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Build and install Perl modules

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README
NAME
    Module::Build - Build and install Perl modules

SYNOPSIS
     Standard process for building & installing modules:
 
       perl Build.PL
       ./Build
       ./Build test
       ./Build install

DESCRIPTION
    This is a beta version of a new module set I've been working on,
    "Module::Build". It is meant to be a replacement for
    "ExtUtils::MakeMaker".

    To install "Module::Build", and any other module that uses
    "Module::Build" for its installation process, do the following:

       perl Build.PL
       Build             # this script is created by 'perl Build.PL'
       Build test
       Build install

    This illustrates initial configuration and the running of three
    'actions'. In this case the actions run are 'build' (the default
    action), 'test', and 'install'. Actions defined so far include:

      build                          help        
      clean                          install     
      dist                           manifest    
      distcheck                      realclean   
      distclean                      skipcheck   
      distdir                        test        
      disttest                       testdb      
      fakeinstall                                

    You can run the 'help' action for a complete list of actions.

    It's like the "MakeMaker" metaphor, except that "Build" is a short Perl
    script, not a long Makefile. State is stored in a directory called
    "_build/".

    Any customization can be done simply by subclassing "Module::Build" and
    adding a method called (for example) "ACTION_test", overriding the
    default 'test' action. You could also add a method called
    "ACTION_whatever", and then you could perform the action "Build
    whatever".

    More actions will certainly be added to the core - it should be easy to
    do everything that the MakeMaker process can do. It's going to take some
    time, though. In the meantime, I may implement some pass-through
    functionality so that unknown actions are passed to MakeMaker.

    For information on providing backward compatibility with
    "ExtUtils::MakeMaker", see the Module::Build::Compat manpage.

METHODS
    I list here some of the most important methods in "Module::Build".
    Normally you won't need to deal with these methods unless you want to
    subclass "Module::Build". But since one of the reasons I created this
    module in the first place was so that subclassing is possible (and
    easy), I will certainly write more docs as the interface stabilizes.

  $m = Module::Build->new(...)

    Creates a new Module::Build object. Arguments to the new() method are
    listed below. The only required argument is the "module_name" argument.

    * module_name
        The "module_name" argument is required, and should be a string like
        "'Your::Module'". We use it for several purposes, including finding
        the version string for this distribution, and creating a
        suitably-named distribution directory.

    * module_version
        The "module_version" argument is optional - if not explicitly
        provided, we'll look for the version string in the module specified
        by "module_name", parsing it out according to the same rules as
        "ExtUtils::MakeMaker" and "CPAN.pm".

    * module_version_from
        Allows you to specify an alternate file for finding the module
        version, instead of looking in the file specified by "module_name".

    * prereq
        An optional "prereq" argument specifies any module prerequisites
        that the current module depends on. The prerequisites are given in a
        hash reference, where the keys are the module names and the values
        are version specifiers:

         prereq => {Foo::Module => '2.4',
                    Bar::Module => 0,
                    Ken::Module => '>= 1.2, != 1.5, < 2.0'},

        These three version specifiers have different effects. The value
        "'2.4'" means that at least version 2.4 of "Foo::Module" must be
        installed. The value "0" means that any version of "Bar::Module" is
        acceptable, even if "Bar::Module" doesn't define a version. The more
        verbose value "'>= 1.2, != 1.5, < 2.0'" means that "Ken::Module"'s
        version must be at least 1.2, less than 2.0, and not equal to 1.5.
        The list of criteria is separated by commas, and all criteria must
        be satisfied.

        One note: currently we don't actually *requre* the user to have
        these modules installed, we just strongly urge. In the future we may
        require it. There's now a "recommended" section for things that
        aren't absolutely required.

    * recommended
        This is just like the "prereq" argument, except that modules in this
        list aren't essential, just a good idea. We'll just print a friendly
        warning if one of these modules aren't found, but we'll continue
        running.

    * c_source
        An optional "c_source" argument specifies a directory which contains
        C source files that the rest of the build may depend on. Any ".c"
        files in the directory will be compiled to object files. The
        directory will be added to the search path during the compilation
        and linking phases of any C or XS files.

    * autosplit
        An optional "autosplit" argument specifies a file which should be
        run through the "Autosplit::autosplit()" function. In general I
        don't consider this a great idea, and I may even go so far as to
        remove this feature later. Let me know if I shouldn't.

  $m->add_to_cleanup

    A "Module::Build" method may call "$self->add_to_cleanup(@files)" to
    tell "Module::Build" that certain files should be removed when the user
    performs the "Build clean" action. I decided to make this a dynamic
    method, rather than a static list of files, because these static lists
    can get difficult to manage. I preferred to keep the responsibility for
    registering temporary files close to the code that creates them.

