api.pod

source of perl for linux application,

  {
   ok => $whether_the_dependency_is_satisfied,
   have => $version_already_installed,
   need => $version_requested, # Same as incoming $version argument
   message => $informative_error_message,
  }

If no version of C<$module> is currently installed, the C<have> value
will be the string C<< "<none>" >>.  Otherwise the C<have> value will
simply be the version of the installed module.  Note that this means
that if C<$module> is installed but doesn't define a version number,
the C<have> value will be C<undef> - this is why we don't use C<undef>
for the case when C<$module> isn't installed at all.

This method may be called either as an object method
(C<< $build->check_installed_status($module, $version) >>)
or as a class method
(C<< Module::Build->check_installed_status($module, $version) >>).

=item check_installed_version($module, $version)

[version 0.05]

Like L<check_installed_status()|/"check_installed_status($module, $version)">,
but simply returns true or false depending on whether module
C<$module> satisfies the dependency C<$version>.

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

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

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

If C<$version> is any non-true value (notably zero) and any version of
C<$module> is installed, we return true.  In this case, if C<$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.

In general you might prefer to use C<check_installed_status> if you
need detailed information, or this method if you just need a yes/no
answer.

=item compare_versions($v1, $op, $v2)

[version 0.28]

Compares two module versions C<$v1> and C<$v2> using the operator
C<$op>, which should be one of Perl's numeric operators like C<!=> or
C<< >= >> or the like.  We do at least a halfway-decent job of
handling versions that aren't strictly numeric, like C<0.27_02>, but
exotic stuff will likely cause problems.

In the future, the guts of this method might be replaced with a call
out to C<version.pm>.

=item config($key)

=item config($key, $value)

=item config() [deprecated]

[version 0.22]

With a single argument C<$key>, returns the value associated with that
key in the C<Config.pm> hash, including any changes the author or user
has specified.

With C<$key> and C<$value> arguments, sets the value for future
callers of C<config($key)>.

With no arguments, returns a hash reference containing all such
key-value pairs.  This usage is deprecated, though, because it's a
resource hog and violates encapsulation.

=item config_data($name)

=item config_data($name => $value)

[version 0.26]

With a single argument, returns the value of the configuration
variable C<$name>.  With two arguments, sets the given configuration
variable to the given value.  The value may be any Perl scalar that's
serializable with C<Data::Dumper>.  For instance, if you write a
module that can use a MySQL or PostgreSQL back-end, you might create
configuration variables called C<mysql_connect> and
C<postgres_connect>, and set each to an array of connection parameters
for C<< DBI->connect() >>.

Configuration values set in this way using the Module::Build object
will be available for querying during the build/test process and after
installation via the generated C<...::ConfigData> module, as
C<< ...::ConfigData->config($name) >>.

The L<feature()|/"feature($name)"> and C<config_data()> methods represent
Module::Build's main support for configuration of installed modules.
See also L<Module::Build::Authoring/"SAVING CONFIGURATION INFORMATION">.

=item conflicts()

[version 0.21]

Returns a hash reference indicating the C<conflicts> prerequisites
that were passed to the C<new()> method.

=item contains_pod($file)

[version 0.20]

[Deprecated] Please see L<Module::Build::ModuleInfo> instead.

Returns true if the given file appears to contain POD documentation.
Currently this checks whether the file has a line beginning with
'=pod', '=head', or '=item', but the exact semantics may change in the
future.

=item copy_if_modified(%parameters)

[version 0.19]

Takes the file in the C<from> parameter and copies it to the file in
the C<to> parameter, or the directory in the C<to_dir> parameter, if
the file has changed since it was last copied (or if it doesn't exist
in the new location).  By default the entire directory structure of
C<from> will be copied into C<to_dir>; an optional C<flatten>
parameter will copy into C<to_dir> without doing so.

Returns the path to the destination file, or C<undef> if nothing
needed to be copied.

Any directories that need to be created in order to perform the
copying will be automatically created.

The destination file is set to read-only. If the source file has the
executable bit set, then the destination file will be made executable.

=item create_build_script()

[version 0.05]

Creates an executable script called C<Build> in the current directory
that will be used to execute further user actions.  This script is
roughly analogous (in function, not in form) to the Makefile created
by C<ExtUtils::MakeMaker>.  This method also creates some temporary
data in a directory called C<_build/>.  Both of these will be removed
when the C<realclean> action is performed.

