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12.19. Program: Finding Versions and Descriptions of Installed Modules

Perl is shipped with many modules. Even more can be found on CPAN. The following program prints out the names, versions, and descriptions of all modules installed on your system. It uses standard modules like File::Find and includes several techniques described in this chapter.

To run it, type:

% pmdesc

It prints a list of modules and their descriptions:

FileHandle (2.00) - supply object methods for filehandles
IO::File (1.06021) - supply object methods for filehandles
IO::Select (1.10) - OO interface to the select system call
IO::Socket (1.1603) - Object interface to socket communications
...

With the -v flag, pmdesc provides the names of the directories the files are in:

% pmdesc -v

<<<Modules from /usr/lib/perl5/i686-linux/5.00404>>>

FileHandle (2.00) - supply object methods for filehandles
    ...

The -w flag warns if a module doesn't come with a pod description, and -s sorts the module list within each directory.

The program is given in Example 12.3.

Example 12.3: pmdesc

#!/usr/bin/perl -w
# pmdesc - describe pm files
# tchrist@perl.com

use strict;
use File::Find      qw(find);
use Getopt::Std     qw(getopts);
use Carp;

use vars (
    q!$opt_v!,              # give debug info
    q!$opt_w!,              # warn about missing descs on modules
    q!$opt_a!,              # include relative paths
    q!$opt_s!,              # sort output within each directory
);

$| = 1;

getopts('wvas')             or die "bad usage";

@ARGV = @INC unless @ARGV;

# Globals.  wish I didn't really have to do this.
use vars (
    q!$Start_Dir!,          # The top directory find was called with
    q!%Future!,             # topdirs find will handle later
);

my $Module;

# install an output filter to sort my module list, if wanted.
if ($opt_s) {
    if (open(ME, "-|")) {
        $/ = '';
        while (<ME>) {
            chomp;
            print join("\n", sort split /\n/), "\n";
        }
        exit;
    }
}

MAIN: {
    my %visited;
    my ($dev,$ino);

    @Future{@ARGV} = (1) x @ARGV;

    foreach $Start_Dir (@ARGV) {
        delete $Future{$Start_Dir};

        print "\n<<Modules from $Start_Dir>>\n\n"
            if $opt_v;

        next unless ($dev,$ino) = stat($Start_Dir);
        next if $visited{$dev,$ino}++;
        next unless $opt_a || $Start_Dir =~ m!^/!;

        find(\&wanted, $Start_Dir);
    }
    exit;
}

# calculate module name from file and directory
sub modname {
    local $_ = $File::Find::name;

    if (index($_, $Start_Dir . '/') == 0) {
        substr($_, 0, 1+length($Start_Dir)) = '';
    }

    s { /              }    {::}gx;
    s { \.p(m|od)$     }    {}x;

    return $_;
}

# decide if this is a module we want
sub wanted {
    if ( $Future{$File::Find::name} ) {
        warn "\t(Skipping $File::Find::name, qui venit in futuro.)\n"
            if 0 and $opt_v;
        $File::Find::prune = 1;
        return;
    }
    return unless /\.pm$/ && -f;
    $Module = &modname;
    # skip obnoxious modules
    if ($Module =~ /^CPAN(\Z|::)/) {
        warn("$Module -- skipping because it misbehaves\n");
        return;
    }

    my    $file = $_;

    unless (open(POD, "< $file")) {
        warn "\tcannot open $file: $!";
            # if $opt_w;
        return 0;
    }

    $: = " -:";

    local $/ = '';
    local $_;
    while (<POD>) {
        if (/=head\d\s+NAME/) {
            chomp($_ = <POD>);
            s/^.*?-\s+//s;
            s/\n/ /g;
            #write;
            my $v;
            if (defined ($v = getversion($Module))) {
                print "$Module ($v) ";
            } else {
                print "$Module ";
            }
            print "- $_\n";
            return 1;
        }
    }

    warn "\t(MISSING DESC FOR $File::Find::name)\n"
        if $opt_w;

    return 0;
}

# run Perl to load the module and print its verson number, redirecting
# errors to /dev/null
sub getversion {
    my $mod = shift;

    my $vers = `$^X -m$mod -e 'print \$${mod}::VERSION' 2>/dev/null`;
    $vers =~ s/^\s*(.*?)\s*$/$1/; # remove stray whitespace
    return ($vers || undef);
}

format  =
^<<<<<<<<<<<<<<<<<~~^<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
$Module,        $_
.


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