Name and lastname search functions won't work. Why? [closed] - c

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I made a function as my project and name search/lastname search functions are not working and giving a runtime error. I can't really see the mistake. So what's wrong it?
Also ID and Mark search system has some bugs with them, whenever you search for an ID it also brings mark = 0, also if you search for Mark, it will bring ID = 0.
Full code:
#include<stdio.h>
#include<string.h>
#include<stdlib.h>
struct Student
{
long long int id;
char firstname[20];
char lastname[20];
int mark;
} student;
void
storeRecord()
{
FILE *fp;
printf("\nEnter Student Details:\n\nID number: ");
scanf_s("%lld",&student.id);
printf("\nName:");
scanf_s("%19s",student.firstname);
printf("\nSurname:");
scanf_s("%19s",student.lastname);
printf("\nMark(0 - 100 integer) : ");
scanf_s("%d",&student.mark);
fp = fopen("studentfile.txt","a+"); /* check if the file was opened */
if (fp == NULL)
return;
fprintf(fp, "\n%lld\t%s\t%s\t%d\t",
student.id,
student.firstname,
student.lastname,
student.mark);
fclose(fp);
printf("A student record has been added successfully...\n");
getchar();
}
int
compareStudentsById(struct Student lhs, struct Student rhs)
{
return (lhs.id == rhs.id);
}
int
compareStudentsByName(struct Student lhs, struct Student rhs)
{
return (strcmp(lhs.firstname, rhs.firstname) == 0);
}
int
compareStudentsByLastame(struct Student lhs, struct Student rhs)
{
return (strcmp(lhs.lastname, rhs.lastname) == 0);
}
int
compareStudentsByMark(struct Student lhs, struct Student rhs)
{
return (lhs.mark == rhs.mark);
}
void
printStudent()
{
printf("\nThe record is found.\n");
printf("\nID: %lld\nName: %s\nSurname: %s\nMark: %d \n",
student.id,
student.firstname,
student.lastname,
student.mark
);
}
void
searchStudent(int(*compare)(struct Student,struct Student), const char *const name, const char *const lastname, long long int id, int mark)
{
FILE *fp;
int found;
int matches;
if (name != NULL)
printf("Searching record with Name = %s.\n", name);
if (lastname != NULL)
printf("Searching record with Surname = %s.\n", lastname);
if (id != -1)
printf("Searching record with ID = %lld.\n", id);
if (mark != -1)
printf("Searching record with Mark = %d.\n", mark);
found = 0;
fp = fopen("studentfile.txt", "r");
if (fp == NULL)
{
printf("IO error\n");
return;
}
do
{
struct Student other;
if (name != NULL)
strcpy(other.firstname, name);
if (lastname != NULL)
strcpy(other.lastname, lastname);
other.id = id;
other.mark = mark;
matches = fscanf(fp,"\n%lld\t%s\t%s\t%d\t",
&student.id,
student.firstname,
student.lastname,
&student.mark);
if (matches == 4)
found = (compare(student, other) != 0);
} while ((matches == 4) && (found == 0));
if (found != 0)
printStudent();
else
printf("Not found...\n");
getchar();
}
void
searchStudentByName()
{
char studentname[20];
printf("\nEnter student first name: ");
scanf_s("%19s", studentname);
searchStudent(compareStudentsByName, studentname, NULL, NULL, NULL);
}
void
searchStudentById()
{
long long int id;
printf("\nEnter ID: ");
scanf_s("%lld", &id);
searchStudent(compareStudentsById, NULL, NULL, id, NULL);
}
void
searchStudentByLastname()
{
char studentlastname[20];
printf("\nEnter student surname: ");
scanf_s("%19s", &studentlastname);
searchStudent(compareStudentsByLastame, NULL, studentlastname, NULL, -1);
}
searchStudentByMark()
{
int mark;
printf("\nEnter Mark: ");
scanf_s("%d", &mark);
searchStudent(compareStudentsByMark, NULL, NULL, NULL, mark);
}
int main()
{
int choice;
choice = 0;
while (choice != 5)
{
printf("\n\tC PROGRAM OF STUDENT DATABASE SYSTEM");
printf("\n1 -> Store a new record in database\n");
printf("2 -> Search a student record by Student First Name\n");
printf("3 -> Search a student record by ID\n");
printf("4 -> Search a student record by Surname\n");
printf("5 -> Search a student record by Mark\n");
printf("6 -> Quit Student Database");
printf("\n\n");
printf("Enter your choice : ");
scanf_s("%d",&choice);
switch(choice)
{
case 1:
storeRecord();
break;
case 2:
searchStudentByName();
break;
case 3:
searchStudentById();
break;
case 4:
searchStudentByLastname();
break;
case 5:
searchStudentByMark();
break;
}
}
getch();
return 0;
}

