shell scrip question

[weixin_38087180]

Hi guys,

How can I change the format of number less than 10 to be 2 digits by adding "0" ahead of it?  I mean by shell script.

Say I have a file a.txt with below contents
a-1.7.3
bc.2.3.11
cde_3.12.9.20

How can I get b.txt with contents like below

a-01.07.03              
bc.02.03.11        
cde_03.12.09.20   



The number can be quoted with period ".". dash "-" or underscire "_"