NAME

IO::Filter::* - Generic input/output filters for Perl IO handles.

SYNOPSIS

 use IO::Filter::External;
 use IO::Filter::bunzip2;
 use IO::Filter::bzip2;
 use IO::Filter::gunzip;
 use IO::Filter::gzip;
 use IO::Filter::lc;
 use IO::Filter::sort;
 use IO::Filter::uc;

 $io = # any Perl IO handle, eg. an IO::File or IO::Socket,
       # opened for writing
 $fio = new IO::Filter::gzip ($io, "w");
 $fio->print ("This text will be written gzip-compressed\n",
              "to the underlying \$io file or socket.\n");
 $fio->close; # also closes underlying $io

 $io = # any Perl IO handle opened for reading
 $fio1 = new IO::Filter::gzip ($io, "r");
 $fio2 = new IO::Filter::gunzip ($fio, "r");
 # reading from $fio2 is an expensive no-op

DESCRIPTION

IO::Filter::* is a set of filter classes which allow you to apply filters to ordinary Perl IO handles. In this way you can, for example, compress data into and out of sockets directly, perform on-the-fly data transformations and so on. You can think of filters as being similar in some ways to Unix filter commands (eg. sort, tr, grep, etc.).

A filter wraps an existing IO handle and gives you back the same interface (see the IO::Handle(3) manpage), so you can use an IO::Filter::* object whenever you would use a normal IO::Handle.

Filters are always unidirectional, meaning that you can use them either in read mode or write mode but not both at the same time.

Note: IO::Filter itself is an abstract superclass. Do not instantiate objects of type IO::Filter directly. Instead, create objects of one of the derived classes such as IO::Filter::gzip.

METHODS

$fio->read ($buffer, $len [, $offset]);
$fio->write ($buffer, $len [, $offset]);
$fio->flush;
$fio->getc;
$fio->getline;
$fio->print (@args);
$fio->printf ($fs, ...);
$fio->close;

BUGS

FILES

AUTHORS

Richard Jones (rich@annexia.org)