Salvador Fandiño García > ctflags-0.04 > ctflags



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ctflags - Perl extension for compile time flags configuration


  use ctflags qw(foo=myapp:f76 debug=myapp:debug:aShu);

  if (foo > 45) {

  debug and warn "hey!, debugging...";

  use ctflags package=>'foo', prefix=>'bar',

  print "foo::bar_d=".foo::bar_d."\n";
  print "foo::bar_K=".foo::bar_K."\n";
  print "foo::mycnt=".foo::mycnt."\n";


ctflags module (and ctflags::parse) allow to easily define flags as perl constant whose values are specified from comand line options or environment variables.


ctflags and ctflags::parse packages allow to dynamically set constants values at compile time (every time the perl script is run) based on environment variables or command line options.

Conceptually, ctflags are unsigned integer variables named with a single letter ('a'..'z', 'A'..'Z', case matters), and structured in namespaces.

Several ctflags with the same name can coexist as long as they live in different namespaces (as perl variables with the same name but living in different packages are different variables).

Namespace names have to be valid perl identifiers composed of letters, the underscore char (_) and numbers. The colon (:) can also be used to simulate nested namespaces.

Examples of valid qualified ctflags names are...

  myapp:a        # ctflag a in namespace myapp
  myapp:A        # ctflag A in namespace myapp
  myapp:debug:c  # ctflag c in namespace myapp:debug
  otherapp:C     # ctflag C in namespace otherapp
  App3:A         # ctflag A in namespace App3

A property of ctflags is that they do not need to be predefined to be used and their default value is 0.


Package ctflags offers a set of utilities to convert ctflags to constants. Basic functionality to set and retrieve ctflag values is also offered but the ctflags::parse package should be preferred for this task.

ctflags::set $ns, $name, $value

sets value of ctflag $name in namespace $ns to be $value.

This function will be useless unless you are able to call it before ctflags are converted to constants, and this means early at compile time, and this means that you will have to use BEGIN {...} blocks. i.e.:

  # at the beginning of your script;
  use ctflags;
    use Getopt::Std;
    our ($opt_v)
    getopts ("v:")
    ctflags::set('myapp', 'v', $opt_v);
  use Any::Module

  # in Any::Module
  package Any::Module;
  use ctflags 'verbose=myapp:v';
ctflags::get $ns, $name

retrieves value of ctflag $name in namespace $ns.

ctflags->import(@options) or...
use ctflags @options;

creates perl constants from ctflag values.

@options can be a combination of key => value option pairs and ctflags-to-constants-conversion-specifications.

Currently supported options are:

prefix => $prefix

When no name is explicitly set for the constant to be created, one is automatically generated as $prefix.$ctflag_name. Default prefix is ctflag_ and this option lets to change it. i.e.:

  use ctflags prefix=>'debug_', 'myapp:debug:abc';

exports ctflags a, b and c in namespace myapp:debug as constants debug_a, debug_b and debug_c.

package => $package

exports the constants to package $package instead of to the current one. i.e.:

  use ctflags package=>'foo', 'flag=myapp:f',
              package=>'bar', 'flag=myapp:b';

exports ctflag f in namespace myapp as perl constant foo::flag and ctflag b in namespace myapp as perl constant bar::flag.

ctflags to constants conversions are specified as:


this expand to a small set of rules:


export all ctflags in namespace foo as constants ctflag_a, ctflag_b,...,ctflag_Z.

(unless prefix option has been used to change generated constant names to say myprefix_a, myprefix_b, etc.)


export ctflags b, a, r in namespace foo as ctflag_b, ctflag_a, ctflag_r.


export ctflag b in namespace foo as constant cnt


when the constant name appears explicitly and more than one ctflag are specified in any way, the value of the constant is the result of combining all the ctflags values with the arithmetic or operator (|). i.e:

  use ctflags qw(anydebug=myapp:debug:*);
  if (anydebug) { open DEBUG, ">/tmp/output" }

Default values can be specified to be used when no value has been previosly assigned explicitly to a ctflag.

They should be composed of digits and appear in the conversion specification just after the ctflag name letter to be affected. i.e.:

  use ctflags qw(foo:bar67)

ctflag_r will return 67 unless foo:r had been previouly defined in any way.

The specification of the default value do not assign it to the ctflag. i.e:

  use ctflags qw(cnt1=foo:r67)
  use ctflags qw(cnt2=foo:r)

if ctflag foo:r was not previusly set, cnt1 will return 67 and cnt2 will return 0.


Uff... well, it depends, see the import function in the previous section.


This is version 0.01, and I am sure that several bugs are going to appear.

Also I reserve the rigth to change the public interface of the module in an incompatible manner if deficiencies in the current one are found (this will not be this way forever, just for some time).

I will really apreciate any correction to the documentation prose, English is not my native tongue and so...


Companion package ctflags::parse, constant package and perlsub for a discusion about how perl constants can be implemented as inlined subrutines.


Salvador Fandiño Garcia, <>

(please, revert to "Salvador Fandino Garcia" if your display charset is not latin-1 compatible :-(


Copyright 2002 by Salvador Fandiño Garcia

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

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