Simple example of using data from a YAML configuration file in a Perl script

Question

I need to create a YAML file to store some configuration data for a Perl script. This seems like it should be really easy but I haven't been able to work it out, I think if I had just one simple example to copy I'd be fine. I want to do something like this:

-----test.yaml-----
image_width: 500
show_values: 0
-------------------

------test.perl------
use YAML;

my (%settings) = Load('test.yaml');
print "The image width is", $settings{image_width};
---------------------

Answer 1

Try this:

#!/usr/bin/perl

use strict;
use warnings;
use 5.010;

use YAML qw(LoadFile);

my $settings = LoadFile('test.yaml');
say "The image width is ", $settings->{image_width};

– Michael

Answer 2

Your fundamental problem here is that Load expects a string containing YAML, not a filename. You wanted LoadFile instead (which is not exported by default). Also, you should use YAML::XS instead of YAML if you can, as it's a better implementation. (But YAML should be adequate for a simple config file.)

The other problem is that LoadFile will return a hash reference (well, if your YAML looks like a hash, as yours does), not a list you can use to initialize a hash.

Try this:

use strict;
use warnings;
use YAML::XS qw(LoadFile);

my $settings = LoadFile('test.yaml');

print "The image width is ", $settings->{image_width};

(You can delete the ::XS if you don't want to (or can't) install YAML::XS. The program will work with no other changes.)

Answer 3

Try dumping out the configuration you want.

use strict;
use warnings;

use YAML;

my %settings = (
        foo => 1,
        bar => [qw/one two three/],
);

print Dump(\%settings);

This prints

---
bar:
  - one
  - two
  - three
foo: 1

Also, wikipedia has a good overview of YAML if the specification is a bit too dense.