Among the files created in C<_build/> is a F<_build/prereqs> file
containing the set of prerequisites for this distribution, as a hash
of hashes.  This file may be C<eval()>-ed to obtain the authoritative
set of prereqs, which might be different from the contents of
F<META.yml> (because F<Build.PL> might have set them dynamically).
But fancy developers take heed: do not put any fancy custom runtime
code in the F<_build/prereqs> file, leave it as a static declaration
containing only strings and numbers.  Similarly, do not alter the
structure of the internal C<< $self->{properties}{requires} >> (etc.)
data members, because that's where this data comes from.

=item current_action()

[version 0.28]

Returns the name of the currently-running action, such as "build" or
"test".  This action is not necessarily the action that was originally
invoked by the user.  For example, if the user invoked the "test"
action, current_action() would initially return "test".  However,
action "test" depends on action "code", so current_action() will
return "code" while that dependency is being executed.  Once that
action has completed, current_action() will again return "test".

If you need to know the name of the original action invoked by the
user, see L</invoked_action()> below.

=item depends_on(@actions)

[version 0.28]

Invokes the named action or list of actions in sequence.  Using this
method is preferred to calling the action explicitly because it
performs some internal record-keeping, and it ensures that the same
action is not invoked multiple times (note: in future versions of
Module::Build it's conceivable that this run-only-once mechanism will
be changed to something more intelligent).

Note that the name of this method is something of a misnomer; it
should really be called something like
C<invoke_actions_unless_already_invoked()> or something, but for
better or worse (perhaps better!) we were still thinking in
C<make>-like dependency terms when we created this method.

See also L<dispatch()|/"dispatch($action, %args)">.  The main
distinction between the two is that C<depends_on()> is meant to call
an action from inside another action, whereas C<dispatch()> is meant
to set the very top action in motion.

=item dir_contains($first_dir, $second_dir)

[version 0.28]

Returns true if the first directory logically contains the second
directory.  This is just a convenience function because C<File::Spec>
doesn't really provide an easy way to figure this out (but
C<Path::Class> does...).

=item dispatch($action, %args)

[version 0.03]

Invokes the build action C<$action>.  Optionally, a list of options
and their values can be passed in.  This is equivalent to invoking an
action at the command line, passing in a list of options.

Custom options that have not been registered must be passed in as a
hash reference in a key named "args":

  $build->dispatch('foo', verbose => 1, args => { my_option => 'value' });

This method is intended to be used to programmatically invoke build
actions, e.g. by applications controlling Module::Build-based builds
rather than by subclasses.

See also L<depends_on()|/"depends_on(@actions)">.  The main
distinction between the two is that C<depends_on()> is meant to call
an action from inside another action, whereas C<dispatch()> is meant
to set the very top action in motion.

=item dist_dir()

[version 0.28]

Returns the name of the directory that will be created during the
C<dist> action.  The name is derived from the C<dist_name> and
C<dist_version> properties.

=item dist_name()

[version 0.21]

Returns the name of the current distribution, as passed to the
C<new()> method in a C<dist_name> or modified C<module_name>
parameter.

=item dist_version()

[version 0.21]

Returns the version of the current distribution, as determined by the
C<new()> method from a C<dist_version>, C<dist_version_from>, or
C<module_name> parameter.

=item do_system($cmd, @args)

[version 0.21]

This is a fairly simple wrapper around Perl's C<system()> built-in
command.  Given a command and an array of optional arguments, this
method will print the command to C<STDOUT>, and then execute it using
Perl's C<system()>.  It returns true or false to indicate success or
failure (the opposite of how C<system()> works, but more intuitive).

Note that if you supply a single argument to C<do_system()>, it
will/may be processed by the systems's shell, and any special
characters will do their special things.  If you supply multiple
arguments, no shell will get involved and the command will be executed
directly.

=item feature($name)

=item feature($name => $value)

[version 0.26]

With a single argument, returns true if the given feature is set.
With two arguments, sets the given feature to the given boolean value.
In this context, a "feature" is any optional functionality of an
installed module.  For instance, if you write a module that could
optionally support a MySQL or PostgreSQL backend, you might create
features called C<mysql_support> and C<postgres_support>, and set them
to true/false depending on whether the user has the proper databases
installed and configured.