  Module::Build->resume

    You'll probably never call this method directly, it's only called from
    the auto-generated "Build" script. The "new()" method is only called
    once, when the user runs "perl Build.PL". Thereafter, when the user runs
    "Build test" or another action, the "Module::Build" object is created
    using the "resume()" method.

  $m->dispatch

    This method is also called from the auto-generated "Build" script. It
    parses the command-line arguments into an action and an argument list,
    then calls the appropriate routine to handle the action. Currently
    (though this may change), an action "foo" will invoke the "ACTION_foo"
    method. All arguments (including everything mentioned in the ACTIONS
    manpage below) are contained in the "$self->{args}" hash reference.

  $m->os_type

    If you're subclassing Module::Build and some code needs to alter its
    behavior based on the current platform, you may only need to know
    whether you're running on Windows, Unix, MacOS, VMS, etc. and not the
    fine-grained value of Perl's "$^O" variable. The "os_type()" method will
    return a string like "Windows", "Unix", "MacOS", "VMS", or whatever is
    appropriate. If you're running on an unknown platform, it will return
    "undef" - there shouldn't be many unknown platforms though.

  $m->check_installed_version($module, $version)

    This method returns true or false, depending on whether (at least)
    version "$version" of module "$module" is installed. The "$module"
    argument is given as a string like ""Data::Dumper"", and the "$version"
    argument can take any of the forms described in the prereq manpage
    above. This allows very fine-grained version checking.

    If the check fails, we return false and set "$@" to an informative error
    message.

    If the check succeeds, the return value is the actual version of
    "$module" installed on the system. This allows you to do the following:

     my $installed = $m->check_installed_version('DBI', '1.15');
     if ($installed) {
       print "Congratulations, version $installed of DBI is installed.\n";
     } else {
       die "Sorry, you must install DBI.\n";
     }

    If "$version" is any nontrue value (notably zero) and any version of
    "$module" is installed, we return true. In this case, if "$module"
    doesn't define a version, or if its version is zero, we return the
    special value "0 but true", which is numerically zero, but logically
    true.

ACTIONS
    There are some general principles at work here. First, each task when
    building a module is called an "action". These actions are listed above;
    they correspond to the building, testing, installing, packaging, etc.
    tasks.

    Second, arguments are processed in a very systematic way. Arguments are
    always key=value pairs. They may be specified at "perl Build.PL" time
    (i.e. "perl Build.PL sitelib=/my/secret/place"), in which case their
    values last for the lifetime of the "Build" script. They may also be
    specified when executing a particular action (i.e. "Build test
    verbose=1"), in which case their values last only for the lifetime of
    that command. Per-action command-line parameters take precedence over
    parameters specified at "perl Build.PL" time.

    The build process also relies heavily on the "Config.pm" module, and all
    the key=value pairs in "Config.pm" are available in

    "$self->{config}". If the user wishes to override any of the values in
    "Config.pm", she may specify them like so:

      perl Build.PL config='siteperl=/foo perlpath=/wacky/stuff'

    Not the greatest interface, I'm looking for alternatives. Speak now!
    Maybe:

      perl Build.PL config-siteperl=/foo config-perlpath=/wacky/stuff

    or something.

    The following build actions are provided by default.

    * help
        This action will simply print out a message that is meant to help
        you use the build process. It will show you a list of available
        build actions too.

    * build
        If you run the "Build" script without any arguments, it runs the
        "build" action.

        This is analogous to the MakeMaker 'make all' target. By default it
        just creates a "blib/" directory and copies any ".pm" and ".pod"
        files from your "lib/" directory into the "blib/" directory. It also
        compiles any ".xs" files from "lib/" and places them in "blib/". Of
        course, you need a working C compiler (probably the same one that
        built perl itself) for this to work properly.

        The "build" action also runs any ".PL" files in your lib/ directory.
        Typically these create other files, named the same but without the
        ".PL" ending. For example, a file lib/Foo/Bar.pm.PL could create the
        file lib/Foo/Bar.pm. The ".PL" files are processed first, so any
        ".pm" files (or other kinds that we deal with) will get copied
        correctly.

        If your ".PL" scripts don't create any files, or if they create
        files with unexpected names, or even if they create multiple files,
        you should tell us that so that we can clean up properly after these
        created files. Use the "PL_files" parameter to "new()":

         PL_files => { 'lib/Foo/Bar_pm.PL' => 'lib/Foo/Bar.pm',
                       'lib/something.PL'  => ['/lib/something', '/lib/else'],
                       'lib/funny.PL'      => [] }

        Note that in contrast to MakeMaker, the "build" action only
        (currently) handles ".pm", ".pod", ".PL", and ".xs" files. They must
        all be in the "lib/" directory, in the directory structure that they
        should have when installed. We also handle ".c" files that can be in
        the place of your choosing - see the "c_source" argument to "new()".

