From: Quintus <sutniuq@...>
Date: 2011-01-26T22:55:20+09:00
Subject: Re: writing on yaml file

Am 26.01.2011 05:00, schrieb Jeremy Bopp:
> On 01/25/2011 07:09 PM, Kamarulnizam Rahim wrote:
>> Hi guys,
>>
>> Is it possible for me to write on existing yaml file (i.e add contents
>> or change contents) using ruby prgramming? Is there any parser available
>> out there?
> 
> The standard library defines the YAML class which can parse and emit
> YAML documents.  There are quite a few examples out there.  I tried a
> couple from here that seemed to work:
> 
> http://yaml4r.sourceforge.net/doc/page/examples.htm
> 
> Some code to get you started:
> 
> require 'yaml'
> # Load the file.
> yaml = YAML.load_stream(File.open('myfile.yaml'))
> # Add a new key-value pair to the root of the first document.
> yaml.documents[0]['new_key'] = 'new_value'
> File.open('myfile.yaml', 'w') do |file|
>   file.write(yaml.emit)
> end
> 
> The above code assumes that you have a valid YAML file in myfile.yaml.
> the first document in that file must have key-value pairs at the root.
> 
> -Jeremy
> 
> 
You can use the YAML module more or less the same way as Marshal,
therefore the following is a bit easier I suppose. It parses the whole
YAML file and converts it into an appropriate data structure (most
likely a hash) with which you can work. Then call YAML.dump with the
modified object and the file where you want to save it in.

-------------------------------------------------
√ quintus@hades => ~
$ cat test.yml
---
a: 5
b: abcdef
√ quintus@hades => ~
$ irb
irb(main):001:0> require "yaml"
=> true
irb(main):002:0> hsh = YAML.load_file("test.yml")
=> {"a"=>5, "b"=>"abcdef"}
irb(main):003:0> hsh["c"] = 12345
=> 12345
irb(main):004:0> File.open("test.yml", "w"){|f| YAML.dump(hsh, f)}
=> #<File:test.yml (closed)>
irb(main):005:0> exit
√ quintus@hades => ~
$ cat test.yml
---
a: 5
b: abcdef
c: 12345
√ quintus@hades => ~
$
-------------------------------------------------

Vale,
Marvin