C：将结构读入链接列表（从文件）

Question

I am new to C programming. I have created a student database to enter student details into a linked list (in the form of structure "phbook") and save linked list onto text file. The part I cannot get to work is to read the text file records onto the linked list. The program runs but does not update the linked list when I close the program then select to "LOAD FROM EXTERNAL FILE". Please can someone help me figure what the problem is. I know everything worked until I coded the "readFile" and "insertFull" function. Friends have told me that the global variable "struct phbook *list = NULL;is causing the problem. Please let me know.

#include <stdio.h>
#include<string.h>
#include<stdlib.h>

struct phbook{
    int number;
    char name[20];
    int mark;
    struct part *next;
};

struct phbook *list = NULL;
struct phbook *find_student(int number);
void insertFull(struct phbook* list, int number, char Name[10],int mark);
int main(void)
{
    int code;
    int opt1;
    int courses, i, k, j, counter;
    for (;;){
        printf("Enter operation code: \n");
        printf("(1) ADD NEW STUDENT DETAILS: \n");
        printf("(2) SEARCH STUDENT DETAILS: \n");
        printf("(3) DISPLAY REPORT OF ALL STUDENTS: \n");
        printf("(4) SAVE ALL STUDENT RECORDS TO EXTERNAL FILE: \n");
        printf("(5) LOAD ALL STUDENT RECORDS FROM EXTERNAL FILE: \n");
        scanf(" %d", &code);
     switch (code){
         case 1 : insert();
                        break;
         case 2 : search();
                        break;
            break;
         case 3 : print();
            break;
         case 4 :
             saveToFile();
                        break;
                   case 5 :
             readFile();
                        break;
         default: printf("Illegal code\n");
}
 printf("\n");
}
    }


struct phbook *find_student(int number)
{
    struct phbook *p;
    for (p = list; p != NULL && number != p->number; p = p->next);//was sorted
    if (p != NULL && number == p->number)
        return p;
        return NULL;
}

void insert(void)
{
    struct phbook *cur;
    struct phbook *prev;
    struct phbook *new_node;
    new_node = (struct phbook*) malloc(sizeof(struct phbook));
    if (new_node == NULL){
        printf("db full er1.\n");
        return;
    }
    printf("enter student id");
    scanf("%d", &new_node->number);
    for (cur = list, prev = NULL; cur!= NULL && new_node->number > cur->number; prev = cur, cur = cur->next);
    printf("Enter name: ");
    scanf("%s", &new_node->name);//readline(new_node->name, NAME_LEN)
    printf("Enter MARK: ");
    scanf("%d", &new_node->mark);

    new_node->next = cur;
    if (prev == NULL)
        list = new_node;
    else
        prev->next = new_node;
}

void search(void)
{
    int number;
    struct phbook *p;
    printf("Enter ID: ");
    scanf("%d", &number);
    p = find_student(number);
    if (p != NULL){
        printf("Name: %s\n", p->name);
        printf("Marks: %d\n", p->mark);
    }
    else
    printf("student not found.\n");
}

void print(void)
{
    struct phbook *p;
    printf("Student_Number Student_Name Student_Mark\n");
    for (p = list; p != NULL; p = p->next)
        printf("%7d %-25s %d\n", p->number, p->name, p->mark);
}
void saveToFile()
{
    FILE* fp;
    fp = fopen ("results.txt","w");


   struct phbook* curr = list;//he
   while(curr!=NULL)
   {
    fprintf(fp,"%s\n", list->name);
    fprintf(fp,"%d\n",curr->number);
    fprintf(fp, "%d\n", curr->mark);
       curr = curr->next;
   }
   fclose(fp);
}

void readFile()
{
    FILE* fp;
    if (!(fp = fopen ("results.txt", "r")))
        printf("File NOT Found");
    else{
        struct phbook *curr;
        struct phbook *prev;
        char TempName[10];
        int TempNumber;
        int TempMark;
        int done = 0;
        int count = 0;
        int success;//dummy
        curr = list;//sets it to the head (first nde of ll)
        if(list == NULL);
        printf("List is null\n");

        if(curr == NULL)
            printf("List is null\n");

        while (curr!=NULL)
        {
            curr = curr->next;
        }
        while (done == 0)
        {
            success = fscanf(fp, "%s", TempName);
            if (success == 1)
                {
                    success = fscanf(fp, "%d", &TempNumber);
                    if (success == 1)
                    {
                        success = fscanf(fp, "%d", &TempMark);

                        if(success == 1)
                        {
                            insertFull(list,TempNumber,TempName,TempMark);
                        }
                    }

                }
                else
                {
                    done = 1;
                }

        }
    }
}
void insertFull(struct phbook* list, int number, char Name[10],int mark)
{
   struct phbook *cur;
    struct phbook *prev;
    struct phbook *new_node;
    new_node = (struct phbook*) malloc(sizeof(struct phbook));
    if (new_node == NULL){
        printf("db full er1.\n");
        return;
    }

    for (cur = list, prev = NULL; cur!= NULL && new_node->number > cur->number; prev = cur, cur = cur->next);
    new_node->number = number;
    new_node->mark = mark;
    strcpy(new_node->name,Name);
    new_node->next = cur;
    if (prev == NULL)
        list = new_node;
    else
        prev->next = new_node;


}

Answer 1

In the procedure

void insertFull(struct phbook* list, int number, char Name[10],int mark)

you are changing your local copy of list, this has no effect on the global phone book list.

You can remove list from the argument lists, thus changing the global variable:

   void insertFull(int number, char Name[10],int mark)

this is not strictly good programming, but it is in line with the rest of your code.