So I've put together a very basic display of how the Devel::Trace::Subs works. Again, it's intrusive; it actually writes into the files you want to capture tracing info from (I wrote this software that another piece of software required, primarily out of sheer curiosity).
Here's the original Perl file we're working with (./test.pl):
use warnings;
use strict;
three(5);
sub three {
return two(shift);
}
sub two {
return one(_helper(shift));
}
sub one {
my $num = calc(shift);
display($num);
}
sub calc {
my $num = shift;
return $num ** 3;
}
sub display {
my $num = shift;
print "$num\n";
}
sub _helper {
my $num = shift;
return ++$num;
}
When run, it produces this output:
216
Very basic. Now, install Devel::Trace::Subs, and from the command line, tell it to become traceable:
perl -MDevel::Trace::Subs=install_trace -e 'install_trace(file => "test.pl")'
...now the test.pl file looks like this:
use warnings;
use Devel::Trace::Subs qw(trace trace_dump); # injected by Devel::Trac
+e::Subs
use strict;
three(5);
sub three {
trace() if $ENV{DTS_ENABLE}; # injected by Devel::Trace::Subs
return two(shift);
}
sub two {
trace() if $ENV{DTS_ENABLE}; # injected by Devel::Trace::Subs
return one(_helper(shift));
}
sub one {
trace() if $ENV{DTS_ENABLE}; # injected by Devel::Trace::Subs
my $num = calc(shift);
display($num);
}
sub calc {
trace() if $ENV{DTS_ENABLE}; # injected by Devel::Trace::Subs
my $num = shift;
return $num ** 3;
}
sub display {
trace() if $ENV{DTS_ENABLE}; # injected by Devel::Trace::Subs
my $num = shift;
print "$num\n";
}
sub _helper {
trace() if $ENV{DTS_ENABLE}; # injected by Devel::Trace::Subs
my $num = shift;
return ++$num;
}
I'd like to point out that the design for this software was to be used within modules not normal scripts, but I digress. In order to get the output from the tracing, you have to add a couple of things to your calling script (in this case, it's the original script itself). We'll pretend we're calling modules infected with the trace software here. Add the trace enabling flag, then after all of your calls have been made you want to get the trace info from, call the dump_trace() function::wq
$ENV{DTS_ENABLE} = 1;
three(5); # this is the original call stack you're running
trace_dump();
Now, you get the original output, but you also get the code flow and stack trace information:
216
Code flow:
1: main::three
2: main::two
3: main::_helper
4: main::one
5: main::calc
6: main::display
Stack trace:
in: main::three
sub: -
file: test.pl
line: 7
package: main
in: main::two
sub: main::three
file: test.pl
line: 13
package: main
in: main::_helper
sub: main::two
file: test.pl
line: 17
package: main
in: main::one
sub: main::two
file: test.pl
line: 17
package: main
in: main::calc
sub: main::one
file: test.pl
line: 21
package: main
in: main::display
sub: main::one
file: test.pl
line: 22
package: main
You can opt via parameters to trace_dump to display just the code flow or the stack trace or both (as is the default as shown above), in text or HTML output formats.
This is a *very* basic example of how I've used this software. Again, we're using it in a single file here. Normally I'd have a test script using external modules, so the command to return your original code is this:
perl -MDevel::Trace::Subs=remove_trace -e 'remove_trace(file => "test.pl")'
...which returns the script back to default, except for the manual lines (which wouldn't normally be in an original .pl file). Delete these lines manually:
$ENV{DTS_ENABLE} = 1;
trace_dump();
I'll try to put together a much better example of how I really use it in the coming days.
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