in reply to Porting Perl 5.6 to Perl 5.8 issue with self-tie

The second tee doesn't work because you didn't save your original STDOUT, so tee doesn't get it. 
#!/usr/bin/perl -wl
$| = 1; # unbuffered output
print $$;
for(1,2){
    open SAVEOUT,">&STDOUT";
    my $pid = open STDOUT,"| tee log_$_";
    open STDERR, ">&STDOUT";
    print "this goes to STDOUT (log_$_)";
    warn "This goes to STDERR (log_$_)";
    sleep 1;
    print "killing $pid";
    kill 15, $pid;
    close STDOUT;
    close STDERR;
    open STDOUT,">&SAVEOUT";
}
__END__
Name "main::SAVEOUT" used only once: possible typo at tee.pl line 4.
14781
this goes to STDOUT (log_1)
This goes to STDERR (log_1) at tee.pl line 8.
killing 14782
this goes to STDOUT (log_2)
This goes to STDERR (log_2) at tee.pl line 8.

[download]
$ cat log_1 log_2
this goes to STDOUT (log_1)
This goes to STDERR (log_1) at tee.pl line 8.
this goes to STDOUT (log_2)
This goes to STDERR (log_2) at tee.pl line 8.

[download]

Of course, if you need to restore STDERR later, save that too. See open. Note that if you remove the sleep 1 line in the above code you will likely not see any output, because then the tee process gets killed too soon.

--shmem

update: fixed inconsistencies stemming from putting a oneliner into a file.. 

_($_=" "x(1<<5)."?\n".q·/)Oo.  G°\        /
                              /\_¯/(q    /
----------------------------  \__(m.====·.(_("always off the crowd"))."·
");sub _{s./.($e="'Itrs `mnsgdq Gdbj O`qkdq")=~y/"-y/#-z/;$e.e && print}

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Re^2: Porting Perl 5.6 to Perl 5.8 issue with self-tie
by fwashbur (Sexton) on Dec 11, 2006 at 22:25 UTC
    Hey shmem,

    This looks like what I'm looking for! I had tried combos of saving STDOUT and killing the tee, but not in this configuration. I'll give this a try. This could explain why I was having trouble with STDERR as well.

    Thanks - Rick

[reply]
      Hi shmem,

      I tried this scheme on my system. It ran into the same issue I had when trying the example out of the O'Reilly book. The first log works great, but the second log attempt results in the following error at the first print statement: tee: write error: Invalid argument

      Are you running this on 5.8? Could there be an issue with my 'tee'?

      Thanks - Rick

[reply]
[d/l]
        Hmm. Yes, I'm running 5.8, and no, I guess it's not an issue with tee. Strange.

        Next I would do is wrapping tee with a shell script which traces tee, to see what it does, specifically open/closes. Log the fileno() of your STDERR and STDOUT to the apache error log (real STDERR ;-) as well as the fileno() of your redirected handles. Ah, and you could omit the close STDOUT - just re-open it. I didn't check the return value of close (shame on me) which you should do.

        Could you provide a condensed version of the code you are running?

        --shmem 

        _($_=" "x(1<<5)."?\n".q·/)Oo.  G°\        /
                              /\_¯/(q    /
----------------------------  \__(m.====·.(_("always off the crowd"))."·
");sub _{s./.($e="'Itrs `mnsgdq Gdbj O`qkdq")=~y/"-y/#-z/;$e.e && print}
[reply]
[d/l]

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