IO::COMPRESS::BZIP2(3pm)

💅 IO::Compress::Bzip2(3pm) 💅

From the Perl Programmers Reference Guide — okay bestie, this is the manual page for IO::Compress::Bzip2, and it is literally all about writing bzip2 files and buffers. 🫶

✨ NAME ✨

IO::Compress::Bzip2 — write bzip2 files/buffers. That's the whole name, no cap. 💖

🌸 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 gives you a Perl interface for writing bzip2 compressed data to files or buffers. Slay. 💅

If you're trying to read bzip2 files/buffers instead, go see the companion module IO::Uncompress::Bunzip2. That one's for the reading girlies. 📖

💖 Functional Interface 💖

There's a top-level function called bzip2 that does "one-shot" compression between buffers and/or files. It's giving convenience, honestly. If you want finer control over the compression process, peek at 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. Periodt. ✨

👑 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, plus zero or more optional parameters — those are the ones in the "Optional Parameters" section.

📥 The $input_filename_or_reference parameter 📥

This parameter defines where the uncompressed data comes from. It can take one of these forms:

• A filename — if $input_filename_or_reference is a simple scalar, it's treated as a filename. That file gets opened for reading, and the input data is read from it.
• A filehandle — if $input_filename_or_reference is a filehandle, the input data is 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 is 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 is read from each file in turn. The complete array will be walked to make sure it only contains valid filenames before any data is compressed.
• An Input FileGlob string — if $input_filename_or_reference is a string delimited by the characters < and >, bzip2 assumes it's 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. That's the vibe check, and it failed.

📤 The $output_filename_or_reference parameter 📤

This parameter controls where the compressed data goes. It can take one of these forms:

• A filename — if $output_filename_or_reference is a simple scalar, it's treated as a filename. That file gets opened for writing, and the compressed data is written to it.
• A filehandle — if $output_filename_or_reference is a filehandle, the compressed data is 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 is stored in $$output_filename_or_reference.
• An Array Reference — if $output_filename_or_reference is an array reference, the compressed data is pushed onto the array.
• An Output FileGlob — if $output_filename_or_reference is a string delimited by the characters < and >, bzip2 assumes it's an output fileglob string. The output is the list of files that match the fileglob. See File::GlobMapper for more details.

⚠️ When $output_filename_or_reference is an fileglob string, $input_filename_or_reference must also be a fileglob string. Anything else is an error. No exceptions, bestie.

🚨 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. Cute and efficient. 💜

🎀 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, bestie:

• 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. It's giving retired icon. 💀
• Append => 0|1 — the behaviour of this option depends on the type of output data stream:
  • 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.
  • 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 examples that show what the module can do. Capabilities reveal! ✨

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

okay so here's the format of the constructor for IO::Compress::Bzip2, bestie, look at it:

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

It takes exactly one mandatory parameter, $output (defined below), plus zero or more OPTS, which live down in "Constructor Options". You can never have too many OPTS, honestly 💅

It returns an IO::Compress::Bzip2 object when things go slay, and undef when they don't 😭. Either way, $Bzip2Error will hold the error message if it failed.

So if you're on Perl 5.005 or better, that $z object you get back from IO::Compress::Bzip2 can be used exactly like an IO::File filehandle. Which is iconic, because it means all the normal output file operations just work on $z. Like, to write to a compressed file or buffer you can do either of these:

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

And here's a super simple example (the original says "exaple", and honestly? relatable) of using the OO interface to make an output file myfile.bz2 and write 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();

There's more down in "Examples" if you want the full menu ✨

That mandatory $output parameter is literally the whole vibe — it controls where the compressed data goes. It can take one of these forms:

📁 A filename

If $output is a simple scalar, it's treated as a filename. The file gets opened for writing and the compressed data goes in there. Simple, clean, no cap.

🖨 A filehandle

If $output is a filehandle, the compressed data is written to it. And guess what — the string - is an alias for standard output 🫶

🎁 A scalar reference

If $output is a scalar reference, the compressed data gets stored in $$output. Cute little in-memory buffer moment.

And if $output is literally any other type? IO::Compress::Bzip2::new just returns undef. It's not mad, it's just disappointed 🙈

---

✨ Constructor Options ✨

OPTS is any combination of zero or more of these bad boys:

• "AutoClose => 0|1" — only valid when $output is a filehandle, bestie. 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 is destroyed. Defaults to 0.
• "Append => 0|1" — opens $output in append mode. But the behaviour depends on what kind of $output you gave it:
  • A Buffer — if $output is a buffer and Append is enabled, all compressed data gets appended to the end of $output. Otherwise $output is cleared before any data gets written to it. Firm but fair.
  • A Filename — if $output is a filename and Append is enabled, the file opens 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 to the end of the file via a call to seek before any compressed data is written. Otherwise the file pointer doesn't move.

