/in/fileReverse.c: In function 'main':
/in/fileReverse.c:12:22: error: 'x' undeclared (first use in this function)
     FILE* fp = fopen(x, "a+");
                      ^
/in/fileReverse.c:12:22: note: each undeclared identifier is reported only once for each function it appears in
/in/fileReverse.c:12:11: error: unused variable 'fp' [-Werror=unused-variable]
     FILE* fp = fopen(x, "a+");
           ^~
/in/fileReverse.c:9:14: error: unused parameter 'argc' [-Werror=unused-parameter]
 int main(int argc, char *argv[]){
              ^~~~
/in/fileReverse.c:9:26: error: unused parameter 'argv' [-Werror=unused-parameter]
 int main(int argc, char *argv[]){
                          ^~~~
cc1: all warnings being treated as errors