У вас есть строки в функции:
#!/bin/bash
clientOne(){
## client1 specific lines
echo "one"
}
clientTwo(){
## client2 specific lines
echo "two"
}
case "$1" in
"client1")
clientOne
;;
"client2")
clientTwo
;;
*)
echo "Wrong option" >&2
;;
esac
## Common lines
echo foo