C语言中的setlinebuf()、utmpname()、rewind函数使用

#include <stdio.h>

void setlinebuf(FILE * stream);

#include <utmp.h>

void utmpname(const char * file);

 #include <stdio.h>

  void rewind(FILE * stream);

typedef struct
{
  int _fd; // 文件号
  int _cleft; // 缓冲区中剩下的字节数
  int _mode; // 文件操作模式
  char * _nextc; // 下一个字节的位置
  char * _buff; // 文件缓冲区位置
}FILE;

#include<iostream.h>
#include<stdio.h>
void main(void)
{
  FILE* stream;
  long l;
  float fp;
  char s[81];
  char c;
  stream = fopen("fscanf.txt","w+");
  if(stream == NULL)/*打开文件失败*/
  {
    printf("the file is opeaned error!\n");
  }
  else/*成功则输出信息*/
  {
    fprintf(stream,"%s %ld %f %c","a_string",6500,3.1415,'x');
    fseek(stream,0L,SEEK_SET);      /*定位文件读写指针*/
    fscanf(stream,"%s",s);
    printf("%ld\n",ftell(stream));
    fscanf(stream,"%ld",&l);
    printf("%ld\n",ftell(stream));
    fscanf(stream,"%f",&fp);
    printf("%ld\n",ftell(stream));
    fscanf(stream," %c",&c);
    printf("%ld\n",ftell(stream));
    rewind(stream);/*指向文件开头*/
    fscanf(stream,"%s",s);
    printf("%s\n",s);
    fclose(stream);/*关闭流*/
  }
}

8
13
22
24
a_string

#include "stdio.h"
void main()
{
  FILE *fp1, *fp2;
  fp1 = fopen("file1.c", "r"); // 源文件
  fp2 = fopen("file2.c", "w"); // 复制到file2.c
  while(!feof(fp1)) putchar(fgetc(fp1)); // 显示到屏幕上
  rewind(fp1);  // fp回到开始位置
  while(!feof(fp1)) fputc(fgetc(fp1), fp2);
  fclose(fp1);
  fclose(fp2);
}