From: dblack@...
Date: 2002-10-22T11:34:02+09:00
Subject: Re: What I did (was Re: functional Ruby equiv to this perl snippet)

Hi --

On Tue, 22 Oct 2002, Bob X wrote:

> Here is what I did...with your help and looking through different ways to
> handle stuff.
>
> # get the servers out of the file
> def load_server_list
>   servers = []
>   filename = 'serverlist.txt'
>   if FileTest.exist?(filename)
>     File.open(filename).each do |line|

Just to point out that you're introducing a wee race condition,
because it's possible for the file to be deleted (by another process)
between the exist? test and the open.  This may not be a practical
consideration in this case, but it's probably not a good construct to
use in general.

>       next unless line =~ /^\S+$/

That's going to reject every line that has whitespace in it (not
counting the final \n); for example, both of these lines will be
rejected:

some_server_name   # this line will be rejected
  another_server_name

>       next if line =~ /^#.*$/

The .*$ part is superfluous -- it will always match if ^# matches :-)

Here's a version that (I think) rejects comment lines and blank lines,
strips trailing comments, and returns the first non-space-containing
string it finds on a line.  (You can wrap it in filetests if you wish
:-)

  def load_server_list
    filename = 'serverlist.txt'
    File.open(filename).map do |line|
      Regexp.last_match[1] if /^\s*([^#\s]+)/.match(line)
    end .compact
  end

On the exception vs. filetest matter: remember that to handle an
exception you don't have to write it into the method.  For example,
when you call the method you can do:

  begin
    load_server_list
  rescue => e
    puts "Something went wrong: #{e}"
  end

(I mention this because I think you said something before about not
wanting to write an exception handler directly in the method
definition.)


David

-- 
David Alan Black
home: dblack@candle.superlink.net
work: blackdav@shu.edu
Web:  http://pirate.shu.edu/~blackdav