第12章文件
【练习12-1】读出例12-1学生成绩文件内容，输出最高分和最低分及相应的学号和姓名。
解答：
#include<>
#include<>
struct student{
long num;
char stname[20];
int score;
};
int main(void)
{
FILE *fp;
int i,max,min,j=0,k=0;
struct student students[5];
if((fp=fopen("","r"))==NULL) {
printf("File open error!\n");
exit(0);
}
fscanf(fp,"%ld%s%d",&students[0].num,students[0].stname,&students[0] .score);
max=min=students[0].score;
for(i=1;i<=4;i++){
fscanf(fp,"%ld%s%d",&students[i].num,students[i].stname,&students[i]. score);
if(maxmax=students[i].score;
j=i;
}
if(min>students[i].score){
min=students[i].score;
k=i;
}
}
printf("Max
score: %d,num:%d,name:%s\n",students[j].score,students[j].num,&studen ts[j].stname);
printf("Min
score: %d,num:%d,name:%s\n",students[k].score,students[k].num,&studen ts[k].stname);
if(fclose(fp)){
printf("Can not close the file!\n");
exit(0);
}
return 0;
}
【练习12-2】请使用例8-9答电码加密函数对民吗字符串进行加密，改写例12-2。解答：
#include<>
#include<>
#include<>
struct sysuser{
char username[20];
char password[8];
};
void encrypt(char *pwd);
int main(void)
{
FILE *fp;
int i;
struct sysuser su;
if((fp=fopen("","w"))==NULL){
printf("File open error!\n");
exit(0);
}
for(i=1;i<=5;i++){
printf("Enter %dth sysuser (name password):",i);
scanf("%s%s",,;
encrypt;
fprintf(fp,"%s %s\n",,;
}
if(fclose(fp)){
printf("Can not close the file!\n");
exit(0);
}
return 0;
}
void encrypt(char *pwd)
{
int i;
for(i=0;iif(pwd[i]=='z')
pwd[i]='a';
else
pwd[i]+=1;
}
【练习12-3】例12-3中为什么在执行fputc（ch，fp2）前要判断ch的值是否等于EOF改写例12-3的程序，在复制用户信息文件后，再统计被复制文件中字符的数量。
解答：
文件结束符EOF是一个值为-1的常量，读文件时可用来判断从文件中读入的字符是否为EOF来决定循环是否继续。
#include<>
#include<>
int main(void)
{
FILE *fp1,*fp2;
char ch;
int count=0;
if((fp1=fopen("","r"))=NULL){
printf("File open error!\n");
exit(0);
}
if((fp2=fopen("","w"))==NULL){
printf("File open error!\n");
exit(0);
}
while(!feof(fp1)){
ch=fgetc(fp1);
if(ch!=EOF) {
fputc(ch,fp2);
count++;
}
}
if(fclose(fp1)){
printf("Can not close the file!\n");
exit(0);
}
if(fclose(fp2)){
printf("Can not close the file!\n");
exit(0);
}
