<!-- GENERATED by docs/sphinx/bin/20-reference (p5) from reference/bundled/IO/Compress/Bzip2.md. Do not edit. -->

```{index} single: IO::Compress::Bzip2
```

# IO::Compress::Bzip2

Write bzip2 files/buffers

## SYNOPSIS

```perl
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](../Uncompress/Bunzip2.md).

## 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.

```perl
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](../../File/GlobMapper.md) 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](../../File/GlobMapper.md) 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.

    - 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 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.

```perl
$ 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

```perl
$ 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`.

```perl
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`.

```perl
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

```perl
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

```perl
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

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

The constructor takes one mandatory parameter, `$output`, defined below and
zero or more `OPTS`, defined in "Constructor Options".

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, `$z`, returned from
IO::Compress::Bzip2 can be used exactly like an [IO::File](../File.md) filehandle.
This means that all normal output file operations can be carried out
with `$z`.
For example, to write to a compressed file/buffer you can use either of
these forms

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

Below is a simple exaple of using the OO interface to create an output file
`myfile.bz2` and write some data to it.

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

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

See the "Examples" for more.

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`.

    - 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.

    - 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.

    - 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

#### Streaming

This very simple command line example demonstrates 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 to STDOUT.

```perl
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 means `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

```perl
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 is

```perl
$z->print($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

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

Compresses and outputs the contents of the `$data` parameter.

Returns true if successful.

### syswrite

Usage is

```perl
$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

```perl
$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

```perl
$z->flush;
```

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

TODO

Returns true on success.

### tell

Usage is

```perl
$z->tell()
tell $z
```

Returns the uncompressed file offset.

### eof

Usage is

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

Returns true if the `close` method has been called.

### seek

```perl
$z->seek($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

```perl
$z->binmode
binmode $z ;
```

This is a noop provided for completeness.

### opened

```perl
$z->opened()
```

Returns true if the object currently refers to a opened file/buffer.

### autoflush

```perl
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

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

This method always returns `undef` when compressing.

### fileno

```perl
$z->fileno()
fileno($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

```perl
$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

```perl
$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

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

## EXAMPLES

### Apache::GZip Revisited

See [IO::Compress::FAQ](https://metacpan.org/pod/IO::Compress::FAQ#Apache-GZip-Revisited)

### Working with Net::FTP

See [IO::Compress::FAQ](https://metacpan.org/pod/IO::Compress::FAQ#Compressed-files-and-Net-FTP)

## SUPPORT

General feedback/questions/bug reports should be sent to
[https://github.com/pmqs/IO-Compress/issues](https://github.com/pmqs/IO-Compress/issues) (preferred) or
[https://rt.cpan.org/Public/Dist/Display.html?Name=IO-Compress](https://rt.cpan.org/Public/Dist/Display.html?Name=IO-Compress).

## SEE ALSO

[Compress::Zlib](../../Compress/Zlib.md), [IO::Compress::Gzip](Gzip.md), [IO::Uncompress::Gunzip](../Uncompress/Gunzip.md), [IO::Compress::Deflate](Deflate.md), [IO::Uncompress::Inflate](../Uncompress/Inflate.md), [IO::Compress::RawDeflate](RawDeflate.md), [IO::Uncompress::RawInflate](../Uncompress/RawInflate.md), [IO::Uncompress::Bunzip2](../Uncompress/Bunzip2.md), [IO::Compress::Lzma](https://metacpan.org/pod/IO::Compress::Lzma), [IO::Uncompress::UnLzma](https://metacpan.org/pod/IO::Uncompress::UnLzma), [IO::Compress::Xz](https://metacpan.org/pod/IO::Compress::Xz), [IO::Uncompress::UnXz](https://metacpan.org/pod/IO::Uncompress::UnXz), [IO::Compress::Lzip](https://metacpan.org/pod/IO::Compress::Lzip), [IO::Uncompress::UnLzip](https://metacpan.org/pod/IO::Uncompress::UnLzip), [IO::Compress::Lzop](https://metacpan.org/pod/IO::Compress::Lzop), [IO::Uncompress::UnLzop](https://metacpan.org/pod/IO::Uncompress::UnLzop), [IO::Compress::Lzf](https://metacpan.org/pod/IO::Compress::Lzf), [IO::Uncompress::UnLzf](https://metacpan.org/pod/IO::Uncompress::UnLzf), [IO::Compress::Zstd](https://metacpan.org/pod/IO::Compress::Zstd), [IO::Uncompress::UnZstd](https://metacpan.org/pod/IO::Uncompress::UnZstd), [IO::Uncompress::AnyInflate](../Uncompress/AnyInflate.md), [IO::Uncompress::AnyUncompress](../Uncompress/AnyUncompress.md)

[IO::Compress::FAQ](https://metacpan.org/pod/IO::Compress::FAQ)

[File::GlobMapper](../../File/GlobMapper.md), [Archive::Zip](https://metacpan.org/pod/Archive::Zip),
[Archive::Tar](../../Archive/Tar.md),
[IO::Zlib](../Zlib.md)

The primary site for the bzip2 program is [https://sourceware.org/bzip2/](https://sourceware.org/bzip2/).

See the module [Compress::Bzip2](https://metacpan.org/pod/Compress::Bzip2)

## AUTHOR

This module was written by Paul Marquess, `pmqs@cpan.org`.

## MODIFICATION HISTORY

See the Changes file.

## COPYRIGHT AND LICENSE

Copyright (c) 2005-2026 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.