void appendwt(){FILE *pFile = fopen("data.txt","ab+");//使用"ab+"每次都插入到最后面,调用fseek也没用char *str="hello,world!45%13ad2014/23/13add\n";    fwrite(str,1,strlen(str),pFile);    fflush(pFile);    fclose(pFile);}

void randwt(){FILE *fp;        fp=fopen("overwrite.bin","rb+"); //使用rb+模式,可以往半中间插入数据,定义到任何位置        {            if(-1 == (fseek(fp,9, SEEK_SET))) /从第9字节开始abcde                    printf("seek error\n");            fwrite("abcde",1, 5, fp);
            fflush(fp);//flush来刷新流，每次读写后都希望立即看到结果，不用重新打开关闭            fclose(fp);        }        else        {            printf("fopen error");        }}

void overwt() {FILE *pFile = fopen("data.txt","w+");    fwrite("hello,world!",1,strlen("hello,world!"),pFile);    fflush(pFile);                    
            //fseek来移动文件的指针，它指向文件下一个要写入的位置    fseek(pFile,0,SEEK_SET);        //文件指针设为起点，写操作覆盖原来的内容    fwrite("欢迎访问",1,strlen("欢迎访问"),pFile);    fseek(pFile,0,SEEK_END);        //文件指针设为终点    int len = ftell(pFile);         //获取文件字节数    char* ch = (char*)malloc(sizeof(char)* (len+1));    //分配内存，多一个字节    memset(ch,0,(len+1));           //清0//  fseek(pFile,0,SEEK_SET);        //文件指针指向头部    rewind(pFile);    fread(ch,1,len,pFile);          //读取文件    fclose(pFile);    printf("%s",ch);}

typedef struct {char c;int h;short n;long m;float f;double d1;char *s;double d2;} st;

void struwt() {FILE *fp;st sa, sb; //定义结构体char *str = "abcdefg"; //结构体赋值sa.c = 'K';sa.h = -3;sa.n = 20;sa.m = 100000000;sa.f = 33.32f;sa.d1 = 78.572;sa.d2 = 33.637;sa.s = str;fp = fopen("st.txt", "w+"); //打开要写的文件if (!fp) {printf("errror!\n");exit(-1);}printf("sa:c=%c,h=%d,n=%d,m=%d,f=%f,d1=%f,s=%s,d2=%f\n", sa.c, sa.h, sa.n,sa.m, sa.f, sa.d1, sa.s, sa.d2);printf("sizeof(sa)=%d:&c=%x,&h=%x,&n=%x,&m=%x,&f=%x,&d1=%x,&s=%x,&d2=%x\n",sizeof(sa), &sa.c, &sa.h, &sa.n, &sa.m, &sa.f, &sa.d1, &sa.s,&sa.d2);fwrite(&sa, sizeof(sa), 1, fp); //写入结构体rewind(fp); //重新指向流fread(&sb, sizeof(sb), 1, fp); //用sb读取printf("sb:c=%c,h=%d,n=%d,m=%d,f=%f,d1=%f,s=%s,d2=%f\n", sb.c, sb.h, sb.n,sb.m, sb.f, sb.d1, sb.s, sb.d2);fclose(fp); //关闭指针}

//从文件读取结构体void strurd() {FILE *fp;st sb;fp = fopen("st.txt", "r"); //打开文件if (!fp) {printf("errror!\n");exit(-1);}fread(&sb, sizeof(sb), 1, fp); //读取结构体printf("sb:c=%c,h=%d,n=%d,m=%d,f=%f,d1=%f,s=%s,d2=%f\n", sb.c, sb.h, sb.n,sb.m, sb.f, sb.d1, sb.s, sb.d2);printf("sizeof(sb)=%d:&c=%x,&h=%x,&n=%x,&m=%x,&f=%x,&d1=%x,&s=%x,&d2=%x\n",sizeof(sb), &sb.c, &sb.h, &sb.n, &sb.m, &sb.f, &sb.d1, &sb.s,&sb.d2);fclose(fp);}