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Ken Williams
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# NAME

Module::Build - Build and install Perl modules

# SYNOPSIS

Standard process for building & installing modules:

  perl Build.PL
./Build
./Build test
./Build install

Or, if you're on a platform (like DOS or Windows) that doesn't like the "./" notation, you can do this:

  perl Build.PL
perl Build
perl Build test
perl Build install

# DESCRIPTION

Module::Build is a system for building, testing, and installing Perl modules. It is meant to be an alternative to ExtUtils::MakeMaker. Developers may alter the behavior of the module through subclassing in a much more straightforward way than with MakeMaker. It also does not require a make on your system - most of the Module::Build code is pure-perl and written in a very cross-platform way. In fact, you don't even need a shell, so even platforms like MacOS (traditional) can use it fairly easily. Its only prerequisites are modules that are included with perl 5.6.0, and it works fine on perl 5.005 if you can install a few additional modules.

See "MOTIVATIONS" for more comparisons between ExtUtils::MakeMaker and Module::Build.

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

  perl Build.PL       # 'Build.PL' script creates the 'Build' script
./Build             # Need ./ to ensure we're using this "Build" script
./Build test        # and not another one that happens to be in the PATH
./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'. Other actions defined so far include:

  build                          html
clean                          install
code                           manifest
config_data                    manpages
diff                           ppd
dist                           ppmdist
distcheck                      prereq_report
distclean                      pure_install
distdir                        realclean
distmeta                       skipcheck
distsign                       test
disttest                       testcover
docs                           testdb
fakeinstall                    testpod
help                           versioninstall

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

# GUIDE TO DOCUMENTATION

The documentation for Module::Build is broken up into three sections:

General Usage (Module::Build)

This is the document you are currently reading. It describes basic usage and background information. Its main purpose is to assist the user who wants to learn how to invoke and control Module::Build scripts at the command line.

Authoring Reference (Module::Build::Authoring)

This document describes the Module::Build API for authors who are writing Build.PL scripts for a distribution or controlling Module::Build processes programmatically. It describes the methods available as well as providing general information on subclassing Module::Build to alter and extend its behavior. Also, there is a section on controlling the Build process from other scripts, including how to construct an object and how to invoke actions through it from an external script.

Cookbook (Module::Build::Cookbook)

This document demonstrates how to accomplish many common tasks. It covers general command line usage and authoring of Build.PL scripts. Includes working examples.

# 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 destdir=/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 cc=gcc --config ld=gcc The following build actions are provided by default. build If you run the Build script without any arguments, it runs the build action, which in turn runs the code and docs actions. This is analogous to the MakeMaker 'make all' target. 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). code This action builds your codebase. 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 the compilation to work properly. The code 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. config_data ... diff This action will compare the files about to be installed with their installed counterparts. For .pm and .pod files, a diff will be shown (this currently requires a 'diff' program to be in your PATH). For other files like compiled binary files, we simply report whether they differ. A flags parameter may be passed to the action, which will be passed to the 'diff' program. Consult your 'diff' documentation for the parameters it will accept - a good one is -u:  ./Build diff flags=-u dist This action is helpful for module authors who want to package up their module for source distribution through a medium like CPAN. It will create a tarball of the files listed in MANIFEST and compress the tarball using GZIP compression. By default, this action will use the external tar and gzip executables on Unix-like platforms, and the Archive::Tar module elsewhere. However, you can force it to use whatever executable you want by supplying an explicit tar (and optional gzip) parameter:  ./Build dist --tar C:\path\to\tar.exe --gzip C:\path\to\zip.exe distcheck Reports which files are in the build directory but not in the MANIFEST file, and vice versa. (See manifest for details.) distclean Performs the 'realclean' action and then the 'distcheck' action. distdir Creates a "distribution directory" named $dist_name-$dist_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 the distribution tarball is created from. distmeta Creates the META.yml file that describes the distribution. META.yml is a file containing various bits of "metadata" about the distribution. The metadata includes the distribution name, version, abstract, prerequisites, license, and various other data about the distribution. This file is created as META.yml in YAML format, so the YAML module must be installed in order to create it. The META.yml file must also be listed in MANIFEST - if it's not, a warning will be issued. The current version of the META.yml specification can be found at http://module-build.sourceforge.net/META-spec-v1.2.html distsign Uses Module::Signature to create a SIGNATURE file for your distribution, and adds the SIGNATURE file to the distribution's MANIFEST. 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. docs This will generate documentation (e.g. Unix man pages and html documents) for any installable items under blib/ that contain POD. If there are no bindoc or libdoc installation targets defined (as will be the case on systems that don't support Unix manpages) no action is taken for manpages. If there are no binhtml or libhtml installation targets defined no action is taken for html documents. 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. 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. With an optional argument specifying an action name (e.g. Build help test), the 'help' action will show you any POD documentation it can find for that action. html This will generate HTML documentation for any binary or library files under blib/ that contain POD. The HTML documentation will only be installed if the install paths can be determined from values in Config.pm. You can also supply or override install paths on the command line by specifying install_path values for the binhtml and/or libhtml installation targets. install This action will use ExtUtils::Install to install the files from blib/ into the system. See "INSTALL PATHS" for details about how Module::Build determines where to install things, and how to influence this process. If you want the installation process to look around in @INC for other versions of the stuff you're installing and try to delete it, you can use the uninst parameter, which tells ExtUtils::Install to do so:  ./Build install uninst=1 This can be a good idea, as it helps prevent multiple versions of a module from being present on your system, which can be a confusing situation indeed. 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$CVS See the distcheck and skipcheck actions if you want to find out what the manifest action would do, without actually doing anything. manpages This will generate man pages for any binary or library files under blib/ that contain POD. The man pages will only be installed if the install paths can be determined from values in Config.pm. You can also supply or override install paths by specifying there values on the command line with the bindoc and libdoc installation targets. ppd Build a PPD file for your distribution. This action takes an optional argument codebase which is used in the generated ppd file to specify the (usually relative) URL of the distribution. By default, this value is the distribution name without any path information. Example:  ./Build ppd --codebase "MSWin32-x86-multi-thread/Module-Build-0.21.tar.gz" ppmdist Generates a PPM binary distribution and a PPD description file. This action also invokes the 'ppd' action, so it can accept the same codebase argument described under that action. This uses the same mechanism as the dist action to tar & zip its output, so you can supply tar and/or gzip parameters to affect the result. prereq_report This action prints out a list of all prerequisites, the versions required, and the versions actually installed. This can be useful for reviewing the configuration of your system prior to a build, or when compiling data to send for a bug report. pure_install This action is identical to the install action. In the future, though, if install starts writing to the file file$(INSTALLARCHLIB)/perllocal.pod, pure_install won't, and that will be the only difference between them.

