NAME

File::Tee - replicate data sent to a Perl stream

SYNOPSIS

use File::Tee qw(tee);

# simple usage:
tee(STDOUT, '>', 'stdout.txt');

print "hello world\n";
system "ls";

# advanced usage:
my $pid = tee STDERR, { prefix => "err[$$]: ", reopen => 'my.log'};

print STDERR "foo\n";
system("cat /bad/path");

DESCRIPTION

This module is able to replicate the data written to a Perl stream to another stream(s). It is the Perl equivalent of the shell utility tee(1).

It is implemeted around fork, creating a new process for every tee'ed stream. That way, there are no problems handling the output generated by external programs run with system or by XS modules that don't go through perlio.

On the other hand, it will probably fail to work on Windows... that's a feature :-)

API

The following function can be imported from this module:

tee $fh, $target, ...

redirects a copy of the data written to $fh to one or several files or streams.

$target, ... is a list of target streams specifications that can be:

• file names with optional mode specifications:

  tee STDOUT, '>> /tmp/out', '>> /tmp/out2';
  tee STDOUT, '>>', '/tmp/out', '/tmp/out2';

  If the mode specification is a separate argument, it will affect all the file names following and not just the nearest one.

  If mode |- is used as a separate argument, the rest of the arguments are slurped as arguments for the pipe command:

  tee STDERR, '|-', 'grep', '-i', 'error';
  tee STDERR, '| grep -i error'; # equivalent

  Valid modes are >, >>, >&, >>& and |-. The default mode is >>.

  File handles can also be used as targets:

  open my $target1, '>>', '/foo/bar';
  ...
  tee STDOUT, $target1, $target2, ...;

• hash references describing the targets

  For instance:

  tee STDOUT, { mode => '>>', open => '/tmp/foo', lock => 1};

  will copy the data sent to STDOUT to /tmp/foo.

  The attributes that can be included inside the hash are:

  open => $file_name

  reopen => $file_name

  sets the target file or stream. It can contain a mode specification and also be an array. For instance:

  tee STDOUT, { open => '>> /tmp/out' };
  tee STDOUT, { reopen => ['>>', '/tmp/out2'] };
  tee STDOUT, { open => '| grep foo > /tmp/out' };

  If reopen is used, the file or stream is reopen for every write operation. The mode will be forced to append after the first write.

  mode => $mode

  Alternative way to specify the mode to open the target file or stream

  lock => $bool

  When true, an exclusive lock is obtained on the target file before writing to it.

  prefix => $txt

  Some text to be prepended to every line sent to the target file.

  For instance:

  tee STDOUT, { prefix => 'OUT: ', lock => 1, mode => '>>', open => '/tmp/out.txt' };
  tee STDERR, { prefix => 'ERR: ', lock => 1, mode => '>>', open => '/tmp/out.txt' };

  process => sub { ... }

  A callback function that can modify the data before it gets sent to the target file.

  For instance:

  sub hexdump {
    my $data = shift;
    my @out;
    while ($data =~ /(.{1,32})/smg) {
        my $line=$1;
        my @c= (( map { sprintf "%02x",$_ } unpack('C*', $line)),
                (("  ") x 32))[0..31];
        $line=~s/(.)/ my $c=$1; unpack("c",$c)>=32 ? $c : '.' /egms;
        push @out, join(" ", @c, '|', $line), "\n";
    }
    join('', @out);
  }
  
  tee BINFH, { process => \&hexdump, open => '/tmp/hexout'};

  autoflush => $bool

  Sets autoflush mode for the target streams. Default is on.

The funcion returns the PID for the newly created process.

Inside the tee pipe process created, data is readed honouring the input record separator $/.

You could also want to set the tee'ed stream in autoflush mode:

open $fh, ...;

my $oldsel = select $fh;
$| = 1;
select $fh;

tee $fh, "> /tmp/log";

BUGS

This is alpha software, not very tested. Expect bugs on it.

Probably, would not work on Windows.

Send bug reports by email or via the CPAN RT web.

SEE ALSO

IO::Tee is a similar module implemented around tied file handles.

COPYRIGHT AND LICENSE

Copyright (C) 2007 by Salvador Fandiño (sfandino@yahoo.com)

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself, either Perl version 5.8.8 or, at your option, any later version of Perl 5 you may have available.