/in/ex6.c:8:16: error: redefinition of 'struct book'
 typedef struct book {
                ^~~~
In file included from /in/ex6.c:7:0:
/in/compile/ex6.h:1:16: note: originally defined here
 typedef struct book {
                ^~~~
/in/ex6.c:12:3: error: conflicting types for 'book'
 } book;
   ^~~~
In file included from /in/ex6.c:7:0:
/in/compile/ex6.h:5:2: note: previous declaration of 'book' was here
 }book;
  ^~~~
/in/ex6.c: In function 'findBook':
/in/ex6.c:25:12: error: expected expression before ')' token
     while () {}
            ^
/in/ex6.c:17:11: error: unused variable 'pPrev' [-Werror=unused-variable]
     book* pPrev = NULL;
           ^~~~~
/in/ex6.c: In function 'removeBook':
/in/ex6.c:28:24: error: unused parameter 'head' [-Werror=unused-parameter]
 book *removeBook(book *head, int number)
                        ^~~~
/in/ex6.c:28:34: error: unused parameter 'number' [-Werror=unused-parameter]
 book *removeBook(book *head, int number)
                                  ^~~~~~
/in/ex6.c: In function 'findBook':
/in/ex6.c:26:1: error: control reaches end of non-void function [-Werror=return-type]
 }
 ^
/in/ex6.c: In function 'removeBook':
/in/ex6.c:32:1: error: control reaches end of non-void function [-Werror=return-type]
 }
 ^
cc1: all warnings being treated as errors