Question

I have this program:

5.times do |i|
  puts "Iteration #{i}"
  system("sleep 3")
end

I want to exit this program after, say 2 iterations, usin Ctrl-C

If I hit Ctrl-C, this happens:

➜  tmp  ruby system.rb 
Iteration 0
^CIteration 1
^CIteration 2
^CIteration 3
^CIteration 4
^C%

The system() command is run 5 times, no matter what.

What can I do so that I’m able to quit the execution using Ctrl-C?

Answer 1

Kernel#system executes a given command in a sub-shell. Which means that Ctrl-C is going to that subshell and not your ruby script, so there’s no use trapping it there. However, the command returns a value which indicates, whether it was completed successfully or not. When the command is stopped via Ctrl-C, it won’t count as a successful completion. So, check the return value.

5.times do |i|
  puts "Iteration #{i}"
  success = system("sleep 3")
  break unless success
end