用系统函数复制文件

#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>


int main(int argc,char *argv[])
{
 int fd1 = -1;
 int fd2 = -1;
 unsigned char tmp = 0;

 if(argc != 3)
 {
  printf("The command should be ./mycp file1 file2\n");
  return 1;
 }

 fd1 = open(argv[1],O_RDONLY);
 if(fd1 < 0)
 {
  printf("Open file %s failed\n",argv[1]);
  return 2;
 }
 
 fd2 = open(argv[2],O_CREAT|O_TRUNC|O_WRONLY,0666);
 if(fd2 < 0)
 {
  printf("Open file %s failed\n",argv[2]);
  close(fd1);
  return 3;
 }

 while(1 == read(fd1,&tmp,1))
 {
  write(fd2,&tmp,1);
 }

 close(fd1);
 close(fd2);
 return 0;
}