Howto parse or eval a config-file?

Ruby
1

I’m currently looking for a simple way to parse a configuration file
in a ruby-script. Is eval a good way to do that? YAML seems a bit an
overkill to learn for such a small task…

Thanks in advance for any suggestions.

So far I’m doing this:

the config-file:

Conf = {
‘host’ => ‘localhost’,
‘title’ => ‘TIITEL’,
‘mailhost’ => ‘mailhost’
}

the eval-code:

begin
eval File.new(configFile).read
rescue ScriptError=>e
warn("An error occurred while reading #{$configFile}: ", e)
else
$host = Conf[‘host’]
$title = Conf[‘title’]
$mailhost = Conf[‘mailhost’]
end

2

On Jan 30, 2007, at 1:30 PM, ChrisKaelin wrote:

I’m currently looking for a simple way to parse a configuration file
in a ruby-script. Is eval a good way to do that? YAML seems a bit an
overkill to learn for such a small task…

YAML is pretty darn simple. You be the judge…

the config-file:

Conf = {
‘host’ => ‘localhost’,
‘title’ => ‘TIITEL’,
‘mailhost’ => ‘mailhost’
}

The equivalent YAML:

host: localhost
title: TIITEL
mailhost: mailhost

end
And loading code:

conf = File.open(“path/to/conf.yaml”) { |f| YAML.load(f) }

James Edward G. II

3

On 1/30/07, ChrisKaelin [email protected] wrote:

Conf = {
warn("An error occurred while reading #{$configFile}: ", e)
else
$host = Conf[‘host’]
$title = Conf[‘title’]
$mailhost = Conf[‘mailhost’]
end

Try using load instead …

begin
load $configFile
resuce Exception => e
warn("An error occurred while reading #{$configFile}: ", e)
end

And just use the configuration hash directly instead of creating lots
of global variables – i.e. change Conf = { in your config file to
$conf = { That way all your classes can just grab what they need
straight from $conf.

Beware of naming collisions in the global variable namespace. Someone
else might think $conf is a great place to store their configuration
items, too.

Blessings,
TwP

4

On 1/30/07, James Edward G. II [email protected] wrote:

Conf = {
mailhost: mailhost
$mailhost = Conf[‘mailhost’]
end

And loading code:

conf = File.open(“path/to/conf.yaml”) { |f| YAML.load(f) }

conf = YAML.load_file(“path/to/conf.yaml”)

TwP

5

On 1/30/07, Luke I. [email protected] wrote:

Upon some thinking, YAML would be a safer option. Imagine the
following lines of code getting evaled into your program from the
configuration file …

require ‘fileutils’
FileUtils.rm_r( ‘/’, :force => true)

And that would be a bummer for anyone :frowning:

Never trust the user! Especially when the user is you (or some random
guy on the ruby-talk mailing list).

As James and Luke have said, YAML is straightforward enough to learn.
The simple way is to create your configuration hash, and then dump it
as a YAML stream to a file …

conf = {
‘host’ => ‘localhost’,
‘title’ => ‘Title’,
‘mailhost’ => ‘mailhost’
}

File.open(“path/to/conf.yaml”,“w”) {|fd| fd.write(YAML.dump(conf))}

And there is your configuration file :slight_smile:

Blessings,
TwP

6

On Wed, 31 Jan 2007 04:30:06 +0900
“ChrisKaelin” [email protected] wrote:

Conf = {
‘host’ => ‘localhost’,
‘title’ => ‘TIITEL’,
‘mailhost’ => ‘mailhost’
}

Can you change the structure of your config file?
If you can, I would suggest writing the config file in yaml and using
Ruby’s built-in YAML stuff like so:

config-file:
Conf:
host: localhost
title: TIITEL
mailhost: mailhost

the ruby
yaml_hash = File.open( ‘config.yml’ ) { |file| YAML::load(file) }
yaml_hash # {“Conf” => { “host” => “localhost”, “title” => “TIITEL”,
“mailhost” => “mailhost” }}

7

Thanks a lot for all your suggestions, what a nice community! I
appreciate that very much, as I’m still learning ruby. I admit YAML
really seems very easy in the first example. My assumption, that YAML
is complicated came from the official documentation, which had no such
easy examples.

I will try all of your propositions.

Greetings

Chris