Features set in this way using the Module::Build object will be
available for querying during the build/test process and after
installation via the generated C<...::ConfigData> module, as
C<< ...::ConfigData->feature($name) >>.

The C<feature()> and C<config_data()> methods represent
Module::Build's main support for configuration of installed modules.
See also L<Module::Build::Authoring/"SAVING CONFIGURATION INFORMATION">.

=item have_c_compiler()

[version 0.21]

Returns true if the current system seems to have a working C compiler.
We currently determine this by attempting to compile a simple C source
file and reporting whether the attempt was successful.

=item install_base_relpaths()

=item install_base_relpaths($type)

=item install_base_relpaths($type => $path)

[version 0.28]

Set or retrieve the relative paths that are appended to
C<install_base> for any installable element. This is useful if you
want to set the relative install path for custom build elements.

With no argument, it returns a reference to a hash containing all
elements and their respective values. This hash should not be modified
directly; use the multi-argument below form to change values.

The single argument form returns the value associated with the
element C<$type>.

The multi-argument form allows you to set the paths for element types.
C<$value> must be a relative path using unix-like paths.  (A series of
directories seperated by slashes.  Eg 'foo/bar'.)  The return value is a
localized path based on C<$value>.

Assigning the value C<undef> to an element causes it to be removed.

=item install_destination($type)

[version 0.28]

Returns the directory in which items of type C<$type> (e.g. C<lib>,
C<arch>, C<bin>, or anything else returned by the L</install_types()>
method) will be installed during the C<install> action.  Any settings
for C<install_path>, C<install_base>, and C<prefix> are taken into
account when determining the return value.

=item install_path()

=item install_path($type)

=item install_path($type => $path)

[version 0.28]

Set or retrieve paths for specific installable elements. This is
useful when you want to examine any explicit install paths specified
by the user on the command line, or if you want to set the install
path for a specific installable element based on another attribute
like C<install_base()>.

With no argument, it returns a reference to a hash containing all
elements and their respective values. This hash should not be modified
directly; use the multi-argument below form to change values.

The single argument form returns the value associated with the
element C<$type>.

The multi-argument form allows you to set the paths for element types.
The supplied C<$path> should be an absolute path to install elements
of C<$type>.  The return value is C<$path>.

Assigning the value C<undef> to an element causes it to be removed.

=item install_types()

[version 0.28]

Returns a list of installable types that this build knows about.
These types each correspond to the name of a directory in F<blib/>,
and the list usually includes items such as C<lib>, C<arch>, C<bin>,
C<script>, C<libdoc>, C<bindoc>, and if HTML documentation is to be
built, C<libhtml> and C<binhtml>.  Other user-defined types may also
exist.

=item invoked_action()

[version 0.28]

This is the name of the original action invoked by the user.  This
value is set when the user invokes F<Build.PL>, the F<Build> script,
or programatically through the L<dispatch()|/"dispatch($action, %args)">
method.  It does not change as sub-actions are executed as
dependencies are evaluated.

To get the name of the currently executing dependency, see
L</current_action()> above.

=item notes()

=item notes($key)

=item notes($key => $value)

[version 0.20]

The C<notes()> value allows you to store your own persistent
information about the build, and to share that information among
different entities involved in the build.  See the example in the
C<current()> method.

The C<notes()> method is essentally a glorified hash access.  With no
arguments, C<notes()> returns the entire hash of notes.  With one argument,
C<notes($key)> returns the value associated with the given key.  With two
arguments, C<notes($key, $value)> sets the value associated with the given key
to C<$value> and returns the new value.

The lifetime of the C<notes> data is for "a build" - that is, the
C<notes> hash is created when C<perl Build.PL> is run (or when the
C<new()> method is run, if the Module::Build Perl API is being used
instead of called from a shell), and lasts until C<perl Build.PL> is
run again or the C<clean> action is run.

=item orig_dir()

[version 0.28]

Returns a string containing the working directory that was in effect
before the F<Build> script chdir()-ed into the C<base_dir>.  This
might be useful for writing wrapper tools that might need to chdir()
back out.

=item os_type()

[version 0.04]

If you're subclassing Module::Build and some code needs to alter its