format compact duration as days, hours, minutes, seconds e.g. 3d23h10s

format_compact_duration.rb

# seconds = duration in seconds as integer i.e. time.to_i
[
 seconds / (60*60*24), # days
 seconds % (60*60*24) / (60*60), # hours
 seconds % (60*60) / 60, # minutes
 seconds % 60 # seconds
].zip(%w(d h m s)).map { |u| u.join unless u.first.zero? }.compact.tap { |a| a << '<1s' if a.none? }.join
# Uses Object#tap rather than Rails Object enhancements like Object#presence