This post originated from an RSS feed registered with Ruby Buzz by Andrew Johnson. Original Post: Use the DATA handle Feed Title: Simple things ... Feed URL: http://www.siaris.net/index.cgi/index.rss Feed Description: On programming, problem solving, and communication. Latest Ruby Buzz Posts Latest Ruby Buzz Posts by Andrew Johnson Latest Posts From Simple things ...

One thing I recommend to newcomers to both Perl and Ruby is to make use of the DATA file(handle/object) for explorative purposes. It is quite useful both in the contexts of language exploration and solution-space exploration.

The basic idea is that within your Perl or Ruby script, any text after the special __END__ token is available to be read into the program via a preopened filehandle/object named DATA (in both languages). In Perl, the token may also be called __DATA__.

Here’s a simple example (Perl and Ruby side by side):

  #!/usr/bin/perl -w                        #!/usr/bin/ruby -w
  use strict;
  while (my $line = <DATA>) {               while line = DATA.gets
    my @arr = split /:/, $line;                arr = line.split(/:/)
    print join '|', @arr;                      print arr.join('|')
  }                                         end
  __END__                                   __END__
  abc:def:ghi                               abc:def:ghi
  123:456:789                               123:456:789

Note: the __END__ token must be flush with the left margin in Ruby code.

There are many ways this can be usefully used, but for my exploratory purposes it is only half of the equation. The other half is your text editor (or perhaps IDE). Many text editors can be configured to run the text (or some selected portion thereof) of the current buffer through an external program (usually as a filter). If you are writing Perl or Ruby code, that external ‘filter’ can be the Perl or Ruby interpreter, and you can arrange for the output to be displayed in another window (pane, buffer, whatever).

For example, I have the following in my .vimrc file:

  noremap <F9> :w !perl -w > ~/.vim/p_buff 2>&1 <NL> :sv ~/.vim/p_buff<CR>
  noremap <F10> :w !ruby -w > ~/.vim/r_buff 2>&1 <NL> :sv ~/.vim/r_buff<CR>

Now hitting the F9 or F10 key sends the selected text to the interpreter, captures the output into a special file, and opens that file in a new buffer window. Both Ruby and Perl can recieve scripts via STDIN, and both leave everything following the __END__ token to be read via the DATA handle.

This means I can have a buffer window open to play around with a new language element or feature, or to explore possible solutions to a problem. And if that problem requires some data reading/munging/parsing, I can paste in some representative lines of data and have one-key convenience for trying out various snippets of code.

__END_

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