IO::Zlib

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IO::Zlib
Perl 5 version 10.0 documentation
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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->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
;

        
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 () {
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
open
s 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.
  
• IO::Zlib::WRITE: OFFSET is not supported
  Offsets of gzipped streams are not supported.
  

SEE ALSO
perlfunc
,
""I/O Operators"" in perlop
,
IO::Handle
,
Compress::Zlib
HISTORY
Created by Tom Hughes .
Support for external gzip added by Jarkko Hietaniemi .
COPYRIGHT
Copyright (c) 1998-2004 Tom Hughes . All rights reserved. This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.
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Page index

• 
  [url=http://perldoc.perl.org/IO/Zlib.html#NAME]NAME
  
  
• 
  SYNOPSIS
  
  
• 
  DESCRIPTION
  
  
• 
  CONSTRUCTOR
  
  
• 
  OBJECT METHODS
  
  
• 
  USING THE EXTERNAL GZIP
  
  
• 
  CLASS METHODS
  
  
• 
  DIAGNOSTICS
  
  
• 
  SEE ALSO
  
  
• 
  HISTORY
  
  
• 
  COPYRIGHT
  

  
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