How to know if a module is installed

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Nobumi Iyanaga - 27 Sep 2006 16:00 GMT

Hello,

This is a newbie question: how can I determine if a specific module
is installed on a client machine?

I would like to do something like this:

if (MacPerl installed is true) {
do this...;
}
else {
do nothing...;
}

Thank you in advance for any help.

Best regards,

Nobumi Iyanaga
Tokyo,
Japan

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David Cantrell - 27 Sep 2006 16:25 GMT

> This is a newbie question: how can I determine if a specific module
> is installed on a client machine?

if(eval "use Whatever::Module") {
do this;
} else {
do that;
}

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Ken Williams - 28 Sep 2006 14:07 GMT

>> This is a newbie question: how can I determine if a specific module
>> is installed on a client machine?
[quoted text clipped - 4 lines]
> do that;
> }

use() isn't documented to have a return value, so you need to do this:

if(eval "use Whatever::Module; 1") {
do this;
} else {
do that;
}

-Ken

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Sherm Pendley - 27 Sep 2006 16:31 GMT

> This is a newbie question: how can I determine if a specific module
> is installed on a client machine?
[quoted text clipped - 9 lines]
>
> Thank you in advance for any help.

Wrap a require() in an eval block, and then check to see if the eval
() succeeded. Untested, typed in Mail, etc.:

my $has_modulename;

BEGIN {
    eval {
        require Module::Name;

        # If you'd ordinarily "use Module::Name qw(foo bar baz);", pass
        # the qw(foo bar baz) to import here.

        import Module::Name qw(foo bar baz);
    };

    # If the eval failed, we don't have the module
    if ($@) {
        $ has_modulename = 0;
    } else {
        $ has_modulename = 1;
    }
}

That's if you want to check within a script - if you want to quickly
check from a command-line, there's an easier way:

perl -MModule::Name -e 'print $Module::Name::VERSION, "\n"'

sherm--

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Mac Forum / Programming / Perl / September 2006

How to know if a module is installed