Break statement doesn't work in loop (gcc) - c

Question

I'm sorta having a problem with my code. The function will not terminate and it keeps looping forever. I'm kinda new when it comes to compiling C in Linux (I came from Dev-C++..)
Here's the code:
#include<stdio.h>
#include<string.h>
#include<stdlib.h>
#define MAX 10
struct student{
char lname[20];
char fname[20];
int idnum[8];
int year;
};
struct course{
char cname[4];
struct student stud[MAX];
};
int main()
{
struct course c[0];
userSelect(&c);
return 0;
}
int userSelect(struct course *p_course)
{
int z=0, x;
printf("1 - Create course\n2 - Edit course\n3 - Add student(s)\n4 - Edit student data\n5 - Delete\n6 - Quit");
scanf("\n%d", &x);
while(z==0){
switch(x){
ccase 1: userCreateCourse(p_course);
break;
//case 2: userEditCourse(&c);
//break;
//case 3: userCreateStudents(&c);
//break;
//case 4: userEditStudents(&c);
//break;
case 6: printf("bye");
z++;
break;
default: printf("Invalid input");
break;
}
}
}
int userCreateCourse(struct course *p_course)
{
int *cnum=0, i;
cnum=(int *)malloc(sizeof(int));
cnum++;
printf("Enter course (ex: BSCS): ");
fgets(p_course[*cnum-1].cname, sizeof(p_course[*cnum-1]), stdin);
puts(p_course[*cnum-1].cname);
}
If I select 1, this is the output:
1 - Create course
2 - Edit course
3 - Add student(s)
4 - Edit student data
5 - Delete
6 - Quit1
Enter course (ex: BSCS): H��4k
Enter course (ex: BSCS): AAAA
AAAA
Enter course (ex: BSCS): AAAA
AAAA
Enter course (ex: BSCS):
and it keeps doing that endlessly until I close the terminal. I really don't know what's wrong.. Someone help :(

Answer 1

You need to read x inside the loop. What happens is that x remains the same value that you inputted the very first time. So case 1: is always executed.
You can use a do-while loop like:
do{
printf("1 - Create course\n2 - Edit course\n3 - Add student(s)\n4 - Edit student data\n5 - Delete\n6 - Quit\n");
scanf("\n%d", &x);
switch(x){
case 1: userCreateCourse(p_course);break;
//case 2: userEditCourse(&c);break;
//case 3: userCreateStudents(&c);break;
//case 4: userEditStudents(&c);break;
case 6: printf("bye");z++;break;
default: printf("Invalid input");break;
}
} while( z==0);
But remember there are a number of issues with the scanf() + fgets() approach.
The scanf() that reads x will leave a newline in the input buffer and fgets() will return immediately without reading input (due to \n).
You can handle this by discarding any input chars left in the input with:
.
int c;
while((c=getchar()) != '\n' && c!=EOF);
(just before fgets() call).
If you input non-numbers input for x, then you'll end up with an infinite loop since scanf() doesn't ignore invalid input(s). You should check the scanf() return value and discard (using getchar() as above) all input chars if it failed.

Answer 2

You should ask for a new x inside the while loop if you want to be able to input a new one. Otherwise the first x will be used time and again since you never exit the loop.

Answer 3

Well it does breaks but it comes back again in your loop since z == 0 remains true. It breaks out of your switch case, not out of your loop. At the end of the switch you should change the value of z for something different than 0 like :
while(z==0){
switch(x){
case 1: userCreateCourse(p_course);break;
//case 2: userEditCourse(&c);break;
//case 3: userCreateStudents(&c);break;
//case 4: userEditStudents(&c);break;
case 6: printf("bye");z++;break;
default: printf("Invalid input");break;
}
z = 1;
}
It'd be best for you to use a boolean like
boolean done = false;
while(!done){
switch(smth){
// do smth
}
done = true
}