Answer 1

If you had compiled this code with warnings switched on (as everyone should do) and fixed the warnings, then this (amended) program would have mostly worked. Search by Mark works but ends the program. I'll leave that as something for you to fix.
void
printStudent()
{
printf("\nThe record is found.\n");
printf("\nID: %lld\nName: %s\nSurname: %s\nMark: %d \n",
student.id,
student.firstname,
student.lastname,
student.mark
);
}
void
searchStudent(int(*compare)(struct Student,struct Student), const char *const name, const char *const lastname, long long int id, int mark)
{
FILE *fp;
int found;
int matches;
if (name != 0)
printf("Searching record with Name = %s.\n", name);
if (lastname != 0)
printf("Searching record with Surname = %s.\n", lastname);
if (id != -1)
printf("Searching record with ID = %lld.\n", id);
if (mark != -1)
printf("Searching record with Mark = %d.\n", mark);
found = 0;
fp = fopen("studentfile.txt", "r");
if (fp == 0)
{
printf("IO error\n");
return;
}
do
{
struct Student other;
if (name != NULL)
strcpy(other.firstname, name);
if (lastname != NULL)
strcpy(other.lastname, lastname);
other.id = id;
other.mark = mark;
matches = fscanf(fp,"\n%lld\t%s\t%s\t%d\t",
&student.id,
student.firstname,
student.lastname,
&student.mark);
if (matches == 4)
found = (compare(student, other) != 0);
} while ((matches == 4) && (found == 0));
if (found != 0)
printStudent();
else
printf("Not found...\n");
getchar();
}
void
searchStudentByName()
{
char studentname[20];
printf("\nEnter student first name: ");
scanf("%19s", studentname);
searchStudent(compareStudentsByName, studentname, 0, 0, 0);
}
void
searchStudentById()
{
long long int id;
printf("\nEnter ID: ");
scanf("%lld", &id);
searchStudent(compareStudentsById, 0, 0, id, 0);
}
void
searchStudentByLastname()
{
char studentlastname[20];
printf("\nEnter student surname: ");
scanf("%19s", studentlastname);
searchStudent(compareStudentsByLastame, 0, studentlastname, 0, -1);
}
searchStudentByMark()
{
int mark;
printf("\nEnter Mark: ");
scanf("%d", &mark);
searchStudent(compareStudentsByMark, 0, 0, 0, mark);
}
int main()
{
int choice;
choice = 0;
while (choice != 5)
{
printf("\n\tC PROGRAM OF STUDENT DATABASE SYSTEM");
printf("\n1 -> Store a new record in database\n");
printf("2 -> Search a student record by Student First Name\n");
printf("3 -> Search a student record by ID\n");
printf("4 -> Search a student record by Surname\n");
printf("5 -> Search a student record by Mark\n");
printf("6 -> Quit Student Database");
printf("\n\n");
printf("Enter your choice : ");
scanf("%d",&choice);
switch(choice)
{
case 1:
storeRecord();
break;
case 2:
searchStudentByName();
break;
case 3:
searchStudentById();
break;
case 4:
searchStudentByLastname();
break;
case 5:
searchStudentByMark();
break;
case 6:
goto lend;
}
}
lend:;
return 0;
}
Hint: add a default clause with error message to the switch(choice) and change the if (choice != 5) to a better test.

Answer 2

Multiple usages of scanning a string like scanf_s("%19s", ...); are incorrect.
Do not use & before studentlastname.
Also pass the size of the buffer. This is the key difference between scanf() and scanf_s(): Sizes passed for char * arguments. A seg fault or other odd behavior may occur without the proper parameters.
Check the result of scanf_s()
char studentname[20];
// scanf_s("%19s", &studentlastname);
if (1 != scanf_s("%s", studentlastname, sizeof studentlastname)) {
Handle_Error();
}
IMO: Do not use scanf() nor scanf_s() for any user input. Instead use fgets() and sscanf() or sscanf_s(), etc.
char studentname[20];
char buffer[2 * sizeof studentname + 2]; // I like 2x buffers
if (fgets(buffer, sizeof buffer, stdin) == NULL) {
Handle_EOF();
}
if (1 != sscanf("%19s", studentlastname)) {
Handle_Error();
}
// or
if (1 != sscanf_s("%s", studentlastname, sizeof studentlastname)) {
Handle_Error();
}
Changing from scanf() to fgets() really works best if all user input is changed this way, including those getting numbers.
int main() --> int main(void) #Dirk Koopman
If the final getch() needed for your environment, if not consider deleting it.
BTW Good exit strategy with checking the result of matches = fscanf(fp,... and good code did not use feof().