        The ".xs" support is currently in alpha. Please let me know whether
        it works for you.

    * test
        This will use "Test::Harness" to run any regression tests and report
        their results. Tests can be defined in the standard places: a file
        called "test.pl" in the top-level directory, or several files ending
        with ".t" in a "t/" directory.

        If you want tests to be 'verbose', i.e. show details of test
        execution rather than just summary information, pass the argument
        "verbose=1".

        If you want to run tests under the perl debugger, pass the argument
        "debugger=1".

        In addition, if a file called "visual.pl" exists in the top-level
        directory, this file will be executed as a Perl script and its
        output will be shown to the user. This is a good place to put speed
        tests or other tests that don't use the "Test::Harness" format for
        output.

    * testdb
        This is a synonym for the 'test' action with the "debugger=1"
        argument.

    * clean
        This action will clean up any files that the build process may have
        created, including the "blib/" directory (but not including the
        "_build/" directory and the "Build" script itself).

    * realclean
        This action is just like the "clean" action, but also removes the
        "_build" directory and the "Build" script. If you run the
        "realclean" action, you are essentially starting over, so you will
        have to re-create the "Build" script again.

    * install
        This action will use "ExtUtils::Install" to install the files from
        "blib/" into the correct system-wide module directory. The directory
        is determined from the "sitelib" entry in the "Config.pm" module. To
        install into a different directory, pass a different value for the
        "sitelib" parameter, like so:

         Build install sitelib=/my/secret/place/

        Alternatively, you could specify the "sitelib" parameter when you
        run the "Build.PL" script:

         perl Build.PL sitelib=/my/secret/place/

        Under normal circumstances, you'll need superuser privileges to
        install into the default "sitelib" directory.

    * fakeinstall
        This is just like the "install" action, but it won't actually do
        anything, it will just report what it *would* have done if you had
        actually run the "install" action.

    * manifest
        This is an action intended for use by module authors, not people
        installing modules. It will bring the MANIFEST up to date with the
        files currently present in the distribution. You may use a
        MANIFEST.SKIP file to exclude certain files or directories from
        inclusion in the MANIFEST. MANIFEST.SKIP should contain a bunch of
        regular expressions, one per line. If a file in the distribution
        directory matches any of the regular expressions, it won't be
        included in the MANIFEST.

        The following is a reasonable MANIFEST.SKIP starting point, you can
        add your own stuff to it:

           ^_build
           ^Build$
           ^blib
           ~$
           \.bak$
           ^MANIFEST\.SKIP$
           CVS

        See the the distcheck manpage and the skipcheck manpage actions if
        you want to find out what the "manifest" action would do, without
        actually doing anything.

    * dist
        This action is helpful for module authors who want to package up
        their module for distribution through a medium like CPAN. It will
        create a tarball of the files listed in MANIFEST and compress the
        tarball using GZIP compression.

    * distcheck
        Reports which files are in the build directory but not in the
        MANIFEST file, and vice versa. (See the manifest manpage for
        details)

    * skipcheck
        Reports which files are skipped due to the entries in the
        MANIFEST.SKIP file (See the manifest manpage for details)

    * distclean
        Performs the 'realclean' action and then the 'distcheck' action.

    * distdir
        Creates a directory called "$(DISTNAME)-$(VERSION)" (if that
        directory already exists, it will be removed first). Then copies all
        the files listed in the MANIFEST file to that directory. This
        directory is what people will see when they download your
        distribution and unpack it.

    * disttest
        Performs the 'distdir' action, then switches into that directory and
        runs a "perl Build.PL", followed by the 'build' and 'test' actions
        in that directory.

AUTOMATION
    One advantage of Module::Build is that since it's implemented as Perl
    methods, you can invoke these methods directly if you want to install a
    module non-interactively. For instance, the following Perl script will
    invoke the entire build/install procedure:

     my $m = new Module::Build (module_name => 'MyModule');
     $m->dispatch('build');
     $m->dispatch('test');
     $m->dispatch('install');

    If any of these steps encounters an error, it will throw a fatal
    exception.

    You can also pass arguments as part of the build process:

     my $m = new Module::Build (module_name => 'MyModule');
     $m->dispatch('build');
     $m->dispatch('test', verbose => 1);
     $m->dispatch('install', sitelib => '/my/secret/place/');

    Building and installing modules in this way skips creating the "Build"
    script.

