Tie *STDOUT, recursion error

[Superfox il Volpone]

Hi, I was thinking to tie the *STDOUT handle to mask the values to be printed in the stardard output. Though, I hit a deep recursion error, probably because I lose the original reference to *STDOUT and invokes my new handle when trying to print:

package hyundai{
  
  sub TIEHANDLE{
    my $class = shift; 
    my $oldhandle = shift;
    return bless ({"handle" => $oldhandle}, $class); 
  }
  
  my $mask = sub{
    (my $text = shift()) =~ s/a/b/g; # replaces a with b
    return $text;
  };
  
  sub PRINT{
    my $self = shift;
    die("Not a ref") if !ref($self); 
    my $text = join('',@_);
    print STDERR ("STDOUT: ", \*STDOUT, "\n"); # prints GLOB(0x880a20)
+ 
    print STDERR ("STDERR: ", \*STDERR, "\n"); # prints GLOB(0x880a80)
    print STDERR ("handle: ", \$self->{"handle"}, "\n"); # prints GLOB
+(0x8806c0)
    
    $self->{"handle"}->print( &$mask($text) ); # infinite recursion !
  }
  
};


print("Hello world 1 aaaaaaa\n");
my $oldhandle = *STDOUT;
undef(*STDOUT);
tie *STDOUT, "hyundai", $oldhandle;
print("Hello world 2 aaaaaaa\n");

I was following this (old) post related to the same issue, though it does not seem that a working solution was proposed. Any idea how to proceed ?

s.fox

[choroba]

Interestingly, the following works:

print { $self->{handle} } $mask->($text);

[Superfox il Volpone]

hi choroba, shouldn't the two syntaxes be equivalent?! also, why is {$self->{"handle"}} and not *{$self->{"handle"}}. My understanding was that { } is used to deference a reference, such as ${ $ref_scalar }, so a sigil was required. But I am wrong as the above code example proves :/

s.fox

[Athanasius]

Hello Superfox il Volpone,

I get no infinite recursion on my system (Windows 8.1, 64-bit):

16:17 >perl 1215_SoPW.pl
Hello world 1 aaaaaaa
STDOUT: GLOB(0x1c94bc8)
STDERR: GLOB(0x1c94c28)
handle: GLOB(0x55c2d8)
Hello world 2 bbbbbbb

16:17 >perl -v

This is perl 5, version 20, subversion 2 (v5.20.2) built for MSWin32-x
+64-multi-thread
...

(Strawberry Perl, portable.)

Hope that is of interest,

[Anonymous Monk]

See Tie::STDOUT and Capture::Tiny

[Superfox il Volpone]

thanks for the reply. I was looking to the source code of Tie::STDOUT. He basically solves it with something like:

    open(my $stdout, ">&", STDOUT); 
...
# in the overloaded method PRINT
    $stdout->print( @_ ); # this refers to the original STDOUT.

I guess this opens a different underlying file handle, while my $oldhandle = STDOUT is an assignment/alias to the same file handle used by STDOUT.

s.fox

[Superfox il Volpone]

hey Athanasius,
it is interesting indeed. In my case I am under perl v5.16.3 on CentOS 7. I am starting to believe this is a non portable behaviour of perl.

s.fox