Splitting a comma separated string into individual rows

Today I got the problem that I my data looks like this:

col1 col2 col3
A B a,b,c
C D c,d,e

but I wanted to have something like that:

col1 col2 col3
A B a
A B b
A B c
C D c
C D d
C D e

Using awk was the fastest solution for me:

cat file.in | awk -F "\t" '{n=split($3,s,";"); for(i=1;i<=n;i++) {$3=s[i];print}}' >> file.out

Written by: Heider