s::Bzip2(3)

📦 version 2.220.0, in opensuse-leap 16.0

💖 IO::Compress::Bzip2(3) — User Contributed Perl Documentation 💖

🌸 NAME 🌸

IO::Compress::Bzip2 — write bzip2 files/buffers, periodt. ✨

🎀 SYNOPSIS 🎀

okay bestie, here's the whole API at a glance:

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 gives you a Perl interface that lets you write bzip2 compressed data to files or buffer. That's the whole serve, no cap. 💅

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, bestie.

🫶 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 these forms:

  • A filename — if $input_filename_or_reference 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 $input_filename_or_reference 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 $input_filename_or_reference 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 $output_filename_or_reference 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 $output_filename_or_reference 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 a fileglob string, $input_filename_or_reference must also be a fileglob string. Anything else is an error. See File::GlobMapper for more details.

If $output_filename_or_reference 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.
    • A Buffer — if Append is enabled, all compressed data will be appended to the end of the output buffer. Otherwise the output buffer will be cleared before any compressed data is written to it.
    • 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.
    • 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.

🔥 Oneshot 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 🌸

Ok bestie, this is the fun part — the object-oriented glow-up. Same compression, but now with a whole object you get to boss around. Main character energy fr. 💅

🎀 Constructor 🎀

Here's the shape of the constructor for IO::Compress::Bzip2:

my $z = IO::Compress::Bzip2->new( $output [,OPTS] )
    or die "IO::Compress::Bzip2 failed: $Bzip2Error\n";

It takes exactly one mandatory parameter, $output (explained below), plus zero or more OPTS, which are all listed down in "Constructor Options".

Success gives you back an IO::Compress::Bzip2 object. Failure gives you undef, and $Bzip2Error will be sitting there holding the error message. 😭

If you're on Perl 5.005 or better, the $z object you get back can be used exactly like an IO::File filehandle — like, all your normal output file operations just work on $z. So to write to a compressed file/buffer you can do either of these:

$z->print("hello world\n");
print $z "hello world\n";

Here's a lil baby example of the OO interface doing its thing — making an output file myfile.bz2 and writing some data into it:

my $filename = "myfile.bz2";
my $z = IO::Compress::Bzip2->new($filename)
    or die "IO::Compress::Bzip2 failed: $Bzip2Error\n";

$z->print("abcde");
$z->close();

More where that came from in "Examples". ✨

That mandatory $output parameter is what controls where the compressed data actually goes. It can be one of these forms:

  • A filename — if $output is a simple scalar, it's assumed to be a filename. The file gets opened for writing and the compressed data goes in there. 🗂️
  • A filehandle — if $output is a filehandle, the compressed data gets written to it. The string '-' works as an alias for standard output. 🖨️
  • A scalar reference — if $output is a scalar reference, the compressed data gets stored in $$output. 🫙

And if $output is literally any other type, IO::Compress::Bzip2::new returns undef. No cap.

🦋 Constructor Options 🦋

OPTS is any combination of zero or more of the following options:

  • AutoClose => 0|1 — only valid when $output is a filehandle. If you set it and the value is true, $output gets closed once either the close method is called or the IO::Compress::Bzip2 object gets destroyed. Defaults to 0.
  • Append => 0|1 — opens $output in append mode. What that actually does depends on what kind of $output you handed over:
    • A Buffer — if $output is a buffer and Append is enabled, all compressed data gets appended to the end of $output. Otherwise $output gets cleared before any data is written to it. 🧹
    • A Filename — if $output is a filename and Append is enabled, the file gets opened in append mode. Otherwise the contents of the file (if there are any) get truncated before any compressed data is written. ✂️
    • A Filehandle — if $output is a filehandle, the file pointer gets positioned at the end of the file via a call to seek before any compressed data is written. Otherwise the file pointer doesn't move at all. 📍

Defaults to 0.

  • BlockSize100K => number — sets how many 100K blocks bzip2 uses while compressing. Valid values are 1 to 9, where 9 is the best compression. Defaults to 1. 🔥
  • WorkFactor => number — how much effort bzip2 should put in before it resorts to the slower fallback compression algorithm. Valid values range from 0 to 250, where 0 means "just use the default value 30". Defaults to 0. 💪
  • Strict => 0|1 — placeholder option. That's it. That's the whole option. 🙈

🌈 Examples 🌈

⭐ Streaming ⭐

This super simple command line example shows off the streaming capabilities of the module. The code reads data from STDIN (or all the files given on the commandline), compresses it, and writes the compressed data out to STDOUT.

use strict ;
use warnings ;
use IO::Compress::Bzip2 qw(bzip2 $Bzip2Error) ;

my $z = IO::Compress::Bzip2->new("-", Stream => 1)
    or die "IO::Compress::Bzip2 failed: $Bzip2Error\n";

while (<>) {
    $z->print("abcde");
}
$z->close();

Notice the "-" there — that means "STDOUT". You can also use \*STDOUT if that vibe is more your thing. 💖

