Announce: Inside 1.00 - Listing installed modules 
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 Announce: Inside 1.00 - Listing installed modules

It often happens that folks need a list of the installed Perl modules.
There are several common ways to get such a list, but none of them works
all of the time. In particular, this is especially difficult to do when
you have limited access to the machine in question, such as when you have
nothing but FTP access to a webserver.

The program 'inside' solves this problem.


Here's the README file.

This program is available on CPAN:


To prepare this program for your system, use a variation on the standard

    perl Makefile.PL
    make test           # this may take a moment to complete

Then, install the file 'inside' as needed for a CGI program on your
system. See your local expert if you're not sure how to do that.

If you're unable to use the standard incantation, try running the
command 'perl inside.PL' instead. Or you may need to manually fix up the
file 'inside' for use as a CGI program on your system.

>From the embedded documentation:

    Inside - Find out what's inside your Perl installation

    This program will try to report which Perl modules are available
    on your machine, along with some other useful information.
    Although it's especially made to be helpful to CGI programmers,
    it may be of use to other Perl users as well.

    Note that I've done more than a few weird things in this code in
    order to make it work in some odd surroundings. The right thing
    to do in general is to fix the broken environments, rather than
    to work around them. But since the purpose of this program is to
    diagnose some of those broken environments, I'm breaking the
    rules. In short: Don't Do As This Code Does! Use the accepted
    techniques, instead.

    You should be able to run this program on nearly any machine
    which has Perl, either as a CGI program or stand-alone, although
    not under Apache/mod_perl's non-CGI environments, like
    Apache::Registry or Apache::PerlRun. (The ordinary Apache CGI
    environment is fine, whether mod_perl is installed or not.) The
    only(?) thing which should need changing in the program text is
    the location of perl in the #!-line, the first line of the
    program. There's also a small Configuration section near the top
    of the source, if you really need to have something to fiddle

    Of course, if you're installing this program on a webserver,
    your local expert may need to help you to get it running. Don't
    ask me to do it! :-)

    * I can't get it to work! What's wrong?
        This program tries hard to work in any normal environment,
        but it may be damaged or misinstalled. If you can run it in
        a shell (as opposed to running it as a CGI program) you may
        get more information about what is happening. Check the
        perldiag manpage for the meaning of any diagnostic messages
        from perl.

        If you get an error about an "Illegal character", you
        probably didn't use text mode ("ASCII mode") to transfer the
        source from one machine to another. Try again, see the
        perldiag manpage for more help, or ask your local expert.

        If the error message says that "Setting locale failed",
        check what the perllocale manpage tells you to do to fix
        your setup.

        If it seems to run and produces no output from the command
        line, check that you didn't run the configuration program
        'inside.PL' rather than the real program 'inside'.

        If the error message in MacPerl complains that it "Can't
        emulate -{symbol} on #! line", or if the program
        mysteriously doesn't run at all, you probably didn't use
        text mode ("ASCII mode") to transfer the source to the Mac.
        Try again or ask your local expert.

        When you're having trouble with a CGI program in Perl,
        here's a handy troubleshooting guide to get you back on


        If you're running the most recent version of this program
        and you're still stuck after using the CGI troubleshooting
        guide (if appropriate), working with your local expert, and
        thinking about it overnight, then you may try asking about
        it in the newsgroup comp.lang.perl.modules or writing to me.
        Don't send me this entire program or its output unless I ask
        for it! If you've got something long you wish for me to see,
        put it on the web and send me just the URL.

    * Where can I get the most recent version of this program?
        It should be available on CPAN.


    * Why doesn't this program work with Apache/mod_perl?
        It does. But this is a CGI program, and Apache::Registry and
        similar modules don't really use CGI. They're a little
        different, so as to give certain benefits to some programs.
        This program couldn't use any of those benefits, even if it
        could be made compatible with those modules. In particular,
        it wouldn't run any faster, since nearly all of its time is
        spent in doing I/O. And are you going to call this program
        hundreds of times every second? I hope not!

        Simply run this as a normal CGI program, and Apache/mod_perl
        will be happy with it. If you're not sure how to do that on
        your machine, check with your local expert.

    * Why did you write this program?
        There are other solutions to this problem. I didn't like
        them. Finding the installed modules is actually a complex
        problem. Most proposed solutions have a number of false
        positives or false negatives (this one has both; see the
        rest of this FAQ for details). Some proposed solutions use
        obfuscated or incorrect code, or don't work on the web with
        all standard web servers and browsers. This program also has
        the advantage of this FAQ and (I hope) clear diagnostic
        messages about problems it may encounter.

