in reply to locking STDOUT

lock doesn't work the way you seem to think it does. Only few operating systems have mandatory file locking, and locking only works between processes, not within a single process.

If you want to prevent other parts of your program from printing output to the screen, you will have to reopen STDOUT to something else:

my $old_STDOUT = \*STDOUT;
my $capture;
open STDOUT, '>', \$capture
    or die "Couldn't do in-memory capture of program output: $!";

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If you have subprocesses that output to the screen, you will have to redirect or capture their output (via shell pipes or IPC::Open or IPC::Open3).

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Re^2: locking STDOUT
by spx2 (Deacon) on Jun 04, 2007 at 12:06 UTC 
    so you suggest filtering all things 
through a shell pipe...im not sure how
i could use that to have lock-similar functionality.
im into multithreading not multiprocesses.
im thinking of making a separate

    my $buffer:shared="";
sub PRINT {
 lock $buffer;
 $buffer.=shift;
}

sub dump_on_screen {
 lock $buffer;
 print $buffer;
 $|++;
 $buffer="";
}

    [download]
    and have a thread say...PRINT_THREAD that
periodically prints stuff to the screen
but in the order they happened in real-time

    my $pt=threads->new(\&PRINT_THREAD);
sub PRINT_THREAD {
 dump_on_screen();
}

    [download]
    




i havent been clear enough in what i want to do
actually, i have a multithreding app and i want
to print stuff on the screen just as they happen.
i want print to be atomic so thats why i want to
lock the screen before i start doing anything.
id like to get the order in wich threads
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      i havent been clear enough in what i want to do actually, i have a multithreding app and i want to print stuff on the screen just as they happen. i want print to be atomic so thats why i want to lock the screen before i start doing anything. id like to get the order in wich threads

      In that case, I don't think you want to lock the screen but set STDOUT to be non-buffering. See the $| entry in perlvar or Suffering from Buffering.

      -derby

      Update: At the beginning of your script, I would set STDOUT to be non-buffering: 

       select STDOUT; $| = 1;

      [download]

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