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man : IO::Zlib
IO::Zlib(3p) Perl Programmers Reference Guide IO::Zlib(3p)
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);
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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?
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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.
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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.
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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 <tomATcompton.nu>.
Support for external gzip added by Jarkko Hietaniemi
<jhiATiki.fi>.
COPYRIGHT
Copyright (c) 1998-2004 Tom Hughes <tomATcompton.nu>. 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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