C语言实现随机读写文件

1、首先打开VC++6.0

2、选择文件，新建

3、选择C++ source file 新建一个空白文档

4、声明头文件和常量#include<stdio.h>#include<stdlib.h>#define NUM 3

5、写主函数和指针，变量main( ){ FILE *fp1; /*定义文件指针*/ char *temp; int i,j;

6、需要一个结构体 struct re罕铞泱殳c{ /*定义结构体类型*/ char id[10]; c茑霁酌绡har name[15]; char department[15]; }record[NUM];

7、主要代码，关键我已注释i酆璁冻嘌f ((fp1=fopen("d:\\infile.txt","wb"))==NULL) /*以二进制只写方式打开文件*/ {printf("cannot open file");/*出错返回*/exit(1); } for( i=0;i<NUM;i++) {printf("Please input id:");scanf("%s",record[i].id); /*从键盘输入*/printf("Please input name:"); scanf("%s",record[i].name);printf("Please input department:"); scanf("%s",record[i].department);fwrite(&record[i],sizeof(struct rec),1,fp1); /* 成块写入*/ } fclose(fp1); /*关闭*/ if((fp1=fopen("d:\\infile.txt","rb+"))==NULL)/*以可读写方式打开文件*/ {printf("cannot open file"); /*出错返回*/exit(1); } printf("************************************\n"); printf("%-10s%-15s%-15s\n","id","name","department"); printf("************************************\n"); for (i=0;i<NUM;i++) { /*显示全部文件内容*/fread(&record[i],sizeof(struct rec),1,fp1);printf("%-10s%-15s%-15s\n",record[i].id,record[i].name,record[i].department); } /*以下进行文件的随机读写*/ fseek(fp1,2*sizeof(struct rec),0); /* 定位文件指针指向第三条记录*/ fwrite(&record[1],sizeof(struct rec),1,fp1); /* 在第三条记录处写入第二条记录*/ rewind(fp1); /*移动文件指针到文件头*/ printf("************************************\n"); printf("%-10s%-15s%-15s\n","id","name","department"); printf("************************************\n"); for (i=0;i<NUM;i++) { /*重新输出文件内容*/fread(&record[i],sizeof(struct rec),1,fp1);printf("%-10s%-15s%-15s\n",record[i].id,record[i].name,record[i].department); } fclose(fp1); /*关闭文件*/ scanf("%d",i);}