From: Dave Thomas <Dave@...>
Date: 2001-08-08T07:28:43+09:00
Subject: [ruby-talk:19314] Re: how to "die" in Ruby

markus jais <info@mjais.de> writes:

> hi,
> in Perl I can write
> open(FH, "/root/.bashrc") or die "error opening file: $!";
> 
> my ruby solution looks like this:
> 
> begin
> 	f = File.new("/root/.bashrc") 
> 	f.each { |line|
> 		print line if line =~ /blue/
> 	}
> rescue Errno::ENOENT
> 	print "no such file or directory\n"
> rescue Errno::EACCES
> 	print "permission denied\n"
> end

I think I'd be tempted to restructure just slightly to make the error
handling reusable. Perhaps something like

     def file_error(ex)
       case ex
       when Errno::ENOENT then puts "No such file or directory"
       when Errno::EACCES then puts "Permission denied"
       else puts $!
       end
     end

     File.open(ARGV[0]) do |file|
       file.each do |line|
         print line if line =~ /blue/
       end
     end rescue file_error($!) 

Then, for this particular example, I'd use the fact the File is
enumerable (heh - twice in two days :)


   puts File.open(ARGV[0]).grep(/blue/) rescue file_error($!) 


Of course, to answer your original question, in Ruby you could write

> open(FH, "/root/.bashrc") or die "error opening file: $!";

as

  f = File.open("/root/.bashrc") rescue raise "Error opening file: $!"

Or you could just leave of the rescue clause altogether and let the
error propagate up naturally.



Regards


Dave