How to print a field of a struct - c

Question

I'm trying to print a struct's field in C, and I have troubles with it.
I'm having 2 problems.
First, when I'm trying to print the field "courseName" of a course named "math" I get: "(null)math══════════════════════════"
Second, when I try to print the field courseNumber, it prints the courseNumber and the courseName.
can someone please tell me what I'm doing wrong?
struct Course {
char courseNumber[6];
char courseName[30];
struct Course* next;
};
struct Course* updateCoursesList(char courseDetails[], struct Course* coursesList)
{
struct Course* head = NULL;
int i = 6, j = 0;
if (coursesList == NULL) {
coursesList = (struct Course*)malloc(sizeof(struct Course));
if (coursesList == NULL)
return NULL;
head = coursesList;
strncpy(coursesList->courseNumber, courseDetails, 5);
coursesList->next = NULL;
while (courseDetails[i] != '\n') {
coursesList->courseName[j] = courseDetails[i];
i++;
j++;
}
}
else {
head = coursesList;
if (strncmp(courseDetails, coursesList->courseNumber, 5) == 0) {
while (courseDetails[i] != '\n') {
coursesList->courseName[j] = courseDetails[i];
i++;
j++;
}
return head;
}
while (coursesList->next != NULL) {
if (strncmp(courseDetails, coursesList->courseNumber, 5) == 0) {
while (courseDetails[i] != '\n') {
coursesList->courseName[j] = courseDetails[i];
i++;
j++;
}
return head;
}
else
coursesList = coursesList->next;
}
coursesList->next = (struct Course*)malloc(sizeof(struct Course));
if (coursesList->next == NULL)
return head;
strncpy(coursesList->next->courseNumber, courseDetails, 5);
coursesList->next->next = NULL;
while (courseDetails[i] != '\n') {
coursesList->next->courseName[j] = courseDetails[i];
i++;
j++;
}
}
return head;
}
int main()
{
struct Course* coursesList = NULL;
char array[30] = "12345 math\n";
coursesList = updateCoursesList(array, coursesList);
printf("%s", coursesList->courseNumber);
printf("%s", coursesList->courseName);
}

Answer 1

You can actually use strncpy for copying both your courseNumber and courseName because both are strings.
strncpy does not terminate the copied string with \0 terminator, so we have add the \0 at the end.
For your input char array[30] = "12345 math\n"; do as follows.
strncpy(coursesList->courseNumber, courseDetails, 5);
coursesList->courseNumber[5] = '\0';
//since your courseName is also string, you need not do piece by piece copy
strncpy(coursesList->courseName, courseDetails+6, 5);
coursesList->courseName[5] = '\0';
and below code is not required in both of your if and else parts
while (courseDetails[i] != '\n')
{
coursesList->courseName[j] = courseDetails[i];
i++;
j++;
}
NOTE: But this very weird way of reading your inputs , instead take inputs from stdin and use them, because the lengths may not be same for all courses.