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.

skipcheck

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

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.

To override the choice of tests to run, you may pass a test_files argument whose value is a whitespace-separated list of test scripts to run. This is especially useful in development, when you only want to run a single test to see whether you've squashed a certain bug yet:

  ./Build test --test_files t/something_failing.t

You may also pass several test_files arguments separately:

  ./Build test --test_files t/one.t --test_files t/two.t

or use a glob()-style pattern:

  ./Build test --test_files 't/01-*.t'
testcover

Runs the test action using Devel::Cover, generating a code-coverage report showing which parts of the code were actually exercised during the tests.

To pass options to Devel::Cover, set the $DEVEL_COVER_OPTIONS environment variable:  DEVEL_COVER_OPTIONS=-ignore,Build ./Build testcover testdb This is a synonym for the 'test' action with the debugger=1 argument. testpod This checks all the files described in the docs action and produces Test::Harness-style output. If you are a module author, this is useful to run before creating a new release. versioninstall ** Note: since only.pm is so new, and since we just recently added support for it here too, this feature is to be considered experimental. ** If you have the only.pm module installed on your system, you can use this action to install a module into the version-specific library trees. This means that you can have several versions of the same module installed and use a specific one like this:  use only MyModule => 0.55; To override the default installation libraries in only::config, specify the versionlib parameter when you run the Build.PL script:  perl Build.PL --versionlib /my/version/place/ To override which version the module is installed as, specify the versionlib parameter when you run the Build.PL script:  perl Build.PL --version 0.50 See the only.pm documentation for more information on version-specific installs. # OPTIONS ## Command Line Options The following options can be used during any invocation of Build.PL or the Build script, during any action. For information on other options specific to an action, see the documentation for the respective action. NOTE: There is some preliminary support for options to use the more familiar long option style. Most options can be preceded with the -- long option prefix, and the underscores changed to dashes (e.g. --use-rcfile). Additionally, the argument to boolean options is optional, and boolean options can be negated by prefixing them with 'no' or 'no-' (e.g. --noverbose or --no-verbose). quiet Suppress informative messages on output. use_rcfile Load the ~/.modulebuildrc option file. This option can be set to false to prevent the custom resource file from being loaded. verbose Display extra information about the Build on output. ## Default Options File (.modulebuildrc) When Module::Build starts up, it will look for a file,$ENV{HOME}/.modulebuildrc. If the file exists, the options specified there will be used as defaults, as if they were typed on the command line. The defaults can be overridden by specifying new values on the command line.

