Adding a zero to single digit variable

Question

Trying to add a zero before the varaible if it\'s less than 10 and create said directory. I can\'t seem to get the zero to add correctly. Keeps resulting in making 02.1.20

Answer 1

path=/tmp
ruby -rfileutils -e '1.upto(31){|x| FileUtils.mkdir "'$path'/02.%02d.2011" % x}'