Recursively changing STDOUT

[casiano]

Dear Monks,

I need to write some recursive subroutine that in each entry has to

1. save STDOUT and STDERR,
2. change it to redirect them to some files,
3. do something with them and call itself under the apropriate conditions
4. recover the old values.

I know how to do it using "old style" with the ">&" descriptor. I.e. something like:

  my $log = ...;
  my $err = ...;
 
  open(SAVEOUT, ">&STDOUT") or die ...
  open(STDOUT,"> $log") or die ..

  open(SAVEERR, ">&STDERR") or die ...
  open(STDERR,"> $err") or die ..

but I need to use lexical variables $SAVEOUT, and $SAVEERR instead of global variables. The problem being that to recover the old values I have now:

  open(STDOUT, ">&SAVEOUT");
  open(STDERR, ">&SAVEERR");

I assume that this construction will not work If I use it with lexical variables? i.e.

  open(STDOUT, ">&$SAVEOUT");
  open(STDERR, ">&$SAVEERR");

How can I do it?

Thanks!

Casiano

[shmem]

This sounds like an XY Problem to me. Are you expicitly doing

    print STDOUT $foo;

somewhere? Or are you just printing to "the default filehandle" as in

    print $foo;

without specifiying it?

If the latter is the case, you'll probably be better of with select and using lexical filehandles.

sub prepare_foo_print {
    my ($foo, $file) = @_;
    open my $fh, '>>', $file or die "bummer: $!\n";
    my $oldfh = select $fh;
    # currently opened $file now is default filehandle
    # (instead of STDOUT)
    print_whatever ($foo);
    select $oldfh;
}
sub print_whatever {
    print shift;
}

[Sidhekin]

moritz gave you half the answer. The one thing remaining, is reopening STDOUT, STDERR with the $SAVEOUT, $SAVEERR. The three-argument open covers that:

open(STDOUT, '>&', $SAVEOUT) or die ...

open(STDERR, '>&', $SAVEERR) or die ...

[moritz]

You can use lexical variables as file handles:

open (my $saveout, ...);

[casiano]

Thanks Moritz,

But to recover the old values I have now:

  open(STDOUT, ">&SAVEOUT");
  open(STDERR, ">&SAVEERR");

¿Can I use this with lexical variables? i.e.

  open(STDOUT, ">&$SAVEOUT");
  open(STDERR, ">&$SAVEERR");

It will not produce a interpolation of the filehandle?

Casiano