    * Why can't I use module ____? This program says it's there.
        This may be a "false positive".

        This program can't tell whether a module is properly
        installed. (The only way to do that is to load and test the
        module. Figuring out how to test an arbitrary piece of code
        for proper functioning is provably impossible, so I decided
        not to try.)

        Of course, maybe the module is properly installed, but
        you're simply using it incorrectly. Stop doing that.

        A proper module should be distributed with tests which you
        can (and should) use before installing it. If your installed
        modules won't pass the tests, you should almost certainly
        (ask your administrator to) rebuild and reinstall that
        module, ensuring this time that it does pass the tests.

        One possible error is that you may have used the wrong
        capitalization in the `use' declaration. Check the module's
        documentation to see how to use it. Neither `use Cgi;' nor
        `use cgi;' will properly start up the CGI module.

    * Why doesn't this program find all of my modules?
        This may be a "false negative".

        The "missing" module is not installed (or not properly
        installed) in one of the search directories. Those

        variable (possibly modified by an environment variable) and
        the extra directories whose names are included in the source
        of this program.

        You probably want to add your private module/library

        section of this program. Also see what the Perl FAQ says
        about keeping your own module/library directory.

    * How can I include my own module/library directory?

        section. There is a similar question in the Perl FAQ, which
        is worth reading.

    * Can't I specify search directories with a web form?
        No. For security reasons, the directory list must be hard-

    * But I want my users to be able to specify their own directories!
        Why? They can look in their own directories any time they
        want, can't they? If they want to install their own copy of
        this program, they can configure it to their needs.

        If you still want this, you probably don't understand the
        security implications.

    * How can I find out about module dependencies?
        Determining which modules are needed by which other modules
        is far beyond the scope of this program.

        There's no way to find module dependencies which always
        works. But any good module should check for its own
        dependencies at installation time. If you use the CPAN
        module to install and upgrade modules, it can help you with

        Similarly, if a program needs a module which isn't supplied
        with perl, this should be made clear in the program's README
        file, or equivalent.

    * How can I automate installing a bunch of modules?
        Some folks want to find out which modules are installed so
        as to automate installing those again on a new system, or
        with a new version of Perl. This program isn't intended to
        help with this. See the CPAN module's `autobundle' function,

    * I copied some of your code to my own program, but...
        Don't do that! I break lots of rules in this program,
        because I have good reasons and I know what I'm doing. You
        don't have good reasons, and you don't know what you're
        doing. :-)

    * Why does the version number for module ____ come out wrong?
        For the same reason that so many version numbers are

    * Why do so many modules show the version number as "unknown"?
        There are several possible reasons. But if you don't have a
        warning that gives another reason, it may be because the
        module author hasn't included the version number in the
        standard format. See the docs for ExtUtils::MakeMaker, in
        the section on VERSION_FROM. But (for technical reasons)
        this code can't be as smart as ExtUtils::MakeMaker, so it
        will sometimes get the version number wrong or not get it at

        Technical note: Okay, if you must know. ExtUtils::MakeMaker
        actually runs some of each module's code in order to
        determine its version. That could be a security hole, if the
        module might contain rogue code. I'm not going to take the
        chance. Version numbers aren't that hard to find out on your

        If you're a module author and this program doesn't do as
        well as ExtUtils::MakeMaker at determining your module's
        version number, please cook up a fix. Preferably, to your
        module, rather than to this program. :-)

    * Why are so many programs listed as "Libraries"?
        Your programs are using the file extension ".pl", which
        means "Perl Library". On many systems, extensions for
        programs aren't needed and shouldn't be used. If you must
        have an extension on your program names, it's best to set up
        your system to use ".plx", which means "Perl Executable",
        then use that extension instead.

        This seems to be a losing battle, since ActiveState (and
        others?) strongly encourage the use of the wrong extension.

        If you wish to keep some of these from showing up, add a

        Configuration section). Unless you have both libraries and
        programs in the same directory (yet another reason for
        different extensions!) you can simply list directory names
        to exclude them and their contents. But listing a program
        won't hurt you any, if you know it's not a library.

    * Why does it take so long to run?
        This program may take perhaps more than a minute to run,
        depending upon your system's load, the number of modules
        installed, and so on. It's gathering a lot of information
        about your system! If you're installing it as a CGI program,
        you may be able to make it work as an NPH-program. (This is
        no faster, but it does produce some output sooner, for the
        benefit of you impatient folks.) Set it up just like any
        other CGI program, but make sure that the first four
        characters of the file's name are "nph-", and it should work
        automatically. If it doesn't make any difference, well, then
        you just have to wait for the output, that's all.

