[PerlFAQ] How do I find which modules are installed on my system?

兰花仙子

3.4: How do I find which modules are installed on my system?

    From the command line, you can use the "cpan" command's "-l" switch:

            $ cpan -l

    You can also use "cpan"'s "-a" switch to create an autobundle file that
    "CPAN.pm" understands and cna use to re-install every module:

            $ cpan -a

    Inside a Perl program, you can use the ExtUtils::Installed module to
    show all installed distributions, although it can take awhile to do its
    magic. The standard library which comes with Perl just shows up as
    "Perl" (although you can get those with Module::CoreList).

            use ExtUtils::Installed;

            my $inst    = ExtUtils::Installed->new();
            my @modules = $inst->modules();

    If you want a list of all of the Perl module filenames, you can use
    File::Find::Rule.

            use File::Find::Rule;

            my @files = File::Find::Rule->
                    extras({follow => 1})->
                    file()->
                    name( '*.pm' )->
                    in( @INC )
                    ;

    If you do not have that module, you can do the same thing with
    File::Find which is part of the standard library.

            use File::Find;
            my @files;

            find(
                {
                    wanted => sub {
                        push @files, $File::Find::fullname
                            if -f $File::Find::fullname && /\.pm$/
                    },
                    follow => 1,
                    follow_skip => 2,
                },
                @INC
            );

            print join "\n", @files;

    If you simply need to quickly check to see if a module is available, you
    can check for its documentation. If you can read the documentation the
    module is most likely installed. If you cannot read the documentation,
    the module might not have any (in rare cases).

            $ perldoc Module::Name

    You can also try to include the module in a one-liner to see if perl
    finds it.

            $ perl -MModule::Name -e1

仙子注曰：
山重水复疑无路，柳暗花明又一村。
方法有时很重要。

hotsnow

我这没 -l 这个参数

$ cpan -l
Unknown option: l
Nothing to install!

$ cpan -v
/usr/bin/cpan script version 1.9, CPAN.pm version 1.9402

$ perl -v

This is perl, v5.10.1 (*) built for i486-linux-gnu-thread-multi

Copyright 1987-2009, Larry Wall

Perl may be copied only under the terms of either the Artistic License or the
GNU General Public License, which may be found in the Perl 5 source kit.

Complete documentation for Perl, including FAQ lists, should be found on
this system using "man perl" or "perldoc perl".  If you have access to the
Internet, point your browser at http://www.perl.org/, the Perl Home Page.