IO::Tee (3pm)

    use IO::Tee;

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

\*(C`IO::Tee\*(C' 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 \*(C`IO::Tee\*(C' constructor, given a list of output handles, returns a tied handle that can be written to. When written to (using print or printf), the \*(C`IO::Tee\*(C' 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 \*(C`IO::File::new\*(C' 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 \*(C`IO::Tee\*(C' 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 \*(C`IO::Tee\*(C' object multiplexes the output to all handles passed to the constructor, as described in the previous paragraph. When read from, the \*(C`IO::Tee\*(C' object reads from the input handle given as the first argument to the \*(C`IO::Tee\*(C' constructor, then writes any data read to the output handles given as the remaining arguments to the constructor.

The \*(C`IO::Tee\*(C' class supports certain \*(C`IO::Handle\*(C' and \*(C`IO::File\*(C' methods related to input and output. In particular, the following methods will iterate themselves over all handles associated with the \*(C`IO::Tee\*(C' object, and return \s-1TRUE\s0 indicating success if and only if all associated handles returned \s-1TRUE\s0 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 \*(C`IO::Tee\*(C' constructor:

input_record_separator

input_line_number

Note that the return value of input multiplexing methods (such as \*(C`print\*(C') 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.

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);

Chung-chieh Shan, [email protected]

Copyright (c) 1998-2001 Chung-chieh Shan. All rights reserved. This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

perlfunc, IO::Handle, IO::File.