/in/ex6.c: In function 'findBook':
/in/ex6.c:14:22: error: unused parameter 'head' [-Werror=unused-parameter]
 book *findBook(book *head, int number) {
                      ^~~~
/in/ex6.c:14:32: error: unused parameter 'number' [-Werror=unused-parameter]
 book *findBook(book *head, int number) {
                                ^~~~~~
/in/ex6.c:15:1: error: control reaches end of non-void function [-Werror=return-type]
 }
 ^
cc1: all warnings being treated as errors