The action name must come at the beginning of the line, followed by any amount of whitespace and then the options. Options are given the same as they would be on the command line. They can be separated by any amount of whitespace, including newlines, as long there is whitespace at the beginning of each continued line. Anything following a hash mark (#) is considered a comment, and is stripped before parsing. If more than one line begins with the same action name, those lines are merged into one set of options.

Besides the regular actions, there are two special pseudo-actions: the key * (asterisk) denotes any global options that should be applied to all actions, and the key 'Build_PL' specifies options to be applied when you invoke perl Build.PL.

  *        verbose=1   # global options
diff     flags=-u
install  --install_base /home/ken
--install_path html=/home/ken/docs/html

If you wish to locate your resource file in a different location, you can set the environment variable 'MODULEBUILDRC' to the complete absolute path of the file containing your options.

# INSTALL PATHS

When you invoke Module::Build's build action, it needs to figure out where to install things. The nutshell version of how this works is that default installation locations are determined from Config.pm, and they may be overridden by using the install_path parameter. An install_base parameter lets you specify an alternative installation root like /home/foo, and a destdir lets you specify a temporary installation directory like /tmp/install in case you want to create bundled-up installable packages.

Natively, Module::Build provides default installation locations for the following types of installable items:

lib

Usually pure-Perl module files ending in .pm.

arch

"Architecture-dependent" module files, usually produced by compiling XS, Inline, or similar code.

script

Programs written in pure Perl. In order to improve reuse, try to make these as small as possible - put the code into modules whenever possible.

bin

"Architecture-dependent" executable programs, i.e. compiled C code or something. Pretty rare to see this in a perl distribution, but it happens.

bindoc

Documentation for the stuff in script and bin. Usually generated from the POD in those files. Under Unix, these are manual pages belonging to the 'man1' category.

libdoc

Documentation for the stuff in lib and arch. This is usually generated from the POD in .pm files. Under Unix, these are manual pages belonging to the 'man3' category.

binhtml

This is the same as bindoc above, but applies to html documents.

libhtml

This is the same as bindoc above, but applies to html documents.

Four other parameters let you control various aspects of how installation paths are determined:

installdirs

The default destinations for these installable things come from entries in your system's Config.pm. You can select from three different sets of default locations by setting the installdirs parameter as follows:

                          'installdirs' set to:
core          site                vendor

uses the following defaults from Config.pm:

lib     => installprivlib  installsitelib      installvendorlib
arch    => installarchlib  installsitearch     installvendorarch
script  => installscript   installsitebin      installvendorbin
bin     => installbin      installsitebin      installvendorbin
bindoc  => installman1dir  installsiteman1dir  installvendorman1dir
libdoc  => installman3dir  installsiteman3dir  installvendorman3dir
binhtml => installhtml1dir installsitehtml1dir installvendorhtml1dir [*]
libhtml => installhtml3dir installsitehtml3dir installvendorhtml3dir [*]

* Under some OS (eg. MSWin32) the destination for html documents is
determined by the C<Config.pm> entry C<installhtmldir>.

The default value of installdirs is "site". If you're creating vendor distributions of module packages, you may want to do something like this:

  perl Build.PL --installdirs vendor

or

  ./Build install --installdirs vendor

If you're installing an updated version of a module that was included with perl itself (i.e. a "core module"), then you may set installdirs to "core" to overwrite the module in its present location.

(Note that the 'script' line is different from MakeMaker - unfortunately there's no such thing as "installsitescript" or "installvendorscript" entry in Config.pm, so we use the "installsitebin" and "installvendorbin" entries to at least get the general location right. In the future, if Config.pm adds some more appropriate entries, we'll start using those.)

install_path

Once the defaults have been set, you can override them.

On the command line, that would look like this:

  perl Build.PL --install_path lib=/foo/lib --install_path arch=/foo/lib/arch

or this:

  ./Build install --install_path lib=/foo/lib --install_path arch=/foo/lib/arch
install_base

You can also set the whole bunch of installation paths by supplying the install_base parameter to point to a directory on your system. For instance, if you set install_base to "/home/ken" on a Linux system, you'll install as follows:

  lib     => /home/ken/lib/perl5
arch    => /home/ken/lib/perl5/i386-linux
script  => /home/ken/bin
bin     => /home/ken/bin
bindoc  => /home/ken/man/man1
libdoc  => /home/ken/man/man3
binhtml => /home/ken/html
libhtml => /home/ken/html

Note that this is different from how MakeMaker's PREFIX parameter works. See "Why PREFIX is not recommended" for more details. install_base just gives you a default layout under the directory you specify, which may have little to do with the installdirs=site layout.