Defaults to 0.

• "BlockSize100K => number" — specifies how many 100K blocks bzip2 uses during compression. Valid values are from 1 to 9, where 9 is the best compression. Default is 1.
• "WorkFactor => number" — specifies how much effort bzip2 should put in before resorting to a slower fallback compression algorithm. Basically how hard it tries before giving up and taking the scenic route 🔥 Valid values range from 0 to 250, where 0 means use the default value 30. Default is 0.
• "Strict => 0|1" — this is a placeholder option. That's it. That's the whole thing. It's giving "we reserve the right to do something here someday" 🎀

---

🌈 Examples

🌊 Streaming

This very simple command line example shows off the streaming capabilities of the module — it's honestly so satisfying to watch. The code reads data from STDIN or all the files given on the commandline, compresses it, and writes the compressed data 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();

Note the use of - to mean "STDOUT" 🫶 Alternatively you can use \*STDOUT.

📂 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 there are 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();

The comment literally says "not forgetting to close the compressed file" and honestly, listen to the comment 😤

---

💅 Methods

🖨 print

Usage is:

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

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

Returns true if it worked ✨

🎀 printf

Usage is:

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

Compresses and outputs the contents of the $data parameter.

Returns true if it worked.

✍️ 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 it didn't work 😭

✏️ 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 it didn't work.

🚿 flush

Usage is:

$z->flush;

Flushes any pending compressed data to the output file/buffer. No holding it in, let it out 🦋

TODO

Returns true on success.

📍 tell

Usage is:

$z->tell()
tell $z

Returns the uncompressed file offset. Important distinction, bestie 👑

🏁 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. Attempting to seek backward is a fatal error. Yeah. Fatal. Don't test it 🙈

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 is:

$z->binmode
binmode $z ;

This is a noop provided for completeness. It's a vibe, it does nothing, we love it anyway 🎀

🔓 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. Live dangerously 🔥

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

Real talk though: the special variable $| cannot be used to set or retrieve the autoflush setting here. Not the vibe, not allowed.

🔢 input_line_number

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

This method always returns undef when compressing. Always. Don't fight it 💀

🏷 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 gets called, fileno returns undef.

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

🔒 close

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

Flushes any pending compressed data and then closes the output file/buffer. The grand finale ✨

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 the object going out of scope). The exceptions are Perl versions 5.005 through 5.00504 and 5.8.0. In those cases close does get called automatically — but not until global destruction of all live objects when the program is terminating. So like, eventually. Sort of.

So if you want your scripts to run on all versions of Perl, call close explicitly. Don't rely on the automatic closing. It's giving "I'll get to it when I get to it" and you deserve better 🫶

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 is:

$z->newStream( [OPTS] )

Closes the current compressed data stream and starts a new one. Fresh start energy 🌸

OPTS consists of any of the options 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. None. Zero. We're low maintenance 💅

• :all — imports bzip2 and $Bzip2Error. Same as doing this:

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

---

🌟 EXAMPLES

🧃 Apache::GZip Revisited

See IO::Compress::FAQ. (Yes, that's the whole thing. Go read the FAQ, bestie.)

📡 Working with Net::FTP

See IO::Compress::FAQ. (Same deal. The FAQ is the main character here 👑)

---

🫶 SUPPORT

General feedback, questions and 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>. They genuinely want to hear from you, no gatekeeping 💖

---

👀 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 behaviour honestly 👑

---

📜 MODIFICATION HISTORY

See the Changes file.

💖 COPYRIGHT AND LICENSE 💖

okay bestie, legal era incoming, but it's actually chill, i promise 🫶

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

That's Paul Marquess, holding it down from 2005 all the way through 2026 — two whole decades of copyright, we love a long-running main character 😌👑

And here's the license tea, fr fr:

This program is free software — you can redistribute it and/or modify it under the same terms as Perl itself. That's it, that's the whole deal. Go build something iconic with it ✨

🎀 quick vibe check: same terms as Perl itself — not some other random license, Perl's terms. Don't get it twisted 💅

---

aaand that's the whole page, bestie! 🦋 no notes, we ate 🍓

For the record, this beauty landed from perl v5.42.3 on 2026-11-03, and it lives under the name IO::Com...s::Bzip2(3pm) (yes the man page name is truncated with an ellipsis, that's just how the footer rolls, don't come for her 😭💀). go forth and bzip2 responsibly, ily 💜🏆