將結構保存在一個文件中

Question

我正在做一個程序來保存文件結構中的聯繫人列表。我嘗試了很多東西，但是當我嘗試去閱讀文件到程序中時，它不會讀取任何內容。

這是我沒有打開文件並保存到文件的程序：

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

struct agenda { 
    int idContacte; 
    char name[50]; 
    struct agenda *nextContacte; 
}; 
struct agenda *pAgenda; 
struct agenda *pFirst = NULL; 
struct agenda *pIndex; 

void insert(); 
void show(); 

int main() 
{ 
    //Menu 
    int opc; 
    while(1){ 
     printf("1.Insert Contact.\n"); 
     printf("2.Show Contacts.\n"); 
     printf("3.Exit\n"); 
     scanf("%d", &opc); 
     switch(opc){ 
      case 1: 
       insert(); 
       break; 
      case 2: 
       show(); 
       break; 
      case 3: 
       return 0; 
     } 
    } 
} 
void insert(){ 
    pAgenda = (struct agenda *)malloc(sizeof(struct agenda)); 
    printf("Insert ID: "); 
    scanf("%d", &pAgenda->idContacte); 
    printf("Insert the name: "); 
    scanf("%s", pAgenda->name); 
    printf("\n"); 
    if (pFirst==NULL || pAgenda->idContacte < pFirst->idContacte) 
    { 
     pAgenda->nextContacte=pFirst; 
     pFirst=pAgenda; 
    } 
    else if (pAgenda->idContacte > pFirst->idContacte){ 
     pIndex=pFirst; 
     while(pIndex->nextContacte && pIndex->nextContacte->idContacte < pAgenda->idContacte) 
     { 
      pIndex = pIndex->nextContacte; 
     } 
     pAgenda->nextContacte = pIndex->nextContacte; 
     pIndex->nextContacte = pAgenda; 
    } 
} 
void show(){ 
    pIndex = pFirst; 
    while(pIndex && pIndex->idContacte <= 100) { 
     printf("\nID: %d", pIndex->idContacte); 
     printf("\nNAME: %s", pIndex->name); 
     printf("\n\n"); 
     pIndex = pIndex->nextContacte; 
    } 
} 

你能幫助我，我怎樣才能從文件在程序開始接觸，然後在插入接觸，改寫文件並再次將所有聯繫人插入文件中？

Answer 1

當你結束你的程序，你應該做以下

int save_list(struct agenda *head) { 
    FILE *save = fopen("file.name", "wb"); 
    if(!save) return -1; 

    while(head) { 
    fwrite(head, sizeof *head - sizeof head, 1, save); 
    head = head->nextContacte; 
    } 

    fclose(save); 
    /* Somebody would free list memory after this function execution */ 
    return 0; 
} 

在你的程序，你應該做以下

struct agenda *restore_list() { 
    FILE *restore= fopen("file.name", "rb"); 
    struct agenda *head = NULL; 
    struct agenda *cur = head; 
    struct agenda temp; 
    if(!restore) return head; 

    while(fwrite(&temp, sizeof temp - sizeof head, 1, save) == 1) { 
    struct agenda *node = malloc(sizeof(struct agenda)); 
    if(NULL == node) { 
     /* Handle out of memory error here, free list */ 
     return NULL; 
    } 
    *node = temp; 
    node->nextContacte = NULL; 
    if(head) { 
     cur->nextContacte = node; 
     cur = node; 
    } else { 
     /* First node */ 
     head = cur = node; 
    } 
    } 

    fclose(restore); 
    return head; 
}