NAME

IO::Tee - Multiplex output to multiple output handles

SYNOPSIS

    use IO::Tee;

    $tee = IO::Tee->new($handle1, $handle2);
    print $tee "foo", "bar";
    my $input = <$tee>;

DESCRIPTION

IO::Tee objects can be used to multiplex input and output in two different ways. The first way is to multiplex output to zero or more output handles. The IO::Tee constructor, given a list of output handles, returns a tied handle that can be written to. When written to (using print or printf), the IO::Tee object multiplexes the output to the list of handles originally passed to the constructor. As a shortcut, you can also directly pass a string or an array reference to the constructor, in which case IO::File::new is called for you with the specified argument or arguments.

The second way is to multiplex input from one input handle to zero or more output handles as it is being read. The IO::Tee constructor, given an input handle followed by a list of output handles, returns a tied handle that can be read from as well as written to. When written to, the IO::Tee object multiplexes the output to all handles passed to the constructor, as described in the previous paragraph. When read from, the IO::Tee object reads from the input handle given as the first argument to the IO::Tee constructor, then writes any data read to the output handles given as the remaining arguments to the constructor.

The IO::Tee class supports certain IO::Handle and IO::File methods related to input and output. In particular, the following methods will iterate themselves over all handles associated with the IO::Tee object, and return TRUE indicating success if and only if all associated handles returned TRUE indicating success:

close
truncate
write
syswrite
format_write
formline
fcntl
ioctl
flush
clearerr
seek

The following methods perform input multiplexing as described above:

read
sysread
readline
getc
gets
eof
getline
getlines

The following methods can be used to set (but not retrieve) the current values of output-related state variables on all associated handles:

autoflush
output_field_separator
output_record_separator
format_page_number
format_lines_per_page
format_lines_left
format_name
format_top_name
format_line_break_characters
format_formfeed

The following methods are directly passed on to the input handle given as the first argument to the IO::Tee constructor:

input_record_separator
input_line_number

Note that the return value of input multiplexing methods (such as print) is always the return value of the input action, not the return value of subsequent output actions. In particular, no error is indicated by the return value if the input action itself succeeds but subsequent output multiplexing fails.

EXAMPLE

    use IO::Tee;
    use IO::File;

    my $tee = new IO::Tee(\*STDOUT,
        new IO::File(">tt1.out"), ">tt2.out");

    print join(' ', $tee->handles), "\n";

    for (1..10) { print $tee $_, "\n" }
    for (1..10) { $tee->print($_, "\n") }
    $tee->flush;

    $tee = new IO::Tee('</etc/passwd', \*STDOUT);
    my @lines = <$tee>;
    print scalar(@lines);

AUTHOR

Chung-chieh Shan, ken@digitas.harvard.edu

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