⭐ Compressing a file from the filesystem ⭐

Say you wanna read the contents of file1.txt and write the compressed data to file1.txt.bz2. You've got a few options. Start by creating the compression object and opening the input file:

use strict ;
use warnings ;
use IO::Compress::Bzip2 qw(bzip2 $Bzip2Error) ;

my $input = "file1.txt";
my $z = IO::Compress::Bzip2->new("file1.txt.bz2")
    or die "IO::Compress::Bzip2 failed: $Bzip2Error\n";

# open the input file
open my $fh, "<", "file1.txt"
    or die "Cannot open file1.txt: $!\n";

# loop through the input file & write to the compressed file
while (<$fh>) {
    $z->print($_);
}

# not forgetting to close the compressed file
$z->close();

💜 Methods 💜

💅 print

Usage:

$z->print($data)
print $z $data

Compresses and outputs the contents of the $data parameter. Behaves exactly like the built-in print.

Returns true if it worked. ✅

💅 printf

Usage:

$z->printf($format, $data)
printf $z $format, $data

Compresses and outputs the contents of the $data parameter.

Returns true if it worked. ✅

💅 syswrite

Usage:

$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 it didn't work. 😬

💅 write

Usage:

$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 it didn't work. 😬

💅 flush

Usage:

$z->flush;

Flushes any pending compressed data out to the output file/buffer.

TODO 🙈

Returns true on success.

💅 tell

Usage:

$z->tell()
tell $z

Returns the uncompressed file offset. 📏

💅 eof

Usage:

$z->eof();
eof($z);

Returns true if the close method has been called. 🏁

💅 seek

$z->seek($position, $whence);
seek($z, $position, $whence);

Gives you a sub-set of the seek functionality, with one big restriction: it's only legal to seek forward in the output file/buffer. Trying to seek backward is a fatal error. 💀

Empty parts of the file/buffer get NULL (0x00) bytes written into them.

The $whence parameter takes one of the usual values, namely SEEK_SET, SEEK_CUR or SEEK_END.

Returns 1 on success, 0 on failure.

💅 binmode

Usage:

$z->binmode
binmode $z ;

Total noop, provided purely for completeness. 🫶

💅 opened

$z->opened()

Returns true if the object currently refers to an 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 non-zero, it enables flushing after every write/print operation. 🚿

If $z is associated with a buffer, this method has no effect and always returns undef.

Ngl, heads up: the special variable $| can't be used to set or retrieve the autoflush setting. Not here. Not today. 🙅‍♀️

💅 input_line_number

$z->input_line_number()
$z->input_line_number(EXPR)

This method always returns undef when you're compressing. Always. 💀

💅 fileno

$z->fileno()
fileno($z)

If the $z object is associated with a file or a filehandle, fileno returns the underlying file descriptor. Once the close method has been called, fileno returns undef.

If the $z object is associated with a buffer, this method returns undef.

💅 close

$z->close() ;
close $z ;

Flushes any pending compressed data, then closes the output file/buffer. 🧼

For most versions of Perl this method gets automatically invoked if the IO::Compress::Bzip2 object is destroyed — either explicitly, or by the variable holding the reference to it going out of scope. The exceptions are Perl versions 5.005 through 5.00504 and 5.8.0. In those cases the close method will be called automatically, but not until global destruction of all live objects when the program is terminating. 😴

So like, if you want your scripts to run on all versions of Perl, just call close explicitly and don't rely on the automatic closing. Bestie advice. 🫶

Returns true on success, otherwise 0.

If the AutoClose option was enabled when the IO::Compress::Bzip2 object was created, and the object is associated with a file, the underlying file gets closed too.

💅 newStream([OPTS])

Usage:

$z->newStream( [OPTS] )

Closes the current compressed data stream and starts a shiny new one. ✨

OPTS is any of the options that are available when you create the $z object in the first place. Peep the "Constructor Options" section for the deets.

🧚 Importing 🧚

Currently IO::Compress::Bzip2 doesn't require any symbolic constants. Iconic of it.

  • :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, and bug reports should go to <https://github.com/pmqs/IO-Compress/issues> (preferred) or <https://rt.cpan.org/Public/Dist/Display.html?Name=IO-Compress>. They're literally waiting for your thoughts. 💌

👑 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@cpan.org". Legend behavior. 👑

💅 MODIFICATION HISTORY 💅

See the Changes file.

Okay bestie, boring-but-important part, don't scroll past it 👀

Copyright (c) 2005-2026 Paul Marquess. All rights reserved.

That's Paul Marquess holding the copyright from 2005 allll the way through 2026 — two whole decades of IO::Compress::Bzip2 slayage, we love longevity 💅

Then the legal bit, and it's genuinely good news:

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

So yes — you can redistribute it, you can modify it, and the terms are exactly the same ones as Perl itself</>, no extra weirdness, no fine-print trap. Just go be free with it, fr fr 🌈

and that's the whole page, bestie!! 🎀✨

You made it to the very end — main character energy honestly 👑 This particular rendering is from perl v5.42.0, dated 2026-05-17, so if you're quoting it in a group chat or a code review, that's the version-and-date receipt you're looking for 🧾🦋

Now go compress something and be iconic about it 💜🌸🫶

📦 where this page comes from