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# -*- perl -*-
package Devel::Trace;
$VERSION = '0.11';
$TRACE = 1;
# This is the important part. The rest is just fluff.
sub DB::DB {
return unless $TRACE;
my ($p, $f, $l) = caller;
my $code = \@{"::_<$f"};
print STDERR ">> $f:$l: $code->[$l]";
}
sub import {
my $package = shift;
foreach (@_) {
if ($_ eq 'trace') {
my $caller = caller;
*{$caller . '::trace'} = \&{$package . '::trace'};
} else {
use Carp;
croak "Package $package does not export `$_'; aborting";
}
}
}
my %tracearg = ('on' => 1, 'off' => 0);
sub trace {
my $arg = shift;
$arg = $tracearg{$arg} while exists $tracearg{$arg};
$TRACE = $arg;
}
1;
=head1 NAME
Devel::Trace - Print out each line before it is executed (like C<sh -x>)
=head1 SYNOPSIS
perl -d:Trace program
=head1 DESCRIPTION
If you run your program with C<perl -d:Trace program>, this module
will print a message to standard error just before each line is executed.
For example, if your program looks like this:
#!/usr/bin/perl
print "Statement 1 at line 4\n";
print "Statement 2 at line 5\n";
print "Call to sub x returns ", &x(), " at line 6.\n";
exit 0;
sub x {
print "In sub x at line 12.\n";
return 13;
}
Then the C<Trace> output will look like this:
>> ./test:4: print "Statement 1 at line 4\n";
>> ./test:5: print "Statement 2 at line 5\n";
>> ./test:6: print "Call to sub x returns ", &x(), " at line 6.\n";
>> ./test:12: print "In sub x at line 12.\n";
>> ./test:13: return 13;
>> ./test:8: exit 0;
This is something like the shell's C<-x> option.
=head1 DETAILS
Inside your program, you can enable and disable tracing by doing
$Devel::Trace::TRACE = 1; # Enable
$Devel::Trace::TRACE = 0; # Disable
or
Devel::Trace::trace('on'); # Enable
Devel::Trace::trace('off'); # Disable
C<Devel::Trace> exports the C<trace> function if you ask it to:
import Devel::Trace 'trace';
Then if you want you just say
trace 'on'; # Enable
trace 'off'; # Disable
=head1 TODO
=over 4
=item *
You should be able to send the trace output to the filehandle of your choice.
=item *
You should be able to specify the format of the output.
=item *
You should be able to get the output into a string.
=back
We'll see.
=head1 Author
=begin text
Mark-Jason Dominus (C<mjd-perl-trace@plover.com>), Plover Systems co.
See the C<Devel::Trace.pm> Page at http://www.plover.com/~mjd/perl/Trace
for news and upgrades.
=end text
=begin man
Mark-Jason Dominus (C<mjd-perl-trace@plover.com>), Plover Systems co.
See the C<Devel::Trace.pm> Page at http://www.plover.com/~mjd/perl/Trace
for news and upgrades.
=end man
=begin html
<p>Mark-Jason Dominus (<a href="mailto:mjd-perl-trace@plover.com"><tt>mjd-perl-trace@plover.com</tt></a>), Plover Systems co.</p>
<p>See <a href="http://www.plover.com/~mjd/perl/Trace/">The <tt>Devel::Trace.pm</tt> Page</a> for news and upgrades.</p>
=end html
=cut
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