#include<bits/stdc++.h>
#define ios ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
using namespace std;
signed main(void){ios; //c ++ 的關流, 不用管
  FILE *fp, *fq; //建立文件的索引指針
  if((fp = fopen("source" , "ra"))){ //打開需備份文件, 并且得到文件索引指針頭
    cout << "success in readfile open!" << endl;
  }else{
    cout << "can\'t open readfile!" << endl;
    exit(1);
  }
  if((fq = fopen("target" , "wa"))){ //建立(打開)目標文件, 并且得到文件索引指針頭
    cout << "success in writefile open!" << endl;
  }else {
    cout << "can\'t open writefile!" << endl;
    exit(1);
  }
  char buffer[20]; //設置一個緩沖區.
  while(fread(buffer, sizeof(char), 20, fp)){ //在需備份中一直獲取內容
    fwrite(buffer, sizeof(char), 20, fq); //獲取內容后一直同步輸入目標文件
  }
  if(!fclose(fp)){ //關閉成功的返回值為0
    cout << "success in readfile close!" << endl;
  }else {
    cout << "can\'t close readfile!" << endl;
    exit(1);
  }
  if(!fclose(fq)){
    cout << "success in writefile close!" << endl;
  }else {
    cout << "can\'t close writefile!" << endl;
    exit(1);
  }
  return 0;
}

#include<bits/stdc++.h>
#define ios ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
using namespace std;
signed main(void){ios; //c ++ 的關流, 不用管
  freopen("source" , "r" , stdin);
  freopen("target" , "w" , stdout);
  char c;
  while((c = getchar()) != EOF) putchar(c);
  return 0;
}

#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
signed main(int argc, char **argv) {
    int fp, fq;  //源文件的文件描述符, 目標文件的文件描述符
    char buffer[20];
    int nread;
    //判斷參數個數是否正確
    if (argc != 3) {
        printf("error~");
        exit(1);
    }
    //打開源文件
    if ((fp = open(argv[1], O_RDONLY)) == -1) {
        printf("Open readfile Erron\n");
        exit(1);
    }
    //創建目標文件
    if ((fq = open(argv[2], O_CREAT | O_WRONLY | O_TRUNC, S_IRUSR | S_IWUSR)) == -1) {
        printf("Open writefile Error\n");
        exit(1);
    }
    //進行文件拷貝
    while ((nread = read(fp, buffer, 20)) > 0) {
        if ((write(fq, buffer, nread)) != nread)  //將buffer中的數據寫到目的文件
            printf("write error");
    }
    close(fp);
    close(fq);
    return 0;
}