    * Why does it run faster after the first time?
        Much of the overhead of running this program is I/O.
        Probably your system has cached the information which it
        read off of your filesystem. Try again after some time, and
        it will be like the first time again.

    * Why do the "modules found" messages at the top always differ?
        There are some things man was not meant to know.

    * Is there any way to configure this program to ____?
        Sometimes folks want to turn part of the output on or off.
        Maybe they want to put their own URL into the output. Maybe
        they want to change something else.

        Well, you probably can't. This program is more like a
        stethoscope than an ultrasound machine. It doesn't have a
        lot of dials and knobs.

        See the intentionally-small "Configuration" section of the
        program, though, if you really wish to tweak something.

        Please, see the license and disclaimer before you change any

    * Why doesn't it find modules relative to the current directory?
        When it's run over the web (that is, as a CGI program) this
        program will ignore relative paths. (These are directory
        paths which don't start with a slash, on Unix. On other
        systems, there may be other kinds of relative paths, but all
        relative paths start from the "current working directory".)

        The current working directory is not part of the CGI
        specification. Since a CGI program can't rely upon it, it
        must always change to a non-relative directory before it can
        safely use a relative path. (A future version of the CGI
        spec may change this - but that won't help existing programs
        and webservers.)

    * But I use `chdir' before I load modules!
        You probably aren't doing that correctly. If you do know
        enough to do this correctly, I can instruct you no further

    * Is this program vulnerable to any security problems?
        Every program is. See the disclaimer elsewhere in the

        One possible problem, which is beyond the scope of this
        program to fix, is a Denial of Service ("DoS") attack.
        Briefly, this program takes time to run. If someone were to
        set up other computers to call this program over the web as
        frequently as possible, your webserver could become very
        slow for all legitimate users. But this can happen, to some
        extent, with any program that remote users can run - even
        with your webserver itself.

        If you worry about DoS attacks using this program, simply
        disable it whenever you're not using it. On most Unix-type
        webservers, that's easy to do by using chmod(1) to set the
        permissions to 0. On some webservers, you may need to change
        the name or remove the program entirely. See your local
        expert for details. No, you can't enable or disable it over
        the web - that would defeat the purpose, wouldn't it?

    * Why don't you use warnings and 'use strict' and....?
        Because this program is purposefully written in a way which
        will work around various system (mis)configurations. And
        actually, barring quirks in some future version of perl, I
        am using warnings and 'use strict'. You just might not be
        able to see how I'm doing it. :-)

    * Why aren't you using taint checking?
        This program shouldn't need that to be secure. A program
        without taint checks can be secure, just as one with them
        can be unsafe.

        When taint checks aren't used, we may use Perl's eval()
        function on a string from another module. Since we first
        check that the module is owned and writable only by the
        system administrator, this doesn't open up any new security
        hole. (If your installed modules aren't safe, though, it
        opens up that existing security hole. :-) That is to say,
        this technique is no more insecure in general than using the
        modules installed on your system.

        If you wish to use taint checking, it can be enabled in the
        usual way, by adding the '-T' option to the $# line at the
        top of the program. Just know that when taint checks are
        enabled, you may not be able to determine the version
        numbers of some modules. Rarely, you may get incorrect
        version numbers from a few modules.

    * Why doesn't this work with perl4?
        Do you remember when O. J. Simpson was known primarily as an
        ex-football player who made TV commercials? Perl 4 is older
        than that. Give it up. It's dead. Besides, such old perl
        can't use modules anyway!



    This program is free software; you can distribute it under the
    same terms as Perl itself. I don't recommend modifying it or
    distributing variant versions. In fact, I discourage modifying
    it, unless you're sure you know what you're doing. And if you do
    modify something, make sure that you've clearly labeled
    whatever you've done. On the other hand, if you come up with a
    cool or useful modification, let me know. And don't forget to
    periodically check CPAN for updates.


    Be cautious that, if you modify this code in any way, you do not
    introduce security holes. Although I have, to the best of my
    knowledge and ability, made this program as safe as is
    practicable, it may have flaws which could cause undesirable
    effects. Still, I don't think it's too bad: I run it myself.


    folks, including (in no particular order) "Tolkin, Steve"

    I've accidentally omitted. It wouldn't have been possible
    without all this help.

Tom Phoenix       Perl Training and Hacking       Esperanto
Randal Schwartz Case:     http://www.*-*-*.com/

Wed, 28 May 2003 02:32:59 GMT  
 [ 1 post ] 

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