Ok here's the bass intro for "I Walk the Line".

G|--------------------------------------|
D|-------------------0-1---1-1-0------3-|
A|-----0-1----1-1-3------1-------3-1----|
E|-1-3-----1----------------------------|
 
G|-----------------------------------------------------|
D|-----------------------------------------------------|
A|-1-1-0------3-3---------3---3-1--0-----3---3---3---3-|
E|--------3-1------1-3-1----3--------3-1---1---1---1---|