How can I enable a debugging mode via a command-line switch for my Perl program?
- by Michael Mao
I am learning Perl in a "head-first" manner. I am absolutely a newbie in this language:
I am trying to have a debug_mode switch from CLI which can be used to control how my script works, by switching certain subroutines "on and off".
And below is what I've got so far:
#!/usr/bin/perl -s -w
# purpose : make subroutine execution optional,
# which is depending on a CLI switch flag
use strict;
use warnings;
use constant DEBUG_VERBOSE => "v";
use constant DEBUG_SUPPRESS_ERROR_MSGS => "s";
use constant DEBUG_IGNORE_VALIDATION => "i";
use constant DEBUG_SETPPING_COMPUTATION => "c";
our ($debug_mode);
mainMethod();
sub mainMethod # ()
{
if(!$debug_mode)
{
print "debug_mode is OFF\n";
}
elsif($debug_mode)
{
print "debug_mode is ON\n";
}
else
{
print "OMG!\n";
exit -1;
}
checkArgv();
printErrorMsg("Error_Code_123", "Parsing Error at...");
verbose();
}
sub checkArgv #()
{
print ("Number of ARGV : ".(1 + $#ARGV)."\n");
}
sub printErrorMsg # ($error_code, $error_msg, ..)
{
if(defined($debug_mode) && !($debug_mode =~ DEBUG_SUPPRESS_ERROR_MSGS))
{
print "You can only see me if -debug_mode is NOT set".
" to DEBUG_SUPPRESS_ERROR_MSGS\n";
die("terminated prematurely...\n") and exit -1;
}
}
sub verbose # ()
{
if(defined($debug_mode) && ($debug_mode =~ DEBUG_VERBOSE))
{
print "Blah blah blah...\n";
}
}
So far as I can tell, at least it works...:
the -debug_mode switch doesn't interfere with normal ARGV
the following commandlines work:
./optional.pl
./optional.pl -debug_mode
./optional.pl -debug_mode=v
./optional.pl -debug_mode=s
However, I am puzzled when multiple debug_modes are "mixed", such as:
./optional.pl -debug_mode=sv
./optional.pl -debug_mode=vs
I don't understand why the above lines of code "magically works".
I see both of the "DEBUG_VERBOS" and "DEBUG_SUPPRESS_ERROR_MSGS" apply to the script, which is fine in this case.
However, if there are some "conflicting" debug modes, I am not sure how to set the "precedence of debug_modes"?
Also, I am not certain if my approach is good enough to Perlists and I hope I am getting my feet in the right direction.
One biggest problem is that I now put if statements inside
most of my subroutines for controlling their behavior under different modes. Is this okay?
Is there a more elegant way?
I know there must be a debug module from CPAN or elsewhere, but I want a real minimal solution that doesn't depend on any other module than the "default".
And I cannot have any control on the environment where this script will be executed...