The exact layout under the directory you specify may vary by system - we try to do the "sensible" thing on each platform.

destdir

If you want to install everything into a temporary directory first (for instance, if you want to create a directory tree that a package manager like rpm or dpkg could create a package from), you can use the destdir parameter:

  perl Build.PL --destdir /tmp/foo

or

  ./Build install --destdir /tmp/foo

This will effectively install to "/tmp/foo/$sitelib", "/tmp/foo/$sitearch", and the like, except that it will use File::Spec to make the pathnames work correctly on whatever platform you're installing on.

First, it is necessary to understand the original idea behind PREFIX. If, for example, the default installation locations for your machine are /usr/local/lib/perl5/5.8.5 for modules, /usr/local/bin for executables, /usr/local/man/man1 and /usr/local/man/man3 for manual pages, etc., then they all share the same "prefix" /usr/local. MakeMaker's PREFIX mechanism was intended as a way to change an existing prefix that happened to occur in all those paths - essentially a s{/usr/local}{/foo/bar} for each path.

However, the real world is more complicated than that. The PREFIX idea is fundamentally broken when your machine doesn't jibe with PREFIX's worldview.

• Many systems have Perl configs that make little sense with PREFIX. For example, OS X, where core modules go in /System/Library/Perl/..., user-installed modules go in /Library/Perl/..., and man pages go in /usr/share/man/.... The PREFIX is thus set to /. Install Foo::Bar on OS X with PREFIX=/home/spurkis and you get things like /home/spurkis/Library/Perl/5.8.1/Foo/Bar.pm and /home/spurkis/usr/share/man/man3/Foo::Bar.3pm. Not too pretty.

The problem is not limited to Unix-like platforms, either - on Windows builds (e.g. ActiveState perl 5.8.0), we have user-installed modules going in C:\Perl\site\lib, user-installed executables going in C:\Perl\bin, and PREFIX=C:\Perl\site. The prefix just doesn't apply neatly to the executables.

• The PREFIX logic is too complicated and hard to predict for the user. It's hard to document what exactly is going to happen. You can't give a user simple instructions like "run perl Makefile.PL PREFIX=~ and then set PERL5LIB=~/lib/perl5".

• The results from PREFIX will change if your configuration of Perl changes (for example, if you upgrade Perl). This means your modules will end up in different places.

• The results from PREFIX can change with different releases of MakeMaker. The logic of PREFIX is subtle and it has been altered in the past (mostly to limit damage in the many "edge cases" when its behavior was undesirable).

• PREFIX imposes decisions made by the person who configured Perl onto the person installing a module. The person who configured Perl could have been you or it could have been some guy at Redhat.

Alternatives to PREFIX

Module::Build offers "install_base" as a simple, predictable, and user-configurable alternative to ExtUtils::MakeMaker's PREFIX. What's more, MakeMaker will soon accept INSTALL_BASE -- we strongly urge you to make the switch.

Here's a quick comparison of the two when installing modules to your home directory on a unix box:

MakeMaker [*]:

  % perl Makefile.PL PREFIX=/home/spurkis
PERL5LIB=/home/spurkis/lib/perl5/5.8.5:/home/spurkis/lib/perl5/site_perl/5.8.5
PATH=/home/spurkis/bin
MANPATH=/home/spurkis/man

Module::Build:

  % perl Build.PL install_base=/home/spurkis
PERL5LIB=/home/spurkis/lib/perl5
PATH=/home/spurkis/bin
MANPATH=/home/spurkis/man

[*] Note that MakeMaker's behaviour cannot be guaranteed in even this common scenario, and differs among different versions of MakeMaker.

In short, using install_base is similar to the following MakeMaker usage:

  perl Makefile.PL PREFIX=/home/spurkis LIB=/home/spurkis/lib/perl5

See "INSTALL PATHS" for details on other installation options available and how to configure them.

# 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 ExtUtils::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 preselected (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. Since these strings aren't documented, and can't be documented (they take on different values depending on the platform, version of perl, version of MakeMaker, etc.), you have no guarantee that your modifications will work on someone else's machine or after an upgrade of MakeMaker or perl.

• 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 separate 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 that just need to be copied from one place to another? My sense was that we could design a system to accomplish this in a flexible, extensible, and friendly manner. Or die trying.

# 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.

 - append to perllocal.pod
- add a 'plugin' functionality

# AUTHOR

Ken Williams <kwilliams@cpan.org>

Development questions, bug reports, and patches should be sent to the Module-Build mailing list at <module-build-general@lists.sourceforge.net>.

Bug reports are also welcome at <http://rt.cpan.org/NoAuth/Bugs.html?Dist=Module-Build>.

An anonymous CVS repository containing the latest development version is available; see <http://sourceforge.net/cvs/?group_id=45731> for the details of how to access it.