IO::Compress::Lzop - Write lzop files/buffers
use IO::Compress::Lzop qw(lzop $LzopError) ; my $status = lzop $input => $output [,OPTS] or die "lzop failed: $LzopError\n"; my $z = IO::Compress::Lzop->new( $output [,OPTS] ) or die "lzop failed: $LzopError\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() ; $LzopError ; # IO::File mode print $z $string; printf $z $format, $string; tell $z eof $z seek $z, $position, $whence binmode $z fileno $z close $z ;
This module provides a Perl interface that allows writing lzop compressed data to files or buffer.
For reading lzop files/buffers, see the companion module IO::Uncompress::UnLzop.
A top-level function, lzop, 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.
lzop
use IO::Compress::Lzop qw(lzop $LzopError) ; lzop $input_filename_or_reference => $output_filename_or_reference [,OPTS] or die "lzop failed: $LzopError\n";
The functional interface needs Perl5.005 or better.
lzop expects at least two parameters, $input_filename_or_reference and $output_filename_or_reference and zero or more optional parameters (see "Optional Parameters")
$input_filename_or_reference
$output_filename_or_reference
The parameter, $input_filename_or_reference, is used to define the source of the uncompressed data.
It can take one of the following forms:
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.
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.
If $input_filename_or_reference is a scalar reference, the input data will be read from $$input_filename_or_reference.
$$input_filename_or_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.
If $input_filename_or_reference is a string that is delimited by the characters "<" and ">" lzop 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.
undef
In addition, if $input_filename_or_reference is a simple filename, the default values for the Name and Time options will be sourced from that file.
Name
Time
If you do not want to use these defaults they can be overridden by explicitly setting the Name and Time options or by setting the Minimal parameter.
Minimal
The parameter $output_filename_or_reference is used to control the destination of the compressed data. This parameter can take one of these forms.
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.
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.
If $output_filename_or_reference is a scalar reference, the compressed data will be stored in $$output_filename_or_reference.
$$output_filename_or_reference
If $output_filename_or_reference is an array reference, the compressed data will be pushed onto the array.
If $output_filename_or_reference is a string that is delimited by the characters "<" and ">" lzop 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.
If the $output_filename_or_reference parameter is any other type, undef will be returned.
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 each be stored in $output_filename_or_reference as a distinct entry.
The optional parameters for the one-shot function lzop 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 lzop 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 lzop has completed.
AutoClose
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.
Append
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.
seek
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.
Here are a few example that show the capabilities of the module.
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::Lzop=lzop -e 'lzop \*STDIN => \*STDOUT' >output.lzo
The special filename "-" can be used as a standin for both \*STDIN and \*STDOUT, so the above can be rewritten as
\*STDIN
\*STDOUT
$ echo hello world | perl -MIO::Compress::Lzop=lzop -e 'lzop "-" => "-"' >output.lzo
To read the contents of the file file1.txt and write the compressed data to the file file1.txt.lzo.
file1.txt
file1.txt.lzo
use strict ; use warnings ; use IO::Compress::Lzop qw(lzop $LzopError) ; my $input = "file1.txt"; lzop $input => "$input.lzo" or die "lzop failed: $LzopError\n";
To read from an existing Perl filehandle, $input, and write the compressed data to a buffer, $buffer.
$input
$buffer
use strict ; use warnings ; use IO::Compress::Lzop qw(lzop $LzopError) ; use IO::File ; my $input = IO::File->new( "<file1.txt" ) or die "Cannot open 'file1.txt': $!\n" ; my $buffer ; lzop $input => \$buffer or die "lzop failed: $LzopError\n";
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::Lzop qw(lzop $LzopError) ; lzop '</my/home/*.txt>' => '<*.lzo>' or die "lzop failed: $LzopError\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::Lzop qw(lzop $LzopError) ; for my $input ( glob "/my/home/*.txt" ) { my $output = "$input.lzo" ; lzop $input => $output or die "Error compressing '$input': $LzopError\n"; }
The format of the constructor for IO::Compress::Lzop is shown below
IO::Compress::Lzop
my $z = IO::Compress::Lzop->new( $output [,OPTS] ) or die "IO::Compress::Lzop failed: $LzopError\n";
It returns an IO::Compress::Lzop object on success and undef on failure. The variable $LzopError will contain an error message on failure.
$LzopError
If you are running Perl 5.005 or better the object, $z, returned from IO::Compress::Lzop 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
$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.
$output
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.
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.
If $output is a scalar reference, the compressed data will be stored in $$output.
$$output
If the $output parameter is any other type, IO::Compress::Lzop::new will return undef.
OPTS is any combination of zero or more the following options:
OPTS
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::Lzop object is destroyed.
close
Opens $output in append mode.
The behaviour of this option is dependent on the type of $output.
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.
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.
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.
Name => $string
Stores the contents of $string in the name field lzop header.
$string
If Name is not specified, no gzip NAME field will be created.
Time => $number
Sets the Time field in the lzop header to $number.
This field defaults to the time the IO::Compress::Lzop object was created if this option is not specified.
TODO
Creates the smallest possible lzop file/buffer.
Disables the creation of all checksums.
No Name is stored.
Strict => 0|1
This is a placeholder option.
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.
$data
print
Returns true if successful.
$z->printf($format, $data) printf $z $format, $data
Compresses and outputs the contents of the $data parameter.
$z->syswrite $data $z->syswrite $data, $length $z->syswrite $data, $length, $offset
Returns the number of uncompressed bytes written, or undef if unsuccessful.
$z->write $data $z->write $data, $length $z->write $data, $length, $offset
$z->flush;
Flushes any pending compressed data to the output file/buffer.
Returns true on success.
$z->tell() tell $z
Returns the uncompressed file offset.
$z->eof(); eof($z);
Returns true if the close method has been called.
$z->seek($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.
$whence
Returns 1 on success, 0 on failure.
$z->binmode binmode $z ;
This is a noop provided for completeness.
$z->opened()
Returns true if the object currently refers to a opened file/buffer.
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.
EXPR
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.
$|
$z->input_line_number() $z->input_line_number(EXPR)
This method always returns undef when compressing.
$z->fileno() fileno($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.
fileno
If the $z object is associated with a buffer, this method will return undef.
$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::Lzop 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::Lzop object was created, and the object is associated with a file, the underlying file will also be closed.
$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.
No symbolic constants are required by IO::Compress::Lzop at present.
Imports lzop and $LzopError. Same as doing this
use IO::Compress::Lzop qw(lzop $LzopError) ;
General feedback/questions/bug reports should be sent to https://github.com/pmqs/IO-Compress-Lzop/issues (preferred) or https://rt.cpan.org/Public/Dist/Display.html?Name=IO-Compress-Lzop.
Compress::Zlib, IO::Compress::Gzip, IO::Uncompress::Gunzip, IO::Compress::Deflate, IO::Uncompress::Inflate, IO::Compress::RawDeflate, IO::Uncompress::RawInflate, IO::Compress::Bzip2, IO::Uncompress::Bunzip2, IO::Compress::Lzma, IO::Uncompress::UnLzma, IO::Compress::Xz, IO::Uncompress::UnXz, IO::Compress::Lzip, IO::Uncompress::UnLzip, 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
This module was written by Paul Marquess, pmqs@cpan.org.
pmqs@cpan.org
See the Changes file.
Copyright (c) 2005-2023 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.
To install IO::Compress::Lzop, copy and paste the appropriate command in to your terminal.
cpanm
cpanm IO::Compress::Lzop
CPAN shell
perl -MCPAN -e shell install IO::Compress::Lzop
For more information on module installation, please visit the detailed CPAN module installation guide.