Playing with Signals in Ruby

What?

Signal trapping and processing in Ruby - it's way easy.

Why?

Signals are very useful, e.g. to detect shutdown and let your program clean up after itself.

How?

Here's a quickie that'll get you started playing.

# Let's see which signals we can trap
{
  "ABRT"=>6, "ALRM"=>14, "BUS"=>7, 
  "CHLD"=>17, "CLD"=>17, "CONT"=>18, 
  "FPE"=>8, "HUP"=>1, "ILL"=>4, 
  "INT"=>2, "IO"=>29, "IOT"=>6, 
  "KILL"=>9, "PIPE"=>13, "PROF"=>27, 
  "QUIT"=>3, "SEGV"=>11, "STOP"=>19, 
  "SYS"=>31, "TERM"=>15, "TRAP"=>5, 
  "TSTP"=>20, "TTIN"=>21, "TTOU"=>22, 
  "URG"=>23, "USR1"=>10, "USR2"=>12, 
  "WINCH"=>28, "XCPU"=>24, "XFSZ"=>25
}.each do |signal,num|
  puts "Set up trap for #{signal} #{num}"
  trap signal do
    puts "#{signal} #{num} was trapped"
  end 
end

# Sleep away and lets press some buttons. Try for example ctr-c
sleep 100

Also check out:

at_exit do
  puts "I'm quitting now!"
end

Very useful!