c - 姓名和姓氏搜索功能将无法使用。为什么？

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我创建了一个函数，因为我的项目和名称搜索/姓氏搜索函数无法正常工作并给出运行时错误。我实在看不出其中的错误。那么到底出了什么问题呢？

此外，ID和Mark搜索系统也存在一些错误，每当您搜索ID时，它也会带来mark = 0，同样，如果您搜索Mark，它也会带来ID = 0。

完整代码:

#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

如果您在打开警告的情况下编译了这段代码(每个人都应该这样做)并修复了警告，那么这个(修改后的)程序基本上可以工作。马克搜索可以工作，但会结束程序。我会把它留给你来解决。

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;
}

提示:将包含错误消息的 default 子句添加到 switch(choice) 并将 if (choice != 5) 更改为更好的测试。