Question

麻烦大家给个用fwrite和fread将链表写入文件并读取的例子，谢谢！！！！

链表示例，谢谢了！！！
struct Country//乡村信息结构体
{
char counnum[5];
char counname[21];
int population;
int family;//depositor存款人
float relief;//救济金
struct Country *next;
};

Answer 1

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

struct Country//乡村信息结构体
{
char counnum[5];
char counname[21];
int population;
int family;//depositor存款人
float relief;//救济金
struct Country *next;
};

typedef struct Country *Lcountry;

//生成数据
int CreateData(Lcountry *head)
{
Lcountry s,p;
int i,num;

printf("输入个数:");
scanf("%d",&num);
if(num < 1)
{
printf("个数不合法\n");
return 0;
}

//录入数据
for(i=1;i<=num;i++)
{
if((s=(Lcountry)malloc(sizeof(struct Country)))==NULL)
{
printf("内存申请出错\n");
return 0;
}

printf("输入counnum counname population family relief,中间用空格隔开\n");
if(scanf("%s%s%d%d%f",s->counnum,s->counname,&s->population,&s->family,&s->relief)!=5)
{
printf("录入数据有误\n");
return 0;
}
s->next=NULL;

if(i==1)
{
*head=p=s;
}
else
{
p->next=s;
p=s;
}
}

return 1;
}

//写入数据
int WriteData(Lcountry head)
{
FILE *fp;
Lcountry p;

if((fp=fopen("f:\\test.txt","wb"))==NULL)//二进制只写方式打开
{
printf("打开文件出错\n");
return 0;
}

p=head;
while(p!=NULL)
{
if(fwrite(p,sizeof(struct Country),1,fp)!=1)
{
printf("写入数据出错\n");
fclose(fp);
return 0;
}
p=p->next;
}

fclose(fp);//关闭文件
return 1;
}

//读入数据
int ReadData(Lcountry *head)
{
Lcountry s,p;

FILE *fp;
if((fp=fopen("f:\\test.txt","rb"))==NULL)//二进制只读方式打开
{
printf("打开文件出错\n");
return 0;
}

while(!feof(fp))//文件不到末尾
{
if((s=(Lcountry)malloc(sizeof(struct Country)))==NULL)
{
printf("内存申请出错\n");
fclose(fp);
return 0;
}
//怎么写就怎么读取
if(fread(s,sizeof(struct Country),1,fp)!=1)//读到末尾或者出错,跳出循环
{
free(s);
break;
}
if(*head==NULL)
*head=p=s;
else
{
p->next=s;
p=s;
}

}

fclose(fp);//关闭文件
return 1;
}

//显示数据
void Print(Lcountry p)
{
printf("counnum \t counname \t population \t family \t relief\n");
while(p!=NULL)
{
printf("%s\t\t%s\t\t%d\t\t%d\t\t%0.1f\n",p->counnum,p->counname,p->population,p->family,p->relief);
p=p->next;
}
}
//释放资源
void Free(Lcountry *head)
{
Lcountry p=*head;
while(p!=NULL)
{
*head=(*head)->next;
free(p);
p=*head;
}
*head=NULL;
}

int main(void)
{
Lcountry head=NULL;

//生成数据
if(CreateData(&head)!=1)
return 1;

//显示数据
Print(head);

//写入数据
if(WriteData(head)!=1)
return 1;

//释放资源
Free(&head);
printf("写入完毕\n");

printf("\n读取数据...\n");
//读入数据
if(ReadData(&head)!=1)
return 1;

//显示数据
Print(head);

//释放资源
Free(&head);
return 0;
}