CODEWITHSUNDEEP
perlmodule
mmccoo
mmccoo

Reputation: 8536

How do I find which file Perl loaded when I use a module?

in Perl, when I do use <module name> <ver>;, the system finds the .pm file for the library somewhere in the @INC path.

Is there a reliable way to which file was actually loaded?

Upvotes: 48

Views: 27102

Answers (10)

Alexx Roche
Alexx Roche

Reputation: 3249

I use the shell script /usr/local/bin/which_perl_module

#!/bin/sh

if [ ! $1 ];then echo "Which perl module should I look for?"; exit; fi

echo -n "You are using: "
perldoc -l $1
echo "which I found by looking in:"
perl -MData::Dump=pp -e 'unshift @INC, '$1'; pp(\@INC)'

Upvotes: 0

Denis Howe
Denis Howe

Reputation: 2412

You can use the instmodsh command: http://perldoc.perl.org/instmodsh.html.

Upvotes: 0

derobert
derobert

Reputation: 51137

Yes, %INC contains the full path a module was loaded from.

Example:

$ perl -M'Data::Dump qw(pp)' -e 'pp(\%INC)'
{
  "Data/Dump.pm"         => "/usr/share/perl5/Data/Dump.pm",
  "Exporter.pm"          => "/usr/share/perl/5.10/Exporter.pm",
  "List/Util.pm"         => "/usr/lib/perl/5.10/List/Util.pm",
  "Scalar/Util.pm"       => "/usr/lib/perl/5.10/Scalar/Util.pm",
  "XSLoader.pm"          => "/usr/lib/perl/5.10/XSLoader.pm",
  "overload.pm"          => "/usr/share/perl/5.10/overload.pm",
  "strict.pm"            => "/usr/share/perl/5.10/strict.pm",
  "vars.pm"              => "/usr/share/perl/5.10/vars.pm",
  "warnings.pm"          => "/usr/share/perl/5.10/warnings.pm",
  "warnings/register.pm" => "/usr/share/perl/5.10/warnings/register.pm",
}

Upvotes: 71

user1121750
user1121750

Reputation: 91

perl -M'LWP' -e 'use Data::Dumper; print Dumper \%INC' | grep LWP

This will list out the LWP module location on the disk and also lists out modules loaded inside LWP.

      'LWP.pm' => '/usr/lib/perl5/5.10.0/LWP.pm',
      'LWP/Protocol.pm' => '/usr/lib/perl5/5.10.0/LWP/Protocol.pm',
      'LWP/UserAgent.pm' => '/usr/lib/perl5/5.10.0/LWP/UserAgent.pm',

Upvotes: 9

Russell Jungwirth
Russell Jungwirth

Reputation: 51

Here is a one-liner (with a bash wrapper) to determine if a module is installed - and where it will be loaded from:

#!/bin/bash
perl -M${1} -le "\$mname=\"${1}.pm\";\$mname=~s#::#/#g;print \"$1 INSTALLED AT \$INC{\$mname}\";" 2>/dev/null || echo "${1} NOT INSTALLED"

Call it with perl's module name syntax:

./find_perl_module  Font::Metrics::Courier

Upvotes: 5

skiphoppy
skiphoppy

Reputation: 102713

If the module has pod documentation, and if you can guarantee that the perldoc utility in your PATH belongs to the same perl that is running your script, then this command will often give you the actual file being found:

perldoc -l ModuleName

Upvotes: 9

brian d foy
brian d foy

Reputation: 132719

You want to look in the %INC variable, which records the filename it loaded for the libraries you load with do, require, or use. See perlvar for the details.

Upvotes: 7

Hudson
Hudson

Reputation: 2061

Module::Mapper provides a way to walk the @INC tree to find modules:

perl -MModule::Mapper -MData::Dumper \
-e 'print Dumper( find_sources( UseINC => 1, Modules => [ @ARGV ] ) )' \
list-of-modules-to-locate

Upvotes: 1

mikegrb
mikegrb

Reputation: 1183

There are a good number of modules in CPAN for finding this information, the most likely candidates look to be Module::Find, Module::Which, and Module::Locate. I'd probably go with Module::Locate:

use strict;
use warnings;
use Module::Locate qw/locate/;

my $to_find = "Some::Module";

print "Perl would use: ", scalar locate($to_find), "\n";

In list context locate returns all found copies of Some::Module in order based on @INC.

Edit: derobert suggests a much better way, I didn't realize %INC already had it... This module based solution would still be useful if you wanted to know before loading the module where it was going to be loaded from.

Upvotes: 5

John
John

Reputation: 16007

From what I found, perl will look in the directories within the path:

perl -le 'print foreach @INC'

Then it will look in the standard library, and then in the current directory.

That gives you a search order.

My source:

Extending the library path

Upvotes: 2

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