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/*fseek()
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范例一：fseek(fp, 0L, SEEK_END);
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解释：文件指针定位到文件末尾，偏移0个字节
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范例二： fseek(fp,50L,0)；或fseek(fp,50L,SEEK_SET);
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解释：其作用是将位置指针移到离文件头50个字节处。
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*/
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#include<stdio.h>
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#include<stdlib.h>
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#include<string.h>
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#define SIZE 50
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void change(){
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system("cls");
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struct TX{
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char name[10];
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char jiguan[20];
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char d1[20],d2[20];
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char ema[30];
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}inf [SIZE];
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FILE *fp;
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char a[20],b[20];
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int i,flag=0,n,f=0;
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fp=fopen("date.dat","rb");//打开二进制文件进行只读；
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printf("\t\t\t\t\t\t请输入需要修改信息的姓名：");
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scanf("%s",a);
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for(i=0;fread(&inf[i],sizeof(struct TX),1,fp)==1;i++){
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if(strcmp(a,inf[i].name)==0){//strcmp为比较函数，若a=inf[i].name则返回0；
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printf("\t\t\t\t\t\t当前信息：\n");
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printf("\t\t\t\t\t\t姓名：%s\n",inf[i].name);
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printf("\t\t\t\t\t\t籍贯：%s\n",inf[i].jiguan);
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printf("\t\t\t\t\t\t电话号码1：%s\n",inf[i].d1);
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printf("\t\t\t\t\t\t电话号码2：%s\n",inf[i].d2);
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printf("\t\t\t\t\t\t邮箱：%s\n\n\n",inf[i].ema);
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flag=1;
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break;
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}
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}fclose(fp);
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fp=fopen("date.dat","rb+");
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fseek(fp,i*sizeof(struct TX),0);//将文件指针移到需要改变数据的位置，否则会出错
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if(flag==0)printf("\t\t\t\t\t\t输入错误!\n\n\n\n\n") ;
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if(flag==1){
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printf("\t\t\t请输入需要修改的信息：1.姓名 2.籍贯 3.电话号码1 4.电话号码2 5.邮箱 6.不需要继续修改了\n");
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printf("\t\t\t\t\t\t修改信息:");
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for(;f==0;){
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scanf("%d",&n);
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switch(n){
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case 1:printf("\t\t\t\t\t\t将姓名修改为：");
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scanf("%s",inf[i].name);
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printf("\n");break;
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case 2:printf("\t\t\t\t\t\t将籍贯修改为：");
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scanf("%s",inf[i].jiguan);printf("\n");break;
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case 3:printf("\t\t\t\t\t\t将电话号码1修改为：");
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scanf("%s",inf[i].d1);printf("\n");break;
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case 4:printf("\t\t\t\t\t\t将电话号码2修改为：");
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scanf("%s",inf[i].d2);printf("\n");break;
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case 5:printf("\t\t\t\t\t\t将邮箱修改为：");
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scanf("%s",inf[i].ema);printf("\n");break;
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case 6:f=1;printf("\n\n\n");break;
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}if(n!=6){
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printf("\t\t\t\t\t\t还需修改的信息是：");
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fwrite(&inf[i],sizeof(struct TX),1,fp);//将修改后的信息写入文件
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}
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}
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fclose(fp);
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}
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}
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