IO::MultiHandle - Operate on multiple file handles as one

This module encapsulates any number of filehandles in a kind of "meta-filehandle". Any operations you perform on the meta-filehandle are delegated to all of the contained handles. This may be similar to the IO::Tee module.

This solution was developed in response to Printing to multiple file handles with one request.

Updated in response to helpful comments from jmcnamara and Aristotle.


=head1 NAME

IO::MultiHandle - Encapsulate multiple handles in one.

=head1 SYNOPSIS

    use IO::MultiHandle;

    my $logfh = IO::File->new( "> $outfile" ) or die "write $outfile: 
+$!";

    # create a multi-handle which will write to both
    # STDERR and the filehandle created above:
    my $mfh = new IO::MultiHandle *STDERR, $logfh;

    print $mfh "A line of output.\n";

=cut
[download]


package Tie::MultiHandle; # do not use directly.
  use IO::Handle;

  sub TIEHANDLE
  {
    my $pkg = shift;
    bless [ @_ ], $pkg
  }

  sub AUTOLOAD
  {
    my( $self, @args ) = @_;
    our( $AUTOLOAD );
    $AUTOLOAD =~ s/.*::(.*)/\L$1/;
    for my $fh ( @$self ) { $fh->$AUTOLOAD( @args ); }
  }

  sub DESTROY
  {
  }


package IO::MultiHandle;
  use Symbol;

  # takes a list of handles
  sub new
  {
    my $pkg = shift;
    my $self = gensym;
    tie *$self, Tie::MultiHandle::, @_;
    bless $self, $pkg
  }
[download]

Comment on IO::MultiHandle - Operate on multiple file handles as one Select or Download Code

Replies are listed 'Best First'.
Re: Print to multiple file handles at once. by Aristotle (Chancellor) on Nov 20, 2002 at 16:18 UTC
Did you test this? The following won't work: `$fh->$AUTOLOAD( @args ) for my $fh @$self;` Perl hasn't seen the my when it sees the first mention of `$fh` so that one refers to the global variable of that name. Either declare the variable on a line by itself or use `$_`. `$_->$AUTOLOAD(@args) for @$self;` Makeshifts last the longest.	[reply] [d/l] [select]
Re: Print to multiple file handles at once. by jmcnamara (Monsignor) on Nov 20, 2002 at 15:58 UTC
That is a nice idea and a nice implementation. However, it has some problems. The `my $fh` won't work with the postfix `for`. You would have to do something like this instead: `$_->$AUTOLOAD(@args) for @$self;` Also, the following won't work because `MultiHandle->new()` doesn't return a GLOB: `print $mfh "A line of output.\n";` The following does work but it isn't as pretty: `$mfh->print("A line of output.\n");` -- John.	[reply] [d/l] [select]


Don't ask to ask, just ask
	PerlMonks