Re^3: Unbelievably Obvious Debugging Tip

[radiantmatrix]

Because I often deal with data containing every char on the keyboard, I use:

print STDERR join("\x1E", @list),"\x1E\n";

This gives me an output with visible record separators (ASCII 0x1E is actuall "Record Separator") quite cleanly, and I use STDERR to avoid bufferring. Default buffering of STDOUT has bitten my debug routines a few times.

If I'm working a large project, I use my own little module that exports a number of debugging "tools", including this:

sub dbg {
    return unless $DEBUG;
    my $dump = 0;
    ($dump = 1 && shift) if ($_[0] eq ':DUMP:');
    $LOGFILE = open_logfile();
    foreach my $item (@_) {
        $str = (($dump && ref $item)  ? Dumper($item) : $item)."\x1E\n
+";
        print $LOGFILE POSIX::strftime("%Y%m%d:%H.%M.%S\x1E",localtime
+).$str if defined $LOGFILE;
        print STDERR $str unless $QUIET;
    }
}

The open_logfile sub returns an opened file handle, or opens a new one if need be, to "DEBUG.LOG". Debug items are written to STDERR unless I set $QUIET, and they are always written to the logfile, prepended by a timestamp.

And, of course, if I unset $DEBUG, then it's basically a no-op.

Run the following with 'you stupid foo' as arguments:

#!/usr/bin/perl
use Private::Debug 'dbg';
$Private::Debug::DEBUG = 1;
$Private::Debug::QUIET = 0;

dbg("Hello there", "You fool");
dbg(':DUMP:', "ARGV:", \@ARGV);

Results in

#DEBUG.LOG
20041214:17.58.22▲Hello there▲
20041214:17.58.22▲You fool▲
20041214:17.58.22▲ARGV:▲
20041214:17.58.22▲$VAR1 = [
          'you',
          'stupid',
          'foo'
        ];
▲

#STDERR
Hello there▲
You fool▲
ARGV:▲
$VAR1 = [
          'you',
          'stupid',
          'foo'
        ];
▲

It works quite well. The '?' you might see actually shows up as an upward triangle in a terminal, so it is very clear.