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

Here's what I did for a script where I'm asking for a day, range of days, regex, etc. with a default to the improved regexes shared by paxdiablo.

for day in $days
    do if [ 1 -eq "${#day}"] ; then
        day="0$day"
    fi

I just run through this at the beginning of my loop where I run a bunch of log analysis on the day in question, buried in directories with leading zeroes.