在END {}中访问Ruby退出代码

Question

Ruby has BEGIN {} and END {} blocks that guarantee they run before and after the main portion of code, respectively.

I have the following code:

BEGIN {
  $my_args = ARGV.dup
  ARGV.clear
} # clean up 'gets'

# For the truly paranoid in all of us
def self.run_away?
  print "You're paranoid. Exit? (Y/n) "
  ans = gets.chomp.downcase
  if ["no", "n"].include?(ans)
    puts "Alright, your call. Let's keep going."
  else
    puts "EXITING"
    log("Exiting at paranoid users request.")
    exit 3
  end
end

END {  } # do stuff here

I have a handful of error codes that I have defined in my script. I would like to be able to read the error code and print a short description based on that code. Eg - EXITING - 3: Exit at user request instead of writing a descriptive string every time I use an exit in my code. Is there a way to do this in the END {} block? Or something else I am missing?

Edit/Note: I'm stuck with Ruby 1.8.7 and the following doesn't work: (see below)

BEGIN { puts "BEGIN block!" }

puts "Main block!"
exit 3

END {
  puts "END block!"
  puts "Current Exception: \n#{$!}"
  puts "Current Backtrace: \n#{$@}"
}

Output:

~: $ ./test.rb 
BEGIN block!
Main block!
~: $ echo $?
3
~: $

Edit #2: I had to define my END block before I exited. Thanks to @Stefan

Answer 1

Kernel#exit raises a SystemExit exception and since the global variable $! contains the current exception, you can get the exit status via $!.status :

END {
  puts "exit status: #{$!.status}"
}
exit 3

Output:

exit status: 3

From the documentation :

When an exception has been raised but not yet handled (in rescue , ensure , at_exit and END blocks) the global variable $! will contain the current exception and $@ contains the current exception's backtrace.

Answer 2

A way to centralize exit message :

module Kernel
  alias :real_exit :exit

  def exit status
    puts "Hello World"
    real_exit status
  end
end

The method is just an around alias on the Kernel#exit method . Be aware that once you will have define this override, all other exit call will go through your override.