[Raleigh-talk] Issues after converting bash to Perl - way to call a config file that contains if/then logic

[Mike South]

On Mon, Feb 21, 2011 at 10:21 PM, John Ricker <sephtin at gmail.com> wrote:

> Just having converted a bash script to Perl, ran across a couple issues,
> and thought maybe sending to the list might obtain a nudge in the right
> direction.. :)
>
> The issue I'm currently trying to tackle is pulling in config info.
> I have a config information I want to include, but it's dependent on a
> variable(s) set in my script.  In bash, I'd just source the file, and it'd
> go through the if statements, and all is well.  In Perl, I can't seem to
> tackle it...
>
> Example:
> #main.pl
> if (stuff) {
>     $varsneeded = "first";
> }
> elsif (otherstuff) {
>     $varsneeded = "second";
> }
> else {
>     $varsneeded = "last";
> }
>
> <need to read in variables here>
> <then do stuff with variables>
>
> ---x---
> #configFile:
> if ($varsneeded eq "first") {
>     $var1 = "1";
>     $var2 = "2";
>     ...
> }
> elseif ($varsneeded eq "second") {
>     $var1 = "somethingelse1";
>     $var2 = "somethingelse2";
>     ...
> }
>
> You get the idea.
>
> So, I've tried:
> --use:  Did testing with use, and thought it was my answer, but
> unfortunately the directory that I need to grab the config file(s) from is
> set from a variable... which isn't defined until after compile time, so use
> doesn't seem to be an option.
> --do/require:  Can't seem to find a way to pass the $varsneeded variable
> into the config file(s) (.pl, .pm, .whatever) when using do or require.  If
> there's an example out there of this, then somehow google has not been kind
> enough to enlighten me.  :P
> --eval `config file`: variable to the config file, same issue as do/require
> attempts.
>
> Obviously I've oversimplified the example.  The script is over 1200 lines,
> so simplified for good reason.  Looking for best practice kind of thing
> here.. if more detail is needed (I expect it may come to that).. I can fill
> in a lot of blanks, just need to know what info might be helpful.
>
> More info--
> After some thought, and after re-reading my question.. thought some
> additional info might be helpful.
>
> The script is for creating custom themes.  I'm taking choices made on a php
> page that are passed to the script, and the script is pulling in variables
> based on those choices... and some other factors.. :P
> Each section is approx. 26 variables right now, and there are 19 different
> possible options with another dozen or two coming soon.
>
> MY answer to this all, is to break up the config file into a file for each
> option, and just pull in the appropriate file... But as this beast grows,
> I'd REALLY like the convenience of a find/replace in ONE file when something
> changes, instead of 50 or more!
>

I don't understand what you're saying here--do you mean that you would like
all the configuration to be in one file?

You could have one single perl data structure with all the data:

my $config={
    theme1=>{
        option1=>{
            var1=>'theme1option1var1',
            var2=>'theme1option1var2',
            var3=>'theme1option1var3',
        },
        option2=>{
            var1=>'theme1option2var1',
            var2=>'theme1option2var2',
            var3=>'theme1option2var3',
        },
    },
    theme2=>{
        option1=>{
            var1=>'theme2option1var1',
            var2=>'theme2option1var2',
            var3=>'theme2option1var3',
        },
        option2=>{
            var1=>'theme2option2var1',
            var2=>'theme2option2var2',
            var3=>'theme2option2var3',
        },
    },
};

my $theme_choice = shift;
my $option_choice = shift;
my $theme_key = 'theme'.$theme_choice;
my $option_key = 'option'.$option_choice;

my $config_to_use = $config->{$theme_key}{$option_key};

foreach my $var_name (qw/var1 var2 var3/) {
    print "var1: $config_to_use->{$var_name}\n";
}

msmbp:~ msouth$ perl glurg.pl 1 a
var1: theme1,optiona,var1
var1: theme1,optiona,var2
var1: theme1,optiona,var3
msmbp:~ msouth$ perl glurg.pl 2 b
var1: theme2,optionb,var1
var1: theme2,optionb,var2
var1: theme2,optionb,var3

That would give you one config file to edit.

If you want to do it per your original description, bash-ish-ly (I don't
recommend this), below is how (I used the environment (accessed via %ENV) to
simulate data coming in that you don't know until runtime--should have used
"shift" to make it easier).  There are some techniques (requiring a file you
didn't know the location of until runtime, sharing a variable via "our")
that might be of interest.

mike

msmbp:~ msouth$ cat bob.pl
use strict;
use warnings;

our $which_config;

our $var1;

our $which_dir = 'bob';

$which_config = 'one';
#$which_config = 'two';

my $theme_sub_dir = $ENV{theme} || die "set theme in the env like this:
theme='test' $0\n";

my $full_path_to_require = "/Users/msouth/$theme_sub_dir";
die "there is not a directory called $full_path_to_require" unless -d
$full_path_to_require;
push @INC, $full_path_to_require;;

require "$which_dir/set_up_bob.pl";

print $var1,$/;
msmbp:~ msouth$ cat bob/set_up_bob.pl
use strict;
use warnings;

our $which_config;
our $var1;

if ($which_config eq 'one') {
    $var1='the one version of var1';
}
elsif ($which_config eq 'two' ) {
    $var1='the two version of var1';
}
else {
    die "you didn't tell me which config in the 'which_config' variable, or
maybe you didn't declare it with 'our'";
}
msmbp:~ msouth$ theme=bob perl bob.pl
the one version of var1
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