C语言程序设计(第3版)何钦铭 颜 晖 第12章 文件(4)

if(fclose(fp2)){

printf(\ exit(0); }

return 0; }

7.(选做) 账户余额管理: 创建一个随机文件，用来存储银行账户和余额信息，程序要求能够查询某个账户的余额，当客户发生交易额时(正表示存入，负表示取出)能够更新余额。账户信息包括账号、账号名和余额三个数据项。试编写相应程序。

文件部分内容如下:

AcctNo AcctName Balance 1 zhangsan 1 000.00 2 lisi 1 300.00 3 wangwu -100.00 …… 解答：

#include #include #include long size;

struct account{ char no[10];

char acctname[50]; double balance; };

FILE *openfile(char *openmode){ FILE *fp;

if((fp=fopen(\ printf(\ exit(0); }

return fp; }

double userbalance(FILE *fp,char *name); void pay(FILE *fp,char *name,double count); int main() {

FILE *fp; int choice; char name[50]; double balance;

double count;

printf(\请输入选择类型：\\n\ printf(\查账户余额\\n\ printf(\账户交易\\n\ printf(\退出按exit\\n\ printf(\选择类型：\ scanf(\ switch(choice){ case 1:

printf(\输入名字\ scanf(\ fp=openfile(\

balance=userbalance(fp,name); printf(\ break; case 2:

printf(\输入名字\ scanf(\ fp=openfile(\

printf(\输入交易金额\ scanf(\ pay(fp,name,count); break; }

default: exit(0); break; }

return 0; }

double userbalance(FILE *fp,char *name){ struct account user; double balance;

rewind(fp);

while(!feof(fp)){

fscanf(fp,\ if(strcmp(user.acctname,name)==0){ balance=user.balance; break; } }

return balance; }

void pay(FILE *fp,char *name,double count){

FILE *fpout;

struct account user; double balance;

balance=userbalance(fp,name); balance=balance+count; rewind(fp);

fpout=fopen(\ while(!feof(fp)){

fscanf(fp,\ if(strcmp(user.acctname,name)==0){ user.balance=balance;

fprintf(fpout,\ } else

fprintf(fpout,\ }

if(fclose(fp)){

printf(\ exit(0); }

if(fclose(fpout)){ printf(\ exit(0); }

unlink(\都是删除文件的函数 rename(\}