for loop only printing last item (C) - c

Question

Hello I am trying to write a C program that basically takes in a structure, stores it in an array, and then prints that structure in this format:
Lastname, Firstname \n
Grade: B
for every item added into the array, now the problem I am having is only the last item that is added is being printed. I know this is happening in the for loop because the code is executing and printing. I am not going to post the entire program because it is a lot of code so I will just put what is important.
void add(char* student_firstname, char* student_lastname, char* student_grade, char* student_level, struct student* list)
{
int i;
for (i = count-1; i < count; i++){
if ((strcmp(list[i].lastName, student_lastname) != 0) && (strcmp(list[i].firstName, student_firstname) != 0)){
strcpy(list[i].firstName, student_firstname);
strcpy(list[i].lastName, student_lastname);
strcpy(list[i].grade, student_grade);
}
else{
printf("This student is already on the list!");
}
//count++;
}
printf("Student added!");
}
The count variable was set to 0 before.
*don't worry about the student_grade
display() function for reference:
void display()
{
int i;
for (i = count-1; i < count; i++){
printf("%s, %s \n", list[i].lastName, list[i].firstName);
printf("Grade: %s \n", list[i].grade);
}
}
Also here is my read() function:
void read()
{
char student_firstName[100];
char student_lastName[100];
char student_grade[30];
char student_level[100];
printf("\nEnter the student's first name:\n");
fgets(student_firstName, sizeof(student_firstName), stdin);
printf("\nEnter the student's last name:\n");
fgets(student_lastName, sizeof(student_lastName), stdin);
printf("\nEnter the student's grade (A+,A,A-,...):\n");
fgets(student_grade, sizeof(student_grade), stdin);
printf("\nEnter the student's education level (f/so/j/s):\n");
fgets(student_level, sizeof(student_level), stdin);
// discard '\n' chars attached to input; NOTE: If you are using GCC, you may need to comment out these 4 lines
student_firstName[strlen(student_firstName) - 1] = '\0';
student_lastName[strlen(student_lastName) - 1] = '\0';
student_grade[strlen(student_grade) - 1] = '\0';
student_level[strlen(student_level) - 1] = '\0';
add(student_firstName, student_lastName, student_grade, student_level, list);
printf("\n"); // newline for formatting
}

Answer 1

Look at the line:
for (i = count-1; i < count; i++)
in both your add and display functions. This goes from count-1 to count, meaning it only ever prints/adds one item at position count-1. You should get rid of the for loop in the add function, increment count, and rewrite the print function to go from 0 to count. This should fix all of the issues you are having.

Answer 2

Your algo for checking for duplicates in add is broken. I need to look more like this, but you should add error checking and protection for bufferoverflow as well.
void add(char* student_firstname, char* student_lastname, char* student_grade, char* student_level, struct student* list)
{
for (int i = 0; i < count; i++){
if ((strcmp(list[i].lastName, student_lastname) == 0) &&
(strcmp(list[i].firstName, student_firstname) == 0)) {
printf("This student is already on the list!");
return;
}
}
strcpy(list[count].firstName, student_firstname);
strcpy(list[count].lastName, student_lastname);
strcpy(list[count].grade, student_grade);
count++;
printf("Student added!");
}
First you need to add protection from that count does not get too big.
Second you need to stop using strcpy and use strncpy instead so as to avoid buffer overflow errors.
Third, you may want to avoid using a linear scan, and figure out how to use a index of some kind, but for a school project that is probably not important.
Similar in your display function, you should adjust the for loop if you expect it to print out all the records, or eliminate the loop if it is only supposed to print the last record.