fread fwrite实例

#include<stdio.h> 

 #include<stdlib.h> 

 #include<string.h> 



 struct user  

{ 

char name[20]; 

char passwd[20]; 

}; 

 

 int gen(); 

 int main() 

 { 

gen(); 

return 0; 

 } 

 int gen() 

 { 

struct user *p; 

FILE *fp; 
  

p=malloc(sizeof(struct user)); 



if ((fp = fopen("admin.txt", 
 "rw+")) == NULL) { 

printf("the file doesnot exist");   

return 0; //failure 
  

} 

scanf("%s",p->name); 

scanf("%s",p->passwd); 

printf("\nname is%s",p->name); 

printf("\npasswd is%s",p->passwd); 

//fwrite(p, 1, sizeof(struct user), fp); 

 
fwrite(p, sizeof(struct user), 1, fp); 

memset(p, ' ', sizeof(struct user) ); 



 
fseek(fp, 0, SEEK_SET);  

fread(p, sizeof(struct user), 1, fp); 

printf("after read\n"); 

printf("\nname is%s",p->name); 

printf("\npasswd is%s",p->passwd); 

fclose(fp); 

}
//红色的三处，哎呀，容易忽视哦~~~