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::Zlibobject. If it receives any parameters, they are passed to the methodopen; if the open fails, the object is destroyed. Otherwise, it is returned to the caller.
OBJECT METHODS
- open ( FILENAME, MODE )
-
opentakes 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 opensYou 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::Zlibis available. Note that this does not mean thatCompress::Zlibis being used: see "gzip_external" and gzip_used. - gzip_external
-
Undef if an external gzip can be used if
Compress::Zlibis 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_externalrequires one boolean argument. - IO::Zlib::import: 'gzip_read_open' requires an argument
-
The
:gzip_externalrequires one string argument. - IO::Zlib::import: 'gzip_read' '...' is illegal
-
The
:gzip_read_openargument must end with the pipe sign (|) and have the%sfor the filename. See "USING THE EXTERNAL GZIP". - IO::Zlib::import: 'gzip_write_open' requires an argument
-
The
:gzip_externalrequires one string argument. - IO::Zlib::import: 'gzip_write_open' '...' is illegal
-
The
:gzip_write_openargument must begin with the pipe sign (|) and have the%sfor 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::Zliband 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@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.