IO::Zlib

• NAME
• SYNOPSIS
• DESCRIPTION
• CONSTRUCTOR
• OBJECT METHODS
• USING THE EXTERNAL GZIP
• CLASS METHODS
• DIAGNOSTICS
• SEE ALSO
• HISTORY
• COPYRIGHT

NAME

IO::Zlib - IO:: style interface to Compress::Zlib

SYNOPSIS

With any version of Perl 5 you can use the basic OO interface:

use IO::Zlib;

$fh = new IO::Zlib;
if ($fh->open("file.gz", "rb")) {
    print <$fh>;
    $fh->close;
}

$fh = IO::Zlib->new("file.gz", "wb9");
if (defined $fh) {
    print $fh "bar\n";
    $fh->close;
}

$fh = IO::Zlib->new("file.gz", "rb");
if (defined $fh) {
    print <$fh>;
    undef $fh;       # automatically closes the file
}

With Perl 5.004 you can also use the TIEHANDLE interface to access compressed files just like ordinary files:

use IO::Zlib;

tie *FILE, 'IO::Zlib', "file.gz", "wb";
print FILE "line 1\nline2\n";

tie *FILE, 'IO::Zlib', "file.gz", "rb";
while (<FILE>) { print "LINE: ", $_ };

DESCRIPTION

IO::Zlib provides an IO:: style interface to Compress::Zlib and hence to gzip/zlib compressed files. It provides many of the same methods as the IO::Handle interface.

Starting from IO::Zlib version 1.02, IO::Zlib can also use an external gzip command. The default behaviour is to try to use an external gzip if no Compress::Zlib can be loaded, unless explicitly disabled by

use IO::Zlib qw(:gzip_external 0);

If explicitly enabled by

use IO::Zlib qw(:gzip_external 1);

then the external gzip is used instead of Compress::Zlib .

CONSTRUCTOR

• new ( [ARGS] )

  Creates an IO::Zlib object. If it receives any parameters, they are passed to the method open; if the open fails, the object is destroyed. Otherwise, it is returned to the caller.

OBJECT METHODS

• open ( FILENAME, MODE )

  open takes two arguments. The first is the name of the file to open and the second is the open mode. The mode can be anything acceptable to Compress::Zlib and by extension anything acceptable to zlib (that basically means POSIX fopen() style mode strings plus an optional number to indicate the compression level).

• opened

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

• close

  Close the file associated with the object and disassociate the file from the handle. Done automatically on destroy.

• getc

  Return the next character from the file, or undef if none remain.

• getline

  Return the next line from the file, or undef on end of string. Can safely be called in an array context. Currently ignores $/ ($INPUT_RECORD_SEPARATOR or $RS when English is in use) and treats lines as delimited by "\n".

• getlines

  Get all remaining lines from the file. It will croak() if accidentally called in a scalar context.

• print ( ARGS... )

  Print ARGS to the file.

• read ( BUF, NBYTES, [OFFSET] )

  Read some bytes from the file. Returns the number of bytes actually read, 0 on end-of-file, undef on error.

• eof

  Returns true if the handle is currently positioned at end of file?

• seek ( OFFSET, WHENCE )

  Seek to a given position in the stream. Not yet supported.

• tell

  Return the current position in the stream, as a numeric offset. Not yet supported.

• setpos ( POS )

  Set the current position, using the opaque value returned by getpos() . Not yet supported.

• getpos ( POS )

  Return the current position in the string, as an opaque object. Not yet supported.

USING THE EXTERNAL GZIP

If the external gzip is used, the following opens are used:

open(FH, "gzip -dc $filename |")  # for read opens
open(FH, " | gzip > $filename")   # for write opens

You can modify the 'commands' for example to hardwire an absolute path by e.g.

use IO::Zlib ':gzip_read_open'  => '/some/where/gunzip -c %s |';
use IO::Zlib ':gzip_write_open' => '| /some/where/gzip.exe > %s';

The %s is expanded to be the filename (sprintf is used, so be careful to escape any other % signs). The 'commands' are checked for sanity - they must contain the %s , and the read open must end with the pipe sign, and the write open must begin with the pipe sign.

CLASS METHODS

• has_Compress_Zlib

  Returns true if Compress::Zlib is available. Note that this does not mean that Compress::Zlib is being used: see gzip_external and gzip_used.

• gzip_external

  Undef if an external gzip can be used if Compress::Zlib is not available (see has_Compress_Zlib), true if an external gzip is explicitly used, false if an external gzip must not be used. See gzip_used.

• gzip_used

  True if an external gzip is being used, false if not.

• gzip_read_open

  Return the 'command' being used for opening a file for reading using an external gzip.

• gzip_write_open

  Return the 'command' being used for opening a file for writing using an external gzip.

DIAGNOSTICS

• IO::Zlib::getlines: must be called in list context

  If you want read lines, you must read in list context.

• IO::Zlib::gzopen_external: mode '...' is illegal

  Use only modes 'rb' or 'wb' or /wb[1-9]/.

• IO::Zlib::import: '...' is illegal

  The known import symbols are the :gzip_external , :gzip_read_open , and :gzip_write_open . Anything else is not recognized.

• IO::Zlib::import: ':gzip_external' requires an argument

  The :gzip_external requires one boolean argument.

• IO::Zlib::import: 'gzip_read_open' requires an argument

  The :gzip_external requires one string argument.

• IO::Zlib::import: 'gzip_read' '...' is illegal

  The :gzip_read_open argument must end with the pipe sign (|) and have the %s for the filename. See USING THE EXTERNAL GZIP.

• IO::Zlib::import: 'gzip_write_open' requires an argument

  The :gzip_external requires one string argument.

• IO::Zlib::import: 'gzip_write_open' '...' is illegal

  The :gzip_write_open argument must begin with the pipe sign (|) and have the %s for the filename. An output redirect (>) is also often a good idea, depending on your operating system shell syntax. See USING THE EXTERNAL GZIP.

• IO::Zlib::import: no Compress::Zlib and no external gzip

  Given that we failed to load Compress::Zlib and that the use of an external gzip was disabled, IO::Zlib has not much chance of working.

• IO::Zlib::open: needs a filename

  No filename, no open.

• IO::Zlib::READ: NBYTES must be specified

  We must know how much to read.

• IO::Zlib::WRITE: too long LENGTH

  The LENGTH must be less than or equal to the buffer size.

SEE ALSO

perlfunc, I/O Operators in perlop, IO::Handle, Compress::Zlib

HISTORY

Created by Tom Hughes <[email protected]>.

Support for external gzip added by Jarkko Hietaniemi <[email protected]>.

COPYRIGHT

Copyright (c) 1998-2004 Tom Hughes <[email protected]>. All rights reserved. This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.