IO::Zlib(3perl)                  Perl Programmers Reference Guide                 IO::Zlib(3perl)



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 "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.

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

HISTORY
       Created by Tom Hughes <tom AT compton.nu>.

       Support for external gzip added by Jarkko Hietaniemi <jhi AT iki.fi>.

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



perl v5.20.2                                2014-12-27                            IO::Zlib(3perl)