mycopy.c

#include<sys/types.h>#include<sys/stat.h>#include<fcntl.h>#include<stdlib.h>#include<errno.h>#include<string.h>#include<unistd.h>#include<stdio.h>int main(int argc,char *argv[]){  int ffd,tfd;  int byteread,bytewrite;  char buffer[1024];  char *ptr;  if(argc != 3)//命令行参数不是三个，显示参数错误  {    printf("parameter fault");    exit(1);  }  if((ffd = open(argv[1],O_RDONLY)) == -1)  //原文件打开错误  {    printf("fail to open source file");    exit(1);  }  if((tfd = open(argv[2],O_WRONLY|O_CREAT,S_IWUSR)) == -1)//新文件创建错误  {    printf("fail to create target file");    exit(1);  }  while(byteread = read(ffd,buffer,1024))  //每次读取1024比特  {    if((byteread == -1)&&(errno != EINTR)) break;//读取错误    else if(byteread > 0)  //把读到的写入另一个文件    {      ptr = buffer;      while(bytewrite = write(tfd,ptr,byteread))      {        if((bytewrite == -1)&&(errno != EINTR)) break; //写入错误        else if(bytewrite == byteread) break;        else if(bytewrite > 0)        {          ptr = ptr + bytewrite;          byteread = byteread - bytewrite;        }      }      if(bytewrite == -1) break;    }  }  close(ffd);  close(tfd);  exit(0);}