STRUCTURE
    Module::Build creates a class hierarchy conducive to customization. Here
    is the parent-child class hierarchy in classy ASCII art:

       /--------------------\
       |   Your::Parent     |  (If you subclass Module::Build)
       \--------------------/
                |
                |
       /--------------------\  (Doesn't define any functionality
       |   Module::Build    |   of its own - just figures out what
       \--------------------/   other modules to load.)
                |
                |
       /-----------------------------------\  (Some values of $^O may
       |   Module::Build::Platform::$^O    |   define specialized functionality.
       \-----------------------------------/   Otherwise it's ...::Default, a
                |                              pass-through class.)
                |
       /--------------------------\
       |   Module::Build::Base    |  (Most of the functionality of 
       \--------------------------/   Module::Build is defined here.)

SUBCLASSING
    Right now, there are two ways to subclass Module::Build. The first way
    is to create a regular module (in a ".pm" file) that inherits from
    Module::Build, and use that module's class instead of using
    Module::Build directly:

      ------ in Build.PL: ----------
      #!/usr/bin/perl
  
      use lib qw(/nonstandard/library/path);
      use My::Builder;  # Or whatever you want to call it
  
      my $m = My::Builder->new(module_name => 'Next::Big::Thing');
      $m->create_build_script;

    This is relatively straightforward, and is the best way to do things if
    your My::Builder class contains lots of code. The
    "create_build_script()" method will ensure that the current value of
    "@INC" (including the "/nonstandard/library/path") is propogated to the
    Build script, so that My::Builder can be found when running build
    actions.

    For very small additions, Module::Build provides a "subclass()" method
    that lets you subclass Module::Build more conveniently, without creating
    a separate file for your module:

      ------ in Build.PL: ----------
      #!/usr/bin/perl
  
      my $class = Module::Build->subclass
        (
         class => 'My::Builder',
         code => q{
          sub ACTION_foo {
            print "I'm fooing to death!\n";
          }
         },
        );
  
      my $m = $class->new(module_name => 'Module::Build');
      $m->create_build_script;

    Behind the scenes, this actually does create a ".pm" file, since the
    code you provide must persist after Build.PL is run if it is to be very
    useful.

MOTIVATIONS
    There are several reasons I wanted to start over, and not just fix what
    I didn't like about MakeMaker:

    *   I don't like the core idea of MakeMaker, namely that "make" should
        be involved in the build process. Here are my reasons:

        +   When a person is installing a Perl module, what can you assume
            about their environment? Can you assume they have "make"? No,
            but you can assume they have some version of Perl.

        +   When a person is writing a Perl module for intended
            distribution, can you assume that they know how to build a
            Makefile, so they can customize their build process? No, but you
            can assume they know Perl, and could customize that way.

        For years, these things have been a barrier to people getting the
        build/install process to do what they want.

    *   There are several architectural decisions in MakeMaker that make it
        very difficult to customize its behavior. For instance, when using
        MakeMaker you do "use MakeMaker", but the object created in
        "WriteMakefile()" is actually blessed into a package name that's
        created on the fly, so you can't simply subclass
        "ExtUtils::MakeMaker". There is a workaround "MY" package that lets
        you override certain MakeMaker methods, but only certain explicitly
        predefined (by MakeMaker) methods can be overridden. Also, the
        method of customization is very crude: you have to modify a string
        containing the Makefile text for the particular target.

    *   It is risky to make major changes to MakeMaker, since it does so
        many things, is so important, and generally works. "Module::Build"
        is an entirely seperate package so that I can work on it all I want,
        without worrying about backward compatibility.

    *   Finally, Perl is said to be a language for system administration.
        Could it really be the case that Perl isn't up to the task of
        building and installing software? Even if that software is a bunch
        of stupid little ".pm" files? Are you getting riled up yet??

    Please contact me if you have any questions or ideas.

TO DO
    The current method of relying on time stamps to determine whether a
    derived file is out of date isn't likely to scale well, since it
    requires tracing all dependencies backward, it runs into problems on
    NFS, and it's just generally flimsy. It would be better to use an MD5
    signature or the like, if available. See "cons" for an example.

    The current dependency-checking is prone to errors. You can make
    'widowed' files by doing "Build", "perl Build.PL", and then "Build
    realclean". Should be easy to fix, but it's got me wondering whether the
    dynamic declaration of dependencies is a good idea.

    - make man pages and install them. - append to perllocal.pod - write
    .packlist in appropriate location (needed for un-install) - write
    dependency list in _build

AUTHOR
    Ken Williams, ken@mathforum.org

SEE ALSO
    perl(1), ExtUtils::MakeMaker(3)

    http://www.dsmit.com/cons/
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