TQuid has asked for the wisdom of the Perl Monks concerning the following question:

I have a small config file I use for a webserver setup script where I work. Here are a few representative lines: 
$transfer_log = eval { "$log_dir/$user_data{site}->[0]-access_log" };
@adduser    = eval { "/usr/sbin/adduser -g $group -G $user_data{site}-
+>[0] -H"
                   . "$home_dir -P $pwd -s $shell $user" };

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$user and such get read in interactively at run-time, so with -w, I get warnings about using an undefined value. eval {} isn't doing what I was expecting, and it doesn't seem to matter whether I use use, require, or do {}. Any input on how to clean this up? --TQuid
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Re: Configuration variables using run-time in put without -w complaints?
by Shendal (Hermit) on Jun 26, 2000 at 23:56 UTC
    I am not sure why you are using eval. If I understand your issue, you want to get input from the user, set that to a few variables, and then use these variables as input to another program (in this case, adduser).

    Why not try this:
    print "Enter something:";
chomp($answer = <STDIN>);
$transfer_log = "$log_dir/$answer";
$adduser = `/usr/sbin/adduser -g $group -G $user ...`;

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    Anyway, I truncated a bit of the data, but I think you get the idea. You want to read in whatever your interested in. In order to run a program (i.e., adduser), use backticks or system().
    Hope that helps,
    Shendal

    Update: As KM pointed out in chat, you'll probably want to enable taint checking (-T). That will warn you on unsafe constructs where you may be running something you don't want to.
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[d/l]
      Sorry, the eval is there as a result of recent thrashing, since I read that it is evaluated at run-time. The problem is that the snippet above is a separate config. file, read in with 
      require '/etc/addvhost2rc';

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      I've also tried using do {}, as suggested in the Cookbook, but the error messages persist regardless. It's important that it be a separate config file, as the script is intended to run on sites with varying directory layouts, adduser command syntax, etc.
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[d/l]
        Oh, okay. Well, if you are doing a require to get the configuration in there, I'd suggest putting everything in the configuration file into a subroutine, then call it when you've done all the necessary set up.

        For example, your config file may look like this:
        # config file
sub initConfig {
    $foo = "$user - bar";
    # ... whatever...
}

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        Where your program file may look like this:
        # program
require 'configuration_file';
print "Username:";
chomp($user = <STDIN>);
# now $user exists, although you'd wanna check it for validity
&initConfig();
# ... continue processing...

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        Does that solve your problem? I've done it this way in the past, and it has worked out well.
        Hope that helps!
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[d/l]
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Re: Configuration variables using run-time in put without -w complaints?
by Adam (Vicar) on Jun 26, 2000 at 23:58 UTC
    When you say the $user is defined at run-time, I assume you mean before you get to these lines. So that would (theoretically) mean that you shouldn't be getting the undef warning. Prove this to yourself using a more defensive programming style. Ie
    if( defined $log_dir and exists $user_data{site} )
{
    $transfer_log = eval { "$log_dir/$user_data{site}->[0]-access_log"
+ };
}
else { print STDERR "log_dir was undef or site wasn't in user_data\n";
+ }

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    My guess is that the vars arn't really defined. Maybe you have them in a loop or something where the last case gets run with undefs.
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[d/l]

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