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




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(1), "I/O Operators" in perlop(1), IO::Handle(3), Compress::Zlib(3)


HISTORY

       Created by Tom Hughes <tom@compton.nu>.

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


COPYRIGHT

       Copyright (c) 1998-2004 Tom Hughes <tom@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 v5.24.0                      2015-10-14                     IO::Zlib(3pm)

perl 5.24 - Generated Mon Nov 14 18:29:13 CST 2016
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